轴对称拉深成形法兰区起皱失稳变形能及临界压边力

在平面应变假设条件下,对轴对称拉深成形法兰区的起皱失稳问题进行了理论分析。首先采用数学方法,将以积分形式表示的应力解析式进行了简化。在此基础上,进一步简化了起皱过程中变形能的计算式。给出的算例表明,对起皱过程中的变形能分别以简化后的计算式和以原积分式进行计算,其结果误差很小,相对误差小于0.8%。该起皱失稳临界压边力的计算和分析简化方法有助于给出简明和符合实际的起皱判据。     

平面应力条件下轴对称拉深成形法兰区起皱和破裂分析

分别采用平面应力和平面应变假设条件,对轴对称拉深成形法兰区的应力分布进行了分析比较,两种情况下的径向应力计算值相差较小,但周向应力计算值相差较大。有限元模拟表明,平面应力条件下得到的解析结果与模拟值非常接近,表明平面应力假设条件比平面应变假设条件更接近于实际情况。在平面应力条件下,建立了轴对称成形法兰区起皱失稳条件和圆筒形件破裂失稳条件,导出了临界压边力的计算式。对于某一具体的拉深成形问题,计算得到了临界压边力与拉深位置的关系曲线。分析结果有助于进一步认识拉深成形各变形区的变形特点,建立更符合实际的起皱、破裂准则,预测成形缺陷及临界压边力。     

采用恒定压边力解决不锈钢拉深起皱问题

在拉深模具结构设计中,采用液压压边装置的恒定压边力有效地解决了不锈钢拉深起皱问题,保证了拉深零件的质量。     

拉深件起皱和破裂起因探讨

针对筒形拉深件起皱和破裂案例,分析了制件在拉深过程中出现起皱和破裂缺陷的原因,从而找到解决和防止各类拉深件破裂与起皱的措施,对拉深生产加工起借鉴和指导作用。     

法兰为整体拉深的矩形盒成形应力分析

为了有效预测矩形盒拉深中的成形力和压料力，在拉深试验和有限元数值模拟的基础上，将法兰直边、曲边作为变形整体进行了应力应变分析。给出极限拉深时板坯下料以及拉深力和压料力的近似计算公式，为进一步开展试验、数值模拟和理论解析提供相应的参考资料。     

薄壁盒形件法兰区起皱影响因素的有限元模拟研究

金属薄壁盒形件在拉深成形过程中,由于模具结构和工艺条件的影响,成形过程中法兰区常发生起皱现象,在生产实践中消除这些问题能够显著降低生产成本和提高产品质量。以NUMISHEET’93国际会议的标准考题之一薄壁方盒形件为例,使用有限元软件ABAQUS模拟研究了模具圆角、润滑条件、压边力,以及板坯形状等因素对法兰区起皱的影响规律,得到了一些改善方盒形件成形质量的工艺措施。     

有凸缘圆筒形拉深件起皱和拉裂的原因及控制方法

阐述了利用模具拉深有凸缘圆筒形件时,产生起皱和拉裂的原因。并提出相应的控制方法,希望能够对模具设计工作人员有一定的帮助。     

圆筒形件拉深失稳及各因素影响分析

对板料成形中圆筒形件拉深的破裂失稳及产生破裂失稳的临界压边力进行研究.由于凸、凹模圆角及其间隙的存在,圆筒形件拉深的筒壁区实际为凸、凹模圆角之间的公切线部分.根据Mises-Hill屈服函数及Tresca准则求出凸缘变形区、凹模圆角区和筒壁区的应力分布,得到危险断面处的应力表达式,从而求出不产生破裂失稳的临界压边力的解析表达式,并进一步分析获得拉深比、硬化指数、厚向异性系数、摩擦因数以及径向推力等因素对临界压边力的影响规律.采用液压压边与周缘加径向推力的拉深模具对08Al板料进行拉深试验,试验结果与理论计算结果具有很好的一致性.     

拉深工艺中脉动压边力控制方法

压边力是板料拉深成形过程的重要工艺参数之一 ,合理控制压边力的大小可避免起皱或破裂缺陷。采用脉动变化的压边力控制拉深工艺 ,可提高成形极限及拉深件的表面质量。本文采用数值模拟方法研究了脉动变化压边力的振幅、振频对成形的影响。     

拉深工艺变压边力控制数值模拟研究

根据实际生产中压边力的控制状况和理论分析确定了几种压边力变化曲线，以非轴对称抛物面车灯反光罩的成形为例，采用Dynaform软件对多种变压边力控制的成形工艺分别进行了数值模拟计算，分析了各种变压边力控制对成形的影响，并确定了对成形最为有利的压边力的变化趋势。     

圆筒件拉深过程中压边力的研究

利用恒定压边力经验公式计算得到的压边力值进行模拟时,圆筒件质量存在明显的缺陷。采用变压边力优化曲线作为圆筒件拉深成形的压边力加载模式,研究了临界防皱变压边力曲线的确定方法,应用Dynaform软件对恒定压边力、优化压边力下圆筒件的拉深成形进行了数值模拟,得出了成形极限图(FLD)和材料厚度变化图。将模拟结果进行对比分析,发现在后者作用下的圆筒件平面外缘厚度变化较小,筒壁等其他部分的材料厚度变化率也较小,采用优化压边力可有效防止圆筒件起皱、拉裂现象,提高圆筒件成形质量。     

