共查询到20条相似文献,搜索用时 164 毫秒
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采用圆锥形凹模拉深工艺可以提高成形极限,但需要用压边圈将板坯先压成与凹模面吻合的形状,当变形程度较大时,板坯很容易起皱。为了克服这一缺点,提出了将圆锥形凹模与径向分块压边方法结合的工艺,该工艺可有效改善压边圈与板坯的约束状态,从而达到抑制起皱的目的。对圆筒形件的拉深成形,采用了刚柔复合的径向分块压边圈结构,设计了圆锥形凹模径向分块多压边圈拉深模,取不同凹模半锥角的圆锥形凹模进行了圆筒形件的拉深成形实验。实验表明,新的压边方法能有效克服初始成形过程的起皱,可与锥度较小的凹模一起使用。采用凹模半锥角为45°的凹模,得到AA5754、AA6061和08Al三种板材的极限拉深系数分别为0.410、0.431、0.373,显著提高了成形极限。对圆锥形凹模的拉深成形,给出了理论计算成形极限的方法,理论与实验结果非常接近。 相似文献
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针对石油射孔弹挤压件,对一次挤压成形和先预挤压再终成形两种工艺进行了对比,确定了合理的工艺方案,模具结构采用预应力挤压组合凹模。采用拉丁超立方方法,分别对预挤压和终成形的组合凹模的径向直径比和过盈系数进行了抽样,应用有限元方法对抽样所得的不同结构进行数值模拟,将所得模拟结果作为响应,建立等效应力与组合凹模结构参数的Kriging模型。以降低凹模内壁最大等效应力为优化目标,分别对预挤压和终成形两个阶段的组合凹模结构参数进行了优化分析。应用Kriging模型结合粒子群算法,在结构参数的变量空间内进行全局寻优,得到了各组合凹模最佳的径向直径比和过盈系数,确定出优化的组合凹模结构尺寸,为该挤压组合凹模的设计提供了定量的优化依据。 相似文献
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多工步连续模是一种高效率、高质量、长寿命的先进模具,应用于大量生产小型冲压件,可以获得显著的经济效益,因而国内外都重视其设计和制造技术的研究。本文介绍国外一种新型设计系统——VSD(Versatile System of Design)的部分资料,可供研制多工步连续模的参考。一、VSD的实质多工步连续模VSD可应用于各种异形平片或成形冲压件。图1是一个例子。无论凸模、凹模用于冲裁或成形工序,也无论其工作部分形状是圆形还是非圆形,凸模、凹模的外形固定部分都加工成圆形。采用这种新型结构,凸模固定板、脱料板和凹模固定板均只需加工圆形安装孔,保证孔距与孔径精度,使加工难度大为降低。这样,高精度多工步连续模的制造难度就集中在 相似文献
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在单点渐进成形技术中,刀具路径是加工时刀具在空间中的运动轨迹。本文使用有限元分析软件ANSYS/LS—DYNA模拟了刀具路径对渐进成形过程的影响。模拟结果表明:当刀具四点压下时,模拟的轮廓曲线对称性最好,底面上凸的幅度较小;同时,板材的最大等效应变和主要变形区节点的塑性应变较小,板材连续逐层变形能力较好。 相似文献
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A contribution on the optimization strategies based on moving least squares approximation for sheet metal forming design 总被引:1,自引:0,他引:1
Giuseppe Ingarao Rosa Di Lorenzo 《The International Journal of Advanced Manufacturing Technology》2013,64(1-4):411-425
Computer-aided procedures to design and optimize forming processes are, nowadays, crucial research topics since industrial interest in costs and times reduction is always increasing. Many researchers have faced this research challenge with various approaches. Response surface methods (RSM) are probably the most known approaches since they proved their effectiveness in the recent years. With a peculiar attention to sheet metal forming process design, RSM should offer the possibility to reduce the number of numerical simulations which in many cases means to reduce design times and complexity. Actually, the number of direct problems (FEM simulations) to be solved in order to reach good function approximations by RSM is a key aspect of their application in sheet metal forming operations design. In this way, the possibility to build response surfaces basing on moving least squares approximations (MLS) by utilizing a moving and zooming region of interest can be considered a very attractive methodology. In this paper, MLS is utilized to solve two optimization problems for sheet metal forming processes. The influence on the optimization results was analyzed basing on MLS peculiarities. The idea is to utilize these peculiarities and make the MLS approximation as flexible as possible in order to reduce the computational effort of an optimization strategy. An innovative optimization method is proposed and the results show it is possible to strongly reduce the computational effort of sheet metal forming processes optimization. In particular, the advantages, in terms of computational effort reduction, with respect to classical RSM approaches have been demonstrated and quantified. 相似文献
