Characterisation on the effects of workpiece microstructure and process parameters on resiudal stresses generated during machining

长期的目标是数值模拟单点车削后加工表面产生的残余应力与工件组织和工艺参数之间的关系。短期研究包括：a)发展一种数值与实验相结合的方法来确定刀屑界面上的摩擦系数，并研究该方法的工作边界；b)采用任意拉格朗日欧拉公式进行设计以模拟顺序切割、刀具刃口半径和进给量对残余应力的影响；c)建立数值模型来模拟工件组织和相变对残余应力的影响；d)数值和实验研究后刀面磨损长度、刀具后刀刃半径与进给比、刀具涂层和工艺参数对残余应力的影响。这项研究将开发一种独特的方法，通过数值和实验两种方法来获取加工过程中产生的实际摩擦系数。还将模拟刀具夹持器在切割过程中对刀具偏转的影响。还将分析连续切割对最终残余应力分布的影响。开发的预测残余应力的有限元模型将基于隐式求解器或解析方法，这将大大减少计算时间。还将开发模型来预测相变和工件微观组织对残余应力的高度复杂的影响。这项研究的意义在于加强对残余应力建模的认识，这将使研究人员能够从最大化大小和渗透深度的残余压应力的角度来优化航空航天、医疗和汽车行业中疲劳载荷部件的加工参数。此外，这项技术将有助于制造方案的设计，减少后加工阶段，如喷丸，改善疲劳性能，并减少由残余应力引起的零件变形。残余应力研讨会将在麦克马斯特为机械、材料和制造工程师举办，以展示来自这笔赠款的研究发现。

The long term objective is to numerically model the effects of workpiece micro structure and process parameters on residual stresses generate in the machined surface after single point turning. Short term research is comprised of studies on a) develop a combine numerical and experimental method to determine the friction coefficient along the tool-chip interface and investigate the operating boundary for this method, b) design using the Arbitrary Lagrangian Eulerian formulation technique to simulate the effects of sequential cut, cutting edge radius and feed on residual stresses, c) develop a numerical model to simulate the effects of workpiece microstructure and phase transformation on residual stresses and d) numerically and experimentally investigate the effects of flank wear length, cutting edge radius to feed ratio, tool coating, and process parameters on residual stresses. This research will develop a unique methodology to acquire actual friction coefficient induced during machining by using both numerical and experimental approaches. The effect of tool holder on tool deflection during the cutting process will also be modeled. Influence of sequential cut on the final residual stress profile will also be analyzed. The F.E. model developed to predict residual stresses will be based on either an implicit solver or analytical approach, which will reduced computational time substantially. Models will also be developed to predict the highly complex effects of phase transformation and workpiece micro structure on residual stresses. The significant of this research is to enhance the knowledge on modeling of residual stresses, which will enable researchers to optimize machining parameters for fatigue loaded components in the aerospace, medical and automotive sectors in terms of maximization of compressive residual stresses in both magnitude and penetration depth. Furthermore, this technology will assist design for manufacture protocol in reduction of post machining stages like shot peening, improved fatigue performance and reduce part distortion induced by residual stresses. Residual stress seminar will be organised at McMaster for Mechanical, Materials & Manufacturing engineers to present research discovery from this grant.