NEW PERSPECTIVES ON THE CUTTING MECHANISM OF DIFFICULT-TO-MACHINE MATERIALS
NEW PERSPECTIVES ON THE CUTTING MECHANISM OF DIFFICULT-TO-MACHINE MATERIALS
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作者：
Wang Wenhu
先进的航空发动机合金如钛和镍基合金被广泛用于机匣和压气机叶片。钛基和镍基合金的切削性能差是由于其固有的特性，包括高的热硬度和强度，导致切削过程中刀具和工件的显著变形，低的热扩散率，快速的加工硬化，导致切削线深度处的严重磨损，以及锯齿形切屑的形成。为了高效、精确地加工这些难加工材料，了解切削机理至关重要。本文综述了锯齿形切屑形成机理的理论和分段切屑有限元模拟的断裂准则。然后讨论了如何确定切削区在高变形速率和温度下的流变应力。应充分考虑应变、应变速率和温度之间的相互作用。分析了温度和残余应力对航空航天薄壁结构变形和加工精度的影响。
Advanced aeroengine alloys such as titanium and nickel-based alloys are widely used for casing and compressor blades. Poor machinability of titanium and nickel-based alloys are due to their inherent characteristics, including high hot hardness and strength, causing sinificant deformation of the cutting tool and workpiece during machining, low thermal diffusivity, rapid work hardening, causing a severe wear at the depth of cut line, and the saw-tooth chip formation. For efficient and precise NC machining of these difficult-to-machine materials, an understanding of the cutting mechanism is essential. This paper provides an overview of the theories of saw-tooth chip formation mechanism and the fracture criteria for the FEM simulation of segmented chips. How to determine the flow stress at high deformation rates and temperatures in the cutting zone is then discussed. The interaction between strain, strain rate and temperature should be sufficiently considered. The temperature and residual stress have a considerable influence on the distortion and machining precision for thin-wall structures as used in the aerospace industry, which are also analyzed in this paper.