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Nodal forces and Von-mises stress

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shiraz883

Automotive
Nov 15, 2006
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Hi,

I am trying to analyze welds in ansys by modeling the weld as couplings (in a shell model) and postprocessing the data in an excel file to calculate stresses in the weld

In the post processing, I select each node (from a set of coupling having 2 nodes, I select one node) and write out the Forces (Fx, Fy and Fz) on the node.

So I have a text file which has node numbers with location and forces Fx, Fy and Fz at the node.

Now using these forces at each node, I analyze what forces would cause shear in the weld and what force will cause tension/compression. The mesh is uniform at the couplings meaning that the element length is same throughout which means when I calculate the stress I use the force and divide it by length of element and throat of weld.

I find the shear stress (tau1 and tau2) - two directions causing shear of weld, and a normal stress (sigma) in the third direction.

Now to get the Von-mises stress, I use the formula sqrt [sigma^2+3*(tau1^2+tau2^2)] and compare with yield strength whereas I compare shear stress with the sy/sqrt(3) (0.57Sy).

Is the approach reasonable??

Shiraz
Sr. Engineer
 
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