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在冷滚打成形过程中,滚打轮对工件击打和滚压的同时,工件变形区域储存了较大的弹性应变能,导致工件成形结束后会出现回弹,回弹现象对成形工件的廓形精度有着较大的影响。本文主要针对滚打轮公转速度与回弹量之间的关系进行研究。建立了冷滚打成形回弹的有限元仿真模型,通过动态仿真分析获得了不同公转速度时成形齿槽截面在切向、轴向和径向的变形规律;通过静态分析获得了成形齿槽截面各部分在不同公转速度下切向、轴向和径向的回弹规律。结果表明,相同工艺条件下冷滚打实验得到的工件廓形与仿真结果吻合,验证了仿真结果的正确性,通过合理选择工艺参数可以有效控制回弹,提高制件成形精度。 相似文献
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大型整体壁板结构参数及成形工艺参数优化需要对壁板成形进行大量的非线性仿真计算,详细模型在计算时间和资源消耗方面难以接受,且不易收敛。通过弹塑性力学及回弹分析,基于应力和回弹后的变形等效,考虑了材料塑性变形强化效应,将整体壁板简化为某一虚拟材料的平板进行弹塑性弯曲等效分析。压弯和滚弯成形数值算例分析表明:在工程常用的弯曲半径范围内,变形计算误差在3.5%以内,应力误差在5%以内;等效模型大大减小了建模时间和资源,计算效率提高了70%以上,且计算易收敛;等效模型可以替代详细模型,为大型整体壁板结构参数及工艺参数优化、大型复杂形状壁板成形提供了快捷的分析方法。 相似文献
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采用碳纤维织物预浸料在阳模上按既定固化工艺制备C型肋零件,利用三坐标测量机测量了模具型面,零件在三端封边、大端切口及大端切口且缘条切边3种状态下的零件内型面,以及大端切口且缘条切边状态下的零件外型面,对零件的回弹进行了分析、验证.结果表明:对于铺层为[(±45°)/(-+45°)]n(3≤n≤6)的三端封边肋零件模具两侧缘条回弹补偿1.35°,大端缘条回弹补偿0.32°;大端切口与未切口状态对比缘条回弹变化很大;大端切口后,缘条切边与未切边状态对比缘条回弹稍有变化;大端切口肋零件模具两侧缘条回弹补偿1.69°,大端缘条回弹补偿1.62°. 相似文献
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建立了考虑材料塑性强化的滚弯成形力学分析解析模型,推导出了应力应变、残余应力以及回弹半径计算公式.基于非线性有限元软件,对滚弯成形进行了动态模拟,对应力应变状态、塑性应变分布、残余应力以及回弹等进行了分析计算,结果表明:板料滚弯成形初始效应明显,下压点附近曲率不均匀;采用足够的滚弯时间后,中间段的曲率均匀度很好;成形半径与上辊下压量呈近似幂函数关系;多道次滚弯可以减小两端的曲率波动和最大应力应变.最后通过与滚弯成形试验数据的对比,分析和验证了解析模型与数值模型的适用性和精度. 相似文献
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Significant springback occurs after tube rotary-draw-bending (RDB), especially for a high-strength Ti-3A1-2.5V tube (HSTT) due to its high ratio of yield strength to Young's modulus. The combination scheme of explicit and implicit is preferred to predict the springback. This simulation strategy includes several numerical parameters, such as element type, number of elements through thickness (NEL), element size, etc. However, the influences of these parameters on spring- back prediction accuracy are not fully understood. Thus, taking the geometrical specification 9.525 mm × 0.508 mm ofa HSTT as the objective, the effects of numerical parameters on prediction accuracy and computation efficiency of springback simulation of HSTT RDB are investigated. The simulated springback results are compared with experimental ones. The main results are: (1) solid and continuum-shell elements predict the experimental results well; (2) for C3DSR elements, NEL of at least 3 is required to obtain reliable results and a relative error of 29% can occur as NEL is varied in the range of 1-3; (3) specifying damping factor typically works well in Abaqus/Emplicit simulation of springback and the springback results are sensitive to the magnitude of damping factor. In addition, the explanations of the effect rules are given and a guideline is added. 相似文献
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《中国航空学报》2020,33(12):3479-3494
Because of the complex constraint effects among layers in multi-layered metallic bellows hydroforming, the stress concentration and defects such as wrinkling and fracture may easily occur. It is a key to reveal the deformation behaviors in order to obtain a sound product. Based on the ABAQUS platform, a 3D-FE model of the four-layered U-shaped metallic bellow hydroforming process is established and validated by experiment. The stress and strain distributions, wall thickness variations and bellow profiles of each layer in the whole process, including bulging, folding and springback stages, are studied. Then deformation behaviors of bellows under different forming conditions are discussed. It is found that the wall thinning degrees of different layer vary after hydroforming, and is the largest for the inner layer and smallest for the outer layer. At folding stage, the wall thinning degree of the crown point increases lineally, and the difference among layers increases as the process going. The displacements of the crown point decrease from the inner layer to the outer layer. After springback, the U-shaped cross section changes to a tongue shape, the change of convolution pitch is much larger than the change of convolution height, and the springback values of the inner layer are smaller than the outer layer. An increase in the internal pressure and die spacing cause the maximum wall thinning degree and springback increase. With changing of process parameters, bellows with deep convolution are easily encountered wall thinning during hydroforming and convolution distortion after springback. This research is helpful for precision forming of multi-layered bellows. 相似文献