Anodizing effect on fatigue life of aluminum alloy



P

Peter Cole

Guest
[email protected] wrote:
> On Apr 23, 4:06 pm, Peter Cole <[email protected]> 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.
 
?

_

Guest
On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), [email protected] wrote:

> On Apr 23, 7:35 pm, Michael Press <[email protected]> wrote:
>> In article
>> <[email protected]>,
>>
>>
>>
>> [email protected] wrote:
>>> On Apr 23, 8:12 am, Peter Cole <[email protected]> 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.
 
On Apr 24, 10:51 am, _ <[email protected]>
wrote:
> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), [email protected] wrote:
> > On Apr 23, 7:35 pm, Michael Press <[email protected]> wrote:
> >> In article
> >> <[email protected]>,

>
> >> [email protected] wrote:
> >>> On Apr 23, 8:12 am, Peter Cole <[email protected]> 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.
 
P

Peter Cole

Guest
[email protected] wrote:
> On Apr 24, 10:51 am, _ <[email protected]>


>> 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?
 
On Apr 24, 12:43 pm, Peter Cole <[email protected]> wrote:
> [email protected] wrote:
> > On Apr 24, 10:51 am, _ <[email protected]>
> >> 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.
 
P

Peter Cole

Guest
[email protected] wrote:
> On Apr 24, 12:43 pm, Peter Cole <[email protected]> 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?
 
M

Michael Press

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Michael Press wrote:
> > In article <[email protected]>,
> > agcou <[email protected]> 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
 
M

Michael Press

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Michael Press wrote:
> > In article
> > <[email protected]>,
> > [email protected] wrote:
> >
> >> On Apr 23, 8:12 am, Peter Cole <[email protected]> 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
 
T

Tim McNamara

Guest
In article
<[email protected]m>,
[email protected] 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.
 
J

Jay Beattie

Guest
On Apr 24, 4:45 pm, Tim McNamara <[email protected]> wrote:
> In article
> <[email protected]m>,
>
>  [email protected] 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.
 
J

jim beam

Guest
Peter Cole wrote:
> [email protected] wrote:
>> On Apr 23, 4:06 pm, Peter Cole <[email protected]> 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.
 
J

jim beam

Guest
[email protected] wrote:
> On Apr 24, 10:51 am, _ <[email protected]>
> wrote:
>> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), [email protected] wrote:
>>> On Apr 23, 7:35 pm, Michael Press <[email protected]> wrote:
>>>> In article
>>>> <[email protected]>,
>>>> [email protected] wrote:
>>>>> On Apr 23, 8:12 am, Peter Cole <[email protected]> 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.
 
J

jim beam

Guest
_ wrote:
> On Thu, 24 Apr 2008 05:59:30 -0700 (PDT), [email protected] wrote:
>
>> On Apr 23, 7:35 pm, Michael Press <[email protected]> wrote:
>>> In article
>>> <[email protected]>,
>>>
>>>
>>>
>>> [email protected] wrote:
>>>> On Apr 23, 8:12 am, Peter Cole <[email protected]> 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.
 
J

jim beam

Guest
Michael Press wrote:
> In article <[email protected]>,
> jim beam <[email protected]> wrote:
>
>> Michael Press wrote:
>>> In article <[email protected]>,
>>> agcou <[email protected]> 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 ****>


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.
 
M

Michael Press

Guest
In article <[email protected]>,
jim beam <[email protected]> wrote:

> Michael Press wrote:
> > In article <[email protected]>,
> > jim beam <[email protected]> wrote:
> >
> >> Michael Press wrote:
> >>> In article <[email protected]>,
> >>> agcou <[email protected]> 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 ****>
>
>
> 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
 
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.  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 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
 
T

Tom Sherman

Guest
[email protected] wrote:
>
> And apples are substantially redder than oranges.[...]


Granny Smith?

