Anodizing effect on fatigue life of aluminum alloy

[Peter Cole]

Interesting article on a fatigue failure of an experimental helicopter
component"

"Anodizing and Fatigue Life", Experimental Helo / May 2007
http://www.experimentalhelo.com/Anodizing&Fatigue.pdf

The article references a paper from 2000:

"Characteristics of Fatigue Strength on Anodized 2014-T6 Aluminum Alloy."
http://sciencelinks.jp/j-east/article/200107/000020010701A0137211.php

"Abstract;In order to investigate the effect of anodized film on fatigue
strength of aluminum alloy, A 2014-T 6, repeated tensile fatigue test
was conducted in laboratory air under the stress ratio, R, of 0.01 using
smooth specimen with anodized film thickness of 3.MU.m. Fatigue strength
of anodized specimen tested under R=0.01 decreased by 18-20% as compared
with that of the untreated one ... The anodized film is fractured at an
early stage of repeated tensile fatigue process, because it is too
brittle to accommodate the substrate metal. Many cracks are induced to
initiate at the substrate by flaws of the anodized film. It was pointed
out through the study that the fatigue strength of anodized aluminum
alloy is controlled by the crack initiation behavior in the substrate
induced by the rupture of the anodized film, which is related to the
deformation of substrate metal during fatigue process."

The article also references a book:

"Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
and Menzemer 1996

You can use the Amazon "Search inside" feature to see the graph on page 100:
http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#

The graph shows very large reductions in fatigue strength for 7075
forgings after cleaning with caustic (C22) or acid (C31) baths. It also
shows drastic reductions in fatigue strength for uncleaned, anodized
samples.

From the above graph, thick (50 micrometer) anodizing, reduced the
fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
micrometer) anodizing reduced it by a factor of 6.

[jim beam]

Peter Cole wrote:
> Interesting article on a fatigue failure of an experimental helicopter
> component"
>
> "Anodizing and Fatigue Life", Experimental Helo / May 2007
> http://www.experimentalhelo.com/Anodizing&Fatigue.pdf
>
> The article references a paper from 2000:
>
> "Characteristics of Fatigue Strength on Anodized 2014-T6 Aluminum Alloy."
> http://sciencelinks.jp/j-east/article/200107/000020010701A0137211.php
>
> "Abstract;In order to investigate the effect of anodized film on fatigue
> strength of aluminum alloy, A 2014-T 6, repeated tensile fatigue test
> was conducted in laboratory air under the stress ratio, R, of 0.01 using
> smooth specimen with anodized film thickness of 3.MU.m. Fatigue strength
> of anodized specimen tested under R=0.01 decreased by 18-20% as compared
> with that of the untreated one ... The anodized film is fractured at an
> early stage of repeated tensile fatigue process, because it is too
> brittle to accommodate the substrate metal. Many cracks are induced to
> initiate at the substrate by flaws of the anodized film. It was pointed
> out through the study that the fatigue strength of anodized aluminum
> alloy is controlled by the crack initiation behavior in the substrate
> induced by the rupture of the anodized film, which is related to the
> deformation of substrate metal during fatigue process."
>
> The article also references a book:
>
> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> and Menzemer 1996
>
> You can use the Amazon "Search inside" feature to see the graph on page
> 100:
> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>
> The graph shows very large reductions in fatigue strength for 7075
> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> shows drastic reductions in fatigue strength for uncleaned, anodized
> samples.
>
> From the above graph, thick (50 micrometer) anodizing, reduced the
> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> micrometer) anodizing reduced it by a factor of 6.


slow day peter? feel the need to do a bit of trolling? and if i told
you that hydrogen embrittlement exists, would you go ahead and conclude
that rims crack because of it? or would you bother to observe the
failure conditions first?

rim cracking has complete correlation with extrusion anisotropy, and
merely coincidental correlation with anodizing cracking. if a rim crack
orientation doesn't follow an anodizing crack orientation, and it
frequently doesn't, then to conclude that coincidence is cause is at
best sloppy and/or ignorant, at worst, an attempt to fudge the facts to
fit an underinformed preconception. simple observation shows the truth.
shame that seems to be so low down the list of priorities around here.

[Peter Cole]

Peter Cole wrote:

> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> and Menzemer 1996
>
> You can use the Amazon "Search inside" feature to see the graph on page
> 100:
> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>
> The graph shows very large reductions in fatigue strength for 7075
> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> shows drastic reductions in fatigue strength for uncleaned, anodized
> samples.
>
> From the above graph, thick (50 micrometer) anodizing, reduced the
> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> micrometer) anodizing reduced it by a factor of 6.

I should point out that these sources agree with what Jobst has
explained all along: thick anodizing has a disastrous effect on fatigue
life, and even thin cosmetic anodizing can have significant
consequences. The mechanism, as described in these sources, agrees with
his causal explanation. This is science, there can be no controversy,
except via willful ignorance.

[jim beam]

Peter Cole wrote:
> Peter Cole wrote:
>
>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>> and Menzemer 1996
>>
>> You can use the Amazon "Search inside" feature to see the graph on
>> page 100:
>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>
>> The graph shows very large reductions in fatigue strength for 7075
>> forgings after cleaning with caustic (C22) or acid (C31) baths. It
>> also shows drastic reductions in fatigue strength for uncleaned,
>> anodized samples.
>>
>> From the above graph, thick (50 micrometer) anodizing, reduced the
>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>> micrometer) anodizing reduced it by a factor of 6.
>
> I should point out that these sources agree with what Jobst has
> explained all along: thick anodizing has a disastrous effect on fatigue
> life, and even thin cosmetic anodizing can have significant
> consequences. The mechanism, as described in these sources, agrees with
> his causal explanation. This is science, there can be no controversy,
> except via willful ignorance.

the only willful ignorance being demonstrated here is from those trying
to make the facts fit preconception!!! yes, anodizing /can/ have a
serious affect on fatigue. BUT, if you or he had ever bothered to
observe the facts, cracking is entirely independent of anodizing crack
orientation. it is therefore NOT the cause in this case.

it doesn't get much simpler peter cole. the human folly of ego and
attempted face saving [including trolling] will be the death of this
species - because observation of scientific fact sure doesn't seem to be
a priority.

[unforgiven99@juno.com]

On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> Peter Cole wrote:
> > "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> > and Menzemer 1996
>
> > You can use the Amazon "Search inside" feature to see the graph on page
> > 100:
> >http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>
> > The graph shows very large reductions in fatigue strength for 7075
> > forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> > shows drastic reductions in fatigue strength for uncleaned, anodized
> > samples.
>
> > From the above graph, thick (50 micrometer) anodizing, reduced the
> > fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> > micrometer) anodizing reduced it by a factor of 6.
>
> I should point out that these sources agree with what Jobst has
> explained all along: thick anodizing has a disastrous effect on fatigue
> life, and even thin cosmetic anodizing can have significant
> consequences. The mechanism, as described in these sources, agrees with
> his causal explanation. This is science, there can be no controversy,
> except via willful ignorance.

It's only causal if you believe that there are no other factors
affecting fatigue life. You could substitute anodizing for mirror
polishing, and it's not going to improve fatigue life if your
extrusion process left internal voids. Without direct observation of
cracks appearing in the anodized layer and propagating into the metal,
it's not causality. It's correlation, and not even real correlation,
as nobody has actually bothered to pin down incidence rates.

[Tom Sherman]

Peter Cole wrote:
> Peter Cole wrote:
>
>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>> and Menzemer 1996
>>
>> You can use the Amazon "Search inside" feature to see the graph on
>> page 100:
>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>
>> The graph shows very large reductions in fatigue strength for 7075
>> forgings after cleaning with caustic (C22) or acid (C31) baths. It
>> also shows drastic reductions in fatigue strength for uncleaned,
>> anodized samples.
>>
>> From the above graph, thick (50 micrometer) anodizing, reduced the
>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>> micrometer) anodizing reduced it by a factor of 6.
>
> I should point out that these sources agree with what Jobst has
> explained all along: thick anodizing has a disastrous effect on fatigue
> life, and even thin cosmetic anodizing can have significant
> consequences. The mechanism, as described in these sources, agrees with
> his causal explanation. This is science, there can be no controversy,
> except via willful ignorance.

I disagree with the last sentence. Besides willful ignorance, the cause
for controversy could be overindulgence in Kentucky Bourbon whiskey.

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

[agcou]

On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:


>
> the only willful ignorance being demonstrated here is from those trying
> to make the facts fit preconception!!! yes, anodizing /can/ have a
> serious affect on fatigue. BUT, if you or he had ever bothered to
> observe the facts, cracking is entirely independent of anodizing crack
> orientation. it is therefore NOT the cause in this case.
>

Another common misconception is that the substrate cracks cause anodization
layer cracks. This is clearly wrong for the same reason. The cracks
aren't oriented, therefore they are not related.

I think Peter realizes the obvious fact that bicycle rims are a special
case wherein annodizing does not have an appreciable effect on fatigue. As
you say, he is merely trolling. You should not feed him.

[Peter Cole]

agcou wrote:
> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>
>
>> the only willful ignorance being demonstrated here is from those trying
>> to make the facts fit preconception!!! yes, anodizing /can/ have a
>> serious affect on fatigue. BUT, if you or he had ever bothered to
>> observe the facts, cracking is entirely independent of anodizing crack
>> orientation. it is therefore NOT the cause in this case.
>>
>
> Another common misconception is that the substrate cracks cause anodization
> layer cracks. This is clearly wrong for the same reason. The cracks
> aren't oriented, therefore they are not related.

I don't think that's a common misconception. This is the first time I've
heard it.

> I think Peter realizes the obvious fact that bicycle rims are a special
> case wherein annodizing does not have an appreciable effect on fatigue.

How could that be?

[Michael Press]

In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
agcou <agcou@agcou.com> wrote:

> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>
>
> >
> > the only willful ignorance being demonstrated here is from those trying
> > to make the facts fit preconception!!! yes, anodizing /can/ have a
> > serious affect on fatigue. BUT, if you or he had ever bothered to
> > observe the facts, cracking is entirely independent of anodizing crack
> > orientation. it is therefore NOT the cause in this case.
> >
>
> Another common misconception is that the substrate cracks cause anodization
> layer cracks.

Not so as I have heard. The crack _initiation_ is as
when you stress the skin under a scab. The scab is
rigid, the underlying tissue is elastic, the scab
fractures providing a stress riser in the tissue
that propagates into perfused tissue, rupturing
capillaries resulting in visible bleeding.

> This is clearly wrong for the same reason. The cracks
> aren't oriented, therefore they are not related.
>
> I think Peter realizes the obvious fact that bicycle rims are a special
> case wherein annodizing does not have an appreciable effect on fatigue. As
> you say, he is merely trolling. You should not feed him.

