Archive for October, 2008

Tolerance used for Tying Slave Nodes in TIED contacts

Published by Suri Bala October 15th, 2008 in LS-DYNA Contact. 2 Comments

TIED contacts help “bond” two surfaces of different mesh densities. When using the default constraint method, the projection distance of the slave node onto to the closest master segment must be zero and this is achieved by LS-DYNA by updating the slave node coordinates such that it lies on the master surface. This coordinate update [...]

Packing LS-DYNA Input Files for Easy Distribution (v1.1a)

Published by Suri Bala October 15th, 2008 in LS-DYNA Bytes. 3 Comments

In a previous post about a simple Python script that scans a LS-DYNA input file to package all INCLUDED files recursively so the entire model can be compressed and sent to the recipient. Based on some new suggestions, largely by Brian Wainscott, I have attached a revised script that handles the included files a little [...]

Damage modeling using GURSON

Published by Suri Bala October 13th, 2008 in LS-DYNA Bytes. 2 Comments

Material parameter identification of GURSON material requires a process of fitting using an optimization package such as LS-OPT to match against a measured response such as a test. Following is a stress-strain curve that is achieved as a process of parameter identification using LS-OPT and LS-DYNA.

Characterizing plasticity material models using data from test

Published by Suri Bala October 9th, 2008 in LS-DYNA Bytes. 0 Comments

It is common to perform a uni-axial tensile test on a material sample to generate stress-strain curve for use in numerical models in LS-DYNA. The problem frequently encountered by analysts is the cleaning of the test data that is usually noisy. I recently wrote a small Python utility that takes any test generated force-deflection curve [...]

Optimizing monotonically increasing load curves

Published by Suri Bala October 9th, 2008 in LS-DYNA Bytes. 2 Comments

In cases where a monotonically increasing curve such as pressure_vs_leakage in *AIRBAG or effective_stress_vs_effective_strain in plasticity models in *MAT are to be parametrically identified by an optimization software such as LS-OPT to match against a physical test, it is important to ensure that the points identified by LS-OPT satisfy the non-negative slope. To satisfy this, [...]

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