Prediction of Microstructural Changes and Residual Stresses in Hard Machining

这笔赠款提供资金用于开发一种计算工具，用于分析和预测使用单点工具切割硬化钢时产生的微观结构变化和残余应力。 计算工具将用于建立切削速度、进给、切削深度和工具几何形状的最佳参数值，这些参数值产生有利的残余应力和没有不期望的微观结构变化（例如，白色层形成）。 为了实现这一目标，冶金相变发生在淬火钢的分析模型将开发和结合使用ABAQUS标准有限元代码开发的二维切削过程的耦合热机械更新拉格朗日有限元模型。 为了验证完整的模型，将对轴承钢进行正交切削实验（例如，AISI 52100）作为工件材料和PCBN刀具材料，使用由模型确定的切削参数。 现有的材料性能数据和/或高温高应变率试验将用于建立模拟中使用的材料流动应力模型。 将使用光学和扫描电子显微镜表征加工工件样品的微观结构，同时使用X射线衍射测量残余应力。如果成功的话，这项研究的结果将提供准确模拟加工硬化钢表面生成的能力，并确定切削条件的最佳窗口，以产生提高硬化钢部件使用寿命的表面特性。 这将有助于降低成本，提高零件质量，并促进硬加工技术的工业应用。 在基础层面上，拟议的研究将推进当前对硬加工中材料和切削过程相互作用的物理理解，特别是从工件微观结构变化的角度来看（例如，白色层形成）和残余应力。 拟议的研究也将提供一个坚实的框架，为未来开发的三维模型模拟硬加工过程，如车削和铣削。

This grant provides funding for the development of a computational tool for analysis and prediction of microstructure changes and residual stresses generated in cutting of hardened steels using single-point tools. The computational tool will be used to establish the optimal parameter values for cutting speed, feed, depth of cut and tool geometry that yield favorable residual stresses and a workpiece surface free of undesirable microstructure changes (e.g., white layer formation) in two-dimensional cutting of a hardened steel material. To achieve this goal, analytical models of the metallurgical phase transformation occurring in quenching of steels will be developed and combined with a coupled thermo-mechanical updated Lagrangian finite element model of the two-dimensional cutting process developed using the ABAQUS Standard finite element code. In order to validate the complete model, orthogonal cutting experiments will be performed with bearing steel (e.g., AISI 52100) as the workpiece material and PCBN tool material using cutting parameters determined from the model. Existing material property data and/or elevated temperature high strain-rate tests will be used to establish the material flow-stress models to be used in the simulations. The microstructure of the machined workpiece samples will be characterized using optical and scanning electron microscopy while residual stresses will be measured using X-ray diffraction. If successful, the results of this research will provide the capability of accurately simulating surface generation in machining of hardened steels and determining an optimal window of cutting conditions to produce surface characteristics that enhance the service-life of hardened steel components. This will in turn help to reduce cost, improve part quality, and promote the industrial use of hard machining technology. On a fundamental level, the proposed research will advance current physical understanding of material and cutting process interactions in hard machining, particularly from a standpoint of workpiece microstructure changes (e.g., white layer formation) and residual stresses. The proposed research will also provide a solid framework for future development of a three-dimensional model for simulating hard machining processes such as turning and milling.