Title page for ETD etd-11072008-063025


Type of Document Master's Thesis
Author Land, J. George
URN etd-11072008-063025
Title An axisymmetric finite element solution for elastic wave propagation through threaded connections
Degree Master of Science
Department Engineering Mechanics
Advisory Committee
Advisor Name Title
Batra, Romesh C. Committee Co-Chair
Kriz, Ronald D. Committee Co-Chair
Henneke, Edmund G. II Committee Member
Keywords
  • threads
  • wave propagation
  • finite element method
  • non-reflecting boundaries
  • rock drill
Date of Defense 1996-12-19
Availability restricted
Abstract

An axisymmetric finite element solution method is developed for axial wave propagation through a series of threaded connections in rock drills. A piston impacts axially on a string of rods held together by threaded joints and the wave propagates through these joints before reaching the bit. The energy lost in the joints limits the maximum effective depth of the drill. Several computational techniques are used to efficiently model the problem. Non-reflecting boundaries are used to numerically absorb the waves as they exit a joint. The stored waves are then re-initiated into the next joint eliminating modeling of the entire assembly of rods. The preload in the threads is modeled by shrinking the threaded sleeve onto the rods. A new dynamic relaxation damping scheme is used which starts with an undamped model and then increases the damping until the solution converges. This method converges more rapidly than the standard constant damping.

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