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Getting started with LS-DYNA

LS-DYNA is used to solve multi-physics problems including solid mechanics, heat transfer, and fluid dynamics either as separate phenomena or as coupled physics, e.g., thermal stress or fluid structure interaction. This manual presents very simple examples to be used as templates (or recipes). This manual should be used side-by-side with the LS-DYNA Keyword User s Manual . The keyword input provides a flexible and logically organized database. Similar functions are grouped together under the same keyword. For example, under the keyword, *ELEMENT, are included solid, beam, and shell elements. The keywords can be entered in an arbitrary order in the input file. However, for clarity in this manual, we will conform to the following general block structure and enter the appropriate keywords in each block. 1. define solution control and output parameters 2. define model geometry and material parameters 3. define boundary conditions

Contact Modeling in LS-DYNA

Contact treatment forms an integral part of many large-deformation problems. Accurate modeling of contact interfaces between bodies is crucial to the prediction capability of the finite element simulations. LS-DYNA offers a large number of contact types. Some types are for specific applications, and others are suitable for more general use. Many of the older contact types are rarely used but are still retained to enable older models to run as they did in the past. Users are faced with numerous choices in modeling contact. This document is designed to provide an overview of contact treatment in LS-DYNA and to serve as a guide for choosing appropriate contact types and parameters.

Element Locking

Under some circumstances the displacements calculated by the finite element method are orders of magnitude smaller than they should be, and when this happens, the elements are said to be locking. The two most common types of locking are shear and pressure locking. Locking occurs in lower order elements because an elementes kinematics arenet rich enough to represent the correct solution. Shear locking occurs when elements are subjected to bending, and pressure locking occurs when the material is incompressible. Most of the research on reducing locking is devoted to elements with linear shape functions, with the remainder devoted to quadratic elements.

Computational plasticity

A material is said to have deformed plastically if it doesn't return to its original shape after the load is removed. The most common application for plasticity in nite element analysis is modeling the deformation of metals. While a great deal of research is available on the plasticity of metals at a very fundamental level, the majority of plasticity models are phenomenological and have no motivation beyond duplicating experimental data. The models discussed here are among the simpler plasticity models, and they are, indeed, completely phenomenological. While there are post hoc rationalizations of why these simple models perform as well as they do, they are still rationalizations.