共查询到18条相似文献,搜索用时 127 毫秒
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低频振动塑性成形粘弹塑性模型的体积效应分析 总被引:1,自引:0,他引:1
采用Kirchner对应变时间历程的基本假设,针对振动拉伸建立一个一维粘弹塑性模型;利用MATLAB中的符号计算,推导粘弹塑性本构方程的显式表达式.通过确立粘弹塑性边界并对本构方程进行数值求解,可以确定金属在振动加工过程中,其应力应变在粘弹性与粘塑性之间的变化情况.通过计算瞬时应变的大小与屈服限建立粘弹性变形和粘塑性变形的判断准则.在考虑粘弹塑性本构关系中的后继屈服情况、应变历程、应变率历程及弹性应变等因素后,可以确定单轴振动拉伸时材料变形的动态应力和平均应力.根据所给定的振型参数和材料力学性能参数,结合特定的振动拉伸实例,分别得出金属在准静态拉伸和振动拉伸时的动态应力-时间、动态应力-应变和平均应力-应变率的变化趋势等,实现基于粘弹塑性本构关系的低频振动塑性成形的体积效应机理分析. 相似文献
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碰撞激发弹粘塑性波传播的动态子结构方法 总被引:1,自引:0,他引:1
基于固定界面模态综合法,将柔性结构划分为多个子结构,采用添加-删除技术处理接触约束,建立柔性结构弹粘塑性碰撞动态子结构模型。考虑冲击载荷作用下出现的材料的应变率效应,采用Cowper-Symonds本构关系,推导柔性结构在模态坐标下的碰撞动力学方程,提出柔性结构碰撞弹粘塑性波传播的动态子结构方法,并通过理论证明主模态的存在性和主模态截断的收敛性。运用该方法分析直杆纵向碰撞和简支梁横向碰撞问题,计算结果表明,弹粘塑性波的传播速度,超应力效应,以及超应力幅值逐步衰减等波传播特征,均符合弹粘塑性波的理论特征。同时,通过将碰撞力和弹粘塑性波的数值计算结果与三维动力有限元解进行对比,验证了该方法的数值收敛性和计算碰撞弹粘塑性波传播的有效性。 相似文献
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刚性质量对自由梁的弹粘塑性次撞击 总被引:2,自引:0,他引:2
采用过应力模型,考虑局部撞击接触变形和自由梁动力响应中的材料应变率效应,提出能够考虑多次撞击接触行为的单轴压缩弹粘塑性局部接触变形模型,并结合有限差分方法和撞击与分离条件,研究刚性质量水平撞击弹粘塑性自由梁的全过程。研究发现,该水平撞击过程实际上是一个复杂的弹粘塑性次撞击过程,梁材料的应变率效应在局部接触变形行为和自由梁的动力响应行为中有着显著的作用,导致撞击力幅值、弹性变形和塑性变形等发生明显的变化。通过与三维动力有限元法的计算结果的比较表明,所提方法是合理的。 相似文献
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利用磁性测量仪FMP30测量不同塑性应变量下S30408板状拉伸试件形变马氏体体积分数,确定形变马氏体体积分数与塑性应变的关系.测量某低温液体半挂车罐体内容器碟形封头上各区域的形变马氏体体积分数,并对马氏体体积分数沿经向的分布规律进行简化,据此推算封头各部位加工历史造成的塑性应变.根据封头各部位的塑性应变确定考虑加工历史时各部位材料的应力应变曲线,并通过非线性有限元计算确定结构的极限承载能力.与不考虑加工历史仅考虑真应力应变关系以及不考虑材料强化仅按弹性理想塑性材料计算的结果相比,得到以下结论:对于S30408碟形封头,考虑材料应变强化特征计算得到的垮塌载荷与极限载荷均明显高于按弹性理想塑性模型计算的结果.加工历史造成的应变强化对结构的垮塌载荷影响不大,但对按双切线法确定的极限载荷影响较大,可较明显地提高结构的极限载荷. 相似文献
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提出一种对单晶体热-粘塑性力学行为的分析方法.该方法跟随加载路径对考虑变温过程的单晶体粘塑性构形演化进行增量计算,而用Hencky对数弹性应变在卸载构形的基础上来计算总量的应力;在对滑移系增量分切应力、分切应变及硬化函数的增量非线性本构关系的计算过程中采用泰勒展开得到了便于求解的线性方程组,同时得到了用于计算有限元刚度矩阵的本构矩阵,该格式在本构计算时不需进行迭代因而有较高的计算效率. 相似文献
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振动拉伸的弹粘塑性模型 总被引:6,自引:0,他引:6
基于弹粘塑性本构关系 ,讨论了附加振动时单轴拉伸的应变及应力变化过程。分析结果表明 ,本文所给出的力学模型 ,再现了振动拉伸过程中的应力超调及平均应力降低等现象 相似文献
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Michael P. Zabinski 《International Journal of Mechanical Sciences》1971,13(12):1011-1024
An analysis of the dynamic problem of a hollow sphere is presented. The medium is assumed elastic/viscoplastic, satisfying Mises condition, isotropic hardening and viscoplastic incompressibility. The cavity is subjected to a radially applied and continuously maintained impact load. The analysis for viscoplastic waves is based on the method of characteristics and a generalized form of Malvern's theory for strain-rate dependent materials. A bilinear shear stress-shear strain curve is considered and calculations are carried out on the IBM 7094 computer. The paper examines the influence of the important parameters governing spherical wave propagation on the response of the sphere; these parameters include the level of strain hardening, the viscosity coefficient, Poisson's ratio and the geometry of the sphere. It is shown that the degree of strain hardening has a significant effect on the amplitude of the oscillations with the period unaffected. The viscosity coefficient becomes more influential as the wall thickness of the sphere increases. 相似文献
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Yoshihiro Tomita Akio Shindo Tomoki Sasayama 《International Journal of Mechanical Sciences》1990,32(7)
