金刚石线锯横向超声振动切割SiC单晶表面 粗糙度预测*

把横向超声振动应用到金刚石线锯切割硬脆材料加工中，基于冲量原理分析了线锯横截面上不同位置处金刚石磨粒对工件的法向锯切力。应用压痕断裂力学理论，定量分析了在法向和切向载荷共同作用下磨粒下方中位/横向裂纹扩展的长度和深度。研究了振动磨粒在工件上间歇加载和卸载使横向裂纹优先扩展并抑制中位裂纹扩展的屏蔽效应。建立了横向振动线锯切割硬脆材料时线锯横截面不同位置处磨粒的材料去除模式模型，得到了横向振动线锯切割硬脆材料晶片表面粗糙度的预测公式。以SiC单晶为切割对象，进行普通线锯和横向超声振动线锯切割对比试验，测定线锯的锯切力和晶片表面粗糙度，并对表面形貌进行观察。结果表明，横向超声振动线锯切割SiC是以脆性去除为主塑性去除为辅的混合材料去除模式;同等试验条件下，超声振动线锯切割能使晶片表面粗糙度降低25.7%。表面粗糙度测试结果与理论预测具有较好的一致性。

Surface Roughness Prediction of SiC Monocrystalline Cut by Diamond Wire-saw Excited by Transverse Ultrasonic Vibration

Applying the transverse ultrasonic vibration to the diamond wire-saw cutting hard-brittle materials processing, the normal cutting force applied to workpiece by diamond abrasive particle at different locations on wire-saw’s cross-section is analysed based on the principle of impulse. Applying indentation fracture mechanics theory, the propagating length and depth of median/lateral crack beneath the abrasive particle induced by normal and tangential load are analysed quantitatively. The shielding effect inhibiting median crack expansion and promoting lateral crack propagation preferentially as vibrating abrasive particle loading and unloading on workpiece surface intermittently is studied. The material removal model by abrasive on different locations of vibrating wire-saw cross-section is discussed, and the formula predicting wafer’s surface roughness is obtained. The comparative experiments of cutting SiC monocrystalline with conventional wire-saw and transverse ultrasonic vibration wire-saw are carried out respectively, in which the cutting force of wire-saw, surface roughness and surface morphology of wafer are measured and observed. The result indicates that the material removal mode of SiC cut by transverse ultrasonic vibration wire-saw is mixing mode which brittle fracturing mode is dominant while the plastic removal mode is minor, the wafer surface roughness decreasing by 25.7% under the same experimental conditions. The result of measuring surface roughness is more consistent with it in theoretical analysis prediction.