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.
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…
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,…
In these days, a finite element model consists of several INCLUDE files either relative or absolute. When collaborating with other people, it is very difficult to remember sending the included files and also if we do remember, it is cumbersome if not difficult to find them and zip them as one file. I recently encountered…
In older versions of LS-DYNA (950 and lower) , when mass-scaling was active and over the course of the simulation when the percentage of added mass was greater than ENDMASS in *CONTROL_TERMINATION , LS-DYNA would terminate that job with no additional message. However, recent versions of LS-DYNA terminate the job AND provide a list of…
Here are the release notes. Features and enhancements included in 971 R3.2 that were not available in 971 R3.1 include the following:New Material Models:*MAT_255 ()Enhanced Material Models:support of user defined failure for:– *MAT_123 (VP=1)– *MAT_103– *MAT_024 (VP=1)*MAT_191 now supports end release for beams*MAT_187 updates*MAT_126 add corotational local coord. system for formulation-1Add V option for aopt=3,4–…
Running LS-DYNA jobs (either interactively or as a batch job) can be interrupted with sense-switch controls by creating files “d3kil”, “D3KIL” and “switch” in the running directory. This works as expected without the use of any “jobid” definition. However, when using a jobid parameter either using *KEYWORD_ID or in the command line (jobid=jobname), LS-DYNA expects…
It is well known that the presence of initial penetrations can spoil the accuracy of the analysis. A few days ago, while working on ODB barrier, some strange spikes in energies was suspicious even with IGNORE turned on. To understand this, I simply did a simple shakedown and generated some 100 d3plots to capture the…
Came across this nice article (PDF, 101kb) about inertia tensors.
The 10th bi-annual LS-DYNA Users Conference is less than a week away. You can visit the conference home page for more details. While you are there, look for information on d3VIEW in booth 101 hosted by FEA Information, Marsha Victory.