You assert a special case but provide no description,
nor substantiation.

--
Michael Press

[jim beam]

agcou wrote:
> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>
>
>> the only willful ignorance being demonstrated here is from those trying
>> to make the facts fit preconception!!! yes, anodizing /can/ have a
>> serious affect on fatigue. BUT, if you or he had ever bothered to
>> observe the facts, cracking is entirely independent of anodizing crack
>> orientation. it is therefore NOT the cause in this case.
>>
>
> Another common misconception is that the substrate cracks cause anodization
> layer cracks. This is clearly wrong for the same reason. The cracks
> aren't oriented, therefore they are not related.

absolutely.


>
> I think Peter realizes the obvious fact that bicycle rims are a special
> case wherein annodizing does not have an appreciable effect on fatigue. As
> you say, he is merely trolling. You should not feed him.

maybe, but on consideration, given that jobst has poisoned the well with
significant misinformation, and that peter cole insists on trying to
perpetuate it, i take the view that the true facts need to be aired,
regardless.

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>> Peter Cole wrote:
>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>> and Menzemer 1996
>>> You can use the Amazon "Search inside" feature to see the graph on page
>>> 100:
>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>> The graph shows very large reductions in fatigue strength for 7075
>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>> shows drastic reductions in fatigue strength for uncleaned, anodized
>>> samples.
>>> From the above graph, thick (50 micrometer) anodizing, reduced the
>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>> micrometer) anodizing reduced it by a factor of 6.
>> I should point out that these sources agree with what Jobst has
>> explained all along: thick anodizing has a disastrous effect on fatigue
>> life, and even thin cosmetic anodizing can have significant
>> consequences. The mechanism, as described in these sources, agrees with
>> his causal explanation. This is science, there can be no controversy,
>> except via willful ignorance.
>
> It's only causal if you believe that there are no other factors
> affecting fatigue life. You could substitute anodizing for mirror
> polishing, and it's not going to improve fatigue life if your
> extrusion process left internal voids. Without direct observation of
> cracks appearing in the anodized layer and propagating into the metal,
> it's not causality. It's correlation, and not even real correlation,
> as nobody has actually bothered to pin down incidence rates.

The sources I cited are pretty unambiguous. It's causal.

[Michael Press]

In article
<d1c13a83-50d5-453d-8018-a2760be24ed5@24g2000hsh.googlegroups.com>,
unforgiven99@juno.com wrote:

> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> > Peter Cole wrote:
> > > "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> > > and Menzemer 1996
> >
> > > You can use the Amazon "Search inside" feature to see the graph on page
> > > 100:
> > >http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
> >
> > > The graph shows very large reductions in fatigue strength for 7075
> > > forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> > > shows drastic reductions in fatigue strength for uncleaned, anodized
> > > samples.
> >
> > > From the above graph, thick (50 micrometer) anodizing, reduced the
> > > fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> > > micrometer) anodizing reduced it by a factor of 6.
> >
> > I should point out that these sources agree with what Jobst has
> > explained all along: thick anodizing has a disastrous effect on fatigue
> > life, and even thin cosmetic anodizing can have significant
> > consequences. The mechanism, as described in these sources, agrees with
> > his causal explanation. This is science, there can be no controversy,
> > except via willful ignorance.
>
> It's only causal if you believe that there are no other factors
> affecting fatigue life. You could substitute anodizing for mirror
> polishing, and it's not going to improve fatigue life if your
> extrusion process left internal voids. Without direct observation of
> cracks appearing in the anodized layer and propagating into the metal,
> it's not causality. It's correlation, and not even real correlation,
> as nobody has actually bothered to pin down incidence rates.

The correlation is in the material Peter cited and quoted.
Anodized structural members are substantially more fatigue prone.

--
Michael Press

[unforgiven99@juno.com]

On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
> unforgive...@juno.com wrote:
> > On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> >> Peter Cole wrote:
> >>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> >>> and Menzemer 1996
> >>> You can use the Amazon "Search inside" feature to see the graph on page
> >>> 100:
> >>>http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
> >>> The graph shows very large reductions in fatigue strength for 7075
> >>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> >>> shows drastic reductions in fatigue strength for uncleaned, anodized
> >>> samples.
> >>> From the above graph, thick (50 micrometer) anodizing, reduced the
> >>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> >>> micrometer) anodizing reduced it by a factor of 6.
> >> I should point out that these sources agree with what Jobst has
> >> explained all along: thick anodizing has a disastrous effect on fatigue
> >> life, and even thin cosmetic anodizing can have significant
> >> consequences. The mechanism, as described in these sources, agrees with
> >> his causal explanation. This is science, there can be no controversy,
> >> except via willful ignorance.
>
> > It's only causal if you believe that there are no other factors
> > affecting fatigue life. You could substitute anodizing for mirror
> > polishing, and it's not going to improve fatigue life if your
> > extrusion process left internal voids. Without direct observation of
> > cracks appearing in the anodized layer and propagating into the metal,
> > it's not causality. It's correlation, and not even real correlation,
> > as nobody has actually bothered to pin down incidence rates.
>
> The sources I cited are pretty unambiguous. It's causal.

Yes, it's causal in the sources you cite. Cite a source that tests
extrusions instead of castings, and you'll have something relevant to
the discussion. CT some cracked rims to prove that they don't have
void defects which could initiate cracking along the line of
anisotropy, and you have reason to believe that anodizing breaks bike
rims. Until then you just have articles written by "experts" who can
build helicopters, but not use spell check.

[jim beam]

Peter Cole wrote:
> unforgiven99@juno.com wrote:
>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>>> Peter Cole wrote:
>>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>>> and Menzemer 1996
>>>> You can use the Amazon "Search inside" feature to see the graph on page
>>>> 100:
>>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>>> The graph shows very large reductions in fatigue strength for 7075
>>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>>> shows drastic reductions in fatigue strength for uncleaned, anodized
>>>> samples.
>>>> From the above graph, thick (50 micrometer) anodizing, reduced the
>>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>>> micrometer) anodizing reduced it by a factor of 6.
>>> I should point out that these sources agree with what Jobst has
>>> explained all along: thick anodizing has a disastrous effect on fatigue
>>> life, and even thin cosmetic anodizing can have significant
>>> consequences. The mechanism, as described in these sources, agrees with
>>> his causal explanation. This is science, there can be no controversy,
>>> except via willful ignorance.
>>
>> It's only causal if you believe that there are no other factors
>> affecting fatigue life. You could substitute anodizing for mirror
>> polishing, and it's not going to improve fatigue life if your
>> extrusion process left internal voids. Without direct observation of
>> cracks appearing in the anodized layer and propagating into the metal,
>> it's not causality. It's correlation, and not even real correlation,
>> as nobody has actually bothered to pin down incidence rates.
>
> The sources I cited are pretty unambiguous. It's causal.

your cite is completely out of context. those materials are not highly
anisotropic like a bike rim, and they have cracking perpendicular to
load, not axial like with bike rims.

bottom line, the principle of anodizing induced fatigue is correct, but
it's NOT OBSERVED to be the cause in our case - and extrusion flaws are.

[jim beam]

Peter Cole wrote:
> agcou wrote:
>> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>>
>>
>>> the only willful ignorance being demonstrated here is from those
>>> trying to make the facts fit preconception!!! yes, anodizing /can/
>>> have a serious affect on fatigue. BUT, if you or he had ever
>>> bothered to observe the facts, cracking is entirely independent of
>>> anodizing crack orientation. it is therefore NOT the cause in this
>>> case.
>>>
>>
>> Another common misconception is that the substrate cracks cause
>> anodization layer cracks. This is clearly wrong for the same reason.
>> The cracks aren't oriented, therefore they are not related.
>
> I don't think that's a common misconception. This is the first time I've
> heard it.

that's not true - i've discussed this principle here many times. and
argued it with you iirc.


>
>> I think Peter realizes the obvious fact that bicycle rims are a
>> special case wherein annodizing does not have an appreciable effect on
>> fatigue.
>
> How could that be?

orientation!!! if not positioned to resolve stress concentration, it,
er, doesn't resolve stress concentration and therefore doesn't cause
fatigue!!!

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:

>> The sources I cited are pretty unambiguous. It's causal.
>
> Yes, it's causal in the sources you cite. Cite a source that tests
> extrusions instead of castings, and you'll have something relevant to
> the discussion. CT some cracked rims to prove that they don't have
> void defects which could initiate cracking along the line of
> anisotropy, and you have reason to believe that anodizing breaks bike
> rims.

If your contention is that extruded aluminum parts contain typically
more void defects than castings, please cite some sources.

There are several reasons (besides anisotropy) that favor
circumferential cracking at spoke holes. The 2 most obvious are that the
rim is under substantial circumferential compression and that the
extrusion is usually thinnest at the center. For some rims, cross
section hoop forces from tire pressure also add a tension component
which favors circumferential crack/fatigue. Finally, hollow section
extrusions, like those of double wall rims, will have circumferential
weld zones, formed after the metal passes the mandrel.

The fact that other factors contribute to cracking/fatigue doesn't alter
the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
90% of its fatigue life in crack initiation mode, anodizing shortens
that phase. The effects of flaws are cumulative. It may be that rim
extrusions are so crappy that anodize treatments don't affect fatigue
life, but I doubt it, real world experience shows otherwise. Again, if
you have any source that shows otherwise please cite it.

[Tim McNamara]

In article
<b3ab6fe8-394b-43a6-bddc-f492e505b387@j22g2000hsf.googlegroups.com>,
unforgiven99@juno.com wrote:

> CT some cracked rims to prove that they don't have void defects which
> could initiate cracking along the line of anisotropy, and you have
> reason to believe that anodizing breaks bike rims.

We've had reason to believe this for years. Mavic did a controlled
experiment for us by producing the MA-2 and the MA-40, which were the
same rim except one was anodized. The anodized one had a reputation for
cracking around the spoke holes, and polished one didn't.

The other reasons to believe that anodizing increases the failure rate
of bicycle rims are the well-known effects of anodizing on aluminum.
This is not new, it's not rocket science, the metallurgy and mechanics
are well-known and have been for a long time. That a few delusional
apologists for Mavic et al can't bring themselves to accept known facts-
mainly because they have cast themselves in knee-jerk opposition to a
certain mechanical engineer with an interest in bicycle wheels- is not
anyone's problem but theirs.