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

jim beam

Guest
[email protected] wrote:
> 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. 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 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.


jobst, let's get this straight. you have made a series of fundamental
errors, which while not apparent to the layperson, are just ridiculous
from anyone purporting to be an engineer. confusing a load calculation
with a strength calculation for example. and yet you are apparently
being /SO/ unable to grasp the fundamentals, not only do you defend
these mistakes, you do so with abusive derision!!! and on top of that,
you have the temerity to complain when someone dares stand up to you,
actually take the time explain your errors, and even pay you back in
your own coin??? jobst brandt, thy name is "ass" [and "hypocrite"].



>
> This was the tone when "the Bicycle Wheel" first appeared on book
> shelves.


with the famous words about spoke tension to be "as high as the rim can
bear". and thus, [inevitably], rims started cracking.


> Many wheel builders, including "Wheelsmith" roundly
> denounced most of what was exposed in that book,


translation: they pointed out your mistakes. a perfectly proper thing
to do.



> although today most
> of it is considered "boilerplate" (standard) engineering.


a dye penetrant test does not determine a cause of cracking. a spoke
tension gauge needs to account for spoke thickness. a load calculation
is not a strength calculation [increasing tension does not increase
strength]. fatigue cannot be eliminated from a material with no fatigue
endurance limit. stainless steel does not strain age - particularly
amazing since both stress/strain graphs are cited in your book, yet the
fundamental differences seem to be unnoticed. you have no clue about
anisotropy and the effect it has on mechanical properties. [etc.]

a "technical" book containing that many fundamental errors is far from
"standard" engineering.


> Time wounds
> all heels.


apparently it makes no difference to those who will not learn and/or
will not correct their mistakes.


the intent of your book has great merit jobst, but the execution is
abysmal. you undermined your cathedral yourself and you can't blame
others for it. if you had any brains, respect for your over-touted alma
mater or even some vestigial form of honor, you'd quit bleating like
you're the victim and actually /fix/ these mistakes. i'll help you if
you can't now do it yourself.
 
On Apr 25, 9:31 am, jim beam <[email protected]> wrote:
>
> jobst, let's get this straight. you have made a series of fundamental
> errors, which while not apparent to the layperson, are just ridiculous
> from anyone purporting to be an engineer.


And yet, the majority of engineers posting here tend to agree with
Jobst and disagree with jim beam - who, of course, is not an engineer,
and lacks the background to understand much of the discussions anyway.

> ... not only do you defend
> these mistakes, you do so with abusive derision!!!


:) This is so far beyond "the pot calling the kettle black" that
it's hilarious!


> a dye penetrant test does not determine a cause of cracking. a spoke
> tension gauge needs to account for spoke thickness....


Welds cannot be designed to resist tension? No bicycle parts are
cast? Profanity is essential in a technical discussion?

- Frank Krygowski
 
?

_

Guest
On Fri, 25 Apr 2008 08:46:58 -0700 (PDT), [email protected] wrote:

> On Apr 25, 9:31 am, jim beam <[email protected]> wrote:
>>
>> jobst, let's get this straight. you have made a series of fundamental
>> errors, which while not apparent to the layperson, are just ridiculous
>> from anyone purporting to be an engineer.

>
> And yet, the majority of engineers posting here tend to agree with
> Jobst and disagree with jim beam - who, of course, is not an engineer,
> and lacks the background to understand much of the discussions anyway.
>
>> ... not only do you defend
>> these mistakes, you do so with abusive derision!!!

>
> :) This is so far beyond "the pot calling the kettle black" that
> it's hilarious!
>
>
>> a dye penetrant test does not determine a cause of cracking. a spoke
>> tension gauge needs to account for spoke thickness....

>
> Welds cannot be designed to resist tension? No bicycle parts are
> cast? Profanity is essential in a technical discussion?
>


No brake bolts or QR spindles are made with cut threads?

Crank cotters are tightened with the nut?

Profanity is a complete refutation of facts? (ooops, you did that one
already...)