Date of Award

Spring 1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Mechanical Engineering - (Ph.D.)

Department

Mechanical and Industrial Engineering

First Advisor

E. S. Geskin

Second Advisor

R. S. Sodhi

Third Advisor

Avraham Harnoy

Fourth Advisor

Nouri Levy

Fifth Advisor

Eugene I. Gordon

Abstract

The objective of this research is to develop new knowledge related to the fundamental physical phenomena of waterjet machining of ductile materials, and to use this knowledge to construct a numerical analysis model. The resulting knowledge will enable enhancement of waterjet cutting efficiency.

Experimental study of fundamental mechanisms and the acquisition of the data detailing micro and macro scale phenomena which occur during the machining process is carried out. It is shown that the material damage mechanism associated with waterjet machining is erosion cavitation which initiates ultrasonic stress wave propagation in the workpiece. Fatigue, an important element in producing material erosion, is enhanced by this high frequency stress and reduces the material endurance limit. Experimental results validate the existence of these stress waves. The frequency is 3 MHz in the case studies.

The acquired information is used to construct a detailed description of the phenomena using finite element numerical modeling and continuum damage mechanics. Numerical results are in good agreement with the experimental results.

The resulting models may be used to optimize the jet generation and jet workpiece interaction with particular focus on the improvement of nozzle design, integration of kinetic, chemical, and thermal energies for material shaping, and use of high speed percussive jets. With these new technologies and techniques, enhancement of material machining will be feasible.

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