模具参数对304不锈钢圆筒拉深件残余应力的影响

发布时间：2018-03-22 16:53

本文选题：残余应力　切入点：切环试验　出处：《湘潭大学》2014年硕士论文　论文类型：学位论文

【摘要】：残余应力直接影响工件的疲劳强度、动载强度、静载强度、断裂韧性、尺寸稳定性及抗腐蚀开裂等性能。在加工或使用过程中，残余应力还可能使工件产生很大的变形，给零件的装配和修理带来相当大的影响。因而残余应力问题日益引起人们的高度重视，减小和消除残余应力的研究具有非常重要的意义。本研究首先开发了一种计算环向残余应力的新型理论模型，并通过ABAQUS有限元软件模拟圆环闭合验证了此理论的可行性和正确性。然后使用厚0.94mm的304不锈钢板在四种不同拉深间隙（C0.9mm、C1.0mm、C1.1mm和C1.2mm）和四种不同凹模口部圆角半径（R3mm、R5mm、R7mm和R9mm）等模具参数下拉深获得圆筒件试样，共7组，，每组拉深3个，总共21个圆筒件，在这21个圆筒件上切环，并将环沿径向剖分张开，测出切环的张开角度代入理论模型计算出圆筒件筒壁的环向残余应力。最后使用ABAQUS有限元软件模拟了7组304不锈钢圆筒件的拉深成形，得到各模具参数下拉深的304不锈钢圆筒件筒壁的残余应力。研究结果表明： 1）304不锈钢圆筒拉深件筒壁的环向残余应力很大（外表面最大为801MPa，内表面最大为-823MPa），且筒壁中部的环向残余应力比口部的大。 2）凹模口部圆角半径的大小对304不锈钢圆筒拉深件筒壁环向残余应力几乎没有影响；304不锈钢圆筒拉深件筒壁环向残余应力先随着拉深间隙的增大而增大，但当拉深间隙增大到大于1mm时，筒壁环向残余应力几乎保持不变。理论计算的304不锈钢拉深圆筒件筒壁环向残余应力比模拟的大得多，其原因可能有： 1）由于304不锈钢在拉深过程中会发生马氏体相变。马氏体的密度比奥氏体的小，因此在马氏体相变过程中会发生体积膨胀，从而加大了304不锈钢圆筒拉深件中筒壁的环向残余应力。但在ABAQUS有限元软件模拟304不锈钢圆筒件拉深成形中，没有考虑此相变产生的残余应力。 2）材料模型是一个很大的不确定因素。本文中有限元模拟采用Mises各向同性等效强化模型，这样的Mises屈服面和材料的真实屈服面存在一定差异。 3）由于拉深过程中的间隙偏小，模具对筒壁的挤压使得筒壁内部的环向残余应力有时候比筒壁表面的环向残余应力大，因此就加大了理论的计算值。
[Abstract]:The residual stress directly affects the fatigue strength, dynamic load strength, static load strength, fracture toughness, dimensional stability and corrosion cracking resistance of the workpiece. The problem of residual stress is paid more and more attention to, and the study of reducing and eliminating residual stress is of great significance. In this study, a new theoretical model is developed to calculate the toroidal residual stress. The feasibility and correctness of the theory are verified by the simulation of ring closure by ABAQUS finite element software. The 304stainless steel plate with thick 0.94mm is then used in four kinds of deep drawing gap (C 0.9mm C 1.0mm C 1.1mm and C 1.2mm) and four kinds of different die orifice radius: r 3mm, R 5mm, R 7mm and R 9mm). Equal die parameters pull down depth to obtain cylinder sample, A total of 7 groups, each group drawing 3, a total of 21 cylinders, cut the ring on the 21 cylinder, and open the ring along the radial section, The annular residual stress of cylinder wall was calculated by using the theoretical model to measure the opening angle of tangent ring. Finally, seven groups of 304 stainless steel cylinder drawing were simulated by using ABAQUS finite element software. The residual stress of 304 stainless steel cylinder wall with various die parameters is obtained. The results show that:. 1the circumferential residual stress of stainless steel cylinder drawing is very large (the maximum of outer surface is 801MPa, and the maximum of inner surface is -823MPa), and the circumferential residual stress in the middle of the cylinder wall is larger than that in the mouth. 2) the radius of the corner of the die has little effect on the annular residual stress of 304 stainless steel cylinder drawing cylinder wall, and the annular residual stress of 304 stainless steel cylinder drawing part increases with the increase of the drawing gap. However, when the deep gap increases to greater than 1mm, the annular residual stress of the cylinder wall remains almost unchanged. The theoretical calculation of the annular residual stress of 304 stainless steel drawing cylinder wall is much greater than that of the simulation. The reasons may be as follows:. 1) since martensite transformation occurs in 304 stainless steel during drawing, the density of martensite is smaller than that of austenite, so volume expansion will occur during martensite transformation. Thus the circumferential residual stress of 304 stainless steel cylinder drawing is increased, but the residual stress generated by this phase transformation is not taken into account in the simulation of 304 stainless steel cylinder drawing with ABAQUS finite element software. 2) the material model is a big uncertain factor. In this paper, the Mises isotropic equivalent strengthening model is used in the finite element simulation. There is some difference between the Mises yield surface and the real yield surface of the material. 3) due to the small gap in the drawing process and the extrusion of the cylinder wall by the die, the circumferential residual stress in the cylinder wall is sometimes larger than that on the surface of the cylinder wall, so the theoretical calculation value is increased.
【学位授予单位】：湘潭大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TG386.32

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