Laser Generated Stress Waves: Their Characteristics and their Effects to Materials

Reproduced with permission from B. P. Fairand and A. H. Clauer, “Laser Generated Stress Waves: Their Characteristics and Their Effects to Materials,” Conference Proceedings #50: Laser-Solid Interactions and Laser Processing – 1978, S. D. Ferris, N. J. Leamy and J. M. Poate (eds.) 27-42. Copyright 1979, American Institute of Physics.
Authored by B. P. Fairand and A. H. Clauer.
INTRODUCTION
The potential of using pulsed lasers to generate high intensity stress waves in materials was first recognized and explored by the early nineteen sixties.1,2 Later work established that a major enhancement in the amplitude of the laser generated stress waves occurred if the absorbent surface was covered with a material transparent to the incident laser light.3-8 Stress waves generated under these conditions were found to be sufficiently intense to plastically deform metals and alloys even when the experiments were conducted in a gas environment such as air at standard conditions.9-11 The ability to generate high intensity pressure environments in materials without imposing the constraint of conducting the experiments in vacuum stimulated interest in using these laser induced pressure waves to alter the properties of materials in a manner similar to high explosive and flyer plate shock deformation of metals and alloys. The laser also offered attractive characteristics as a source of high intensity pressure environments which provided added incentive for investigating the properties and applications of laser peening generated stress waves.
This paper examines the types of high amplitude pressure environments one can generate with a pulsed laser and defines important parameters governing the interaction mechanisms and their impact on the resultant pressures. This analysis is confined to a pulsed neodymium-glass laser because it was the experimental facility used in essentially all of our investigations; however, other lasers with wave-lengths ranging from the infrared to the visible and near ultra-violet have the potential of producing similar environments.
The effects of these stress waves to the surface and in-depth-properties of materials also is investigated in this paper. These effects range from increasing the surface hardness to improvements in yield strength and increases in the fatigue life of other metals.
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