Abstract: In order to realize the non-destructive, rapid, and accurate detection of subsurface damage (SSD) depth, a prediction model of SSD depth produced in lapping process of optical material is established. With this model, the influence law of lapping parameters on SSD can be predicted. Then, SSD depth of lapped K9 glass is measured by using magnetorheological finishing (MRF) spot technique in a bid to verify the validity of the prediction model. Finally, an effective lapping procedure is proposed to improve the machining efficiency of optical elements. The results show that SSD depth can be effectively predicted by using the prediction model according to lapping parameters. SSD depth is directly proportional to granularity of abrasive grains, hardness of lapping plate and lapping pressure, while inversely proportional to lapping velocity and concentration of lapping liquid. Moreover, the influence of granularity of abrasive grains on SSD depth is more significant than lapping pressure, and the influence of hardness of lapping plate, lapping velocity and concentration of lapping liquid are minor. In order to improve machining efficiency of optical elements, selecting a high lapping velocity and a high concentration of lapping liquid is suggested in order to reduce SSD depth and increase material removal rate simultaneously.

Key words: Indentation, Lapping, Magnetorheological finishing (MRF), Subsurface damage (SSD)