ZrO2陶瓷切向超声辅助磨削表面及亚表面损伤机制

Surface and subsurface damage mechanisms in tangential ultrasonic-assisted grinding of ZrO_(2) ceramics

为进一步揭示切向超声辅助磨削过程中硬脆材料的表面及亚表面损伤机理,基于应变率模型对其磨削过程中材料的动态力学性能进行分析,并在此基础上建立了硬脆材料的脆-塑转变临界切削深度模型与微裂纹损伤深度模型。研究发现,脆-塑转变临界切削深度和微裂纹损伤深度均与应变率有关,其中临界切削深度随着应变率的增加而增加,而横向裂纹损伤深度与中位裂纹损伤深度均随应变率的增加而减小。通过ZrO2陶瓷切向超声辅助磨削试验进行验证。试验结果表明:由于切向超声振动的引入提高了材料应变率,进而提高了材料的动态断裂应力以及动态断裂韧性,从而扩大了ZrO2陶瓷的塑性域去除范围,降低了加工表面的横向裂纹与中位裂纹损伤深度,使得ZrO2陶瓷的表面及亚表面质量得到明显改善。试验结果与理论分析相一致,为进一步揭示切向超声辅助磨削过程中硬脆材料的表面及亚表面微观损伤机理提供了理论参考。

To further reveal the surface damage and subsurface damage mechanisms of hard-brittle materials in Tangential Ultrasonic-Assisted Grinding(TUAG),the dynamic mechanical properties of the hard-brittle materials during TUAG are analyzed based on the strain rate model.On this basis,the brittle-ductile transition’s critical cutting depth and the crack depth for hard-brittle materials in TUAG are obtained.The study found that the critical cutting depth and the crack depth are related to the strain rate.The critical cutting depth increases with the increase of the strain rate,and both the transverse crack depth and the median crack depth decrease with the increase of strain rate.Grinding test of ZrO2 ceramics was conducted to verify the theoretical analysis.The test results show that due to the introduction of tangential ultrasonic vibration,the strain rate of the material increases,which then improves the dynamic fracture stress and dynamic fracture toughness of the material.As a result,the plastic removal range of ZrO2 ceramics was increased,the depth of transverse crack and mediate crack were reduced,and the surface and subsurface quality of ZrO2 ceramics was significantly improved.The test results are consistent with the theoretical analysis.This study provides a theoretical reference for further revelation of the surface and subsurface damage mechanisms of hard-brittle materials in TUAG.