【作者】 王昊；

【导师】 孙玉文；

【作者基本信息】 大连理工大学 ， 机械工程（专业学位）， 2018， 硕士

【摘要】 随着航空航天、能源动力和精密仪器等领域的发展,薄壁零件的使用量大幅增加,精度要求也不断提高。由于薄壁零件自身的结构刚度差,切削加工过程中,其在夹紧力、切削力和残余应力等因素的作用下会产生较大变形,零件的加工精度往往难以保证。而纯铁材料作为一种难加工材料,本身的切削加工性较差,导致纯铁薄壁零件的精密加工问题长期无法得到解决,制约了相关行业的应用和发展。因此,围绕纯铁薄壁零件的精密加工问题,采用有限元仿真等技术手段,研究加工过程,优化加工工艺,对纯铁薄壁零件加工精度的提高有着重要的理论意义和实用价值。本文以纯铁薄壁曲面回转类零件为对象,针对其车削加工变形问题,采用有限元分析和切削实验等方法,考虑切削力、装夹力以及残余应力等多种影响因素,对薄壁回转件车削加工过程中的变形问题进行了研究,以揭示各因素对加工变形的影响规律,并据此优化加工工艺。具体研究工作如下:基于大型通用有限元软件ABAQUS建立了弹性工件—夹具接触模型,预测了纯铁薄壁壳体的装夹变形。以相同装夹条件下的装夹变形最小为目标,对提出的不同装夹方案进行了优选。考虑定位面不同轮廓形式,对定位面存在平面度和平行度误差情形时的装夹变形进行了分析,并提出了相应的改进建议。研究了金属切削仿真的关键技术,并以此为基础,建立了三维热力耦合切削仿真模型,模拟了纯铁材料切削加工带状切屑成型过程,对加工过程的切削力以及产生的残余应力进行了预测,基于仿真结果对纯铁材料切削加工的特点进行了研究,验证了切削变形理论。基于映射法预测构件整体变形的基本原理,考虑薄壁复杂曲面回转构件加工过程中由相关参数变化引起的应力场的非均匀性,通过多维插值重构了非均匀残余应力场,建立了非均匀应力场下工件整体变形预测模型。借助ABAQUS二次开发功能,利用该模型对薄壁曲面回转构件车削加工变形进行了准确预测。对纯铁材料进行了车削实验,利用Kistler切削力测试系统测试了纯铁车削加工过程中的切削力,利用Prism残余应力测试系统测试了纯铁切削加工表面沿层深的残余应力分布,并与仿真结果进行对比,验证了三维热力耦合切削仿真模型的准确性。更多还原

【Abstract】 With the development of aerospace,energy and precision instruments,the use of thin-walled parts has increased significantly,and the accuracy requirements have also been improved.Because of the weak structural stiffness of the thin-walled parts,large deformation will be produced by the factors such as clamping force,cutting force and residual stress in the process of cutting,and the machining precision of the parts is often difficult to guarantee.As a difficult-to-machine material,pure iron has poor machinability,and the precision machining of pure iron thin-walled parts cannot be solved for a long time,which restricts the application and development of the related industries.Therefore,around the precision machining of pure iron thin-walled parts,the finite element simulation and other technical means are used to study the machining process and optimize the machining technology.It has important theoretical and practical value for the improvement of the machining precision of the pure iron thin-walled parts.In this paper,thin-walled revolving part of pure iron is taken as the object.In order to reveal the influence of various factors on the machining deformation and optimize the processing technology according to this,in view of the problem of turning deformation,considering cutting force,clamping force and residual stress,the finite element analysis and cutting experiments are adopted to study the problems of the deformation in the turning process of the thin-walled revolving part.The specific research work is as follows:Based on large general finite element software ABAQUS,the elastic contact model of workpiece and fixture is established,and the clamping deformation of the thin-walled shell of pure iron is predicted.With minimum clamping deformation under the same clamping condition as the goal,different clamping schemes proposed are optimized.Considering the different profile of locating plane,the clamping deformation when locating plane has flatness and parallelism error is analyzed,and the corresponding improvement suggestions are put forward.The key technology of metal cutting simulation is studied.On the basis of this,a simulation model of three-dimensional thermomechanical coupled cutting is established.The cutting process of continuous chip forming of pure iron is simulated,the cutting force and the residual stress in the process are predicted.Based on the simulation results,the characteristics of pure iron material cutting are studied,and the theory of cutting deformation is verified.Based on the basic principle of deformation prediction by mapping method,considering the nonuniformity of the stress field caused by the change of the related parameters in the machining process of the thin-walled complex curved surface,the non uniform residual stress field is reconstructed by multidimensional interpolation,and the prediction model of the global deformation of the workpiece under the non-uniform stress field is established.With the help of the secondary development function of ABAQUS,the model is used to predict the turning deformation of the thin-walled revoving part.The turning experiments of pure iron material are carried out.The cutting forces in the turning process of pure iron are tested by the Kistler cutting force test system.The residual stress distributions along the depth of the pure iron cutting surface are tested by the Prism residual stress testing system and compared with the simulation results.The accuracy of the three-dimensional thermomechanical coupled cutting simulation model is verified.更多还原