[jim beam]

Michael Press wrote:
> In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
> agcou <agcou@agcou.com> wrote:
>
>> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>>
>>
>>> the only willful ignorance being demonstrated here is from those trying
>>> to make the facts fit preconception!!! yes, anodizing /can/ have a
>>> serious affect on fatigue. BUT, if you or he had ever bothered to
>>> observe the facts, cracking is entirely independent of anodizing crack
>>> orientation. it is therefore NOT the cause in this case.
>>>
>> Another common misconception is that the substrate cracks cause anodization
>> layer cracks.
>
> Not so as I have heard. The crack _initiation_ is as
> when you stress the skin under a scab. The scab is
> rigid, the underlying tissue is elastic, the scab
> fractures providing a stress riser in the tissue
> that propagates into perfused tissue, rupturing
> capillaries resulting in visible bleeding.
>
>> This is clearly wrong for the same reason. The cracks
>> aren't oriented, therefore they are not related.
>>
>> I think Peter realizes the obvious fact that bicycle rims are a special
>> case wherein annodizing does not have an appreciable effect on fatigue. As
>> you say, he is merely trolling. You should not feed him.
>
> You assert a special case but provide no description,
> nor substantiation.
>


word of the day is "orientation". a scab [sic] that cracks does so
perpendicular to applied stress. from then on, it's a stress
concentration thing. if it were cracked axial to the applied stress,
the wound would not open and thus no more damage would occur. and this
is exactly the case with cracked anodizing - if the cracks are not
oriented to resolve stress concentration, they're not going to initiate
fatigue. pretty basic.

[jim beam]

Michael Press wrote:
> In article
> <d1c13a83-50d5-453d-8018-a2760be24ed5@24g2000hsh.googlegroups.com>,
> unforgiven99@juno.com wrote:
>
>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>>> Peter Cole wrote:
>>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>>> and Menzemer 1996
>>>> You can use the Amazon "Search inside" feature to see the graph on page
>>>> 100:
>>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>>> The graph shows very large reductions in fatigue strength for 7075
>>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>>> shows drastic reductions in fatigue strength for uncleaned, anodized
>>>> samples.
>>>> From the above graph, thick (50 micrometer) anodizing, reduced the
>>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>>> micrometer) anodizing reduced it by a factor of 6.
>>> I should point out that these sources agree with what Jobst has
>>> explained all along: thick anodizing has a disastrous effect on fatigue
>>> life, and even thin cosmetic anodizing can have significant
>>> consequences. The mechanism, as described in these sources, agrees with
>>> his causal explanation. This is science, there can be no controversy,
>>> except via willful ignorance.
>> It's only causal if you believe that there are no other factors
>> affecting fatigue life. You could substitute anodizing for mirror
>> polishing, and it's not going to improve fatigue life if your
>> extrusion process left internal voids. Without direct observation of
>> cracks appearing in the anodized layer and propagating into the metal,
>> it's not causality. It's correlation, and not even real correlation,
>> as nobody has actually bothered to pin down incidence rates.
>
> The correlation is in the material Peter cited and quoted.
> Anodized structural members are substantially more fatigue prone.
>

"orientation". look up how it affects stress concentration.

[unforgiven99@juno.com]

On Apr 23, 7:35 pm, Michael Press <rub...@pacbell.net> wrote:
> In article
> <d1c13a83-50d5-453d-8018-a2760be24...@24g2000hsh.googlegroups.com>,
>
>
>
> unforgive...@juno.com wrote:
> > On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> > > Peter Cole wrote:
> > > > "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> > > > and Menzemer 1996
>
> > > > You can use the Amazon "Search inside" feature to see the graph on page
> > > > 100:
> > > >http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>
> > > > The graph shows very large reductions in fatigue strength for 7075
> > > > forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> > > > shows drastic reductions in fatigue strength for uncleaned, anodized
> > > > samples.
>
> > > > From the above graph, thick (50 micrometer) anodizing, reduced the
> > > > fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> > > > micrometer) anodizing reduced it by a factor of 6.
>
> > > I should point out that these sources agree with what Jobst has
> > > explained all along: thick anodizing has a disastrous effect on fatigue
> > > life, and even thin cosmetic anodizing can have significant
> > > consequences. The mechanism, as described in these sources, agrees with
> > > his causal explanation. This is science, there can be no controversy,
> > > except via willful ignorance.
>
> > It's only causal if you believe that there are no other factors
> > affecting fatigue life. You could substitute anodizing for mirror
> > polishing, and it's not going to improve fatigue life if your
> > extrusion process left internal voids. Without direct observation of
> > cracks appearing in the anodized layer and propagating into the metal,
> > it's not causality. It's correlation, and not even real correlation,
> > as nobody has actually bothered to pin down incidence rates.
>
> The correlation is in the material Peter cited and quoted.
> Anodized structural members are substantially more fatigue prone.
>
> --
> Michael Press

And apples are substantially redder than oranges. Again, it's only
causal if anodizing is the only factor affecting fatigue life. This
is not the case, as bicycle rims have high grain anisotropy and the
potential for extrusion induced flaws, which also make members more
fatigue prone. These factors are competing with the anodizing to
break your rim, and there's plenty of evidence that much of the time
they're winning.

[Tim McNamara]

In article <fuonpc$cc$1@registered.motzarella.org>,
Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> wrote:

> Peter Cole wrote:
> > Peter Cole wrote:
> >
> > I should point out that these sources agree with what Jobst has
> > explained all along: thick anodizing has a disastrous effect on
> > fatigue life, and even thin cosmetic anodizing can have significant
> > consequences. The mechanism, as described in these sources, agrees
> > with his causal explanation. This is science, there can be no
> > controversy, except via willful ignorance.

Other sources available on the Interwebs, which also conform what Jobst
has said on the topic, have been posted multiple times (for example from
www.anodizing.org) to no avail. The facts are unambiguous to everyone
with a reasonable ounce or two of wit.

> I disagree with the last sentence. Besides willful ignorance, the
> cause for controversy could be overindulgence in Kentucky Bourbon
> whiskey.

Or just plain pissiness.

[Michael Press]

In article <l66dnUkCrdaeY5LVnZ2dnUVZ_uGdnZ2d@speakeasy.net>,
jim beam <spamvortex@bad.example.net> wrote:

> Michael Press wrote:
> > In article
> > <d1c13a83-50d5-453d-8018-a2760be24ed5@24g2000hsh.googlegroups.com>,
> > unforgiven99@juno.com wrote:
> >
> >> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> >>> Peter Cole wrote:
> >>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> >>>> and Menzemer 1996
> >>>> You can use the Amazon "Search inside" feature to see the graph on page
> >>>> 100:
> >>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
> >>>> The graph shows very large reductions in fatigue strength for 7075
> >>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> >>>> shows drastic reductions in fatigue strength for uncleaned, anodized
> >>>> samples.
> >>>> From the above graph, thick (50 micrometer) anodizing, reduced the
> >>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> >>>> micrometer) anodizing reduced it by a factor of 6.
> >>> I should point out that these sources agree with what Jobst has
> >>> explained all along: thick anodizing has a disastrous effect on fatigue
> >>> life, and even thin cosmetic anodizing can have significant
> >>> consequences. The mechanism, as described in these sources, agrees with
> >>> his causal explanation. This is science, there can be no controversy,
> >>> except via willful ignorance.
> >> It's only causal if you believe that there are no other factors
> >> affecting fatigue life. You could substitute anodizing for mirror
> >> polishing, and it's not going to improve fatigue life if your
> >> extrusion process left internal voids. Without direct observation of
> >> cracks appearing in the anodized layer and propagating into the metal,
> >> it's not causality. It's correlation, and not even real correlation,
> >> as nobody has actually bothered to pin down incidence rates.
> >
> > The correlation is in the material Peter cited and quoted.
> > Anodized structural members are substantially more fatigue prone.
> >
>
> "orientation". look up how it affects stress concentration.

Orientation is irrelevant. When rigid material bonded to
elastic material is strained, and the rigid material is
taken beyond its elastic limit it fractures. The fracture
creates a stress riser that rips apart the elastic material
below. The elastic material is not free to elonagate
where the rigid material is intact, and so all of the
elastic material's elongation must occur where the bonded
rigid material fractures. Typically this is more strain
than the elastic material can sustain and it yields. This
is the nature of fatigue crack initiation in anodized Al
structural elements.

--
Michael Press

[Michael Press]

In article <l66dnUoCrdb2Y5LVnZ2dnUVZ_uGdnZ2d@speakeasy.net>,
jim beam <spamvortex@bad.example.net> wrote:

> Michael Press wrote:
> > In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
> > agcou <agcou@agcou.com> wrote:
> >
> >> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
> >>
> >>
> >>> the only willful ignorance being demonstrated here is from those trying
> >>> to make the facts fit preconception!!! yes, anodizing /can/ have a
> >>> serious affect on fatigue. BUT, if you or he had ever bothered to
> >>> observe the facts, cracking is entirely independent of anodizing crack
> >>> orientation. it is therefore NOT the cause in this case.
> >>>
> >> Another common misconception is that the substrate cracks cause anodization
> >> layer cracks.
> >
> > Not so as I have heard. The crack _initiation_ is as
> > when you stress the skin under a scab. The scab is
> > rigid, the underlying tissue is elastic, the scab
> > fractures providing a stress riser in the tissue
> > that propagates into perfused tissue, rupturing
> > capillaries resulting in visible bleeding.
> >
> >> This is clearly wrong for the same reason. The cracks
> >> aren't oriented, therefore they are not related.
> >>
> >> I think Peter realizes the obvious fact that bicycle rims are a special
> >> case wherein annodizing does not have an appreciable effect on fatigue. As
> >> you say, he is merely trolling. You should not feed him.
> >
> > You assert a special case but provide no description,
> > nor substantiation.
> >
>
>
> word of the day is "orientation". a scab [sic] that cracks does so
> perpendicular to applied stress. from then on, it's a stress
> concentration thing. if it were cracked axial to the applied stress,
> the wound would not open and thus no more damage would occur. and this
> is exactly the case with cracked anodizing - if the cracks are not
> oriented to resolve stress concentration, they're not going to initiate
> fatigue. pretty basic.

Orientation is irrelevant. When rigid material bonded to
elastic material is strained, and the rigid material is
taken beyond its elastic limit it fractures. The fracture
creates a stress riser that rips apart the elastic material
below. The elastic material is not free to elonagate
where the rigid material is intact, and so all of the
elastic material's elongation must occur where the bonded
rigid material fractures. Typically this is more strain
than the elastic material can sustain and it yields. This
is the nature of fatigue crack initiation in anodized Al
structural elements.

