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为研究半冲孔成形过程中韧性损伤的演化以及部分工艺参数对成形质量的影响规律,本文在ABAQUS有限元模拟软件中建立了半冲孔轴对称有限元模型,并通过VUMAT用户子程序引入GTN(Gurson-Tvergaard-Needle-man)损伤模型,结合同时考虑空穴形状与体积变化影响的韧性断裂准则,进行弹塑性大变形有限元分析.基于该有限元模犁,预测了半冲孔工艺中静水压力、等效应力、等效应变、应力三轴度以及损伤断裂的产生和发展趋势,分析了反顶力、压边力和冲裁间隙对零件的影响规律,并与实验结果进行对比分析,验证了数值模拟的准确性. 相似文献
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近净成形工艺是含能材料的主要成形方式之一,当原料通过近净成形工艺成形后,为了保证退模过程中冲头受力均匀和退模过程顺利,需要对退模过程进行研究。采用通用有限元分析软件ABAQUS建立含能材料柱状近净成形有限元模型,对其退模工艺全过程进行仿真分析,得到了退模过程中模具和冲头的最大应力,并且给出退模过程中的退模力-冲头位移曲线。进一步分析了退模加载速度对退模力的影响,分析了两种典型的加载速度工况下的退模力。结果表明,本文建立的有限元仿真模型能够有效地模拟近净成形退模工艺,为退模工艺的相关参数设计和工程实践提供指导。 相似文献
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镦挤拔模斜度对成形的影响规律研究 总被引:3,自引:0,他引:3
由于坯料在镦挤变形过程中要经过镦粗和挤压变形,给模具参数的选择带来一定的难度。凹模的拔模斜度是影响成形工艺的一个重要参数,关于拔模斜度大小的选取,目前尚无准确的公式、曲线或表格。论文以数值仿真技术为依托,建立了基于刚粘塑性有限元法的镦挤热成形工艺有限元模拟模型,利用塑性成形仿真软件DEFORM-3D对镦挤工艺进行模拟仿真,分析讨论了不同拔模斜度对镦挤热成形过程的影响以及成形过程中可能产生的缺陷,建立了基于数值模拟仿真模拟结果的最佳拔模斜度成形规律曲线,为指导镦挤工艺设计中凹模拔模斜度的选择提供了理论依据,也为其它挤压凹模斜度的选择提供了参考。 相似文献
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直齿轮冲挤——镦挤成形过程数值模拟分析 总被引:1,自引:1,他引:0
针对直齿轮精锻成形工艺存在齿形充填困难和成形载荷大的两个问题,本文采用三维有限元分析软件DEFORM-3D对浮动凹模形式下,直齿轮冲挤—镦挤成形过程进行了数值模拟。通过分析金属材料内部的应力场、应变场的分布,挤压载荷和温度的变化,以及工艺参数对成形过程的影响,认为采用浮动凹模结构不仅有利于齿腔角部金属的充满,还可以极大地降低金属在成形终了阶段的变形力,从而为直齿轮精锻成形工艺的实用化提供了理论指导。 相似文献
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以某轻型汽车半轴渐开线花键为研究对象,利用有限元软件Deform-3D,采用数值模拟的方法,探讨了坯料直径、凹模引导区长度及定径带长度对花键冷挤压成形的影响规律。分析结果表明,随坯料直径增加,成形力上升,齿形成形效果显著提高,但坯料直径过大,回弹现象影响齿形精度;引导区长度对花键冷挤成形性有影响,若引导长度设计太短,挤压过程不稳定或不能成形;定径带长度对花键的成形质量和成形力影响显著,随定径带长度增加,齿形越饱满,齿槽越深,挤压力越大。优化设计了冷挤花键组合式凹模的关键参数,工艺试验表明,分析准确,设计合理。 相似文献
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J. ChenK. Chandrashekhara C. MahimkarS.N. Lekakh V.L. Richards 《Journal of Materials Processing Technology》2011,211(2):245-255
Cold rolling is used to eliminate void defects in cast materials thus improving the material performance during service. A comprehensive procedure is developed using finite element analysis and neural network to predict the degree of void closure. A three-dimensional nonlinear dynamic finite element model was used to study the mechanism of void deformation. Experiments were conducted to investigate void closure during the cold flat rolling process. Experimental results are compared to the three-dimensional finite element predictions to validate the model. The void reduction predictions from finite element analysis are in good agreement with experimental findings. Plastic strain, principal stress distribution around the void and void reduction ratio are presented for various case studies. As finite element simulation is time-consuming, a back-propagation neural network model is also developed to predict void closure behavior. Based on the correlation analysis, the reduction in sheet thickness, the dimension of the void and the size of the rollers were selected as the inputs for the neural network. The neural network model was trained based on results obtained from finite element analysis for various simulation cases. The trained neural network model provides an accurate and efficient procedure to predict void closure behavior in cold rolling. 相似文献
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Using rigid-plastic finite element DEFORM-2D and -3D software, this study simulates the plastic deformation of metal sheets at the roll gap during the sheet rolling process. The study focuses specifically upon the deformation of porous metal sheets containing internal void defects. The present numerical analysis investigates the relative density distributions, the void closure behavior, the deformation mechanisms and the stress–strain distributions around the internal voids for various rolling conditions. The influences on the dimensions of the final void of the thickness reduction, the initial internal void dimensions, the friction factors and the relative density are systematically discussed. The critical rolling conditions also investigated. A series of sheet rolling experiments are performed in order to verify the validity of the simulation results. The current numerical results provide a valuable source of reference for the design of pass schedules for porous metals undergoing rolling processes. 相似文献
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工艺参数对铝型材挤压变形规律的影响 总被引:9,自引:0,他引:9
通过引进一个反映金属流速不均衡性的参数———流速均方差 ,有效地控制型材挤压成形时金属流动的不均匀性。采用有限变形弹塑性有限元方法 ,对不同挤压参数 (挤压比、摩擦因子 )下铝型材挤压过程进行了数值模拟研究 ,获得了挤压压力、流速均方差和型材件内部应力应变场随挤压参数变化的规律 ,为铝型材挤压工艺参数优化提供了理论参考。 相似文献
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在板料成形过程中应力状态对板料(板材和管材)的成形极限有很大影响,通过对板料施加法向应力可以提高板料的成形极限。文章综述并分析了法向应力对板料成形极限影响的理论模型、有限元模型以及实验研究方面的进展。理论模型方面的主要进展,是根据经典塑性失稳理论和M-K理论,建立了考虑法向应力影响的成形极限理论模型,可以准确地预测法向应力对板料成形极限的影响;有限元分析的主要进展,是在韧性断裂准则的基础上,利用体单元建立了考虑法向应力影响的数值模型;有关实验研究方面只是初步的探索,还有待进行深入的研究;对影响法向应力提高板料成形极限的因素进行了总结分析。 相似文献
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《Acta Materialia》2004,52(10):3001-3007
A novel method for the quantification of void nucleation rates in sheet material is presented. An incremental sheet forming process is employed to create large regions of homogeneous deformation, such that material density changes can then be used to quantify the evolution of void volume fraction with applied strain. This technique is employed to calibrate the void nucleation behaviour of three automotive aluminum sheet alloys (AA5182, AA5754 and AA6111) for incorporation into finite element method models which employ the Gurson–Tvergaard–Needleman (GTN) constitutive softening equations. 相似文献