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Principal Stresses calculation problem
3

Principal Stresses calculation problem

Principal Stresses calculation problem

(OP)
Dear All,
I have a structure for which i have carried out frequency response analysis using Hypermesh as pre-processor and NASTRAN as solver. I have the following queries:
1) In the .f06 output file, the principal stresses are not printed.
2) I have used hex-hedral meshing for the entire structure. After carrying out the meshing and frequency response analysis only Normal shear stress are printed. When i use the formula(see attachment) to calculate 3d principal stresses, at some points, i am unable to calculate the angle due to incorrect values(of the terms inside bracket of cos inverse-see attachment). Please tell me how can i resolve this issue? Moreover i have not given any damping value for the material during frequency response.

Please advise.

RE: Principal Stresses calculation problem

2
The f06 file will not have principal stress output for Sol 111. You can use a post-processor to get the principal stress with output files like *.xdb, *.op2 or *.DBALL/MASTER.

RE: Principal Stresses calculation problem

(OP)
Thank you very much your single line helped me out in getting out of the confusion i had for the last two weeks. I have extracted the principal stresses from the program.
But now the problem is that what does "negative" values of principal stresses signify? Can you help me out in understanding that?

RE: Principal Stresses calculation problem

compression

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