--
Michael Press

[jim beam]

Tim McNamara wrote:
> In article <fuonpc$cc$1@registered.motzarella.org>,
> Tom Sherman <sunsetss0003@REMOVETHISyahoo.com> wrote:
>
>> Peter Cole wrote:
>>> Peter Cole wrote:
>>>
>>> I should point out that these sources agree with what Jobst has
>>> explained all along: thick anodizing has a disastrous effect on
>>> fatigue life, and even thin cosmetic anodizing can have significant
>>> consequences. The mechanism, as described in these sources, agrees
>>> with his causal explanation. This is science, there can be no
>>> controversy, except via willful ignorance.
>
> Other sources available on the Interwebs, which also conform what Jobst
> has said on the topic, have been posted multiple times (for example from
> www.anodizing.org) to no avail. The facts are unambiguous to everyone
> with a reasonable ounce or two of wit.

seems timmy the retard can't be bothered to read the word of the day
either. "orientation" timmy. it's the key to many things. not least
of which is "anisotropy", a word used when discussing rim extrusions.


>
>> I disagree with the last sentence. Besides willful ignorance, the
>> cause for controversy could be overindulgence in Kentucky Bourbon
>> whiskey.
>
> Or just plain pissiness.

which isn't clinical retardation.

[_]

On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), unforgiven99@juno.com wrote:

> On Apr 23, 7:35 pm, Michael Press <rub...@pacbell.net> wrote:
>> In article
>> <d1c13a83-50d5-453d-8018-a2760be24...@24g2000hsh.googlegroups.com>,
>>
>>
>>
>> unforgive...@juno.com wrote:
>>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>>> > Peter Cole wrote:
>>> > > "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>> > > and Menzemer 1996
>>
>>> > > You can use the Amazon "Search inside" feature to see the graph on page
>>> > > 100:
>>> > >http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>
>>> > > The graph shows very large reductions in fatigue strength for 7075
>>> > > forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>> > > shows drastic reductions in fatigue strength for uncleaned, anodized
>>> > > samples.
>>
>>> > > From the above graph, thick (50 micrometer) anodizing, reduced the
>>> > > fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>> > > micrometer) anodizing reduced it by a factor of 6.
>>
>>> > I should point out that these sources agree with what Jobst has
>>> > explained all along: thick anodizing has a disastrous effect on fatigue
>>> > life, and even thin cosmetic anodizing can have significant
>>> > consequences. The mechanism, as described in these sources, agrees with
>>> > his causal explanation. This is science, there can be no controversy,
>>> > except via willful ignorance.
>>
>>> It's only causal if you believe that there are no other factors
>>> affecting fatigue life. You could substitute anodizing for mirror
>>> polishing, and it's not going to improve fatigue life if your
>>> extrusion process left internal voids. Without direct observation of
>>> cracks appearing in the anodized layer and propagating into the metal,
>>> it's not causality. It's correlation, and not even real correlation,
>>> as nobody has actually bothered to pin down incidence rates.
>>
>> The correlation is in the material Peter cited and quoted.
>> Anodized structural members are substantially more fatigue prone.
>>
>> --
>> Michael Press
>
> And apples are substantially redder than oranges. Again, it's only
> causal if anodizing is the only factor affecting fatigue life. This
> is not the case, as bicycle rims have high grain anisotropy and the
> potential for extrusion induced flaws, which also make members more
> fatigue prone. These factors are competing with the anodizing to
> break your rim, and there's plenty of evidence that much of the time
> they're winning.

No.

They don't compete - if they exist, they collude.

Anodizing is a bad idea, nomatter what "jim beam" says.

[Tom Sherman]

unforgiven99@juno.com wrote:
>
> And apples are substantially redder than oranges.[...]

Granny Smith?

--
Tom Sherman - Holstein-Friesland Bovinia
The weather is here, wish you were beautiful

[unforgiven99@juno.com]

On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
> unforgive...@juno.com wrote:
> > On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
> >> The sources I cited are pretty unambiguous. It's causal.
>
> > Yes, it's causal in the sources you cite. Cite a source that tests
> > extrusions instead of castings, and you'll have something relevant to
> > the discussion. CT some cracked rims to prove that they don't have
> > void defects which could initiate cracking along the line of
> > anisotropy, and you have reason to believe that anodizing breaks bike
> > rims.
>
> If your contention is that extruded aluminum parts contain typically
> more void defects than castings, please cite some sources.
>
> There are several reasons (besides anisotropy) that favor
> circumferential cracking at spoke holes. The 2 most obvious are that the
> rim is under substantial circumferential compression and that the
> extrusion is usually thinnest at the center. For some rims, cross
> section hoop forces from tire pressure also add a tension component
> which favors circumferential crack/fatigue. Finally, hollow section
> extrusions, like those of double wall rims, will have circumferential
> weld zones, formed after the metal passes the mandrel.
>
> The fact that other factors contribute to cracking/fatigue doesn't alter
> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
> 90% of its fatigue life in crack initiation mode, anodizing shortens
> that phase. The effects of flaws are cumulative. It may be that rim
> extrusions are so crappy that anodize treatments don't affect fatigue
> life, but I doubt it, real world experience shows otherwise. Again, if
> you have any source that shows otherwise please cite it.

I never said that anodize treatments don't affect fatigue life, just
that they aren't always the limiting factor. Even in the best of
extrusions, high anisotropy results in reduced fatigue life. If a
crack nucleates around an internal void or grain boundary, then it
does not matter if the part was anodized. It will fail before cracks
have a chance to nucleate in the surface layer.


Problems of fatigue crack growth in strongly anisotropic Al-alloys
Cerny, Ivo (SVUM a.s.); Ocenasek, Vladivoj; Hnilica, Frantisek Source:
Key Engineering Materials, v 251-252, 2003, p 61-72
ISSN: 1013-9826 CODEN: KEMAEY
Conference: Advances in Fracture and Damage Mechanics, Sep 2-4 2003,
Paderborn, Germany
Publisher: Trans Tech Publications Ltd

Abstract: An Al 4114 (8090 type) alloy, a material to be used in
aircraft structures, is manufactured by extrusion resulting in a
strongly oriented anisotropic microstructure. Fatigue crack growth
(FCG) data and mechanisms affecting the FCG process are an important
knowledge for an assessment of reliability and safety of structures
containing crack-like defects. As a basis, FCG characteristics in the
directions of extrusion and the perpendicular one are needed. The FCG
properties and mechanisms in the Al 4114 alloy were investigated using
CT specimens with side notches to prevent cracking in inappropriate
directions caused by the anisotropy. Unlike FCG in the direction
perpendicular to extrusion, when dependencies typical for Paris region
of stable growth were ascertained, FCG in the extrusion direction was
connected with regions of acceleration and retardation resulting in
significant scatter. Crack closure measurements and fractographical
analyses were performed to explain the irregularities and FCG
mechanisms.

Comparison of unextruded air slip direct chill cast 6061 ingot with
bar stock extruded from conventional direct chill cast 6061 ingot
Bergsma, S.C. (Northwest Aluminum Co); Kassner, M.E. Source: Journal
of Materials Engineering and Performance, v 6, n 4, Aug, 1997, p
469-472
ISSN: 1059-9495 CODEN: JMEPEG
Publisher: ASM International

Abstract: Air Slip direct chill cast 6061 small diameter ingots
(Direct Forge) were compared with 6061 extruded bar stock. The T6
mechanical properties were compared for both the Direct Forge ingot
and the extruded bar stock, as well as cold impact extruded cylinders
produced from Direct Forge small diameter ingot and extruded stock. It
was found that the tensile and fatigue properties of Direct Forge
ingot and cylinders from this ingot were significantly superior to
those of extruded stock and cylinder produced from this stock. The
improved properties are a result of higher solidification rates
leading to smaller alloy-constituent dispersed particles and, thus,
the production of smaller and more stable grain sizes. Direct Forge
has the additional advantages of (a) not requiring hot or cold work
prior to forming impacted extruded or forged parts, (b) being utilized
in the T6 temper without any prior deformation, (c) having isotropic
and consistent properties, (d) not requiring machining to remove
surface segregation or defects, and (e) having more consistent and
refined grain sizes.

[frkrygow@gmail.com]

On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
> unforgive...@juno.com wrote:
> > On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
> >> The sources I cited are pretty unambiguous. It's causal.
>
> > Yes, it's causal in the sources you cite. Cite a source that tests
> > extrusions instead of castings, and you'll have something relevant to
> > the discussion. CT some cracked rims to prove that they don't have
> > void defects which could initiate cracking along the line of
> > anisotropy, and you have reason to believe that anodizing breaks bike
> > rims.
>
> If your contention is that extruded aluminum parts contain typically
> more void defects than castings, please cite some sources.
>
> There are several reasons (besides anisotropy) that favor
> circumferential cracking at spoke holes. The 2 most obvious are that the
> rim is under substantial circumferential compression and that the
> extrusion is usually thinnest at the center. For some rims, cross
> section hoop forces from tire pressure also add a tension component
> which favors circumferential crack/fatigue. Finally, hollow section
> extrusions, like those of double wall rims, will have circumferential
> weld zones, formed after the metal passes the mandrel.

Regarding various stresses Peter mentions: Has anyone published a
detailed FEA representation of the stresses in the rim's material?
(Or, for that matter, results of experimental stress analysis, like
brittle coating?)

It would be interesting to see what stresses looked like a) between
spoke holes, b) at spoke holes, when 1) directly at the bottom of a
loaded wheel, and 2) rotated away from the bottom. Admittedly,
modeling it correctly wouldn't be trivial, but if successful, it could
tell us a lot.

>
> The fact that other factors contribute to cracking/fatigue doesn't alter
> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
> 90% of its fatigue life in crack initiation mode, anodizing shortens
> that phase. The effects of flaws are cumulative. It may be that rim
> extrusions are so crappy that anodize treatments don't affect fatigue
> life, but I doubt it, real world experience shows otherwise. Again, if
> you have any source that shows otherwise please cite it.

I'm sure that this must have been mentioned before, but: All the
influences Peter describes have always existed in bike rims, to one
degree or other. If rim cracks became much more frequent once
anodized rims became popular, that's strong indication (but not proof)
that the anodizing was a big factor. Not the only factor, but perhaps
the one that pushed things over the limit.

- Frank Krygowski

[jim beam]

Peter Cole wrote:
> unforgiven99@juno.com wrote:
>> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
>
>>> The sources I cited are pretty unambiguous. It's causal.
>>
>> Yes, it's causal in the sources you cite. Cite a source that tests
>> extrusions instead of castings, and you'll have something relevant to
>> the discussion. CT some cracked rims to prove that they don't have
>> void defects which could initiate cracking along the line of
>> anisotropy, and you have reason to believe that anodizing breaks bike
>> rims.
>
> If your contention is that extruded aluminum parts contain typically
> more void defects than castings, please cite some sources.
>
> There are several reasons (besides anisotropy) that favor
> circumferential cracking at spoke holes. The 2 most obvious are that the
> rim is under substantial circumferential compression and that the
> extrusion is usually thinnest at the center. For some rims, cross
> section hoop forces from tire pressure also add a tension component
> which favors circumferential crack/fatigue. Finally, hollow section
> extrusions, like those of double wall rims, will have circumferential
> weld zones, formed after the metal passes the mandrel.
>
> The fact that other factors contribute to cracking/fatigue doesn't alter
> the fact that anodizing weakens rims in fatigue.

no, that is absolutely not OBSERVED to be the case.



