Machining by abrasion - Experimental and theoretical analysis

Based on the use of loose abrasive grains (three-body abrasion) or grains bonded together (grinding wheels) or to a backing (two-body abrasion), abrasive machining operations are extremely diverse and of great practical importance: grinding operations on steel slabs or blooms produced by continuous casting, the manufacture or finishing by grinding of all kinds of mechanical parts (tools for shaping metals by plastic deformation or by polymer injection, bearing components, machine parts...), sanding wood, polishing marble, granite..., and the fabrication of microelectronic circuits or high-resolution optical components through polishing. Furthermore, abrasive machining is the only economical option for:

• machining materials of very high hardness and/or high brittleness: martensitic bearing steels, high-speed steels in their as-received condition, refractory alloys, metal carbides, glass, and ceramics;

• achieve the extremely low surface roughness (on the order of nanometers) required for certain applications.

It should be noted that the interactions between abrasive grains and the workpiece are very similar to the interactions between rubbing parts that lead to abrasive wear—one of the most significant modes of wear in forming tools, machine components, and manufactured products. The performance of abrasive machining processes continues to improve due to growing industrial needs. However, despite their great economic importance, abrasive machining processes remain largely unknown, and their scientific aspects are poorly understood and shrouded in mystery.

The article [BM 7 052] , the first part of this series on abrasive machining, presents the main processes and provides a brief overview of material rheology. It states Preston-Archard’s law, demonstrates how it enables a macroscopic mechanical analysis of abrasive machining processes—using lapping as an example—and discusses its physical origin. The objective of this article [BM 7 053] is to describe in greater detail the mechanical phenomena involved at the microscopic scale in abrasive machining and, thereby, to provide models for estimating the abrasion rate k of the Preston-Archard law and the final surface finish of the workpieces. To this end, it describes the implementation procedures and results of various experimental and theoretical methods for studying the phenomena involved in abrasion; these consist of two types of tests:...