Commenting LS-DYNA Keyword Blocks

A clever way to comment out blocks of keyword can be easily achieved using the *COMMENT keyword. Example: In the following example, the keyword *MAT_ELASTIC and all cards until the next keyword is commented out by simply adding a *COMMENT in front of it. *MAT_ELASTIC 1, 1.0e-9, 210.00, 0.3 *SOME_OTHER_KEYWORD …. …. to *COMMENT*MAT_ELASTIC 1,…

April 24, 2014 | by

Cohesive Element Timestep

Cohesive material models are well suited for representing the behavior of structural and non-structural adhesives that is now increasingly used. To accommodate extreme dimensions of the element such as zero volume or near-zero volume, the timestep of the Cohesive element is based on the characteristic stiffness and mass of the element instead of the characteristic…

March 11, 2014 | by

Parameter DIR in DEFINE_COORDINATE_SYSTEM

In earlier versions of LS-DYNA, the axis N1-N2 was always set as the local-x but in new versions (since LS-DYNA v971), the N1-N2 vector can be configured to be either X,Y,or Z. Image below shows the influence of DIR in the local system set up.

December 9, 2013 | by

Total Mass, Physical Mass and Added Mass

LS-DYNA reports three types of mass information for the model. The total mass and the physical mass is the same which is the mass of the model before any added mass is calculated. Added mass is the mass required to add to the nodes for all elements whose timestep is below abs(DT2MS). The effective mass…

May 2, 2013 | by

Air particles and relaxation when using Particle based airbag inflation

When using particle based airbag inflation method using *AIRBAG_PARTICLE, the initial air in the airbag can be modeled using control-volume approach or as particles. This is governed by the parameter IAIR. When IAIR=1, a uniform-pressure model is used to specify the initial atmospheric temperature inside the bag. When IAIR=2, one can specify the number of…

April 29, 2013 | by

MPP LS-DYNA Intermittent Profiling Information

During MPP LS-DYNA execution, often there is a need to know how each of the “threads” are doing in terms of overal CPU utilization. Until now, one has to wait till the job is fully finished so we can review the load-balance information from the main D3HSP file. From LS-DYNA 971 r7 onwards, there is…

September 26, 2012 | by

TSRFAC – Gradual introduction of strains in Airbags with Reference Geometry

In Airbags with reference geometry (*AIRBAG_REFERENCE_GEOMETRY), when the airbag bag element in folded state is smaller or larger than the reference state, stress needs to develop. LS-DYNA suppresses these initial strains so no stresses develop to avoid bag distortion and to improve stability. This may cause the bag to deploy but its final shape may…

June 19, 2012 | by