Publications

Koteras, James R.

Abstract not provided.

International Journal for Numerical Methods in Engineering

Koteras, James R.; Lehoucq, R.B.

The goal of our paper is to demonstrate the cost-effective use of the Lanczos method for estimating the critical time step in an explicit, transient dynamics code. The Lanczos method can provide a significantly larger estimate for the critical time-step than an element-based method (the typical scheme). However, the Lanczos method represents a more expensive method for calculating a critical time-step than element-based methods. Our paper shows how the additional cost of the Lanczos method can be amortized over a number of time steps and lead to an overall decrease in run-time for an explicit, transient dynamics code. We present an adaptive hybrid scheme that synthesizes the Lanczos-based and element-based estimates and allows us to run near the critical time-step estimate provided by the Lanczos method. Copyright © 2006 John Wiley & Sons, Ltd.

Koteras, James R.

Presto is a Lagrangian, three-dimensional explicit, transient dynamics code for the analysis of solids subjected to large, suddenly applied loads. Presto is designed for problems with large deformations, nonlinear material behavior, and contact. There is a versatile element library incorporating both continuum and structural elements. The code is designed for a parallel computing environment. This document describes the input for the code that gives users access to all of the current functionality in the code. Presto is built in an environment that allows it to be coupled with other engineering analysis codes. The input structure for the code, which uses a concept called scope, reflects the fact that Presto can be used in a coupled environment. This guide describes the scope concept and the input from the outermost to the innermost input scopes. Within a given scope, the descriptions of input commands are grouped based on code functionality. For example, all material input command lines are described in a section of the user's guide for all of the material models in the code.

Koteras, James R.; Brown, Kevin H.; Koteras, James R.; Longcope, Donald B.; Warren, Thomas L.

Cavity expansion is a method for modeling the penetration of an axisymmetric or wedge-shaped solid body--a penetrator--into a target by using analytic expressions to capture the effects of the target on the body. Cavity expansion has been implemented as a third-party library (CavityExpansion) that can be used with explicit, transient dynamics codes. This document describes the mechanics of the cavity expansion model implemented as a third-party library. This document also describes the applications interface to CavityExpansion. A set of regression tests has been developed that can be used to test the implementation of CavityExpansion in a transient dynamics code. The mechanics of these tests and the expected results from the tests are described in detail.

Koteras, James R.; Koteras, James R.; Gullerud, Arne S.; Gullerud, Arne S.

Presto is a Lagrangian, three-dimensional explicit, transient dynamics code for the analysis of solids subjected to large, suddenly applied loads. Presto is designed for problems with large deformations, nonlinear material behavior, and contact. There is a versatile element library incorporating both continuum and structural elements. The code is designed for a parallel computing environment. This document describes the input for the code that gives users access to all of the current functionality in the code. Presto is built in an environment that allows it to be coupled with other engineering analysis codes. The input structure for the code, which uses a concept called scope, reflects the fact that Presto can be used in a coupled environment. This guide describes the scope concept and the input from the outermost to the innermost input scopes. Within a given scope, the descriptions of input commands are grouped based on code functionality. For example, all material input command lines are described in a section of the user's guide for all of the material models in the code.

Koteras, James R.; Koteras, James R.; Stone, Charles M.

Presto is a Lagrangian, three-dimensional explicit, transient dynamics code for the analysis of solids subjected to large, suddenly applied loads. Presto is designed for problems with large deformations, nonlinear material behavior, and contact.