LS-DYNA is a general-purpose simulation software. This is a good thing for analysts since it provides tremendous flexibility in simulating a wide range of events. The downside to this is the fact that every simulation requires ‘best practices’ to ensure it meets the quality and accuracy requirements of th event that is being simulated. Additionally, LS-DYNA is super backward-compatible. You can run legacy models that could be a couple of decades old using the latest release with no change to the input file. Backward compatibility however requires that default values that was found to work in the past may no longer be applicable today as better alternatives may be available. This post highlights some important non-default settings that must be present in all simulations.
- INN, Invariant node numbering
- OSU, Objective Stress Update (Complete model or for a subset of parts)
- ESORT, Full Sorting of Triangular Elements
- THEORY, use BWC as default element formulation
- BWC, Warping Stiffness
- PROJ, Full Projection
- NFAIL1 and NFAIL4, Remove and Proceed when Element Quality Deteriorates
- SSTHK, Actual Shell Thickness for SINGLE SURFACE contact
- RWPNAL, Treat rigid bodies impacting RIGIDWALL
- IGNORE, Ignore initial penetrations
- SPOTTHIN, Ignore interaction of segments used in spotwelds
- TYPE = -2 to include shells
- ESORT , Auto sorting of tetrahedrons, wedges to use improved element formulations
- NPOPT, Suppress nodal coordinate and element connectivity information
- NEECHO, Node and element printing
7. Strain-rate Effects
Viscoplasticity is now available to almost all material models that has strain-rate effects. Using VP=1 greatly reduces the noise in the simulations and also provides a more accurate stress as a function of strain-rate. It must be warned that VP=1 requires an accurate input such that the convergence for the shells (plane-stress treatment) is achieved.
8. Airbag Contact
Older versions of LS-DYNA allowed a time-dependent of thinning the airbag thickness to allow interpenetration to exist in folded bags. This is no longer necessary as the segment-to-segment contact (SOFT=2) takes care of this automatically with improved contact treatment.
This is an important file that must be reviewed for every run.
Use type 2 (Flanagan Belytscho Formulation).
HGEN =2 to account for hourglass energy balance.
The above list will be updated so do check back.