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…
A simple ‘C’ program is included to extract the processor based timing information from D3HSP file and output load balance summary. Future versions of MPP-LS-DYNA may include more information such as the summary shown below. Usage: load_balance_checker d3hsp_file_name {threshold_factor} Download Source Preview /* Load Balance Diagnosis for MPP LS-DYNA Author: Suri Bala, Livermore Software Copyright:…
You may have read the previous post on deformable to rigid switching which works by turning a predefined set of deformable components into a rigidbody at a user-defined time to save on element processing costs. This may not necessarily be true when running using any of the MPP-LSDYNA executables since the domain decomposition routines do…
Analyses involving automotive seat designs for loadcases such as FMVSS 207/210 has shown some poor load balance on compute nodes when using the default decomposition in MPP LS-DYNA. In FMVSS 207/210 type simulations, the computationally expensive portion of the model lies at the seat and its immediate viscinity while the rest of the model involves…
In several loading situations, initial velocities are often defined along directions that do not coincide with the global coordinate system. In such cases it is very cumbersome to determine the directional components along global axes when the vector direction does not coincide the global system. In such instances, the easiest modeling approach would be to…
Curves are used widely to define a XY data that are used by several entities in LS-DYNA. They help us to define either a time-dependent function, used in loads and boundary conditions, and/or a strain/strain-rate dependent function used frequently in constitutive models. Three most salient features of curve representation, that occur internally in LS-DYNA and…
