Principal stresses at surface nodes
Principal stresses at surface nodes
(OP)
Dear all, I am a new user of forum. In my job I use Nastran/Patran. I noticed that FEM analysis leads to incorrect values of the principal stresses at nodes of a surface. For example, suppose you have a meshed volume consists of HEXA elements (8 nodes). Well, Nastran calculates value of stress at the centroid and at the corners of the element. In Patran I want to see the values of the principal stresses at nodes, but on surface it gives me the output values of all 3 principal stresses (this is against the classical theory: on the surface of a solid there are only 2 values of principal stresses if on surface there are no forces). My question is: how do I calculate the exact values of principal stresses at a node on the surface? I use Nastran/Patran but the problem exists in any solver.
Thank you all ;)
Thank you all ;)





RE: Principal stresses at surface nodes
Brian
www.espcomposites.com
RE: Principal stresses at surface nodes
When it comes to FE modeling, nodal values (nodal forces, displacements) are always more accurate than derived values (strains, stresses). You're essentially solving a system of equations based on Hook's Law: -{f} = [k]{d}.
What's the amplitude of your phantom stress? If your model is, in fact, correct then it should be small when compared to your other principal stresses and should reduce when you refine your mesh or use higher ordered elements.
//signed//
Christopher K. Hubley
Mechanical Engineer
Sunpower Incorporated
Athens, Ohio
--
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RE: Principal stresses at surface nodes
TOP
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