扁球壳体的整体无模成形理论与实验

对不同轴比和不同瓣数的不锈钢扁球壳体进行了整体无模胀形成形实验研究及理论探讨。首先介绍了壳体成形的几何调节原理和材料调节原理 ,讨论了扁球壳体的应力分布特点和塑性变形顺序。对实验壳体的尺寸变化、变形过程中的内外表面应变分布、变形前后的壁厚变化规律进行了测试分析 ,探讨了各种壳体的趋球变形过程 ,壳体的长短轴变化趋势及塑性变形规律。实验证明 ,在封闭扁球壳体内塑性趋球规律仍然起作用 ,扁球无模液压整体成形是一项有发展前途的新工艺     

椭球壳体无模液压成形实验探索

对椭球壳体的整体无模胀形成形工艺进行了实验研究。实验壳体采用单曲率椭球内接多面壳体。对实验壳体的尺寸变化、变形过程中的表面应变分布、变形前后的壁厚变化规律进行了测试分析，探讨了壳体的趋球变形过程，壳体的长短轴变化趋势及塑性变形规律。实验证明，在封闭椭球壳体内塑性趋球规律仍然起作用，椭球无模液压整体成形工艺值得进一步探讨研究。     

中厚板球形容器成形新方法的模拟研究(Ⅱ)——中厚板角焊缝反弯曲拉伸的实验研究

为研究新型球形容器成形技术中整体成形对近焊缝区变形及其金属组织的影响。本文首次采用中厚板低碳钢角焊缝反弯曲试样模拟结构的变形与硬度分布、金相组织,焊条组配类型之关系。通过对板厚为4mm,8mm,16mm,24mm试样的实验研究,认为焊缝的强度和性能及塑性变形可以满足工艺的要求。     

板料成形拉延筋技术研究现状

拉延筋在汽车覆盖件拉深成形中起着十分重要的作用。利用拉延筋可以调节和控制板料的变形程度和变形分布,抑制破裂、起皱、面畸变等多种冲压质量问题的产生。在很多情况下,拉延筋的设置合理与否将决定覆盖件拉深的成败。较系统地总结了板料成形拉延筋技术以及拉延筋作用原理、阻力模型、影响因素等的研究现状。     

板材激光弯曲成形数值模拟的研究现状及展望

板材的激光弯曲成形是一种利用高能激光束扫描金属板材表面产生非均匀分布的热应力 ,从而使板材发生塑性变形的金属板材柔性成形新工艺。数值模拟已逐渐成为板材激光弯曲成形研究中的热点内容。综述了近年来国内外对激光弯曲成形过程的温度场及变形场进行数值模拟的研究现状 ,并对其应用范围和发展前景作了展望     

型材压弯变形力的计算

目前角钢和型钢压弯、压凹时的变形力多根据经验确定,笔者由功的平衡原理出发,考虑其变形时的应力状态,得出型材在压弯成形时的精确变形,并对所得数学式进行试验验证,二者结果十分接近,该式有很好的推广应用价值。     

端盖精密成形的有限元模拟

采用有限元 (FEM)的方法对分流法精密成形端盖进行了计算机模拟 ,对坯料成形载荷 行程曲线、应力、模具的弹性变形等参量进行分析得出 :分流法是一个降低变形抗力和模具弹性变形 ,适于精密成形的有效的方法     

冲击载荷下螺栓预紧力对应力波影响分析

目的 研究拉伸冲击载荷作用下螺栓预紧力对应力波的影响.方法 针对螺栓弹性变形、塑性变形和冲击破坏3种情形,对螺栓未施加预紧力及施加不同预紧力下的连接结构进行冲击数值模拟,对比分析连接结构的测点应变及螺栓响应,并与霍普金森拉伸实验结果进行对比.结果 螺栓达到断裂或塑性变形时,预紧力对测点应变及螺栓最大应力影响较小;螺栓弹性变形时,预紧力对测点应变及螺栓最大应力影响较大.结论 螺栓达到断裂或塑性变形时,螺栓拉伸变形远大于预紧力变形,此时预紧力影响可忽略;螺栓在弹性变形时,螺栓拉伸变形与预紧力变形程度接近,此时预紧力影响不可忽略,且预紧力越高,螺栓变形越大.     

分子动力学中应变分析的统计矩方法及应用

分子动力学模拟研究金属的力学性质,需要采用合适的应变分析方法研究金属的变形特征及其演化规律.金属材料复杂变形的局部应变特征缺乏简便有效的分析手段,整体变形也没有合适的描述方法.本文提出分子动力学中应变分析的统计矩方法,通过统计矩建立了微观量和宏观应变的关联.在单晶单轴加载、纳米多晶剪切和冲击加载下的应用表明,矩应变分析方法可以很好的描述和评估材料的局部变形和整体变形特征,并通过应变不均匀度鉴别材料的局部塑性变形和弹性变形,是深入研究复杂结构材料变形机理的一种有效的通用分析方法.     

