共查询到19条相似文献,搜索用时 62 毫秒
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文献介绍了弹粘塑性有限无解的数值方法,给出了Mises屈服准则的H矩陈表达式。本文对工程中常用的四种屈服准则,即Mises,Tresca,Mohr-coulomb,Drucker-Prager准则,给出了H矩阵的统一格式,提供厂消除Tresca,Mohr-Coulomb准则奇异性的方法并给出了公式。 相似文献
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本文采用刚塑性有限元理论,开发了一个二维数值模拟程序系统,对盒形件拉延成形中的法兰变形区进行了较全面的数值模拟,研究了冲压成过程中法兰变形区的金属流动规律。 相似文献
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管坯所受磁压力的准确求解是电磁成形变形分析,优化成形系统工艺参数的基础.通过ANSYS/EMAG软件,用远场单元来说明磁场在远场区间的耗散问题,对电磁胀形时作用在管坯上的磁压力进行准确计算.在线圈长度一定的条件下,讨论了管坯尺寸对磁压力瞬态分布和磁场扩散的影响,并根据管坯端部径向磁压力和中部径向磁压力的比值,提出以磁压力分布不均匀系数来反映磁场不均匀分布的程度.计算结果表明:当管坯和线圈的相对长度大于1时,管坯上与线圈等高处承受轴向拉应力,磁场扩散现象不严重;当相对长度小于0.92时,管坯端部承受轴向压应力,磁场扩散现象严重,相对长度0.92时为电磁胀形均匀成形的条件. 相似文献
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本文从化爆产生的土中自由场地冲击出发,采用一维波理论和Lagrange方程,建立了土中浅埋钢筋砼板的运动微分方程,进行了刚塑性动力响应分析,本文的计算结果与试验结果符合较好。 相似文献
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板材屈服准则与塑性失稳模型是精准描述高性能构件成形或服役过程的基础与前提。在板材塑性成形过程中,试样几何尺寸、材料晶粒大小、自由表面粗化和织构分布等都会对材料的塑性变形行为产生不可忽略的影响,导致单一尺度下的本构模型和断裂准则不能有效预测微观尺度下的材料变形行为和各种缺陷,大大限制了合金板材在航空、航天、汽车、医疗等工业上的应用。对现有屈服准则的研究进展进行了较为全面的回顾,从Hill、Hershey-Hosford和Drucker这3个系列出发,分别进行了对比分析,并总结了目前国内外用于验证屈服准则的金属板材双向拉伸实验机发展状况。基于不同的破裂失稳机理,将失稳模型分为宏观失稳准则、韧性断裂准则和耦合材料损伤演化的韧性断裂准则,并分别进行了归纳和阐述。此外,随着微成形技术的逐步推广,也对宏观塑性成形理论在微尺度下的应用进展进行了说明,指出了宏观屈服准则和失稳模型在微尺度下的不足和缺陷。最后讨论了宏观屈服准则和失稳模型今后的发展趋势以及宏观塑性成形理论在微尺度下的应用前景。 相似文献
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从力学、耐热、传热及经济性等方面对冷却塔中导热塑料管替代铜管的可行性进行介绍和分析。指出冷却塔中采用导热塑料管能够大大降低耗铜量。 相似文献
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The electromagnetic free-bulging of tubular work pieces of aluminium alloy samples of different hardness, annealed cartridge brass and commercially pure copper has been investigated. For a given capacitance and workpiece metal, a logarithmic plot of the maximum true hoop strain against the electrical energy discharged per unit tube thickness was found to be linear. These results could be expressed by an equation of identical form to a theoretical relationship, enabling the identification of the electrical and material properties concerned. The strain hardening characteristics of the workpiece material were found to play a vital role. For a given electrical energy per unit workpiece thickness, increase in capacitance yielded an increase in tube deformation, as predicted by theory. Deviations from theory occurred with the hard materials and with annealed copper. The former can be explained in terms of the breakdown of assumptions made in the derivation of the theoretical equation and the necessary corrections have been made. In the case of copper, the deviation was considered to be due to the strain rate sensitivity of the material. 相似文献
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Ludovic Vitu Nathalie Boudeau Pierrick Malécot Gérard Michel Aurélien Buteri 《International Journal of Material Forming》2018,11(5):671-686
It is now well recognized that the material data obtained from a tensile test is less appropriate than those from a Tube Bulging Test (TBT) for a finite element simulation of tube hydroforming. However, the manufacturers still use classical data (often tensile test data) for designing metal operations due to the lack of standard for the TBT and a more complex post processing analysis of experimental measures. Getting the hardening curve from the tube bulging test requires the use of an analytical or numerical model. In this paper, three models for post-processing measures obtained from the TBT are compared based on the same experimental procedure. Thanks to a preliminary step, consisting of the validation of the analytical models through the use of finite element simulations of the TBT, it highlights that the results obtained for the local (stress and strain) and global components (the thickness distribution along the tube and the deformed tube profile) are very close, whatever the models. The test configuration (die radius and free length) seems to have no significant impact on the resulting stress-strain curve for the three models. The three models are used for post processing tube bulging tests performed on AISI304, INCONEL and Copper tubes validating their capacity for tube characterization on different materials. Finally, this study demonstrates that the Boudeau-Malécot Model can be used to obtain hardening curve from TBT without a loss of accuracy compared to more complex post-processing models and with an important gain of quality compared to tensile test. 相似文献
