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Anodizing effect on fatigue life of aluminum alloy
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/articl...01A0137211.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/0070...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. |
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#2
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Anodizing effect on fatigue life of aluminum alloy
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/articl...01A0137211.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/0070...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. |
#3
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Anodizing effect on fatigue life of aluminum alloy
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/0070...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. |
#4
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Anodizing effect on fatigue life of aluminum alloy
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/0070...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. |
#5
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Anodizing effect on fatigue life of aluminum alloy
On Apr 23, 8:12 am, 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/0070...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. |
#7
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Anodizing effect on fatigue life of aluminum alloy
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? |
#8
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Anodizing effect on fatigue life of aluminum alloy
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. |
#9
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Anodizing effect on fatigue life of aluminum alloy
On Apr 23, 4:06 pm, Peter Cole wrote:
wrote: On Apr 23, 8:12 am, 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/0070...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. |
#10
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Anodizing effect on fatigue life of aluminum alloy
In article ,
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. 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 |
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