help! !! residual stress of the welded struct

[jamesli]

I have conducted coupled field analysis using ANSYS, to simulate 3D welding and to find its residual stresses. I have used physics option and calculate separately the thermal problem and structural problem.i import the temperatrues from the thermal analysis for structural analysis .I have calculated the residual stress , But I found the maxcimal residual stress are higher than the yield stress (about its 1.6 times) ,and von Mises stress exceed the yield stress too.i have defined the yield stress in different temperatrue and define the plastic behavior.
its residual stress may be exceed the yield stress a little,
but it is too large
why?would you tell me the reasons
thinks a lot

james

 

[tld23]

jamesli
I am not a regular Ansys user so I cannot advise you on the details of what you are doing, but check the following:
1) The direct stresses can exceed (by a very large amount in some cases) the yield stress because of constraint effects.
2) The mises stress can exceed the yield stress for the following reasons:
(a) you have work hardening of the material
(b) you have not used the correct yielding option or you have made somother mistake
(c) errors caused by extrapolation of the integration point values to the
nodes - unless you have a very course mesh I would not expect these to
be as large as you indicate.

See if your model is straying out side the range of material properties that you have defined and check the material property extrapolation that Ansys uses.

Otherwise we will need more details of your analyses.



TERRY

 

[tannerad]

How do your predicted results compare to any residual stress measurements that you have done or that are available in literature?

David.