文献翻译原文-在新材料精密加工的材料去除机制

Material removal mechanisms in precision machining of

new materials

Abstract

Modern-day products are characterised by high-precision components.

A wide range of materials, includingmetals and their alloys, ceramics, glasses and semiconductors, are finished to a given geometry, finish,accuracy and surface integrity to meet the service requirements. For advanced technology systems, demandsfor higher fabrication precision are complicated by the use of brittle materials. For efficient and economicalmachining of these materials, an understanding of the material removal mechanism is essential. This paperfocuses on the different material removal mechanisms involved in machining of brittle materials. 2001Published by Elsevier Science Ltd.

Keywords: Brittle; Defects; Ductility; Material removal; Precision machining

1. Introduction

Ultra-precision machining technology has been developed over recent years for the manufactureof cost-effective and quality-assured precision parts for several industrial applications such aslasers, optics, semiconductors, aerospace and automobile applications. Precision manufacturingdeals with the realisation of products with high shape accuracy and surface quality. The accuracymay be at the nanometric level. Several machining techniques can be mentioned here like diamondturning, grinding, lapping, polishing, honing, ion and electron-beam machining, laser machining,etc. Efficient overviews of the processes are given in Refs. [1–3].

Ultra-precision machining technology has been highly developed since the 1980s mainlybecause of its high accuracy and high productivity in the manufacturing of optical, mechanicaland electronic components for industrial use. For many advanced technology systems, higherfabrication precision is complicated by the use of brittle materials. The past decade has seen atremendous resurgence in the use of ceramics in structural applications. The excellent thermal,chemical and wear resistance of these materials can be realised because of recent improvementsin the overall strength and uniformity of advanced

ceramics [4].

Ceramic materials have been widely adapted as functional materials as well as structuralmaterials in various industrial fields and their application to precision parts is also increasing [5].

However, the high dimensional accuracy and good surface quality required for precision parts arenot necessarily obtained by the conventional forming and sintering process of ceramic powders.Thus precision finishing of the ceramics after forming and sintering is recognised as a key technologyto precision ceramic parts [6].

The quantity of ceramic material to be removed by the finishing process must be very small,so that microcracks do not remain on the finished surface. Abrasive processes such as grindingor lapping with diamond abrasives have generally been adopted for precision finishing of ceramics[7–9].

However, it is expected that better surface integrity and higher production rates can berealised by cutting processes. Compared with other processes, cutting is also advantageous inmachining complex shapes.Brittle materials can be divided into three groups: amorphous glasses, hard crystals andadvanced ceramics. Advanced ceramics are a modern development. They are made from fineporous particles that are formed, consolidated and thermally treated under precisely controlledconditions. Use of these materials enables development of high-technology devices and systemsthat simply could not be produced otherwise [10].

The same statement could be made about theuse of certain crystalline materials (e.g., semiconductors) and advanced high-temperature glasses.

2. Ductile regime machining

Improvements in machining tolerances have enabled researchers to expose the ductile materialremoval of brittle materials. Under certain controlled conditions, it is possible to machine brittlematerials like ceramics using single- or multi-point diamond tools so that material is removed byplastic flow, leaving a crack-free surface (Fig. 4). This process is called ductile regime machining.