Fracture analysis of brittle workpiece during elastic deformation molding process

As a newly developed aspheric machining technology, elastic deformation molding process (EDMP) can convert complex aspheric surface machining to simple flat surface machining and has been successfully applied to aspheric surface machining. But during the machining process, workpiece made of brittle materials sometimes fractured, which seriously affected the reliability of the new machining method. In this paper, fragment analysis of fractured workpiece and finite element analysis of thermal stress have been carried out. Water leakage was observed during machining process which caused a high temperature difference inside workpiece, and the corresponding maximum thermal stress was up to 7 MPa near the boundary of contact area. Considering the tensile stress caused by elastic deformation in attaching process, the total tensile stress on attached surface of workpiece has exceeded the admissive bending strength of workpiece material which caused random fracture. Sealing measures like the use of silicone rubber sealant can effectively improve the stability of elastic deformation molding process.