Unloading in MAT_FABRIC (MAT_034)

This is a post by Guest Author Satish Pathy who works full time for LSTC In *MAT_FABRIC, element formulation 4 & 14 will allow you to input unloading curve for the material. Recently in a model it was noticed, that when a large compressive stress develops in the fibers, lsdyna would release some of these…

April 15, 2010 | by

Shell, Solid and Beam Formulations for Explicit and Implicit

Control cards are often handy to overwrite local values. A good example would be if we need all parts to use a certain element formulation THEORY which is specified in *CONTROL_SHELL. As with any global control cards that manipulate local values, the global values specified in *CONTROL keywords are used ONLY if the local values…

February 22, 2010 | by

Modeling rigid bodies

LS-DYNA allows the modeling of rigid-bodies by assigning any part with the MAT_RIGID material law (MAT_020). This is by far the most easiest method available when compared with all finite element codes. When using MAT_RIGID, there are three distinct ways to model a rigid part and they are briefly explaine below. 1. Finite Element based…

January 13, 2010 | by

Significance of IGAP Parameter in *CONTACT in Implicit Analyses

In traditional explicit analysis, there is no convergence criteria that is checked for each time step. However, in Implicit calculations, incremental displacements are evaluated such that a displacement norm and the energy norm are within a pre-defined tolerance before convergence is assumed to be obtained. This is the so-called iterative scheme in Implicit Non-Linear Analyses…

September 1, 2009 | by

Boundary prescribed motion and Contact

When nodes are involved in both contact (penalty) and prescribed motion, contact failure is expected to occur. This is because the boundary conditions are always processed after all the contacts are handled that results in nodal accelerations being updated to enforce the boundary conditions. I will soon publish some examples to illustrate this phenomenon.

August 9, 2009 | by

Mass calculations for Discrete Beams

Discrete beams, like discrete springs, require valid mass at the nodes to compute the timestep. Unlike continuum based elements, the length of the discrete beams, are not used in the timestep calculations. Hence realistic density in the discrete beam material model must be used. There are two methods this can be achived. Density (RHO) in…

May 13, 2009 | by