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what caused this failure?

Discussion in 'The Hokey Ass Message Board' started by GreggAz, Apr 11, 2008.

  1. GreggAz
    Joined: Apr 3, 2001
    Posts: 929


    ok, these parts were in a rear suspension, the clevis is stainless, and the rod is "hardened" steel, according to the manufacturer. it was in a double shear situation and one of the shear points is at the failure. also the parts have been chromed.




    I am just looking to confirm my suspicions, and help to prevent others from having a similar failure.

  2. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    We need 38 Chevy the metallurgist here...I wanna see how he interprets this!
    In my fascinated ignorant look at this disaster, I see a clear utterly worthless interpretation is piece of crap steel surface hardened to glass...surface cracked, leaving the ring, then the rest just failed right on through.
    An issue...why RIGHT THERE on both??? Why not at end of threads?? Did something about the actual use or geometry stress them there somehow??? What did this stuff look like on the car?
  3. super plus
    Joined: Dec 14, 2006
    Posts: 566

    super plus

    The chroming made the parts brittle
  4. What were they used for? Does the OD of the bar get smaller where it broke?

    Steel and hardened steel will neck down before it fails, cast iron and other cast alloys will just break without necking. You should have someone do a Rockwell test to see what the hardness is.

    It looks like it could be embrittlement due to the chroming process. See the ring around the part, that is where the base material was penatrated by the solution.

    That also does NOT look like hardened steel. See how the material looks grainey, it looks more like a cast something or another.

  5. 34toddster
    Joined: Mar 28, 2006
    Posts: 1,482

    from Missouri

    The first thing I'd do is lose the Chrome plating, then look at the set-up, combination of factors those being first on my list! This is both sides or two different times same side?
  6. ray
    Joined: Jun 25, 2001
    Posts: 3,767

    from colorado

    hydrogen embrittlement. it happens when you chrome hardened steel, and it's only an issue with hardened steel. there is a process to bake the parts afterwards to help reduce the chances of it being a problem. too late in this case!
  7. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,426

    Von Rigg Fink
    from Garage

    Ditto on what ray said..Hydrogen Embrittlement. chrome shit loks nice but as far as suspension parts go or parts under alot of stress ..well as some Harley guys put dont get ya home.
  8. 65 impala
    Joined: Jan 12, 2007
    Posts: 1,086

    65 impala

    chrome wont get you home but it may get you laid lol
  9. DrJ
    Joined: Mar 3, 2001
    Posts: 9,418


    Still trying to figure out what the application is.
    Don't look like anything I remember seeing on a hotrod.
    IRS on a tuner/ricer, and that's why you didn't say?
    How could and why would that be used in a bending/sheer situation?
    A rod like that is usually only used in a tension/compression situation.
    Joined: Oct 6, 2007
    Posts: 700


  11. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,426

    Von Rigg Fink
    from Garage

    I doubt it..women dont pay attention to that shit..unless its your Member that is chromed:D:eek:
  12. Gregg, can you Email me some more details about this? maybe a picture of the rods in the car before they broke?

    Very crystiline break. But what is odd is the case hardening type ring of brighter material around the break line. Because it almost looks like a welded area where a bolt or something was attached to make the rod longer.
  13. KernCountyKid
    Joined: Jul 11, 2006
    Posts: 376

    from Arkansas


  14. Bruce Lancaster
    Joined: Oct 9, 2001
    Posts: 21,682

    Bruce Lancaster
    Member Emeritus

    From what 38 has said in the past, hydrogen embrittlement only happens to highly toughened steel...I suspect this is something more streetrod, like surface hardened rebar with cast clevises...lots of chrome stuff I suspect fails because custom biker/streetrodder parts are often cheap material, not real good steel improperly plated.
    HE was first noticed on Navy combat carrier planes when superduper landing gear pieces, plated to resist salt, started failing...
    I think a big part of this is why fail THERE on both?? What put the stress in the same place in both?? Maybe a geometry problem...or maybe just both were nicked by a vise in the same area at some stage of work.
  15. Von Rigg Fink
    Joined: Jun 11, 2007
    Posts: 13,426

