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961.
An experimental investigation was performed to study a specific axial crush configuration response of steel, square box components under quasi-static testing conditions. For a specific cross-sectional geometry/fabrication process, test specimens were obtained from commercially produced, welded tube lengths of ASTM A36 and ASTM A513 Type 1 plain low-carbon steels and AISI 316 and AISI 304 austenitic stainless steels. Removable grooved caps were used to constrain tube test specimen ends, and collapse initiators in the form of shallow machined grooves were used to control the initial transverse deformations of the test specimen sidewalls. The progressive plastic deformation for all of the test specimens was restricted to the prototype configuration response (fold formation process and the corresponding axial load-axial displacement curve shape) of the symmetric axial crush mode. Crush characteristics were evaluated and, for each material type, observed differences were less than 7% for maximum and minimum load magnitudes and less than 2% for energy absorption, displacement, and mean load quantities in both the initial phase and the secondary folding phase cycles. Overall, results of the study indicate that for a significant range of material strengths, a controlled and repeatable energy absorption process can be obtained for commercially produced steel box components undergoing symmetric axial crush response. 相似文献
962.
EXACT SOLUTION OF LARGE DEFORMATION BASIC EQUATIONS OF CIRCULAR MEMBRANE UNDER CENTRAL FORCE 总被引:1,自引:0,他引:1
Exact solution of the nonlinear boundary value problem for the basic equation and boundary condition of circular membrane under central force was obtained by using new simple methods. The existence and uniqueness of the solution were discussed by using of modern immovable point theorems. Although specific problem is treated, the basic principles of the methods can be applied to a considerable variety of nonlinear problems. 相似文献
963.
本文根据变形功与熔化热能的关系,将简单拉伸实验方法推广应用到了熔化热能和变形热效应的测量上。按简单拉伸实验方法测得的熔化热能与热力学的测量结果吻合较好。该研究实现了力学实验方法与物理实验方法的互换,因此,具有重要的实际应用价值。 相似文献
964.
变形梯度张量极分解中转动张量的直接表示及其应用 总被引:1,自引:0,他引:1
本文通过变分途径建立了变形梯度张量的极分解和加法分解之间的联系.采用工程界通常采用的变形梯度张量的加法分解形式,得到了三维空间中极分解的转动张量和伸长张量的直接表示,即实现了转动和变形的分离.由这些直接表示,可以得到各种有用的近似表示. 相似文献
965.
隧洞围岩力学性态预报的随机介质模型 总被引:1,自引:0,他引:1
本文基于系统学观点,利用随机过程以及概率与数理统计方法,视岩体为一随机不确定性系统,建立了描述变形概率密度函数演化所服从的方程,详细讨论了变形发展的概率预报,最后给出了一些有意义的结论和意见。 相似文献
966.
967.
Twinnability is the property describing the ease with which a metal plastically deforms by twinning relative to deforming by dislocation-mediated slip. In this paper a theoretical measure for twinnability in face-centered-cubic (fcc) metals is obtained through homogenization of a recently introduced criterion for deformation twinning (DT) at a crack tip in a single crystal. The DT criterion quantifies the competition between slip and twinning at the crack tip as a function of crack orientation and applied loading. The twinnability of bulk material is obtained by constructing a representative volume element of the material as a polycrystal containing a distribution of microcracks and integrating the DT criterion over all possible grain and microcrack orientations. The resulting integral expression depends weakly on Poisson's ratio and significantly on three interfacial energies: the stacking-fault energy, the unstable-stacking energy and the unstable-twinning energy. All these four quantities can be computed from first principles. The weak dependence on Poisson's ratio is exploited to derive a simple and accurate closed-form approximation for twinnability which clarifies its dependence on the remaining material parameters. To validate the new measure, the twinnability of eight pure fcc metals is computed using parameters obtained from quantum-mechanical tight-binding calculations. The ranking of these materials according to their theoretical twinnability agrees with the available experimental evidence, including the low incidence of DT in Al, and predicts that Pd should twin as easily as Cu. 相似文献
968.
969.
本文证明了若取客观应力率为 Kirchhoff 应力的 Oldroyd 导数,对于 Lame 参数λ、μ为常数的情况,率形式弹性本构律的可积条件为 λ=0。这显然表明在大变形情况下率形式弹塑性本构律与超弹性条件这两者之间在一般情况下并不协调。文中还讨论了几种弹性本构律可以近似用于大变形描述的情况。 相似文献
970.
制成了15%应变量的三维有限变形线性光弹性材料,可供对橡胶类零件的应力分析之用;在该材料中,以尼龙6作内含体,可以制作初应力很小的三维有限变形复合光弹性模型。 相似文献