The thermocoupled flow localization of plane strain tension blocks has been investigated. These blocks have a relatively low strain rate sensitivity and comply with an elasto-viscoplastic constitutive equation which has a viscoplastic strain rate noncoaxial with the stress tensor. Attention has been paid to deformations with a strain rate in the range of 0.02–2000/s under isothermal, conductive and adiabatic conditions. A full plane strain finite element analysis of the velocity and temperature fields has partially clarified the effects of the deformation rate, material strain rate sensitivity, thermal conductivity and size of the blocks on flow localization, including the shear band type of flow localization. 相似文献
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电子封装SnPb钎料和底充胶的材料模型及其应用 总被引:6,自引:1,他引:5
采用统一型粘塑性Anand模型描述SnPb钎料的非弹性力学行为,基于试验数据和弹塑性蠕变本构模型,确定了92.5Pb5Sn2.5Ag和60Sn40Pb两种钎料Anand模型的材料参数。采用线性粘弹性Maxwell模型,描述了一种倒装焊底充胶U8347-3材料的模量松弛和体积松弛,得到了相应的松弛参数,研究对所给出的材料模型和参数进行了验证。另外,利用有限元法模拟了倒装焊在热循环条件下的应力应变行为,分析了SnPb焊点的塑性应变和热循环寿命。结果表明,采用上述材料模型和参数,可以合理描述SnPb钎料和底充胶的力学本构,并可应用于电子封装的可靠性模拟和分析。 相似文献
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弹/粘塑性材料成形的变形力计算 总被引:1,自引:0,他引:1
用特征值方法证明了材料在弹性与粘塑性变形时平面主应力方向的一致性;引入了一种坐标变换的三参数σm、μσ、J′,结合Laplace变换,有效地分析了弹/粘塑性材料按平面计算成形的变形力。文中用矩形条料的压缩为例说明这一求解过程。 相似文献
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Void growth and coalescence in ductile materials deformed at elevated temperatures is analyzed by finite element calculations and by an analytical approach. The void growth model is based on an extension of Gurson's model to elastic–viscoplastic materials. Coalescence is treated as transition to uniaxial straining in the intervoid ligament by micromechanical analysis. A very simple closed form for the stress in the intervoid ligament at coalescence is given. This closes the micromechanical analysis. Finally, a heuristic estimate (based on the finite element analysis) for the overall strain at void coalesce is given. 相似文献
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R.I. Nepershin 《International Journal of Mechanical Sciences》1997,39(8):899-912
An analysis of the plane rigid—plastic flow of a thin layer compressed by flat rigid dies coupled with the heat transfer in the die-layer system is considered. The numerical model of the thin layer compression includes non-homogeneous plastic dissipation rate, heat flux of the contact friction and thermal resistance of the die-layer interface boundary. The rigid—viscoplastic relation of the effective yield stress with accumulated plastic strain, effective strain rate and temperature is assumed for the layer. The effects of the contact friction, thermal resistance and the die velocity on the hot compression of the thin steel workpiece are investigated. 相似文献
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A thermo-elastic–viscoplastic model using explicit finite element code Abaqus was developed to investigate the effect of sequential cuts and tool–chip friction on residual stresses in a machined layer. Chip formation, cutting forces and temperature were also examined in the sequential cuts. The affected layer from the first cut slightly changes the chip thickness, cutting forces, residual strain and temperature of the machined layer, but significantly affects the residual stress distribution produced by the second cut. Residual stress is sensitive to friction condition of the tool–chip interface. Simulation results offer an insight into residual stresses induced in sequential cuts. Based on simulation results, characteristics of residual stress distribution can be controlled by optimizing the second cut. 相似文献