    Von Rigg Fink
    from Garage

  16. magnet
    Joined: Jul 15, 2002
    Posts: 853


    it stretched.. elastic forces... where do they mount on the vehicle?
  17. 1950ChevySuburban
    Joined: Dec 20, 2006
    Posts: 6,188

    Member Emeritus
    from Tucson AZ

    I'm intrigued that they broke in the same place. Hecho en China?
  18. 1950ChevySuburban
    Joined: Dec 20, 2006
    Posts: 6,188

    Member Emeritus
    from Tucson AZ

    Seriously, is there any part that could have hit them while in use?
  19. This thread is useless without knowing the application.
  20. 19Fordy
    Joined: May 17, 2003
    Posts: 7,227


    Hydrogen embrittlement induced by crome plating process.
  21. Flatdog
    Joined: Jan 31, 2003
    Posts: 1,285

    Member Emeritus

    I know some people say chrome won,t affect some steels. BULLSHIT chrome on inportant parts is just asking for trouble.
  22. NoSurf
    Joined: Jul 26, 2002
    Posts: 4,169


    I just went through my book "Understanding How Components Fail" by Donald J. Wulpi- and it looks exactly like the brittle fracture example; origin area, brittle fracture ring, and ductile fracture area cream filling.
  23. It might be me misunderstanding, but I don't see how the rod was in shear stress at the failure point. And, similar to what Dr J said, these parts look to be tension/compression members, so they're not designed to take much in the way of side loads. The angle at the break suggests a tensile failure to some extent, but at less of an angle (~45*) which suggests a 'less ductile/more brittle' material. The base material looks very grainy, so it seems like the wrong material for tension. If the chroming process made it brittle, I think it only effected the penetrated area, therefore reducing the effective diameter of the rod.

    Ha ha- I'm taking stabs at it from what I can remember from 'learning' about this Shiite. What's the prize? And, "NO FAIR!" if Nosurf wins, he used a reference!

  24. narducci
    Joined: Jan 3, 2008
    Posts: 194


    They dont look like any part that SHOULD be used on a rear suspension!
  25. toddc
    Joined: Nov 25, 2007
    Posts: 981


    Totally. Embrittlement can affect ANY metal. Looks like poor component design to me. The grain structure isn't too bad for a "medium" hard steel. I don't think a rod that long ought to have shear loads placed upon it, at least not rear suspension type shear loads.
  26. noboD
    Joined: Jan 29, 2004
    Posts: 7,700


    I'm with Bruce on this one. Notice how the parts didn't bend or stretch before they failed? Looks like cheapassed material in the wrong application to me.
  27. HotRodChassis
    Joined: Jan 23, 2005
    Posts: 2,282

    Alliance Vendor

    In my humblest of humble opinions, I would say two additional things (meaning a combination of the three I will mention.)

    1. Under engineering. As with a lot of parts sold as "Street Rod" or "Hot Rod" parts, they are skimpy on the steel. I think they (the manufacturer) things that it's a street car, so they can skimp on the materials. When in fact it will be driven on the street, a monster power plant is usually hanging out the front. The small diameter of the links mixed with the Hydrogen embrittlement, caused part of the failure.

    2. Stress. If the clevis end of these links was metal to metal with the axle, that means that the only vibration isolation was the tires. Not a lot there. As all of us have seen on anything Henry Ford produced before Ford discovered rubber in the suspension components, the cars a laced with stress fractures. From suspension components to the frame to the body itself, most early cars suffered from it. One of the many reasons we try not to use metal to metal rear suspension components unless the car is intended for racing only, or it's just not going to be driven that much.
  28. publicenemy1925
    Joined: Feb 4, 2007
    Posts: 3,187

    from OKC, OK

    From my humble knowledge is that if you need shiny suspension parts you can nickel plate them, but you cannot chrome them. Case in point, Penske did this on his indy cars for years.
  29. I just looked at a front axle done with Electroless Nickel and then scotch-brited to dull it a bit. Looks fantastic.
  30. enjenjo
    Joined: Mar 2, 2001
    Posts: 2,539

    from swanton oh

    Nickel is as bad as chrome for embrittlement. It's the procees, not the metal that generates the hydrogen. The reason nickle was allowed on race cars at indy, and not chrome, chromed parts are difficult to magnaflux, as chrome masks the cracks.

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