> Aluminum spends perhaps
> 90% of its fatigue life in crack initiation mode, anodizing shortens
> that phase. The effects of flaws are cumulative. It may be that rim
> extrusions are so crappy that anodize treatments don't affect fatigue
> life, but I doubt it,

"doubt"??? do some scientific observation then!!!


> real world experience shows otherwise.

no, real world experience shows the results of excessive spoke tension
and anisotropy.

> Again, if
> you have any source that shows otherwise please cite it.

just buy a magnifier and examine a cracked rim for yourself!!! if you
or jobst had ever bothered with this simple procedure, you wouldn't be
embarrassing yourself in public like you are right now.

[unforgiven99@juno.com]

On Apr 24, 10:51 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com>
wrote:
> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), unforgive...@juno.com wrote:
> > On Apr 23, 7:35 pm, Michael Press <rub...@pacbell.net> wrote:
> >> In article
> >> <d1c13a83-50d5-453d-8018-a2760be24...@24g2000hsh.googlegroups.com>,
>
> >> unforgive...@juno.com wrote:
> >>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
> >>> > Peter Cole wrote:
> >>> > > "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
> >>> > > and Menzemer 1996
>
> >>> > > You can use the Amazon "Search inside" feature to see the graph on page
> >>> > > 100:
> >>> > >http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>
> >>> > > The graph shows very large reductions in fatigue strength for 7075
> >>> > > forgings after cleaning with caustic (C22) or acid (C31) baths. It also
> >>> > > shows drastic reductions in fatigue strength for uncleaned, anodized
> >>> > > samples.
>
> >>> > > From the above graph, thick (50 micrometer) anodizing, reduced the
> >>> > > fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
> >>> > > micrometer) anodizing reduced it by a factor of 6.
>
> >>> > I should point out that these sources agree with what Jobst has
> >>> > explained all along: thick anodizing has a disastrous effect on fatigue
> >>> > life, and even thin cosmetic anodizing can have significant
> >>> > consequences. The mechanism, as described in these sources, agrees with
> >>> > his causal explanation. This is science, there can be no controversy,
> >>> > except via willful ignorance.
>
> >>> It's only causal if you believe that there are no other factors
> >>> affecting fatigue life. You could substitute anodizing for mirror
> >>> polishing, and it's not going to improve fatigue life if your
> >>> extrusion process left internal voids. Without direct observation of
> >>> cracks appearing in the anodized layer and propagating into the metal,
> >>> it's not causality. It's correlation, and not even real correlation,
> >>> as nobody has actually bothered to pin down incidence rates.
>
> >> The correlation is in the material Peter cited and quoted.
> >> Anodized structural members are substantially more fatigue prone.
>
> >> --
> >> Michael Press
>
> > And apples are substantially redder than oranges. Again, it's only
> > causal if anodizing is the only factor affecting fatigue life. This
> > is not the case, as bicycle rims have high grain anisotropy and the
> > potential for extrusion induced flaws, which also make members more
> > fatigue prone. These factors are competing with the anodizing to
> > break your rim, and there's plenty of evidence that much of the time
> > they're winning.
>
> No.
>
> They don't compete - if they exist, they collude.
>
> Anodizing is a bad idea, nomatter what "jim beam" says.

They exist, and collusion is unlikely. A crack may only originate
from one location. For collusion between internal and surface cracks,
they would need to form close enough together to intersect. In
reality, anodizing is not the only feature of a rim affecting its
fatigue life. It is only a bad idea under conditions in which
anodizing overrides other features as the limiting factor of fatigue
life, ie. thick, hard anodizing on a low delta extrusion.

[jim beam]

_ wrote:
> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), unforgiven99@juno.com wrote:
>
>> On Apr 23, 7:35 pm, Michael Press <rub...@pacbell.net> wrote:
>>> In article
>>> <d1c13a83-50d5-453d-8018-a2760be24...@24g2000hsh.googlegroups.com>,
>>>
>>>
>>>
>>> unforgive...@juno.com wrote:
>>>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>>>>> Peter Cole wrote:
>>>>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>>>>> and Menzemer 1996
>>>>>> You can use the Amazon "Search inside" feature to see the graph on page
>>>>>> 100:
>>>>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>>>>> The graph shows very large reductions in fatigue strength for 7075
>>>>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>>>>> shows drastic reductions in fatigue strength for uncleaned, anodized
>>>>>> samples.
>>>>>> From the above graph, thick (50 micrometer) anodizing, reduced the
>>>>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>>>>> micrometer) anodizing reduced it by a factor of 6.
>>>>> I should point out that these sources agree with what Jobst has
>>>>> explained all along: thick anodizing has a disastrous effect on fatigue
>>>>> life, and even thin cosmetic anodizing can have significant
>>>>> consequences. The mechanism, as described in these sources, agrees with
>>>>> his causal explanation. This is science, there can be no controversy,
>>>>> except via willful ignorance.
>>>> It's only causal if you believe that there are no other factors
>>>> affecting fatigue life. You could substitute anodizing for mirror
>>>> polishing, and it's not going to improve fatigue life if your
>>>> extrusion process left internal voids. Without direct observation of
>>>> cracks appearing in the anodized layer and propagating into the metal,
>>>> it's not causality. It's correlation, and not even real correlation,
>>>> as nobody has actually bothered to pin down incidence rates.
>>> The correlation is in the material Peter cited and quoted.
>>> Anodized structural members are substantially more fatigue prone.
>>>
>>> --
>>> Michael Press
>> And apples are substantially redder than oranges. Again, it's only
>> causal if anodizing is the only factor affecting fatigue life. This
>> is not the case, as bicycle rims have high grain anisotropy and the
>> potential for extrusion induced flaws, which also make members more
>> fatigue prone. These factors are competing with the anodizing to
>> break your rim, and there's plenty of evidence that much of the time
>> they're winning.
>
> No.
>
> They don't compete - if they exist, they collude.
>
> Anodizing is a bad idea, nomatter what "jim beam" says.

not if you ever ride outside of palo alto. other parts of the world
experience "rain" you see, and anodizing protects the material from all
kinds of nasty "corrosion" stuff.

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
>>>> The sources I cited are pretty unambiguous. It's causal.
>>> Yes, it's causal in the sources you cite. Cite a source that tests
>>> extrusions instead of castings, and you'll have something relevant to
>>> the discussion. CT some cracked rims to prove that they don't have
>>> void defects which could initiate cracking along the line of
>>> anisotropy, and you have reason to believe that anodizing breaks bike
>>> rims.
>> If your contention is that extruded aluminum parts contain typically
>> more void defects than castings, please cite some sources.
>>
>> There are several reasons (besides anisotropy) that favor
>> circumferential cracking at spoke holes. The 2 most obvious are that the
>> rim is under substantial circumferential compression and that the
>> extrusion is usually thinnest at the center. For some rims, cross
>> section hoop forces from tire pressure also add a tension component
>> which favors circumferential crack/fatigue. Finally, hollow section
>> extrusions, like those of double wall rims, will have circumferential
>> weld zones, formed after the metal passes the mandrel.
>>
>> The fact that other factors contribute to cracking/fatigue doesn't alter
>> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
>> 90% of its fatigue life in crack initiation mode, anodizing shortens
>> that phase. The effects of flaws are cumulative. It may be that rim
>> extrusions are so crappy that anodize treatments don't affect fatigue
>> life, but I doubt it, real world experience shows otherwise. Again, if
>> you have any source that shows otherwise please cite it.
>
> I never said that anodize treatments don't affect fatigue life, just
> that they aren't always the limiting factor. Even in the best of
> extrusions, high anisotropy results in reduced fatigue life. If a
> crack nucleates around an internal void or grain boundary, then it
> does not matter if the part was anodized. It will fail before cracks
> have a chance to nucleate in the surface layer.
>
>
> Problems of fatigue crack growth in strongly anisotropic Al-alloys
> Cerny, Ivo (SVUM a.s.); Ocenasek, Vladivoj; Hnilica, Frantisek Source:
> Key Engineering Materials, v 251-252, 2003, p 61-72
> ISSN: 1013-9826 CODEN: KEMAEY
> Conference: Advances in Fracture and Damage Mechanics, Sep 2-4 2003,
> Paderborn, Germany
> Publisher: Trans Tech Publications Ltd
>
> Abstract: An Al 4114 (8090 type) alloy, a material to be used in
> aircraft structures, is manufactured by extrusion resulting in a
> strongly oriented anisotropic microstructure. Fatigue crack growth
> (FCG) data and mechanisms affecting the FCG process are an important
> knowledge for an assessment of reliability and safety of structures
> containing crack-like defects. As a basis, FCG characteristics in the
> directions of extrusion and the perpendicular one are needed. The FCG
> properties and mechanisms in the Al 4114 alloy were investigated using
> CT specimens with side notches to prevent cracking in inappropriate
> directions caused by the anisotropy. Unlike FCG in the direction
> perpendicular to extrusion, when dependencies typical for Paris region
> of stable growth were ascertained, FCG in the extrusion direction was
> connected with regions of acceleration and retardation resulting in
> significant scatter. Crack closure measurements and fractographical
> analyses were performed to explain the irregularities and FCG
> mechanisms.

What's the point? All this says is that crack growth rate is uniform
perpendicular to the extrusion axis and erratic parallel.

>
> Comparison of unextruded air slip direct chill cast 6061 ingot with
> bar stock extruded from conventional direct chill cast 6061 ingot
> Bergsma, S.C. (Northwest Aluminum Co); Kassner, M.E. Source: Journal
> of Materials Engineering and Performance, v 6, n 4, Aug, 1997, p
> 469-472
> ISSN: 1059-9495 CODEN: JMEPEG
> Publisher: ASM International
>
> Abstract: Air Slip direct chill cast 6061 small diameter ingots
> (Direct Forge) were compared with 6061 extruded bar stock. The T6
> mechanical properties were compared for both the Direct Forge ingot
> and the extruded bar stock, as well as cold impact extruded cylinders
> produced from Direct Forge small diameter ingot and extruded stock. It
> was found that the tensile and fatigue properties of Direct Forge
> ingot and cylinders from this ingot were significantly superior to
> those of extruded stock and cylinder produced from this stock. The
> improved properties are a result of higher solidification rates
> leading to smaller alloy-constituent dispersed particles and, thus,
> the production of smaller and more stable grain sizes. Direct Forge
> has the additional advantages of (a) not requiring hot or cold work
> prior to forming impacted extruded or forged parts, (b) being utilized
> in the T6 temper without any prior deformation, (c) having isotropic
> and consistent properties, (d) not requiring machining to remove
> surface segregation or defects, and (e) having more consistent and
> refined grain sizes.

