Mechanical & Materials Engineering, Department of


Date of this Version

Summer 8-14-2009

Document Type



A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Mechanical Engineering. Under the supervision of Professor John D. Reid
Lincoln, Nebraska: August, 2009
Copyright (c) 2009 Ling Zhu


LS-Dyna simulations have been widely used in research and design to reduce fiscal and time costs. In order to improve the simulation’s efficiency, the components which experience negligible deformations are usually modeled as rigid bodies. However, the use of rigid bodies is always restricted. Though the use of more rigid bodies can save computing resources for a particular simulation, less rigid bodies are preferred for building a model in order to broaden its applications. Meanwhile, if a simulation task has multiple events, the application of rigid bodies in the particular simulation is always minimized so that it can satisfy all of the events. The restrictions of applying rigid bodies can be overcome if the components are able to switch back and forth between the rigid and deformable statuses. Currently, LS-Dyna provides several commands to switch the deformable components to rigid bodies and vice versa. However, the way of properly implementing deformable and rigid (D-R) switches has not been clarified. In order to avoid the potential issues during D-R switches and to extend the future application of D-R switches, investigations were performed herein. First, the features of each command were compared, and examples are provided to illustrate the implementations of the commands. Then, a series of simple-model investigations was performed to identify the key factors for the D-R switch. Results revealed that the D-R switch was influenced by the element choices, the inter-component connections, the boundary conditions, and the choice of the master body. Finally, based on the findings from the simple-model investigations, a procedure for applying D-R switch was developed. A couple of examples were then provided to demonstrate the benefits of using the D-R switch and to verify the proposed procedure.