Effect to the Surface Composition in Ultrasonic Vibration-Assisted Grinding of BK7 Optical Glass

Pei Yi Zhao,Bin Jiang,Xian Li Liu,Ming Zhou

doi:10.3390/app10020516

Pei Yi Zhao, Bin Jiang + Show 2 more

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https://doi.org/10.3390/app10020516

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Abstract

Because of the changes in cutting conditions and ultrasonic vibration status, the proportion of multiple material removal modes are of uncertainty and complexity in ultrasonic vibration-assisted grinding of optical glass. Knowledge of the effect of machined surface composition is the basis for better understanding the influence mechanisms of surface roughness, and also is the key to control the surface composition and surface quality. In the present work, 32 sets of experiments of ultrasonic vibration-assisted grinding of BK7 optical glass were carried out, the machined surface morphologies were observed, and the influence law of machining parameters on the proportion of different material removal was investigated. Based on the above research, the effect of surface composition was briefly summarized. The results indicated that the increasing of spindle rotation speed, the decreasing of feed rate and grinding depth can improve the proportion of ductile removal. The introduction of ultrasonic vibration can highly restrain the powdering removal, and increase the proportion of ductile removal. Grinding depth has a dominant positive effect on the surface roughness, whereas the spindle rotation speed and ultrasonic amplitude both have negative effect, which was caused by the reduction of brittle fracture removal.

Highlights

Optical glass is a typical hard and brittle material
When the instantaneous cutting depth of the abrasive grains reached beyond the critical cutting depth, micro cracks are generated inside the material, as the micro cracks propagates onto the machined surfaces, the material was removed by brittle fracture [4] and powdering [5,6]
Original crack density, strain rate, and grinding coolant are considered, the results showed that the crack damage depth would reach a maximum value while the material removal mode is semi-brittle [21]

Summary

Introduction

Optical glass is a typical hard and brittle material. Because of its unique excellent properties, it has a wide range of applications in the fields of optics, inertial confinement nuclear fusion, aerospace, and defense [1,2]. One of the most prominent features of optical glass materials is high brittleness and low fracture toughness. The critical cutting depth of the material is extremely small. When the instantaneous cutting depth of the abrasive grains did not reach the critical cutting depth, the material is removed by plastic deformation [3]. When the instantaneous cutting depth of the abrasive grains reached beyond the critical cutting depth, micro cracks are generated inside the material, as the micro cracks propagates onto the machined surfaces, the material was removed by brittle fracture [4] and powdering [5,6]

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Conclusion