Glenn Posted April 12, 2008 Share Posted April 12, 2008 What exactly is metal fatigue? Is thee any way to tell if a piece of metal has been fatigued before you use it to make a project? Quote Link to comment Share on other sites More sharing options...
easilyconfused Posted April 12, 2008 Share Posted April 12, 2008 I've heard that if you coat the metal in white or similar coloured paint and wipe off the excess, you can see the micro fractures that develop with fatigue. Quote Link to comment Share on other sites More sharing options...
irnsrgn Posted April 12, 2008 Share Posted April 12, 2008 Continued flexing of a piece as in a shaft with 3 bearings on it and one of them being out of line. like bending a piece of wire till it seperates, gives crystalline look to the seperation, lots of people say it crystallized because of the appearance. Quote Link to comment Share on other sites More sharing options...
fat pete Posted April 12, 2008 Share Posted April 12, 2008 cant answer questions quickly ....words are blurry....addin and subtracting are tuff ...are all signs of mental fatigue Quote Link to comment Share on other sites More sharing options...
jayco Posted April 13, 2008 Share Posted April 13, 2008 One trick I've used (similar to what easilyconfused said), is to apply a thin colored liquid or even just water to the area of a suspected crack or fracture.......wipe the area as near dry as possible........and apply some 'clean' heat to the area(handheld propane torch, etc). If any of the liquid has found a crack, the applied heat will usually cause it to ooze back out of the crack. I've used that trick to find leaks in steel hydraulic lines and also radiators. Machine shops often have special lights and special chemical solutions to find cracks in engine blocks,etc. Quote Link to comment Share on other sites More sharing options...
habu68 Posted April 13, 2008 Share Posted April 13, 2008 Magnaflux From Wikipedia, the free encyclopedia This article does not cite any references or sources. (November 2007) Please help improve this article by adding citations to reliable sources. Unverifiable material may be challenged and removed. Magnafluxing, developed originally by Carl E. Betz, is a method of testing ferrous metals for surface and subsurface flaws. The component being tested must be made of a ferromagnetic material such as iron, nickel or cobalt, or some of their alloys. This test is often used on industrial tools, and engine parts during maintenance inspections. It can also be used to diagnose failure, as in crash investigations. It works by applying a magnetic field to the component under test, using e.g. a permanent magnet. This will cause a high concentration of magnetic flux at surface cracks, which can be made visible by dusting iron powder or a similar magnetic material over the component. Parts can be tested using one of two methods. The wet method consist of bathing the parts in a solution containing iron oxide particles. The wetted part is then placed in a magnetic field and inspected using a black light (ultraviolet light). The iron oxide particles are attracted to surface discontinuities or cracks, where the magnetic field is discontinuous. The particles flux around the imperfections and the patterns are visible under the black light. The dry method is based on the same principle. Parts are dusted with iron oxide particles and charged using a yoke. The particles are attracted to the discontinuities and are visible by black light.Magnaflux - Wikipedia, the free encyclopediaUpdates Quote Link to comment Share on other sites More sharing options...
easilyconfused Posted April 13, 2008 Share Posted April 13, 2008 Machine shops often have special lights and special chemical solutions to find cracks in engine blocks,etc. That got me thinking. According to my General Internal Medicine Class, a way to possibly, if crude and not 100% correct either way, determine if an animal has antifreeze poisoning is to use UV light on the urine. It has chemical's added to fluoresce so the mechanics can find a leak. Wonder if that would work, or if the chemicals would stick around on the whole piece after wiping away the excess. Quote Link to comment Share on other sites More sharing options...
B. Norris Posted April 13, 2008 Share Posted April 13, 2008 What exactly is metal fatigue? Is thee any way to tell if a piece of metal has been fatigued before you use it to make a project? Metal fatigue is the presence of small cracks that are not visible to the naked eye. They are the result of the metal being stressed in some way. I have had good luck with etching leaf springs heavily before I make anything from them. A good long etch will show up any cracks that are present because the acid gets in the crack and removes enough material that they become large enough to be visible. Quote Link to comment Share on other sites More sharing options...
Ten Hammers Posted April 13, 2008 Share Posted April 13, 2008 Aircraft struts and other parts are magnafluxed periodically to show cracks. I'm sure the MEK we used was not good on us. I'm sure if my bones were etched they would show some fatigue ( lol ). As noted the fatigue ( cracks ) is from some sort of stress applied. A black light on the right die shows cracks really nice. Quote Link to comment Share on other sites More sharing options...
