Finite element analysis of nonlinear wave propagation in a one-dimensional structure.

摘要

This thesis presents application-specific finite element analysis program, JIFEA (Jar Impact Finite Element Analysis), as an efficient and accurate tool for solving 1D wave propagation representative of Jarring in a drilling assembly.; Custom elements were created to model the pipe, Coulomb damping, viscous damping and axial contact. The response of each element was verified against analytical solutions and two commercial FEA programs, ANSYS and ADINA showing good agreement. Three time-integration methods were implemented in JIFEA, Central Difference, Newmark and Wilson and verified with ANSYS and ADINA but with JIFEA performing 30 times faster.; A sample drill string model was created to test the elements and solution strategy. Viscous and Coulomb damping rapidly decayed the wave response. Jar placement offers one of the few controls to alter the generated force magnitude.; JIFEA's speed and accuracy makes it a perfect tool for performing this type of analyses.