ANick
Mechanical
- Sep 24, 2011
- 11
Hello all,
I am interested in implementation of the co-called Segalman-Reese method for RMS von Mises stress calculation (see paper attached). This method employs modal behavior information allowing reduction of the computational cost. There are several commercial solvers like ANSYS, Altair HyperWorks Ostruct, Structural Analysis Toolkit which include this procedure. However, I would like to implement it by myself. As the eigenvalue solver I use Nastran.
My implementation and all relevant files you can find here: The example problem is 1x1x0.05m Alu plate. Plate mass: 130kg, excitation: constant 10g^2/Hz PSD in Z direction from 10 up to 2000 Hz, critical damping: 0.02. Structure Analysis toolkit for FEMAP reports 1sigma RMS=4661024 MPa for the element #1. My implementation gives 7935461 MPa.
I think the mistake might be in the wrong usage of the SF matrix (eq.9, attached paper) denoted for “input force cross spectral density matrix”. I assume that SF is the square matrix, where all elements except the ones on the diagonal corresponding to Z degree of freedom are zero. All other elements are equal PSD value multiplied with the plate mass (force calculation).
Could you please take a look and suggest the solution. I would greatly appreciate any help. If any details regarding the code or implementation in general are needed, I will be happy to respond.
Thanks.
I am interested in implementation of the co-called Segalman-Reese method for RMS von Mises stress calculation (see paper attached). This method employs modal behavior information allowing reduction of the computational cost. There are several commercial solvers like ANSYS, Altair HyperWorks Ostruct, Structural Analysis Toolkit which include this procedure. However, I would like to implement it by myself. As the eigenvalue solver I use Nastran.
My implementation and all relevant files you can find here: The example problem is 1x1x0.05m Alu plate. Plate mass: 130kg, excitation: constant 10g^2/Hz PSD in Z direction from 10 up to 2000 Hz, critical damping: 0.02. Structure Analysis toolkit for FEMAP reports 1sigma RMS=4661024 MPa for the element #1. My implementation gives 7935461 MPa.
I think the mistake might be in the wrong usage of the SF matrix (eq.9, attached paper) denoted for “input force cross spectral density matrix”. I assume that SF is the square matrix, where all elements except the ones on the diagonal corresponding to Z degree of freedom are zero. All other elements are equal PSD value multiplied with the plate mass (force calculation).
Could you please take a look and suggest the solution. I would greatly appreciate any help. If any details regarding the code or implementation in general are needed, I will be happy to respond.
Thanks.