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Abstract The elasto‐plastic endochronic theory is extended to describe the material behavior of tubes under cyclic bending. Experimental data of cyclic bending of 6061‐T6 aluminum and 1018 steel was used for comparison. It is shown that by using the complete differential equations of the theory and by assuming a linear relation between the strain and the curvature, the theory is capable of predicting the moment‐curvature response. 相似文献
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We consider localized bulging of an inflated cylindrical hyperelastic tube of arbitrary thickness that is helically reinforced by two families of fibres. It is shown that localized bulging may become impossible, irrespective of the end conditions, when the tube wall becomes thick enough. This is in sharp contrast with an isotropic hyperelastic tube without fibre reinforcement for which localized bulging has previously been shown to be possible no matter how thick the tube wall is and for which the membrane theory provides a very good approximation for the ratio of wall-thickness/radius as large as 0.67. Our findings provide a feasible explanation on why aneurysms cannot occur in healthy arteries but become possible following pathological changes. They can also be used to guide the design of tubular structures where localized bulging should be prevented. 相似文献
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《材料与设计》2015
The microstructure, texture and mechanical properties of annealed 5A02 Al alloy tubes after electromagnetic bulging have been systematically studied using transmission electron microscopy (TEM), electron backscattered diffraction (EBSD) and uniaxial tensile test. Microstructural characterizations showed that the formation of dense dislocation bands and dislocation walls in the bulged samples is due to the effect of high strain rate of electromagnetic forming and solute–dislocation interactions in the Al alloy. The texture examination revealed that the volume fraction of α-fiber texture increases after deformation, while the brass texture component in β-fiber increases, and the copper and S texture components decrease with increasing strain, indicating the occurrence of texture rotation from the initial state to a more stable orientation. In addition, the lack of cross-slip activity and high strain rate accompanied by the electromagnetic deformation in the studied Al alloy also play a role in the texture evolutions. Finally, mechanical properties of the post-bulged samples were examined by uniaxial tensile test, which shows a significant increase in yield strength and fracture strength, but decrease in fracture elongation. The enhancement of strength was discussed on the basis of the dislocation boundary strengthening mechanism, which was in good agreement with the experimental results. 相似文献
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《International Journal of Impact Engineering》1987,6(3):225-240
A simple theoretical procedure is presented for the analysis of a free-free beam which is made from a rigid-perfectly plastic material and subjected to a dynamic pressure pulse. Exact theoretical solutions are presented for a uniform beam under a triangular pressure load and a step beam subjected to uniform pressure pulse. In one case, it was observed that only 25% of the external energy was converted into plastic work for an ideal impulse. The remaining 75% of the energy caused a rigid-body acceleration of the beam. It is concluded that it is more difficult to break a free-free beam, as found in space, than a supported beam. The article concludes with a simplified study of the dynamic failure of an idealized aerospace vehicle. 相似文献