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mechengdude (Mechanical) (OP)
17 Jan 08 11:28
A couple of questions here with the aim of evaulting FEA stress results.

Problem: A 6063-T52 aluminum tube is subjected to a clamping force that results in localized Von-Mises stress in excess of yield.
Questions:
1. Can anyone provide data on the compressive strength of the above mentioned material?
2. Is there a relationship or rule of thumb relative to Ultimate or yield strength I can use?

Thank you
Helpful Member!  CoryPad (Materials)
17 Jan 08 14:50
Are you talking about uniform compression to the tube's cross section?  If so, then the compression strength is essentially equal to the tensile strength.  

If you are talking about localized force application (like from a fastener), then you need to consider the allowable surface pressure.  There is not a lot of published data on this.  A rule of thumb is the allowable surface pressure is approximately equal to the ultimate tensile strength.

Regards,

Cory

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mechengdude (Mechanical) (OP)
17 Jan 08 15:06
Thanks for your response.

I am refering to local stress developed on the exterior surface of the tube as a result of a fastener nearby. The clamping action produces a local area with stress as high as 46Ksi. The Ultimate tensile for the material is about 25Ksi. I beleieve there is potentail to permenantly deform and or crack the tube with the current design and I wanted to make sure I understand the problem before I go waving the white flag.

thanks
CoryPad (Materials)
17 Jan 08 15:10
You are correct, that will deform the part.  If you didn't do a non-linear analysis that accounts for the stress-strain curve of the material, then you can't say for certain what will happen after yielding.

Regards,

Cory

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arunmrao (Materials)
18 Jan 08 8:24
Corypad,
Please pardon and correct me if I am wrong. I faintly remember that ratio of compression strength to tensile strength is about 3:1 for some specific L/D ratio and considering friction effect at the ends during  compression testing.

Save water Drink Beer

CoryPad (Materials)
18 Jan 08 9:03
Arun,

You are right concerning plane strain indentation: initiation of yielding occurs when the surface pressure is 3 times the yield stress.  However, a bolted joint has a hole in it, so the allowable surface pressure is not the same as for plane strain indentation.

Regards,

Cory

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