This is about a special billet casting process. It has nothing to do
with the subject under discussion. Please stop wasting our time with
irrelevant references.

[jim beam]

unforgiven99@juno.com wrote:
> On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
>>>> The sources I cited are pretty unambiguous. It's causal.
>>> Yes, it's causal in the sources you cite. Cite a source that tests
>>> extrusions instead of castings, and you'll have something relevant to
>>> the discussion. CT some cracked rims to prove that they don't have
>>> void defects which could initiate cracking along the line of
>>> anisotropy, and you have reason to believe that anodizing breaks bike
>>> rims.
>> If your contention is that extruded aluminum parts contain typically
>> more void defects than castings, please cite some sources.
>>
>> There are several reasons (besides anisotropy) that favor
>> circumferential cracking at spoke holes. The 2 most obvious are that the
>> rim is under substantial circumferential compression and that the
>> extrusion is usually thinnest at the center. For some rims, cross
>> section hoop forces from tire pressure also add a tension component
>> which favors circumferential crack/fatigue. Finally, hollow section
>> extrusions, like those of double wall rims, will have circumferential
>> weld zones, formed after the metal passes the mandrel.
>>
>> The fact that other factors contribute to cracking/fatigue doesn't alter
>> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
>> 90% of its fatigue life in crack initiation mode, anodizing shortens
>> that phase. The effects of flaws are cumulative. It may be that rim
>> extrusions are so crappy that anodize treatments don't affect fatigue
>> life, but I doubt it, real world experience shows otherwise. Again, if
>> you have any source that shows otherwise please cite it.
>
> I never said that anodize treatments don't affect fatigue life, just
> that they aren't always the limiting factor. Even in the best of
> extrusions, high anisotropy results in reduced fatigue life. If a
> crack nucleates around an internal void or grain boundary, then it
> does not matter if the part was anodized. It will fail before cracks
> have a chance to nucleate in the surface layer.
>
>
> Problems of fatigue crack growth in strongly anisotropic Al-alloys
> Cerny, Ivo (SVUM a.s.); Ocenasek, Vladivoj; Hnilica, Frantisek Source:
> Key Engineering Materials, v 251-252, 2003, p 61-72
> ISSN: 1013-9826 CODEN: KEMAEY
> Conference: Advances in Fracture and Damage Mechanics, Sep 2-4 2003,
> Paderborn, Germany
> Publisher: Trans Tech Publications Ltd
>
> Abstract: An Al 4114 (8090 type) alloy, a material to be used in
> aircraft structures, is manufactured by extrusion resulting in a
> strongly oriented anisotropic microstructure. Fatigue crack growth
> (FCG) data and mechanisms affecting the FCG process are an important
> knowledge for an assessment of reliability and safety of structures
> containing crack-like defects. As a basis, FCG characteristics in the
> directions of extrusion and the perpendicular one are needed. The FCG
> properties and mechanisms in the Al 4114 alloy were investigated using
> CT specimens with side notches to prevent cracking in inappropriate
> directions caused by the anisotropy. Unlike FCG in the direction
> perpendicular to extrusion, when dependencies typical for Paris region
> of stable growth were ascertained, FCG in the extrusion direction was
> connected with regions of acceleration and retardation resulting in
> significant scatter. Crack closure measurements and fractographical
> analyses were performed to explain the irregularities and FCG
> mechanisms.

good post.



>
> Comparison of unextruded air slip direct chill cast 6061 ingot with
> bar stock extruded from conventional direct chill cast 6061 ingot
> Bergsma, S.C. (Northwest Aluminum Co); Kassner, M.E. Source: Journal
> of Materials Engineering and Performance, v 6, n 4, Aug, 1997, p
> 469-472
> ISSN: 1059-9495 CODEN: JMEPEG
> Publisher: ASM International
>
> Abstract: Air Slip direct chill cast 6061 small diameter ingots
> (Direct Forge) were compared with 6061 extruded bar stock. The T6
> mechanical properties were compared for both the Direct Forge ingot
> and the extruded bar stock, as well as cold impact extruded cylinders
> produced from Direct Forge small diameter ingot and extruded stock. It
> was found that the tensile and fatigue properties of Direct Forge
> ingot and cylinders from this ingot were significantly superior to
> those of extruded stock and cylinder produced from this stock. The
> improved properties are a result of higher solidification rates
> leading to smaller alloy-constituent dispersed particles and, thus,
> the production of smaller and more stable grain sizes. Direct Forge
> has the additional advantages of (a) not requiring hot or cold work
> prior to forming impacted extruded or forged parts, (b) being utilized
> in the T6 temper without any prior deformation, (c) having isotropic
> and consistent properties, (d) not requiring machining to remove
> surface segregation or defects, and (e) having more consistent and
> refined grain sizes.

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 24, 10:51 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com>

>> They don't compete - if they exist, they collude.
>>
>> Anodizing is a bad idea, nomatter what "jim beam" says.
>
> They exist, and collusion is unlikely. A crack may only originate
> from one location. For collusion between internal and surface cracks,
> they would need to form close enough together to intersect. In
> reality, anodizing is not the only feature of a rim affecting its
> fatigue life. It is only a bad idea under conditions in which
> anodizing overrides other features as the limiting factor of fatigue
> life, ie. thick, hard anodizing on a low delta extrusion.

Whatsa "low delta" extrusion?

[jim beam]

unforgiven99@juno.com wrote:
> On Apr 24, 10:51 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com>
> wrote:
>> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), unforgive...@juno.com wrote:
>>> On Apr 23, 7:35 pm, Michael Press <rub...@pacbell.net> wrote:
>>>> In article
>>>> <d1c13a83-50d5-453d-8018-a2760be24...@24g2000hsh.googlegroups.com>,
>>>> unforgive...@juno.com wrote:
>>>>> On Apr 23, 8:12 am, Peter Cole <peter_c...@verizon.net> wrote:
>>>>>> Peter Cole wrote:
>>>>>>> "Fatigue Design of Aluminum Components & Structures", Sharp, Nordmark
>>>>>>> and Menzemer 1996
>>>>>>> You can use the Amazon "Search inside" feature to see the graph on page
>>>>>>> 100:
>>>>>>> http://www.amazon.com/gp/reader/0070569703/ref=sib_dp_pt#
>>>>>>> The graph shows very large reductions in fatigue strength for 7075
>>>>>>> forgings after cleaning with caustic (C22) or acid (C31) baths. It also
>>>>>>> shows drastic reductions in fatigue strength for uncleaned, anodized
>>>>>>> samples.
>>>>>>> From the above graph, thick (50 micrometer) anodizing, reduced the
>>>>>>> fatigue life by a factor of about 60 (@35ksi), while even thin (2.5
>>>>>>> micrometer) anodizing reduced it by a factor of 6.
>>>>>> I should point out that these sources agree with what Jobst has
>>>>>> explained all along: thick anodizing has a disastrous effect on fatigue
>>>>>> life, and even thin cosmetic anodizing can have significant
>>>>>> consequences. The mechanism, as described in these sources, agrees with
>>>>>> his causal explanation. This is science, there can be no controversy,
>>>>>> except via willful ignorance.
>>>>> It's only causal if you believe that there are no other factors
>>>>> affecting fatigue life. You could substitute anodizing for mirror
>>>>> polishing, and it's not going to improve fatigue life if your
>>>>> extrusion process left internal voids. Without direct observation of
>>>>> cracks appearing in the anodized layer and propagating into the metal,
>>>>> it's not causality. It's correlation, and not even real correlation,
>>>>> as nobody has actually bothered to pin down incidence rates.
>>>> The correlation is in the material Peter cited and quoted.
>>>> Anodized structural members are substantially more fatigue prone.
>>>> --
>>>> Michael Press
>>> And apples are substantially redder than oranges. Again, it's only
>>> causal if anodizing is the only factor affecting fatigue life. This
>>> is not the case, as bicycle rims have high grain anisotropy and the
>>> potential for extrusion induced flaws, which also make members more
>>> fatigue prone. These factors are competing with the anodizing to
>>> break your rim, and there's plenty of evidence that much of the time
>>> they're winning.
>> No.
>>
>> They don't compete - if they exist, they collude.
>>
>> Anodizing is a bad idea, nomatter what "jim beam" says.
>
> They exist, and collusion is unlikely. A crack may only originate
> from one location. For collusion between internal and surface cracks,
> they would need to form close enough together to intersect. In
> reality, anodizing is not the only feature of a rim affecting its
> fatigue life. It is only a bad idea under conditions in which
> anodizing overrides other features as the limiting factor of fatigue
> life, ie. thick, hard anodizing on a low delta extrusion.

indeed.

[jim beam]

frkrygow@gmail.com wrote:
> On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
>>>> The sources I cited are pretty unambiguous. It's causal.
>>> Yes, it's causal in the sources you cite. Cite a source that tests
>>> extrusions instead of castings, and you'll have something relevant to
>>> the discussion. CT some cracked rims to prove that they don't have
>>> void defects which could initiate cracking along the line of
>>> anisotropy, and you have reason to believe that anodizing breaks bike
>>> rims.
>> If your contention is that extruded aluminum parts contain typically
>> more void defects than castings, please cite some sources.
>>
>> There are several reasons (besides anisotropy) that favor
>> circumferential cracking at spoke holes. The 2 most obvious are that the
>> rim is under substantial circumferential compression and that the
>> extrusion is usually thinnest at the center. For some rims, cross
>> section hoop forces from tire pressure also add a tension component
>> which favors circumferential crack/fatigue. Finally, hollow section
>> extrusions, like those of double wall rims, will have circumferential
>> weld zones, formed after the metal passes the mandrel.
>
> Regarding various stresses Peter mentions: Has anyone published a
> detailed FEA representation of the stresses in the rim's material?

you do it professor. you have access to the methods and equipment.



