基于定位强化感应加热技术的磨削表面残余应力控制研究

发布时间：2018-11-24 19:18

【摘要】：镍基高温合金Inconel718具有良好的高温强度和高耐蚀性能,广泛应用于制造航空工业特别是燃气涡轮发动机的高温构件。为了获得较高的尺寸精度和表面质量,常在其加工的最终阶段安排磨削工艺。然而磨削工艺往往会使零件的表面产成较大的残余拉应力,这对零件的疲劳强度和疲劳寿命非常不利。因此需要保证在磨削表面形成较小的拉应力甚至压应力,以提高加工零件的疲劳寿命。本文介绍了Inconel718合金的应用背景及现有加工工艺需求,从而引出本文所研究的主要问题是对其磨削表面残余应力进行主动调控。对国内外在磨削残余应力的形成原因、改善方法以及测量技术等方面的研究现状进行了综述和总结。基于降低工件表层及亚表层磨削温度梯度的原理出发,本论文提出一种复合磨削工艺,即利用控制良好的感应加热工艺将热源嵌入到工件亚表层,以实现主动调节镍基高温合金零件表面的磨削残余应力分布。首先分析了通过调控磨削梯度改变残余应力的形成机理,在此基础上提出亚表层加热温度的目标。采用无接触的感应加热结合表面冷却技术来实现内部温度的植入,并研究了定位强化感应加热原理以及聚能器在电磁热转换过程中的作用机理。基于有限元数值模拟技术与所搭建的感应加热实验系统,研究了影响感应加热过程的重要工艺参数,并建立了温度场分布的数学预测模型。通过实例分析和实验验证,证明了所建立的温度控制模型能够有效实现温度场的精确预测和调控。结合感应加热模型以及合适的磨削热分析模型,建立了集成新工艺系统的残余应力有限元数值分析模型。该新工艺过程分析及控制模型能够完成新工艺加工过程中工件层的温度场计算和应力场计算。为了实现最终残余应力分布状态的主动调控,建立了残余应力与重要工艺参数之间的响应曲面数学控制模型。并在此基础上,研究了残余应力的主动调控方法以及残余应力调控参数的优化分析。最后建立了感应加热辅助磨削集成工艺系统实验平台,并进行了大量的集成实验研究。结果表明,与普通磨削相比,新工艺下的磨削表层残余应力得到了较大的改善,进一步验证了本文所提出的通过温度梯度调控磨削残余应力机理的可行性。同时研究了影响最终残余应力分布的新工艺参数,并结合仿真分析结果,最终实现了集成工艺下残余应力的主动调控。
[Abstract]:Nickel base superalloy Inconel718 has good high temperature strength and high corrosion resistance. It is widely used to manufacture high temperature components of aeronautical industry, especially gas turbine engine. In order to obtain high dimensional accuracy and surface quality, grinding process is usually arranged in the final stage of machining. However, grinding process often results in large residual tensile stress on the surface of the parts, which is unfavorable to the fatigue strength and fatigue life of the parts. Therefore, it is necessary to form small tensile stress or even compressive stress on the grinding surface to improve the fatigue life of the machined parts. In this paper, the application background of Inconel718 alloy and the requirement of existing processing technology are introduced. Thus, the main problem studied in this paper is to regulate the residual stress of grinding surface actively. In this paper, the reasons for the formation of grinding residual stress, improvement methods and measurement techniques are summarized and summarized. Based on the principle of reducing the temperature gradient of workpiece surface grinding and subsurface grinding, this paper proposes a composite grinding technology, in which the heat source is embedded into the sub-surface layer of the workpiece by a well-controlled induction heating process. In order to realize active adjustment of grinding residual stress distribution on the surface of nickel-based superalloy parts. The formation mechanism of changing residual stress by controlling grinding gradient is analyzed, and the goal of subsurface heating temperature is put forward. The contact free induction heating combined with surface cooling technology is used to realize the implantation of internal temperature. The principle of the orientation enhanced induction heating and the mechanism of the accumulator in the electromagnetic heat transfer process are studied. Based on the finite element numerical simulation technology and the experimental system of induction heating, the important technological parameters affecting the induction heating process are studied, and the mathematical prediction model of temperature field distribution is established. Through the example analysis and experimental verification, it is proved that the established temperature control model can effectively predict and regulate the temperature field. Based on the induction heating model and the suitable grinding thermal analysis model, the finite element numerical analysis model of residual stress of integrated new process system is established. The new process analysis and control model can be used to calculate the temperature field and stress field of workpiece layer. In order to realize the active control of the final residual stress distribution, a mathematical control model of response surface between residual stress and important process parameters is established. On this basis, the active control method of residual stress and the optimization analysis of residual stress control parameters are studied. Finally, an experimental platform of induction heating assisted grinding integrated process system is established, and a large number of integrated experiments are carried out. The results show that the surface residual stress in the new grinding process has been greatly improved compared with the common grinding process, which further verifies the feasibility of the mechanism of grinding residual stress controlled by temperature gradient in this paper. At the same time, the new process parameters which affect the distribution of final residual stress are studied. Finally, the active control of residual stress under integrated process is realized by combining the results of simulation and analysis.
【学位授予单位】：清华大学
【学位级别】：博士
【学位授予年份】：2015
【分类号】：TG580.6

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