# Effect to the Surface Composition in Ultrasonic Vibration-Assisted Grinding of BK7 Optical Glass
## 1 Introduction
Therefore, there are often plastic removal methods, brittle removal methods, and powder removal methods in the process. Moreover, under the combination of different processing parameters, the proportion of the above three material removal methods on the machined surface will also change, this change would be certainly depended on process parameters and grinding wheel parameters. The mapping relationship between them needs to be studied. [PERSON] developed a critical function for crack propagation based on single grit scratching test, by using this function, he further presented a model for predicting the change of material removal mode. In his model, original crack density, strain rate, and grinding coolant are considered, the results showed that the crack damage depth would reach a maximum value while the material removal mode is semi-brittle [21]. [PERSON] investigated the influence law of spindle rotation speed on grinding force and specific grinding energy, he also claimed that the cracks and brittle-fractured pits sizes would become enormous because of the transition of material removal mechanism (ductile regime to completely brittle regime) [22]. [PERSON] has taken consideration of coupling effects of multiple abrasive grains on cracks propagation to simulate actual grinding process. He pointed that the micro cracks sizes would be significantly affected by the separation distance of two abrasive grains [23]. However, there are few reports on the mapping relationship between process parameters and material removal methods in the process of ultrasonic vibration grinding of optical glass. When the material is removed in different ways, it will produce different processed surface topography, which will also produce different degrees of subsurface damage. Therefore, the proportion of these removal methods on the machined surface determines the final machined surface quality and subsurface damage. Although studies at home and abroad have been able to control the surface roughness [24; 25; 26], processing efficiency [27; 28], force and energies [29; 30] or damages [31] by adjusting the process parameters, for the precision machining of brittle materials that pay attention to the surface quality and subsurface damage at the same time, the intrinsic relationship between the proportion of the material removal modes and the process parameters and the parameters of the grinding wheel is still not clear. The effective control of the material removal modes proportion is the basis and key to exploring the technical measures to jointly improve the processing surface and subsurface quality. In this paper, to comprehensively investigate the effect of grinding parameters and ultrasonic parameters to surface composition, 32 sets of experiments of ultrasonic vibration grinding of optical glass are carried out first. Second, based on the measurement results, the effect of grinding parameters and ultrasonic parameters on surface roughness was investigated, the changes of machined surface morphologies and the proportion of three material removal modes in different grinding parameters are analyzed. At last, the effect of processing parameters on surface composition in ultrasonic vibration-assisted grinding of optical glass is briefly summarized.