Optimization method research of ultrasonic assisted grinding processing for thin-wall reflectors of hard and brittle materials

Hard and brittle materials, represented by silicon carbide, single-crystal silicon, and ceramic-based composites, possess excellent mechanical, physical, and chemical properties. They have various applications in aerospace, aviation, microelectronics, medicine, and other fields. However, the hardness, brittleness, and weak rigidity of thin wall parts made of hard and brittle materials pose challenges to their processing. In this paper, considering the processing efficiency and quality, an optimization strategy of variable thickness ultrasonic assisted machining of thin-walled parts of hard and brittle materials is proposed. Under the condition that the volume of the material removed in each process is constant, the shape of the workpiece is optimized based on the finite element method to minimize the maximum stress, reduce the deformation of the workpiece during the machining process, and improve the machining efficiency. The results showed that compared with traditional machining, the maximum stress was decreased by 39.02 %-47.72 %, and the maximum deformation of planes A and B was reduced by 19.61 % and 60.97 %, respectively. Furthermore, optimal machining is verified by experiments, revealing that it effectively mitigated the deformation of thin-wall parts while enhancing processing efficiency by 41.16 %. Finally, this optimization strategy was applied to machining off-axis aspheric mirrors on single-crystal silicon. The measured surface shape accuracy PV is 60.895 mu m, and RMS is 11.221 mu m. The research has specific technical guidance for improving the high efficiency and high-quality precision machining of weak, rigid, thinwalled mirrors.