基于ABAQUS的镍基高温合金锯齿形切屑演变过程及机理研究

利用ABAQUS软件建立正交切削有限元模型。该切削有限元模型采用修正的Johnson-Cook非线性热黏塑性本构关系和修正的Coulomb摩擦理论以及金属切削切屑剪切失效断裂准则,并通过模拟与试验的对比分析,验证了其正确性。模拟与分析结果表明:锯齿形切屑的演变过程由锯齿雏形、锯齿雏形到锯齿节块、锯齿节块到锯齿切屑三个阶段组成。温度弱化作用使剪切滑移变形始于切削层下部(靠近刀尖区域),并呈尖峰状向切削层顶表面方向扩展;当刀尖处金属发生热塑失稳时,剪切滑移瞬间扩展至切削层顶表面,形成了完整的剪切滑移窄带,形成锯齿雏形;剪切滑移窄带内的金属基本均处于热塑失稳状态,锯齿雏形将沿着整个变形窄带发生集中剪切滑移变形,形成锯齿节块;锯齿节块进入第Ⅱ变形区后,集中滑移窄带内的金属仍处于热塑失稳状态,在前刀面的推挤作用下,锯齿节块将继续沿着集中滑移窄带发生集中剪切滑移变形,直至离开第Ⅱ变形区,形成锯齿切屑。

Study on Mechanism and Evolution of Serrated-Chip of Ni-Base Superalloy Based on ABAQUS

A finite element model of orthogonal cutting is constructed using the analysis software ABAQUS.In the model,some key technologies such as the modified Johnson-Cook visco-plastic constitutive relation,the separation criterion of chip damaged in shearing and the corrected friction theory are adopted.The accuracy of the model is verified through the contrast analysis of simulation and experiment.The results show that the evolution process of serrated chip is composed of three phases,which are the formation processes of the rudiment of sawtooth,and then the rudiment of sawtooth to the sawtooth segment,and finally the sawtooth segment to the serrated chip.The shear-slipping deformation begins to appear on lower cutting layer near the tool-tip region due to temperature weakening,and it extends in the direction from tool tip to top surface of cutting layer,which shows as "spikes".When the thermoplastic instability in tool-tip region happens,the shear-slipping extends to the top surface of cutting layer immediately,and the shear-slipping narrow-band is formed completely, and the rudiment of sawtooth is finished.Because the metal in narrow-band is in the state of thermoplastic instability,local shear-slipping deformation occurs along narrow-band,and the sawtooth segment is shaped.After the sawtooth segment comes into the second deformation zone,the metal in narrow-band has still been being in the state of thermoplastic instability.Because of pushing of the rake face,the local shear-slipping deformation has been continuing in the field of narrow-band until it leaves the second deformation zone,and the serrated chip is formed finally.