原油储罐应力及风险分析

针对某油库6#储罐,采用ANSYS建立有限元模型,对其罐壁板单元进行网格划分,对比分析了满载时罐体未变形及变形两种情况的应力分布,通过变形罐体的应力云图可以看出该储罐罐体已经产生变形,且局部变形比较严重。变形前后应力数据显示罐体多处已经处在材料屈服极限范围内,甚至接近于屈服极限上限290 MPa,具有一定危险。提出应及时检测其它储罐,并采取相应措施防止罐体出现较大变形。     

板料冲压成形和回弹分析过程的三维动态模拟

利用ANSYS/LS DYNA非线性动力有限元程序的显式 隐式连续求解功能 ,模拟了板料成形过程与卸载后板料回弹变形的全过程 ,得到了成形过程中任一时刻各处的应力和应变值及卸载后板料的回弹结果     

连接管件的先进塑性成形技术试验研究

介绍了 3种先进的连接管件成形技术 ,即小弯曲半径管内压推弯成形技术、球形管接头的胀形成形技术和管件的内径滚压成形技术 ,对其基本成形过程进行了描述 ,并通过铝合金、不锈钢和钛合金管件的成形试验获得了主要工艺参数对成形的影响规律 ,结果表明采用这些方法成形所需的连接管件是非常有效的     

板料成形有限元分析的牛顿一致迭代算法

此文针对塑性成形有限元分析大增量加载的收敛性困难,推导了用于板料成形弹塑性有限元分析的牛顿一致迭代公式.数值算例表明,此迭代算法对于大增量步长加载,也能保证解的收敛,是无条件稳定的.     

Prediction of flange wrinkling in deep drawing process using bifurcation criterion

Surface distortions in the form of wrinkles are often observed in sheet metals during stamping and other forming operations. Because of the trend in recent years towards thinner, higher-strength sheet metals, wrinkling is increasingly becoming a more common and troublesome mode of failure in sheet metal forming. The prediction and prevention of wrinkling during a sheet forming process are important issues for the design of part geometry and processing parameters. This paper treats the phenomenon of flange wrinkling as a bifurcated solution of the equations governing the deep drawing problem when the flat position of the flange becomes unstable. Hill’s bifurcation criterion is used to predict the onset of flange wrinkling in circular and square cup drawing. In particular, the maximum cup height that can be drawn without the onset of flange wrinkling is predicted for the given set of process parameters. A parametric study of the maximum cup height is also carried out with respect to various geometric, material and process parameters. Finite element formulation, based on the updated Lagrangian approach, is employed for the analysis. The incremental logarithmic strain measure, which allows the use of a large incremental deformation, is used. The stresses are updated in a material frame. The material is assumed to be elastic–plastic, strain hardening, yielding according to an anisotropic yield criterion of Barlat et al. (2005) [23] (named as Yld2004-18p). Isotropic power law hardening is assumed. Inertia forces are neglected due to small accelerations. Modified Newton–Raphson iterative technique is used to solve the nonlinear incremental equations.     

Springback control of sheet metal air bending process

Press brake bending is a commonly used process for sheet metal part fabrication. It has been observed that the final bend angle, which is the angle achieved upon removal of the punch, is smaller than the initial bend angle. This springback is due to the elastic recovery of the sheet metal. Various theoretical models have been proposed to predict the springback using the tooling geometry and the known properties of the sheet metal. However, in a production environment, the actual properties of any given workpiece may vary from the nominal properties of the lot. This variation causes the actual springback to deviate from the theoretical predictions. This paper presents a practical incremental bending methodology to control punch displacement to achieve more accurate final bend angles. In the proposed approach, workpiece properties are estimated from measured loaded and unloaded bend angles. The estimated properties are used to determine the final punch position required to obtain the desired bend angle after springback. A series of bending experiments was performed. It was found that the proposed method can better predict springback and effectively control the bend angle variation in a production environment.     

板材成形新技术及其发展趋势(Ⅰ)

近些年来,面对全球化的竞争,越来越需要小批量、多样化、周期短的新的成形技术.薄板成形技术在成形工艺中占有很重要的地位,其多样化趋势已经变得越来越明显,出现了多种加工方法,它对将来的工业结构和产品的生产技术将是一场革命.文中介绍了变压边力技术、成对液压成形技术、粘介质成形技术、无模分层成形技术等几种柔性化程度高的板材成形技术及其发展趋势.     

端头多半圆弯曲工艺改进与模具设计

端头多半圆弯曲件比较常见,但质量难以保证。此文通过对成形弯曲工艺的分析,提出了改进措施,并介绍了两种典型模具结构,及其零部件的设计。     

小曲率轿车覆盖件拉深模设计

在分析小曲率轿车覆盖件成形特点的基础上,指出采用阶梯拉深是提高材料塑性变形、减少回弹的有效措施,以一个典型零件前盖外板为例,设计了其拉深工艺补充面,并给出了有限元模拟结果以验证有效性。     

金属板材成形的静力隐式有限元分析与程序设计

阐述了用于板材成形过程静力隐式数值模拟的弹塑性大变形有限元方法 ,基于给出的方法编制了板材成形过程数值模拟软件 ,并对矩形板的液压胀形进行了有限元分析 ,计算结果与典型的实验结果吻合很好。对球形模具拉伸成形过程进行了数值模拟 ,给出了计算结果     

Modeling and validation of deformation process for incremental sheet forming

Incremental Sheet Forming (ISF) is an emerging sheet metal prototyping technology where a part is formed as one or more stylus tools are moving in a pre-determined path and deforming the sheet metal locally while the sheet blank is clamped along its periphery. A deformation analysis of incremental forming process is presented in this paper. The analysis includes the development of an analytical model for strain distributions based on part geometry and tool paths, numerical simulations of the forming process with LS-DYNA, and experimental validation of strain predictions using Digital Image Correlation (DIC) techniques. Three kinds of parts include hyperbolic cone, skew cone and elliptical cone are constructed and used as examples for the study. Analytical, numerical and experimental results are compared, and excellent correlations are found. It is demonstrated that the analytical model developed in this paper is reliable and efficient in the prediction of strain distributions for incremental forming process.