Title page for ETD etd-11072008-063025
|Type of Document
||Land, J. George
||An axisymmetric finite element solution for elastic wave propagation through threaded connections
||Master of Science
|Batra, Romesh C.
|Kriz, Ronald D.
|Henneke, Edmund G. II
- wave propagation
- finite element method
- non-reflecting boundaries
- rock drill
|Date of Defense
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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