基于有限元的薄壁件切削加工变形影响的研究

发布时间：2018-03-24 07:07

  本文选题：有限元　切入点：薄壁件　出处：《武汉理工大学》2015年硕士论文

【摘要】：由于对产品功能、质量等性能的特殊要求,薄壁件在航空以及造船等行业广泛存在,其结构主要由侧壁或腹板组成,结构形状复杂。这样的零部件的轮廓尺寸相比截面尺寸要大很多,有的还对平面度和变形精度要求较高,因此加工起来刚度稳定性较低,往往需要采用特殊的加工工艺及误差控制方法,导致加工效率较低且制造成本较高。采用计算机辅助工程(Computer Aided Engineering,CAE)可有效缓解这一问题。本文首先简单介绍了切削加工仿真需要的关键有限元法(Finite Element Method,FEM)技术和切削加工特点,分析和阐述了国内外解决复杂非线性热-力仿真分析问题常采用的Johnson-Cook材料塑性模型、Johnson-Cook材料失效模型、ABAQUS/Explicit仿真环境中的损伤演化模型,以及切削中刀具和工件材料的接触特点、仿真软件对于接触特性的计算特点和相应的摩擦模型建立。其次,分别采用以上涉及到的相关方法和技术对简化二维正交切削和三维斜角切削模型作了相应的仿真分析,模拟了不同形貌切屑的成形过程以及加工中生热和应力-应变问题,分析了不同切削厚度、不同切削速度、不同刀具角度对切削力和切削温度的影响。验证了该仿真方法的可行性。然后,运用上述方法对薄壁板的三维切削加工模型进行了仿真模拟。本文全部模型都是基于各项同性材料,仿真过程中不考虑刀具的磨损和变形以及切削液的影响。由于薄壁零部件刚性差,在加工过程中很容易产生“让刀”变形现象,所以分别针对“仅底端约束”、“底部和两端面约束”这两种约束状态的薄壁板的切削加工模型进行了仿真模拟,分析了其加工过程中的加工误差以及相应的切削热大小、应力分布情况等。经仿真分析,与后一个模型相比,仅底端约束的模型的薄壁板更容易产生切削变形,加工误差更大,其加工变形误差从板的上端往下逐渐减小,并且由于加工过程中薄板上端的挠曲变形和两端挠曲变形的综合作用,最终在薄壁板底端正中间产生一个“凹坑”状区域;底部和两端均约束的模型在薄壁板的正中间才产生最大加工变形误差,并且误差从上往下呈逐渐减小的趋势。在本文最后,针对某镜座零部件的镜框台阶面的切削加工进行了仿真模拟。提取加工面的变形误差绘制成曲线图,并与实验结果进行对比分析,结果表明:采用ABAQUS/Explicit能够有效对薄壁零部件的切削加工进行有限元仿真计算。
[Abstract]:Due to the special requirements for the function and quality of products, thin-walled parts are widely used in aviation and shipbuilding industries, and their structures are mainly made up of side walls or web plates. The shape of the structure is complex. The contour size of such parts is much larger than the cross-section size, and some require higher flatness and deformation accuracy, so the stiffness stability is low when machined. Special processing techniques and error control methods are often required. As a result of low machining efficiency and high manufacturing cost, this problem can be effectively alleviated by using computer Aided engineering (CAE). This paper first introduces the key finite element method finite Element method for machining simulation and the characteristics of cutting machining. The damage evolution model of Johnson-Cook material failure model in Abaqus / explicit simulation environment, and the contact characteristics of cutting tools and workpiece materials in cutting are analyzed and expounded, which are often used to solve complex nonlinear thermo-mechanical simulation problems at home and abroad, such as Johnson-Cook material plastic model and Johnson-Cook material failure model. The simulation software is used to calculate the contact characteristics and establish the corresponding friction model. Secondly, the simplified two-dimensional orthogonal cutting model and the three-dimensional diagonal cutting model are simulated and analyzed using the methods and techniques mentioned above. The forming process of chips with different morphologies and the problems of heat generation and stress-strain in machining are simulated. The different cutting thickness and cutting speed are analyzed. The effects of different tool angles on cutting force and cutting temperature are verified, and the feasibility of the simulation method is verified. The three-dimensional machining model of thin-walled plate is simulated by using the above method. All the models in this paper are based on the same materials. In the simulation process, the wear and deformation of the tool and the influence of the cutting fluid are not considered. Due to the rigidity of the thin-walled parts, it is easy to "make the knife" deform in the process of machining. Therefore, the machining models of thin-walled plate with "only bottom constraint" and "bottom and end face constraint" are simulated, and the machining error and the corresponding cutting heat are analyzed. Through simulation analysis, compared with the latter model, the thin-walled plate with only the bottom end constraint is more likely to produce cutting deformation, and the machining error is larger, and the machining deformation error decreases gradually from the top end to the bottom of the plate. And because of the comprehensive action of bending deformation at the upper end of thin plate and flexural deformation at both ends of the thin plate during the machining process, a "pit" region is finally produced in the middle of the bottom end of the thin-walled plate. The model with both bottom and end constraints produces the maximum machining deformation error in the middle of the thin-walled plate, and the error decreases gradually from top to bottom. At the end of this paper, The cutting process of the mirror frame step surface of a mirror seat component is simulated. The deformation error of the machining surface is drawn into a curve, and the results are compared with the experimental results. The results show that ABAQUS/Explicit can effectively simulate the machining of thin-wall parts by finite element method.
【学位授予单位】：武汉理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TG506
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本文编号：1657229