In an earlier post on simulation based product design we saw that in many cases a large portion of effort early on in the design cycle is usually spent on determining the best practices to simulate a physical event. We can speed up such simulations by the discrete variable support in LS-OPT version [...]
Archive for April, 2007
Speeding up numerical studies using Discrete Optimization in LS-OPT
Published by April 30th, 2007 in LS-DYNA Bytes. 0 CommentsSinusoidal Motion using *DEFINE_CURVE_FUNCTION
Published by April 25th, 2007 in LS-DYNA Bytes. 0 CommentsHere is a simple way to prescribe sinusoidal motion using *DEFINE_CURVE_FUNCTION.
*PARAMETER
ramp, 10.0
rfreq, 600
rshift, 0.0
*DEFINE_CURVE_FUNCTION
curve_id
&*sin(&freq*TIME+&shift)
The parameter “amp” is the amplitude, “freq” is the frequency of the oscillation (2PI/T, T is the time period), and “shift” is the phase shift. TIME is the simulation time that will be replaced with the current simulation time by LS-DYNA. The [...]
There are three different ways to model unloading behavior when using material model MAT_083. They are graphically depicted below (these figures may appear in the next release of the LS-DYNA keyword and theory manual).
Option 1 - Default (Click image to enlarge)
In the default option (1), HU=0, and the table is positive which then refers to [...]
Time Integration, Characteristic Length, and Mass Scaling
Published by April 17th, 2007 in LS-DYNA Bytes. 8 CommentsA short presentation on the Explicit and Implicit time integration schemes which I use in my advanced LS-DYNA class is included here. Its a evolving document but the latest version is available for download.
Time Integration (PDF, 346 Kb)
Note: Fixed the corrupted PDF file. Sorry for the inconvenience.
Stress Relaxation in Viscoelastic Material Models
Published by April 16th, 2007 in LS-DYNA Bytes and LS-DYNA Materials. 1 CommentLS-DYNA allows several ways to model of stress relaxation often seen in viscoelastic materials when subjected to a sudden constant strain. The methods to model the stress relaxation is briefly discussed here.
1. Curve Input
When using MAT_GENERAL_VISCOELASTIC material model, one can directly input the time log dependence of the relaxation modulus using LCID parameter. The [...]
A modified version of the NHTSA finite element model of the USSID is now available at no charge. LSTC USSID version 1.0 (LSTC FTP site)
LSTC USSID
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