基于走刀轨迹的316L不锈钢立式铣削表面完整性研究

发布时间：2017-12-30 23:15

本文关键词：基于走刀轨迹的316L不锈钢立式铣削表面完整性研究　出处：《上海交通大学》2015年硕士论文　论文类型：学位论文

【摘要】：论文以自然科学基金“核主泵叶轮多轴数控加工工艺规划及优化方法研究(No.51175339)”为依托。作为核主泵的核心部件,叶轮需要在高温、高压、核辐射的恶劣环境下进行长时间安全可靠的工作,要求叶轮表面具有很好的机械物理性能和水力特性。根据叶轮的特殊工作环境,常采用AISI-316L不锈钢作为叶轮加工材料,这种材料具有很好的耐酸性、耐磨性、韧性以及良好的焊接性能,尤其具有很强的抗腐蚀性能,但同时它的切削加工性能较差,属于难加工金属材料。因此,针对AISI-316L不锈钢材料铣削加工表面完整性的研究,对于提高叶轮加工表面的机械物理性能、水力特性、减少应力腐蚀裂纹、增加使用寿命等具有重要意义。基于此,以探索AISI-316L不锈钢材料平面立铣加工表面完整性作为研究目标,采用有限元仿真与试验分析相结合的研究方法。分析了铣削加工工艺中走刀轨迹、铣削参数以及相邻刀具路径之间重叠率对于工件加工表面完整性的影响,以表面残余应力、表面加工硬化、和表面粗糙度三个方面作为衡量指标。首先,为了模拟不同走刀轨迹条件下的平面立铣加工过程,基于Abaqus软件建立了AISI-316L不锈钢材料的三维热-力耦合立铣有限元模型,此模型同时考虑了切削力与切削热的作用,模拟过程与实际铣削加工过程基本符合。研究得到了工件表面残余应力分布、沿深度方向残余应力分布、以及表面塑性应变分布等结果。同时,基于此模型,研究了主轴转速、进给速度、铣削深度三要素对加工表面残余应力和塑性应变的影响。其次,通过数控加工中心对AISI-316L不锈钢材料进行平面立铣加工试验,研究中对工件加工表面残余应力、显微硬度、粗糙度以及三维表面轮廓等表面完整性指标进行了测量。论文对比了表面残余应力有限元预测结果和试验测量结果,模型预测误差不超过27%,验证了所建立的三维热-力耦合立铣有限元模型的有效性。论文同时分析了四种走刀轨迹以及铣削参数对表面加工硬化和表面粗糙度的影响,提出了改善加工表面完整性的走刀轨迹以及铣削参数优化组合选取措施。铣削加工过程中,由于行间距小于刀具直径,从而使得相邻刀具路径之间存在重叠区域,重叠区域会出现两次甚至多次重复切削现象。论文针对这种重叠现象,考虑重叠率K和重叠方向两种因素,研究了重叠现象对工件加工表面完整性的影响,为平面立式铣削中根据不同的刀具直径选择合适的行间距以及走刀轨迹提供参考。
[Abstract]:The thesis is based on the Natural Science Foundation "Research on the process Planning and Optimization method of Multi-axis NC Machining of the Impeller of Nuclear main pump No. No. 51175339)". As the core part of the nuclear main pump, the impeller needs to be at high temperature. Under the harsh environment of high pressure and nuclear radiation, it is required that the impeller surface have good mechanical, physical and hydraulic properties, according to the special working environment of the impeller. AISI-316L stainless steel is often used as impeller processing material. This material has good acid resistance, wear resistance, toughness and good welding performance, especially has very strong corrosion resistance. But at the same time, its cutting performance is poor, so it is difficult to process metal materials. Therefore, the surface integrity of milling AISI-316L stainless steel materials is studied. It is of great significance to improve the mechanical and physical properties of the impeller surface, hydraulic characteristics, reduce stress corrosion cracking, increase service life and so on. The goal of this study is to explore the surface integrity of AISI-316L stainless steel by planar end-milling. The influence of cutter path, milling parameters and overlap rate between adjacent tool paths on the surface integrity of workpiece was analyzed by means of finite element simulation and experimental analysis. The surface residual stress, surface work hardening, and surface roughness are taken as the measurement indexes. Firstly, in order to simulate the process of plane end-milling under different path path conditions. Based on Abaqus software, a three-dimensional thermo-mechanical coupled end-milling finite element model of AISI-316L stainless steel is established, which considers the effect of cutting force and cutting heat. The simulation process is basically consistent with the actual milling process. The residual stress distribution along the depth direction and plastic strain distribution on the surface of the workpiece are obtained. At the same time, based on this model. The effects of spindle speed, feed speed and milling depth on the residual stress and plastic strain of the machined surface are studied. The surface residual stress and microhardness of AISI-316L stainless steel were studied by means of plane end milling test in NC machining center. The roughness and 3D surface contours are measured. The prediction error of the model is less than 27%. The finite element prediction results of surface residual stress and the experimental results are compared in this paper. The effectiveness of the three-dimensional thermal-mechanical coupled end-milling finite element model is verified. The effects of four kinds of cutter paths and milling parameters on the surface work hardening and surface roughness are also analyzed. This paper puts forward some measures to improve the integrity of machining surface, such as the path path and the optimal selection of milling parameters. In the milling process, the line spacing is smaller than the diameter of the cutter. Therefore, there are overlapping regions between adjacent tool paths, which will occur two or more times repeated cutting. In this paper, the overlap rate K and overlap direction are considered. The influence of overlap phenomenon on machining surface integrity of workpiece is studied, which provides a reference for choosing appropriate row spacing and tool path according to different tool diameters in planar vertical milling.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG54

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