Mechanical Engineering ETDs

Jamey Bond

Publication Date

2-9-2010

Abstract

Dynamic simulations provide insight into the operation of complex mechanisms under dynamic loading conditions. These types of analyses are important to understand design margins and assure that a product meets its functional requirements during all operational environments. Rigid body dynamic modeling techniques can be utilized to simulate mechanisms that experience small loads relative to the strength of the piece parts with movement that primarily occurs as rigid body motion. The main advantage of a rigid body dynamic approach is that the number of unknowns that must be determined at each time step is dramatically less than the number of unknowns for a direct finite element approach. Rigid body dynamic codes can incorporate the capability to model flexible piece parts within a primarily rigid body model through the use of component mode synthesis (CMS) techniques. CMS is a method of coupling substructures to represent a large finite element problem as a collection of smaller ones. The number of degrees of freedom are reduced but the CMS method also provides design information and capabilities that are not available with a direct finite element approach. One significant limitation of the CMS implementation is that only linear or non-linear elastic responses can be modeled, requiring a different analysis technique for problems with geometric or material non-linearity. In this dissertation, a framework is developed to couple non-linear material behavior with a fixed interface CMS technique. This new approach allows non-linear material behavior, such as plastic deformation, to be approximated without requiring the transition to a direct finite element model. The plastic strain is determined from the modal response using classical plasticity theory and applied to the modal solution by projecting an effective nodal force vector on the modal coordinates to induce plastic deformation. The method can be tailored to the frequency range of interest to provide excellent correlation with a full-fidelity finite element solution. Numerical examples are provided to investigate the accuracy and convergence characteristics of the new method for specific problems.

Keywords

Dynamics, Rigid--Computer simulation, Live loads--Computer simulation, Plastic analysis (Engineering), Finite element method.

Degree Name

Mechanical Engineering

Level of Degree

Doctoral

Department Name

Mechanical Engineering

First Committee Member (Chair)

Leseman, Zayd

Second Committee Member

Tarefder, Rafiqul

Third Committee Member

Greenwood, William

Document Type

Dissertation

Language

English

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