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板料柔性成形是基于产品的数字化信息,由产品的三维CAD模型直接驱动,通过高度可调的基本体构成包络面,实现三维曲面零件成形的技术。典型的板料柔性成形方法是增量成形与多点成形。增量成形通过一个成形工具头沿x、y轴方向的运动及z轴方向的进给,逐层形成零件的三维包络面,从而实现板料的渐进成形;多点成形的核心是规则排列的基本体阵列,通过控制基本体z方向的位置坐标使其构成所需包络面,进行板料快速成形。介绍了以数控多点柔性成形新工艺进行新产品开发试制的应用。 相似文献
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遥感相机焦面CCD机械拼接中重叠像元数的确定 总被引:6,自引:4,他引:2
针对推扫式遥感相机前后摆成像中焦面拼接的CCD其像片间出现视场漏缝的问题,提出了一种焦面CCD的非均匀重叠像元数机械拼接方法.首先,构造了相机前后摆的成像原理模型;接着,分析了CCD间产生地面视场漏缝的原因,并依据模型推导出相机前摆和后摆时各CCD视场间漏缝大小的数学公式,从而得到各片间容许的最少重叠像元数量公式.在此基础上,进一步给出了后续电子学图像拼接与配准中片间重复像元数的函数形式,为实现图像无缝拼接提供了软件实现依据.分析表明,该方法的理论误差ε小于一个像元尺寸,即|ε/D|<1.最后,给出了工程应用实例. 相似文献
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金属板料渐进成形有限元仿真过程中复杂成形路径的构建方法 总被引:3,自引:0,他引:3
提出一种用于获得复杂空间运动轨迹的方法——虚拟靠模导向法。该方法借鉴了数控加工中COPY铣的思想,利用轨迹生成球在由零件派生出的虚拟靠模表面上的持续运动来模拟实际成形工具的运动过程,从而获得最终成形路径。基于该思想和简单的运动学原理,轨迹球与虚拟靠模有限元模型被构建起来。通过对计算过程进行分析,确定运用该法时适合的加载力、成形速度及计算精度的影响因素。因该法完全基于有限元模拟计算,故获得的成形路径可直接导入至后续的金属板料成形过程的模拟分析。该法已在有限元软件PAMSTAMP平台上得以实现,并主要用于金属板料渐进成形过程的有限元仿真。 相似文献
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介绍了一种新型差动电容式传感器及其构成的控制系统。这种传感器由两片固定金属极板和一片可动极板形成差动式电容结构,在微小偏移作用下,通过动极板引起极板之间电容参数值的变化,进而实现对卷绕机微小偏移量的测量和控制。该控制系统结构简单,反应迅速,能够较好地应用于卷绕机纠偏装置中。 相似文献
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Since plane air bending of slender parts, controlled only by the motion of both end supports has been established as a feasible metal forming process from the theoretical, experimental and technological point of view the fundamentals shall now be elaborated also for the corresponding spatial forming process. After presenting the basic kinematic relations the resultant forces and moments, acting on the material cross sections are introduced as generalized stresses producing work against the associated generalized strain rates. The equilibrium and the incremental compatibility conditions are formulated mutually with a generalized elastic–plastic constitutive law. Limitations to the forming process due to hurting the yield condition are also discussed. As a special event the deformation of the Bernoulli beam is examined, particularly due to moving yield hinges. The general theory is illustrated as the example of forming a helicyclic spiral. 相似文献
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A communication instrument has been developed for use by a quadriplegic person who is limited solely to eye motion as a control input. The instrument uses an infrared-emitting diode/phototransistor sensor mounted on the frame of a pair of eyeglasses to transform deliberate lateral eye motion into a contact-closure output form. A software program has also been developed for use with this instrument to display letters of the alphabet in a series of six lines. The lines are slowly scrolled until the desired line is reached, then stopped by a lateral eye motion. The scrolling then continues for each character in that line until the desired character is reached. Again, lateral eye movement causes the scrolling to stop and the character becomes part of a string. This process continues until a command character is selected whereby the string can be sent to a printer, spoken through a speech synthesizer, or erased. 相似文献
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一种求解6-3构型并联机器人机构位置正解的逼近算法 总被引:3,自引:0,他引:3
根据机构运动的同一性原理 ,给出一种求解 6 - 3构型并联机构位置正解的杆长逼近算法。该算法的主要特点是通过逐步自动修正迭代初值、缩小搜索区间和步长、提高逼近精度 ,将二维搜索的杆长逼近简化为一维搜索的杆长逼近。因此只要在分支的有效活动区域内任选初值 ,即可保证其收敛性并且不受机构奇异位形的影响 ,大大简化了搜索逼近过程并提高了迭代效率。文中给出了求解过程和逼近步骤及求解实例 ,其逼近精度达 10 - 5。 相似文献