*INTERFACE_SPRINGBACK provides an easy way to store a part’s state at the end of a simulation for later use. The part’s state consists of element history variables such as stress and strain tensor (in the form of *INITIAL_STRESS/*INITIAL_STRAIN) and also nodal values such as its final coordinates (*NODE). Optionally, when using the THICKNESS option, it…
In the area of distributed computing using Massively Parrallel Processing (MPP) LS-DYNA, finite element model decomposition is performed after initial processing of the input deck to “distribute” the model content to compute nodes. There are two primary goals for model decomposition. First goal is of of course to “break-down” the given problem into smaller pieces…
The ASCII file “RCFORC” contains the incremental forces contributed by contact algorithms. Due to the nature of the contact-impact interactions, the raw output tends to be very noisy and is of little value. To eliminate the inherent noise in the contact force output, LS-DYNA averages the force magnitude over the preceing output interval which results…
Starting in LS-DYNA v971, nodal accelerations can be filtered before being output to the ASCII file “NODOUT”. The type of filter can either be a built-in filter based on low-pass Butterworth frequency filter or can be user-defined. The filtering process is turned on by setting the IACCOP=2 in *CONTROL_OUTPUT keyword. The filtering process works by…
This 4 part article, orignally published in the FEAINFORMATION newsletter between August and December 2001, can be downloaded here: Contact Modeling.pdf
In the area of numerical simulations involving the use of airbags to absorb impact energy, passively or actively, accurate definitions of airbag leakage parameters play a crucial role in predicting the response of impacting objects (ex. occupants). LSDYNA provides various options for airbag leakage modeling that may appear overwhelming at first but are actually quite…
Among several simple yet powerful techniques available in LS-DYNA, switching of bodies that affects their deformability (at run time) is certainly one of them. Switching of bodies with negligible internal strains to a rigidbody at user’s specification can be useful to eliminate the calculation of element-centered variables such as stresses, which in many applications could…
Element count in finite element simulations are increasing faster than the “Moores law” used in chips. There are several reasons for this increase among which the single-model-multi-loadcase philosophy is certainly one of them. Earlier approach of building load-case-dependent models were both cumbersome, data duplication and big challenges for design change integrations. In today’s simulations, one-model…
The known advantage with implicit simulations is that the solution is unconditionally stable allowing larger values of timestep. In implicit static simulations (IMASS=0 in *CONTROL_IMPLICIT_DYNAMICS), the simulation time has no real significance but is rather an indication of the applied load magnitude. For example if we have a simulation where a load is applied linearly…
This post will give you a brief summary of one-way and two-way contact definitions. The one-way/two-way refers to the treatment of slave nodes impacting the master segments. One-Way Contacts One-way was one of the first implementations in contact treatment and was done so such that it is computationally efficient. In the one-way contact treatment, the…