An elastoplastic analysis of flange wrinkling in deep drawing process

The onset of flange wrinkling of a deep drawing cup is analyzed as an elastoplastic bifurcation problem. The flange is modeled as an elastoplastic annular plate subject to axisymmetric radial tension along its inner edge. As observed in the laboratory as well as practical industrial applications, aluminum alloy sheets usually wrinkle in the plastic range. Therefore, the critical condition governing the onset of elastoplastic wrinkling is formulated within the context of the general bifurcation theory. A closed-form solution for the critical drawing stress is developed based on an assumed nonlinear plastic stress field and the deformation theory of plasticity. The theory properly accounts for the plastic anisotropy of the aluminum sheets and the critical drawing stress at the onset of wrinkling is also compared against the one employing the flow theory of plasticity. The predicted critical bifurcation stress and the wave numbers are compared to those obtained by Senior's one-dimensional theory. It is demonstrated that there is a strong dependency of the critical bifurcated stress at the onset of wrinkling on the shear stress induced on the flange. The effects of flange width, drawing ratios, material properties, strain hardening on the onset of wrinkling are investigated. The differences between the present theoretical approach and Senior's theory are emphasized.     

充液拉深设备柔性控制系统的研究

针对充液拉深新工艺对设备的控制精度和操作灵活性的要求,对充液拉深控制系统的结构、压力控制和用户编程等关键问题进行了全面地研究。充液拉深控制系统采用了"高性能PLC+大屏幕触摸屏"的结构形式,以使加工过程可视化并支持用户编程技术。设计了压力闭环控制系统并采取了分段积分的控制算法,以解决电磁比例溢流阀单独使用时压力调节存在静差的问题。以高性能PLC为控制器,采用结构化编程和人机界面技术开发了支持用户编程的柔性控制系统,以满足新工艺对设备操作灵活性的要求。采用上述技术研制的多台充液拉深设备已投入实际生产。实践结果表明:设备压力控制的稳态精度和调节时间均满足要求,且用户可根据新工艺要求,灵活地设定手动调试操作和自动加工流程。     

板料拉深中压边力及其数值模拟技术的研究

描述板料拉深过程中最小压边力及压边力变化规律的确定方法,介绍国内外压边力控制技术研究进展及数值模拟技 术在优化压边力中的应用,指出了目前压边力研究存在的问题及未来的研究动向。     

The effect of normal stress on hydro-mechanical deep drawing process

Normal stress has some role in the deformation analysis of hydroforming processes. In this study, analytical modeling is pursued to evaluate the effect of normal stress on the hydro-mechanical deep drawing (HDD) process. Analyses are carried out for axisymmetric elements of the formed cup-shaped part for increments of the punch travel. The formulations are obtained using mechanical and geometrical relations and the finite difference method, thereby being solved by proper numerical algorithms. Furthermore, in the present work, part thickness is variable, the loading and straining are non-proportional, and bending/unbending effects over the part curvature are considered. The results show that there are some differences between thickness values, radial and circumferential strains and stresses, and punch force under plane stress and three-dimensional stress conditions. Thus, the normal stress should be considered in the design of HDD processes in order to improve accuracy.     

小盖拉深胀形镦压模具设计

小盖拉深胀形镦压模具是用来生产GHT6472盘式制动器轮廓组件上轴承的防尘盖零件．该零件虽然结构不复杂，但尺寸精度要求较高．给成形带来困难，为解决此问题，通过对零件的工艺分析、计算，零件拉深成形的特点分析，成形工艺的确定，胀形镦压的条件验算．进行了合理的模具结构设计。     

板料拉深成形摩擦系数测量系统

建立了一套基于自主开发的探针式组合传感器的摩擦系数测量系统，并将此传感器耦合到拉深凹模结构中，以此来实时测量板料法兰平面测量点处所受到的垂向正向压力和径向切向拉力，并根据计算公式μ（摩探系数）=P（切向拉力）／F（正向压力）直接计算出该测量点处的实时摩擦系数大小，进而通过选择几个特征点来推导出整个板料法兰平面的摩擦分布情况及其变化规律。最后实际试验数据证明，该系统能够真实地反映板料拉深成形过程中法兰平面亡的实际摩擦分布情况。     

Hydrodynamic deep drawing process assisted by radial pressure with inward flowing liquid

A radial pressure can reduce drawing force and increase drawing ratio in hydrodynamic deep drawing. However, conventional hydrodynamic deep drawing cannot attain a radial pressure higher than the pressure in the die cavity. In this research, a modified method, named hydrodynamic deep drawing assisted by radial pressure with inward flowing liquid, was proposed and investigated using both primarily experimental and numerical simulation analysis. A radial pressure higher than the pressure in the die cavity was realized by means of the inward flowing of the liquid during this process. After preliminary experimental validation, FEM was used to explore the forming process. The results from the simulation were compared with those from the experiment. The effects of the radial pressure on the wall thickness distribution, punch force, and compressive stress in the blank flange were studied with assistance of numerical simulation. The process window for radial pressures versus drawing ratios was established in 2Al2O alloy experimentally and cups with drawing ratio of 2.85 were successfully formed.