irnsrgn Posted April 13, 2008 Share Posted April 13, 2008 there is also a 3 part spray liquid method available at most automotive stores, it consists of 3 spray cans, a cleaner, a dye penetrant and a developer. I used it quite often in the shop on wheel rims, looking for pin holes if they brought them in dismounted first. it was reasonable in cost, easy to use and efficient, just don't get the red dye on your hands, it has to wear off. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted April 14, 2008 Share Posted April 14, 2008 Metal fatigue is the build up of dislocations in the crystalline structure of the metal. It may not have resulted in cracking---yet. In this case heating above the dislocation climb temperature will make it go away. When you have a lot of dislocations in the structure the metal cannot deform and so starts cracking rather than deforming. Once it's started cracking you are better off with replacing it with known good metal. Forge welding *may* work to close up micro cracks; but may not if rust and gunk has built up in it. Quote Link to comment Share on other sites More sharing options...
eseemann Posted February 17, 2020 Share Posted February 17, 2020 Mr. Thomas, I am doing what "read this first" tells you to do, look at the older posts. This is just the information I needed. I have some old (very well used) steel from a field cultivator that I was thinking about using and wondering if forge welds would help and metal fatigue. Thanks for the info. Quote Link to comment Share on other sites More sharing options...
pnut Posted February 17, 2020 Share Posted February 17, 2020 Just about anything you can think of has been asked. It's just a matter of finding it. When I read without posting unlike now, I usually have a notebook to hand. I'm a note taker though. Always have been. Pnut Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 17, 2020 Share Posted February 17, 2020 A note taker and a heart breaker, pnut? I can come up with some interesting stories with that thought, thank you. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
pnut Posted February 17, 2020 Share Posted February 17, 2020 Don't forget money maker $$$$$ Pnut Quote Link to comment Share on other sites More sharing options...
Savage11 Posted February 18, 2020 Share Posted February 18, 2020 Metal fatigue in engineering is a series of scholarly books that will answer all your questions you may have and more. Its worth a look. Quote Link to comment Share on other sites More sharing options...
Irondragon Forge ClayWorks Posted February 18, 2020 Share Posted February 18, 2020 I found it as a free pdf download at EPDF. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 18, 2020 Share Posted February 18, 2020 6 hours ago, pnut said: Don't forget money maker $$$$$ Pnut Forge on pnut! A guy can get lost reading about metal fatigue, crystal boundaries and that takes you to mono-crystaline and amorphous casting. The field grows faster than a guy can read the headers. I barely skim the latest when something joggles my elbow. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 18, 2020 Share Posted February 18, 2020 There is some really cool stuff you can do with metal glasses. I have a pattern welded billet that was made by stacking alternating layers of steel and metal glass and clamping and heating. Quote Link to comment Share on other sites More sharing options...
anvil Posted February 18, 2020 Share Posted February 18, 2020 Metal glasses as in eye glass frames? Or is "metal glass" a new product just created in this incredible age of designer steels? Quote Link to comment Share on other sites More sharing options...
Neal the smith Posted February 18, 2020 Share Posted February 18, 2020 Metal glass is a (relatively) new product. Instead of having a regular crystalline structure it has a more random composition - like glass. It's also known as amorphous metal, but I'm sure Mr Powers will have more knowledge of their uses than I. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 18, 2020 Share Posted February 18, 2020 They are made by cooling a molten metal so fast that crystals cannot form---not an easy task. The method I was familiar with involved spinning a liquid helium cooled copper disk at high speeds and touching the surface of a molten alloy with it resulting in it shooting off a ribbon of metal glass. Some of the neat applications of it were based on the extremely high rates of atomic diffusion in it; for an example: solid phase welding of jet engine turbine blades at temps way below typical SPW ones. It's been 35 years since I was a friend of a metallurgist working in that area so I hope things have radically progressed since then. Quote Link to comment Share on other sites More sharing options...
Frosty Posted February 18, 2020 Share Posted February 18, 2020 Metal glass isn't necessarily steel, it's a state in crystallography of many metals. Many metals can have the same crystallography as optical glass or crystal. The earliest I recall is the lead glass used in atomic reactors from the late 40's and early 50's so reactor techs could actually look at the core. Dad had a couple pieces and they weighed a little less than an equal volume of lead. The didn't show a good conchoidal fracture plane either so making arrow heads was out of my plans. <sigh> I doubt the lead glass in Dad's collection ever saw a reactor, they had broken sides and zero readings on a geiger counter unlike his Autunite crystals, they made it scream. Yeah, Dad had a geiger counter AND the calibration kit for it. My question is how hot did you have to get the billet Thomas? Clean, stack, clamp, and heat as in Mokume Gane? Pics please, or we're going to have one HECK of a time believing such a billet exists. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
ThomasPowers Posted February 18, 2020 Share Posted February 18, 2020 Actually the billet was a gift from a friend whose father was a research metallurgist at Batelle in Columbus OH. My friend actually got a patent for making cutlery from such billets. Long past the protected date these days. I'll see if I can dig it up, it looks a lot like one of my BSB&PS billets only without the signs of having been in the forge. Quote Link to comment Share on other sites More sharing options...
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