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Surface and subsurface damage (SSD) is often induced in a machined part made of such a material.ĭue to the ever-increasing requirement for better surface integrity of mechanical and optical parts, the tolerance for surface and subsurface damage is getting tighter and tighter. However, these materials are also difficult to machine due to their hard and brittle nature. Among hard and brittle materials, single crystalline silicon is the predominant substrate material for integrated circuits (IC) optical glasses are for optical windows and lens as well as high-power laser components ceramic materials are commonly used for bearings, cutting tools and machine parts. Hard and brittle materials are widely used because of their excellent physical and mechanical properties, such as high hardness and strength at elevated temperatures, wear and corrosion resistances, etc. These methods are promising because they can provide a capacity of rapid scan and detection of subsurface damage in spatial distribution. Non-destructive methods usually suffer from uncertainty factors, but may provide global information on subsurface damage distribution. Although more reliable, destructive methods are typically time-consuming and confined to local damage information.

This paper presents a review of the methods for detection of subsurface damage, both destructive and non-destructive. An efficient detection of subsurface damage directly leads to quality improvement and time saving for machining of hard and brittle materials. However, subsurface damage is often covered with a smearing layer generated in a machining process, it is rather difficult to directly observe and detect by optical microscopy.

To manufacture a high quality part, it is necessary to detect and remove the machining induced subsurface damage by the subsequent processes. It is detrimental to the strength, performance and lifetime of a machined part. Subsurface damage is easily induced in machining of hard and brittle materials because of their particular mechanical and physical properties.