Mechanical Engineering Commons^™

Improvement Of Waterjet And Abrasive Waterjet Nozzle, Zheng Li

Dissertations

This investigation is concerned with the improvement of the nozzle design for water and abrasive water jet machining. The mechanism of formation and characteristics of pure water and abrasive water jets are investigated in order to determine quasi-optimal process conditions.

To improve the pure water jet machining, a pulsed water jet nozzle, which employs the principle of the Helmholtz type resonator, is investigated experimentally and numerically. The experiments show the advantages of this nozzle over the commercial nozzle in cutting and cleaning. A numerical solution of the differential equations of continuity, momentum conservation, turbulent kinetic energy and dissipation for two …

Machining Of Silicon Wafers With An Abrasive Water Jet Cutter, Frank J. Marciniak

Theses

This thesis consists of a study of the effects of abrasive water jet cutting on brittle silicon substrates. In total, 26 different cuts were made in a single crystal silicon substrate with an abrasive water jet cutter under different conditions of water flow, water pressure, and abrasive flow rate. These cuts were analyzed for surface roughness, and microstructure.

The roughness measurements were compared in order to determine the best possible cutting conditions. The cut with the best roughness of 0.000170 inches was obtained under cutting conditions of 30 KSI water pressure, 1 inch/minute cutting speed, and an abrasive flow rate …

Investigation Of The Striation Formation In The Course Of Abrasive Waterjet Cutting, Jo-Fei Chao

Dissertations

The principal defect of the surfaces generated by abrasive waterjet machining is excessive waviness (striation). The existing theories of striation formation are not adequate to explain this phenomenon. The presented study is concerned with the development of an understanding of the mechanism of striation formation.

A spectral analysis of temporal process and spatial surface characteristics demonstrated that the striation is caused by nozzle vibration that is due to the conditions of the motion control of the nozzle. This enabled us to discover a means for improving the surface finish. From a study of the surface spectra, it was found that …

Investigation Of Waterjet-Workpiece Interaction, Hung-Yuan Li

Dissertations

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 …

Size Reduction Of Polymeric Particulates By Jet Milling, Cheng Hua

Theses

A basic theory for the size reduction operation by jet milling has been developed.

Typical samples of feedstock have been analyzed using screen analysis to determine the initial distribution of polymeric particulate sizes prior to jet milling.

A statistical theory .was developed using probabilities to represent the likelihood that specific size reductions would occur. These probabilities include the effects of various equipment.

The theory was then used to predict the distribution of polymeric particulate sizes after jet milling. The agreement between the predictions and actual results was within 5 %.

Encouraged by the successful work of the simulation of the …