A 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.
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
LS-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.…
SPH is now widely used in several high strain-rate and large-deformation problems which may otherwise be difficult to simulate when using traditional mesh based approaches. LS-DYNA allows mesh-based and mesh-free techniques such as SPH to exist and interact in one simulation allowing users to take advantage of both procedures. The interaction or coupling between the…
Interface component analysis is a unique feature that helps to speed design variation studies for non-structural components using a model fragment of the full system model. It works by first storing the displacement time history of user-defined nodes to a disk on a file system. The stored file is a binary file and its name…
A powerful feature of LS-DYNA v970 and beyond that has yet to gain widespread popularity is the *CASE keyword. Here are two examples to highlight the use of *CASE. Sequential and Independent Simulations Ex: Head Impact (FMVSS 201) *keyword $ $ Impact 1 $ *case_begin_1 *title position 1 impact *include vehicle_model.i *include head_position_1.i *case_end_1 $…
Honeycomb cell structures are popular among weight conscious designers due to their high strength to weight ratio. In the automotive space, aluminum based honeycomb structures are widely used to represent barriers to simulate a controlled energy absorption. Honeycomb structures are highly anisotropic and requires adequate testing to characterize them. This post focusses on the characterization…
There are two different methods that are available in LS-DYNA to treat nodes impacting a rigidwall (also referred as stonewall). The first method, which is the default method, is the constraint type that is used for all deformable nodes impacting a rigidwall. The second optional method is the penalty approach that is used for ALL…
As LS-DYNA model sizes continue to grow, there is a greater need to reduce the file sizes or rather the model footprint. If good modeling practices are maintained, there can be tremendous file size reductions even for large models and this post will review some of the best practices aimed to reduce the model input/output…
Beginning LS-DYNA versions 971, a new option for SOFT=2 contact called DPRFAC in Optional Card ‘C’ in *CONTACT keyword allows transient removal of any initial penetrations. This option is useful to quickly zero out any initial penetrations rather than just to remember them. The following figure shows how the effective penetration that is used to…