> (Or, for that matter, results of experimental stress analysis, like
> brittle coating?)
>
> It would be interesting to see what stresses looked like a) between
> spoke holes, b) at spoke holes, when 1) directly at the bottom of a
> loaded wheel, and 2) rotated away from the bottom. Admittedly,
> modeling it correctly wouldn't be trivial, but if successful, it could
> tell us a lot.
>
>> The fact that other factors contribute to cracking/fatigue doesn't alter
>> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
>> 90% of its fatigue life in crack initiation mode, anodizing shortens
>> that phase. The effects of flaws are cumulative. It may be that rim
>> extrusions are so crappy that anodize treatments don't affect fatigue
>> life, but I doubt it, real world experience shows otherwise. Again, if
>> you have any source that shows otherwise please cite it.
>
> I'm sure that this must have been mentioned before, but: All the
> influences Peter describes have always existed in bike rims, to one
> degree or other. If rim cracks became much more frequent once
> anodized rims became popular, that's strong indication (but not proof)
> that the anodizing was a big factor. Not the only factor, but perhaps
> the one that pushed things over the limit.
>
> - Frank Krygowski

[jim beam]

Peter Cole wrote:
> unforgiven99@juno.com wrote:
>> On Apr 24, 10:42 am, Peter Cole <peter_c...@verizon.net> wrote:
>>> unforgive...@juno.com wrote:
>>>> On Apr 23, 4:06 pm, Peter Cole <peter_c...@verizon.net> wrote:
>>>>> The sources I cited are pretty unambiguous. It's causal.
>>>> Yes, it's causal in the sources you cite. Cite a source that tests
>>>> extrusions instead of castings, and you'll have something relevant to
>>>> the discussion. CT some cracked rims to prove that they don't have
>>>> void defects which could initiate cracking along the line of
>>>> anisotropy, and you have reason to believe that anodizing breaks bike
>>>> rims.
>>> If your contention is that extruded aluminum parts contain typically
>>> more void defects than castings, please cite some sources.
>>>
>>> There are several reasons (besides anisotropy) that favor
>>> circumferential cracking at spoke holes. The 2 most obvious are that the
>>> rim is under substantial circumferential compression and that the
>>> extrusion is usually thinnest at the center. For some rims, cross
>>> section hoop forces from tire pressure also add a tension component
>>> which favors circumferential crack/fatigue. Finally, hollow section
>>> extrusions, like those of double wall rims, will have circumferential
>>> weld zones, formed after the metal passes the mandrel.
>>>
>>> The fact that other factors contribute to cracking/fatigue doesn't alter
>>> the fact that anodizing weakens rims in fatigue. Aluminum spends perhaps
>>> 90% of its fatigue life in crack initiation mode, anodizing shortens
>>> that phase. The effects of flaws are cumulative. It may be that rim
>>> extrusions are so crappy that anodize treatments don't affect fatigue
>>> life, but I doubt it, real world experience shows otherwise. Again, if
>>> you have any source that shows otherwise please cite it.
>>
>> I never said that anodize treatments don't affect fatigue life, just
>> that they aren't always the limiting factor. Even in the best of
>> extrusions, high anisotropy results in reduced fatigue life. If a
>> crack nucleates around an internal void or grain boundary, then it
>> does not matter if the part was anodized. It will fail before cracks
>> have a chance to nucleate in the surface layer.
>>
>>
>> Problems of fatigue crack growth in strongly anisotropic Al-alloys
>> Cerny, Ivo (SVUM a.s.); Ocenasek, Vladivoj; Hnilica, Frantisek Source:
>> Key Engineering Materials, v 251-252, 2003, p 61-72
>> ISSN: 1013-9826 CODEN: KEMAEY
>> Conference: Advances in Fracture and Damage Mechanics, Sep 2-4 2003,
>> Paderborn, Germany
>> Publisher: Trans Tech Publications Ltd
>>
>> Abstract: An Al 4114 (8090 type) alloy, a material to be used in
>> aircraft structures, is manufactured by extrusion resulting in a
>> strongly oriented anisotropic microstructure. Fatigue crack growth
>> (FCG) data and mechanisms affecting the FCG process are an important
>> knowledge for an assessment of reliability and safety of structures
>> containing crack-like defects. As a basis, FCG characteristics in the
>> directions of extrusion and the perpendicular one are needed. The FCG
>> properties and mechanisms in the Al 4114 alloy were investigated using
>> CT specimens with side notches to prevent cracking in inappropriate
>> directions caused by the anisotropy. Unlike FCG in the direction
>> perpendicular to extrusion, when dependencies typical for Paris region
>> of stable growth were ascertained, FCG in the extrusion direction was
>> connected with regions of acceleration and retardation resulting in
>> significant scatter. Crack closure measurements and fractographical
>> analyses were performed to explain the irregularities and FCG
>> mechanisms.
>
> What's the point? All this says is that crack growth rate is uniform
> perpendicular to the extrusion axis and erratic parallel.

which is one of the reasons why orientation is relevant!



>
>>
>> Comparison of unextruded air slip direct chill cast 6061 ingot with
>> bar stock extruded from conventional direct chill cast 6061 ingot
>> Bergsma, S.C. (Northwest Aluminum Co); Kassner, M.E. Source: Journal
>> of Materials Engineering and Performance, v 6, n 4, Aug, 1997, p
>> 469-472
>> ISSN: 1059-9495 CODEN: JMEPEG
>> Publisher: ASM International
>>
>> Abstract: Air Slip direct chill cast 6061 small diameter ingots
>> (Direct Forge) were compared with 6061 extruded bar stock. The T6
>> mechanical properties were compared for both the Direct Forge ingot
>> and the extruded bar stock, as well as cold impact extruded cylinders
>> produced from Direct Forge small diameter ingot and extruded stock. It
>> was found that the tensile and fatigue properties of Direct Forge
>> ingot and cylinders from this ingot were significantly superior to
>> those of extruded stock and cylinder produced from this stock. The
>> improved properties are a result of higher solidification rates
>> leading to smaller alloy-constituent dispersed particles and, thus,
>> the production of smaller and more stable grain sizes. Direct Forge
>> has the additional advantages of (a) not requiring hot or cold work
>> prior to forming impacted extruded or forged parts, (b) being utilized
>> in the T6 temper without any prior deformation, (c) having isotropic
>> and consistent properties, (d) not requiring machining to remove
>> surface segregation or defects, and (e) having more consistent and
>> refined grain sizes.
>
> This is about a special billet casting process. It has nothing to do
> with the subject under discussion. Please stop wasting our time with
> irrelevant references.

[unforgiven99@juno.com]

On Apr 24, 12:43 pm, Peter Cole <peter_c...@verizon.net> wrote:
> unforgive...@juno.com wrote:
> > On Apr 24, 10:51 am, _ <jtayNOSPAM...@hfDONTSENDMESPAMx.andara.com>
> >> They don't compete - if they exist, they collude.
>
> >> Anodizing is a bad idea, nomatter what "jim beam" says.
>
> > They exist, and collusion is unlikely. A crack may only originate
> > from one location. For collusion between internal and surface cracks,
> > they would need to form close enough together to intersect. In
> > reality, anodizing is not the only feature of a rim affecting its
> > fatigue life. It is only a bad idea under conditions in which
> > anodizing overrides other features as the limiting factor of fatigue
> > life, ie. thick, hard anodizing on a low delta extrusion.
>
> Whatsa "low delta" extrusion?

Sorry, I was under the impression that I was talking to someone who
knows something about material processing. Delta is the ratio of
thickness to die contact area. It's the kind of thing that's going to
increase if you're trying to make a very light rim. As it increases,
so does the probability of internal void formation.

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 24, 12:43 pm, Peter Cole <peter_c...@verizon.net> wrote:

>> Whatsa "low delta" extrusion?
>
> Sorry, I was under the impression that I was talking to someone who
> knows something about material processing.

I'm flattered. Also embarrassed I didn't make the same assumption.


> Delta is the ratio of
> thickness to die contact area. It's the kind of thing that's going to
> increase if you're trying to make a very light rim. As it increases,
> so does the probability of internal void formation.

Don't you mean decrease? Funny, I've never heard the term and can't seem
to find any on-line references. Know any?

[unforgiven99@juno.com]

On Apr 24, 2:25 pm, Peter Cole <peter_c...@verizon.net> wrote:
> unforgive...@juno.com wrote:
> > On Apr 24, 12:43 pm, Peter Cole <peter_c...@verizon.net> wrote:
> >> Whatsa "low delta" extrusion?
>
> > Sorry, I was under the impression that I was talking to someone who
> > knows something about material processing.
>
> I'm flattered. Also embarrassed I didn't make the same assumption.
>
> > Delta is the ratio of
> > thickness to die contact area. It's the kind of thing that's going to
> > increase if you're trying to make a very light rim. As it increases,
> > so does the probability of internal void formation.
>
> Don't you mean decrease? Funny, I've never heard the term and can't seem
> to find any on-line references. Know any?

The term is pretty standard, and particularly well described in
Hosford and Caddell. Unfortunately, you're probably going to have to
track that down in good old analog format.

[Ben C]

On 2008-04-24, unforgiven99@juno.com <unforgiven99@juno.com> wrote:
> On Apr 24, 2:25 pm, Peter Cole <peter_c...@verizon.net> wrote:
>> unforgive...@juno.com wrote:
>> > On Apr 24, 12:43 pm, Peter Cole <peter_c...@verizon.net> wrote:
>> >> Whatsa "low delta" extrusion?
>>
>> > Sorry, I was under the impression that I was talking to someone who
>> > knows something about material processing.
>>
>> I'm flattered. Also embarrassed I didn't make the same assumption.
>>
>> > Delta is the ratio of
>> > thickness to die contact area. It's the kind of thing that's going to
>> > increase if you're trying to make a very light rim. As it increases,
>> > so does the probability of internal void formation.
>>
>> Don't you mean decrease? Funny, I've never heard the term and can't seem
>> to find any on-line references. Know any?
>
> The term is pretty standard, and particularly well described in
> Hosford and Caddell. Unfortunately, you're probably going to have to
> track that down in good old analog format.

While we're on the subject of extrusion and fatigue, I have read here
that Mavic make their rims out of a particular flavour of aluminium
(6106) that is not as strong as the stuff some other manufacturers use
but allows you to make prettier extrusions.

Their more pricey rims are made of something they call "Maxtal" but the
CXP 23 and others are made of 6106.

So, is 6106 better from the point of view of void formation and does it
mean that for a given delta you get a more fatigue resistant rim even if
it means sacrificing some yield strength?

[Peter Cole]

unforgiven99@juno.com wrote:
> On Apr 24, 2:25 pm, Peter Cole <peter_c...@verizon.net> wrote:
>> unforgive...@juno.com wrote:
>>> On Apr 24, 12:43 pm, Peter Cole <peter_c...@verizon.net> wrote:
>>>> Whatsa "low delta" extrusion?

