多力热场非线性叠加作用的薄壁件铣削残余应力重分布生成机理研究

This proposal investigates the mapping between the multiple force-thermal source and residual stress of milling for thin-walled part, and proposes a new method by controlling the residual stress field, so that the long-term stability of the machining precision of thin-wall parts can be improved. The specific contents include: Based on the control of the force and thermal in the single / multiple process, to reduce or suppress the influence of the residual stress distribution, a calculation model, boundary and initial conditions is built; Transforming the issue of residual stress generation affected by many factors into controlling the input source of the force and heat, establishing the macro-quantitative correlation evaluation model of direct characterization of residual stress; based on this model, exploring the effect of single factor on the superposition of residual stress respectively, revealing the generation rules of re-distribution of residual stress in the milling of the thin-wall parts, and putting forward the process optimization scheme by coupling the multiple stress field; eventually forming the theoretical method, processing scheme and simulation technology, which is based on the case and principle, so that the deformation of the thin-wall part is improved by controlling the residual stress. The project aims to break through the technical bottleneck of residual stress which is difficult to control in the milling process of thin-walled parts, guide the design and optimization of processing in the actual production process scheme, form the core technology with independent property rights on the to solve the issue of residual stress of the thin-walled parts.

本项目研究薄壁件铣削中多力热源与残余应力之间的映射关系，提出一种控制残余应力场，以提高薄壁件加工精度长期稳定性的新方法。具体内容包括：基于单/多工序中力热控制，建立以减小或抑制残余应力分布影响为控制目标的计算模型及其边界与初始条件；将残余应力重分布生成的多影响因素问题转化为以力热为输入源控制，建立直接表征残余应力的宏观定量相关性评估模型；在此模型基础上，分别探索单因素作用下的残余应力叠加关系，揭示薄壁件铣削残余应力的重分布生成规律，并提出耦合多应力场的工艺优化方案；最终形成一套基于案例和原则的控制残余应力以改善薄壁件二次变形的理论方法、工艺方案与仿真技术。本项目旨在突破薄壁件铣削加工中残余应力难以控制的技术瓶颈，指导实际生产中加工工艺方案的设计与优选，形成具有自主知识产权的解决薄壁件残余应力问题的核心技术。

残余应力不均匀分布对于航空航天薄壁件加工后二次变形具有突出的影响，而且薄壁件弱刚度易变形的特征也成为了制约其加工难的技术瓶颈。本项目首先从单/多工序薄壁件加工平/曲面入手，量化及构建了表征残余应力重分布的模型及验证平台，获得了不同热处理工况下初始残余应力分布；并以此为输入条件，进一步构建相应的残余应力和变形预测叠加模型，揭示了初始残余应力、加工残余应力叠加机理，获得了定量分析及评估力热对残余应力的生成影响因子，发现残余应力受切削力影响明显大于温度的作用，起主导作用，切削力对径向残余应力作用大于切向残余应力，而温度的作用则径向大于切向。其次，基于工艺参数方案，从平/曲面特征入手，分别以未变形切屑厚度和未变形切削体积为中间计算指标，获得了工艺参数与残余应力分布表征的数学模型；基于获得的残余应力分布结果，发现了不同工艺条件下已加工工件存在残余冲击应力现象，以及已加工表面多次切削时存在等残余应力面积传递的规律，并由此提出了相应的优化工艺准则及方案。最后，以某航天薄壁件为案例，以控制平/曲面特征加工残余应力为目标，研究及提出了表面/亚表面残余应力体积定义并证明其作为重分布与变形的关键衡量指标，发现了薄壁件多工序加工过程中残余应力重分布的叠加和传递规律；同时，以切削力和加工时间为目标，从工艺参数和加工路径入手进行了优化，得到最佳工艺方案，薄壁件整体加工效率和质量提升20~30%以上。本项目的研究成果，从力热载荷与残余应力生成的量化关系及其模型上获得了较好的突破，并提出了残余应力体积及冲击应力等在内的关键评价指标，通过模型与实验法，获得的关键数据将为航空航天领域薄壁件加工的残余应力主动控制提供有效的理论及实验依据。