Researching Effect Of Germanium Single-crystal Anisotropy In Ultra-precision Machining

As an important semiconductor material, Germanium single-crystal is widely used in solar cells, detectors and infrared optical system. Germanium single-crystal infrared optical components often require high surface roughness and good surface accuracy. As a brittle material, germanium single-crystal has an unconducvie processing characteristic with fragility and high hardness. The traditional turning, milling and other processing methods cannot meet the requirements of parts, and it is necessary to adopt ultra-precision processing technology to process germanium single-crystal. However, in the actual processing of the germanium crystal anisotropy will cause fluctuations of the cutting force, which affects the finished surface roughness of the workpiece. Therefore, researching the effect of germanium single-crystal anisotropy in ultra-precision machining is of great significance.Firstly, ultra-precision machining model of germanium single-crystal has been established in this paper, linking germanium single-crystal anisotropy with shear angle, elastic modulus, shear modulus and cutting force. The shear angle, elastic modulus and shear modulus with different crystal planes and crystal orientations have been solved, and horizontal cutting force and radial cutting force in germanium single-crystal ultra-precision turning have been calculated theoretically. And multi-objective optimization of tool geometry parameters has been done, so that the cutting forces achieve the optimal values.Secondly, ultra-precision cutting finite element model of germanium single-crystal has been established, integrated the chip formation model proposed by the previous, using pure deformation theory and adaptive grid technology and taking into account the impact of the tool edge radius in cutting process. The commercial software ABAQUS has been used to simulate the ultra-precision cutting process of germanium single-crystal, analyzing the effect of cutting parameters and tool geometry parameters on the cutting forces of the cutting process, comparing the cutting forces in the different crystal planes and crystal orientations. Finally, the cutting experiments of germanium single-crystal have been done on the single point diamond turning machine; simultaneously the surface roughness of the machined workpiece has been measured by the aspheric surface measurement system. During the experiment, the workpieces with different cutting parameters and planes have been respectively machined; the changes of the surface roughness have been analyzed.