A study on the effect of ultrasonic vibration in nanosecond laser machining

Abstract

Laser machining has been used in various industrial manufacturing fields. However the surface finish of a machined surface becomes degraded by the recast layer that is created by the agglomeration of nanoparticles re-deposited on a work surface. In this study, ultrasonic vibration was applied to a nanosecond laser machining process in order to improve the quality of machined surface. A resonance type ultrasonic vibration module was designed to realize a unidirectional motion. To investigate the effects of ultrasonic vibration on the work surface, the morphological change of particles re-deposited on the machined area was observed in various process conditions. The results showed that the surface finish was improved by the near-field surface cooling enhancement induced by ultrasonic vibration. And it was found that such a vibration effect was remarkable in a repetitive machining process. From the chemical composition analysis of a machined surface, it was verified that the vibration can prevent the surface oxidation and the formation of recast layer. As a result, the ultrasonic vibration in ns-laser machining process was effective for improving both the physical and chemical quality of a machined surface. (C) 2012 Elsevier Ltd. All rights reserved.