>>> Delta is the ratio of
>>> thickness to die contact area. It's the kind of thing that's going to
>>> increase if you're trying to make a very light rim. As it increases,
>>> so does the probability of internal void formation.
>> Don't you mean decrease? Funny, I've never heard the term and can't seem
>> to find any on-line references. Know any?
>
> The term is pretty standard, and particularly well described in
> Hosford and Caddell. Unfortunately, you're probably going to have to
> track that down in good old analog format.

Hosford and Caddell use the term "delta parameter". I've seen no mention
of it in extrusion, but have seen it used to describe wire drawing dies.
The term was defined in that context as the ratio of the mean diameter
of the die to the (contact) depth of the die. I don't have the text of
Hosford and Caddell, but they seem to use it in the same context (wire
and rod drawing). Is this what you mean?

How do you use this term in the context of a hollow extrusion? What size
billet would be used for a rim extrusion? Would the billet be preformed?

[jim beam]

Michael Press wrote:
> In article <l66dnUoCrdb2Y5LVnZ2dnUVZ_uGdnZ2d@speakeasy.net>,
> jim beam <spamvortex@bad.example.net> wrote:
>
>> Michael Press wrote:
>>> In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
>>> agcou <agcou@agcou.com> wrote:
>>>
>>>> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>>>>
>>>>
>>>>> the only willful ignorance being demonstrated here is from those trying
>>>>> to make the facts fit preconception!!! yes, anodizing /can/ have a
>>>>> serious affect on fatigue. BUT, if you or he had ever bothered to
>>>>> observe the facts, cracking is entirely independent of anodizing crack
>>>>> orientation. it is therefore NOT the cause in this case.
>>>>>
>>>> Another common misconception is that the substrate cracks cause anodization
>>>> layer cracks.
>>> Not so as I have heard. The crack _initiation_ is as
>>> when you stress the skin under a scab. The scab is
>>> rigid, the underlying tissue is elastic, the scab
>>> fractures providing a stress riser in the tissue
>>> that propagates into perfused tissue, rupturing
>>> capillaries resulting in visible bleeding.
>>>
>>>> This is clearly wrong for the same reason. The cracks
>>>> aren't oriented, therefore they are not related.
>>>>
>>>> I think Peter realizes the obvious fact that bicycle rims are a special
>>>> case wherein annodizing does not have an appreciable effect on fatigue. As
>>>> you say, he is merely trolling. You should not feed him.
>>> You assert a special case but provide no description,
>>> nor substantiation.
>>>
>>
>> word of the day is "orientation". a scab [sic] that cracks does so
>> perpendicular to applied stress. from then on, it's a stress
>> concentration thing. if it were cracked axial to the applied stress,
>> the wound would not open and thus no more damage would occur. and this
>> is exactly the case with cracked anodizing - if the cracks are not
>> oriented to resolve stress concentration, they're not going to initiate
>> fatigue. pretty basic.
>
> Orientation is irrelevant.

wow.


<snip ignorant crap>


no michael, a crack has a root tip radius. as the radius decreases,
stress concentration increases. [you can look that up.] its simple
geometry to orientate a crack so the effective radius is infinite, and
thus have no stress concentration. ergo, orientation /is/ relevant.

[Jay Beattie]

On Apr 24, 4:45*pm, Tim McNamara <tim...@bitstream.net> wrote:
> In article
> <b3ab6fe8-394b-43a6-bddc-f492e505b...@j22g2000hsf.googlegroups.com>,
>
> *unforgive...@juno.com wrote:
> > CT some cracked rims to prove that they don't have void defects which
> > could initiate cracking along the line of anisotropy, and you have
> > reason to believe that anodizing breaks bike rims.
>
> We've had reason to believe this for years. *Mavic did a controlled
> experiment for us by producing the MA-2 and the MA-40, which were the
> same rim except one was anodized. *The anodized one had a reputation for
> cracking around the spoke holes, and polished one didn't.

And you had to pay an addititional $10 for a black G40/MA40!
Personally, I object to paying more for something I really don't need
and that has lame initials like "SUP" or "UB." I don't recall having
any problems in the '70s because my ModEs were not black and did not
have sidewalls with UB/SUP/BLT etc., etc.

I used the ModE, E2, MA2, MA40, G40 -- all basically the same rim (and
the GP4 tubular rim). The black ones did crack more around the spoke
holes. But I did get cracking in one polished silver MA2 rim --
shortly after one of these threads many years ago about how the silver
MA2s never crack (after Jobst hoarded about a thousand of them and
people were picking over NOS). I broke a Shimano crank shortly after
writing about how my Shimano cranks never break (unlike Campy NR).
This group is a jinx. -- Jay Beattie.

[jobst.brandt@stanfordalumni.org]

Jay Beattie wrote:

>>> CT some cracked rims to prove that they don't have void defects
>>> which could initiate cracking along the line of anisotropy, and
>>> you have reason to believe that anodizing breaks bike rims.

>> We've had reason to believe this for years. Â*Mavic did a controlled
>> experiment for us by producing the MA-2 and the MA-40, which were
>> the same rim except one was anodized. Â*The anodized one had a
>> reputation for cracking around the spoke holes, and polished one
>> didn't.

> And you had to pay an additional $10 for a black G40/MA40!
> Personally, I object to paying more for something I really don't
> need and that has lame initials like "SUP" or "UB." I don't recall
> having any problems in the '70s because my ModEs were not black and
> did not have sidewalls with UB/SUP/BLT etc., etc.

> I used the ModE, E2, MA2, MA40, G40 -- all basically the same rim
> (and the GP4 tubular rim). The black ones did crack more around the
> spoke holes. But I did get cracking in one polished silver MA2 rim
> -- shortly after one of these threads many years ago about how the
> silver MA2s never crack (after Jobst hoarded about a thousand of
> them and people were picking over NOS). I broke a Shimano crank
> shortly after writing about how my Shimano cranks never break
> (unlike Campy NR). This group is a jinx.

Not only did they crack around spoke holes but some rims separated
circumferentially so that the spokes were still attached in the bed of
the rim while the tire remained attached to a U-shaped hoop that
rattled while slightly interlocked with the inner part of the rim from
which it separated.

The term "hard anodized"was used freely to imply hardness, toughness,
and durability in excess of former non-anodized rims. The defense of
that ploy began in those days before a "former metallurgist"joined the
fray. I don't understand what defending bad engineering holds for
readers of wreck.bike. It could be that hey feel exposed by
explanations of how things work, thinking "I should have known that"
and along comes this ass and makes fun of me.

This was the tone when "the Bicycle Wheel" first appeared on book
shelves. Many wheel builders, including "Wheelsmith" roundly
denounced most of what was exposed in that book, although today most
of it is considered "boilerplate" (standard) engineering. Time wounds
all heels.

Jobst Brandt

[Michael Press]

In article <j6Wdnes-AtGfy4zVnZ2dnUVZ_qfinZ2d@speakeasy.net>,
jim beam <spamvortex@bad.example.net> wrote:

> Michael Press wrote:
> > In article <l66dnUoCrdb2Y5LVnZ2dnUVZ_uGdnZ2d@speakeasy.net>,
> > jim beam <spamvortex@bad.example.net> wrote:
> >
> >> Michael Press wrote:
> >>> In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
> >>> agcou <agcou@agcou.com> wrote:
> >>>
> >>>> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
> >>>>
> >>>>
> >>>>> the only willful ignorance being demonstrated here is from those trying
> >>>>> to make the facts fit preconception!!! yes, anodizing /can/ have a
> >>>>> serious affect on fatigue. BUT, if you or he had ever bothered to
> >>>>> observe the facts, cracking is entirely independent of anodizing crack
> >>>>> orientation. it is therefore NOT the cause in this case.
> >>>>>
> >>>> Another common misconception is that the substrate cracks cause anodization
> >>>> layer cracks.
> >>> Not so as I have heard. The crack _initiation_ is as
> >>> when you stress the skin under a scab. The scab is
> >>> rigid, the underlying tissue is elastic, the scab
> >>> fractures providing a stress riser in the tissue
> >>> that propagates into perfused tissue, rupturing
> >>> capillaries resulting in visible bleeding.
> >>>
> >>>> This is clearly wrong for the same reason. The cracks
> >>>> aren't oriented, therefore they are not related.
> >>>>
> >>>> I think Peter realizes the obvious fact that bicycle rims are a special
> >>>> case wherein annodizing does not have an appreciable effect on fatigue. As
> >>>> you say, he is merely trolling. You should not feed him.
> >>> You assert a special case but provide no description,
> >>> nor substantiation.
> >>>
> >>
> >> word of the day is "orientation". a scab [sic] that cracks does so
> >> perpendicular to applied stress. from then on, it's a stress
> >> concentration thing. if it were cracked axial to the applied stress,
> >> the wound would not open and thus no more damage would occur. and this
> >> is exactly the case with cracked anodizing - if the cracks are not
> >> oriented to resolve stress concentration, they're not going to initiate
> >> fatigue. pretty basic.
> >
> > Orientation is irrelevant.
>
> wow.
>
>
> <snip ignorant crap>
>
>
> no michael, a crack has a root tip radius. as the radius decreases,
> stress concentration increases. [you can look that up.] its simple
> geometry to orientate a crack so the effective radius is infinite, and
> thus have no stress concentration. ergo, orientation /is/ relevant.

When a brittle material bonded to an elastic material is
strained, and the brittle material is taken beyond its
elastic limit it fractures. The fracture creates a stress
riser that rips apart the elastic material below. The
elastic material is not free to elonagate where the brittle
material is intact, and so all of the elastic material's
elongation must occur where the bonded brittle material
fractures. Typically this is more strain than the elastic
material can sustain and it yields. This is the nature
of fatigue crack initiation in anodized Al structural
elements. The Al2O3 anodized layer is extremely brittle,
and cracks when the structural member flexes.

--
Michael Press

[jim beam]

Michael Press wrote:
> In article <j6Wdnes-AtGfy4zVnZ2dnUVZ_qfinZ2d@speakeasy.net>,
> jim beam <spamvortex@bad.example.net> wrote:
>
>> Michael Press wrote:
>>> In article <l66dnUoCrdb2Y5LVnZ2dnUVZ_uGdnZ2d@speakeasy.net>,
>>> jim beam <spamvortex@bad.example.net> wrote:
>>>
>>>> Michael Press wrote:
>>>>> In article <sa2iechv6thr$.1j5ck2xh78u7a$.dlg@40tude.net>,
>>>>> agcou <agcou@agcou.com> wrote:
>>>>>
>>>>>> On Wed, 23 Apr 2008 05:57:27 -0700, jim beam wrote:
>>>>>>
>>>>>>
>>>>>>> the