Ultrasonic assisted fixed abrasive machining of hard-brittle materials

Ultrasonics has been identified as a practical and vital technique in manufacturing, especially in the high efficiency and precision machining of difficult-to-machine materials, which, in some cases, is otherwise considerably difficult to be accomplished without ultrasonics. Traditional machining in the presence of ultrasonics can be categorized into ultrasonic machining (USM) and ultrasonic assisted machining (UAM). The USM involves the use of ultrasonics to energize loose abrasives and the energized abrasives impinge upon surfaces of workpieces to remove material in the form of mechanical actions such as hammering, rolling and sliding of abrasives and occasionally chemical actions- ultrasonic cavitation erosion. In contrast with USM, UAM refers to machining that ultrasonics is incorporated into widespread machining techniques such as cutting and grinding. The UAM has proven to enhance the machinability of difficult-tomachine materials and/or improve the quality of workpiece surfaces, which is due greatly to exceptional ability to dispel machining debris and/or to reduce machining forces and resultant machining heating. This chapter concentrates on the introduction of the UAM technique where ultrasonics is applied to fixed abrasive machining as there is an increasing tendency to supersede loose abrasives owing mainly to low-efficiency and cost-ineffectiveness of loose abrasive machining. The chapter commences with a succinct introduction of the principles of the USM and the UAM and then proceeds to internal grinding with the aid of ultrasonics, which is followed by ultrasonic assisted grinding of mono-crystalline silicon and sapphire, and ends with a recently proposed technique of ultrasonic assisted fixed abrasive polishing of optical glass. In each part, processing principle and apparatus will be described concisely and the machining methods are ultimately evaluated in terms of surface roughness and/or material removal rate, etc.