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51.
Kinetics of deformation and fracture of nickel–iron alloy Inconel 718 under dynamic shear loading was measured using a split
torsional Hopkinson bar facility and high-speed photography. Tubular specimens with a reduced gage length and a starter notch
were sheared at strain rates up to 6 × 103 s−1. High-speed photographs of fiducial lines scribed on the specimen surface showed the development of local strains and cracking.
This paper describes the experimental and analytical procedures, illustrates average and local plastic strain evolution, and
presents shear crack initiation times and propagation speeds. 相似文献
52.
53.
Jiann-Quo Tarn 《Journal of Elasticity》2002,69(1-3):1-13
The issue of stress singularity in an elastic cylinder of cylindrically anisotropic materials is examined in the context of
generalized plane strain and generalized torsion. With a viewpoint that the singularity may be attributed to a conflicting
definition of anisotropy at r=0, we study the problem through a compound cylinder in which the outer cylinder is cylindrically anisotropic and the core
is transversely isotropic. By letting the radius of the core go to zero, the cylinder becomes one with the central axis showing
no conflict in the radial and tangential directions. Closed-form solutions are derived for the cylinder under pressure, extension,
torsion, rotation and a uniform temperature change. It is found that the stress is bounded everywhere, and singularity does
not occur if the anisotropy at r=0 is defined appropriately.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
54.
The purpose of this research is to investigate the simple torsion problem for a solid circular cylinder composed of isotropic
hyperelastic incompressible materials with limiting chain extensibility. Three popular models that account for hardening at
large deformations are examined. These models involve a strain-energy density which depends only on the first invariant of
the Cauchy–Green tensor. In the limit as a polymeric chain extensibility tends to infinity, all of these models reduce to
the classical neo-Hookean form. The main mechanical quantities of interest in the torsion problem are obtained in closed form.
In this way, it is shown that the torsional response of all three materials is similar. While the predictions of the models
agree qualitatively with experimental data, the quantitative agreement is poor as is the case for the neo-Hookean material.
In fact, by using a global universal relation, it is shown that the experimental data cannot be predicted quantitatively by
any strain-energy density which depends solely on the first invariant. It is shown that a modification of the strain energies
to include a term linear in the second invariant can be used to remedy this defect. Whether the modified strain-energies,
which reflect material hardening, are a feasible alternative to the classic Mooney–Rivlin model remains an open question which
can be resolved only by large strain experiments.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献
55.
56.
本文利用Luthar-Passi方法,研究了五次交错群A_5与六阶二面体群D_6直积的整群环的挠单位,得到了该群的Zassenhaus猜想成立. 相似文献
57.
Various classes of simple torsion modules are classified over the quantum spatial ageing algebra (this is a Noetherian algebra of Gelfand-Kirillov dimension 4). Explicit constructions of these modules are given and for each module its annihilator is found. 相似文献
58.
59.
圆环在均布扭力矩作用下的变形特殊且容易发生跳跃,不考虑稳定性而得到的一些结论将可能不存在。本文利用最小势能原理导出圆截面圆环在均布扭力矩作用下的平衡路径,并根据系统稳定性的能量判据,对圆环的平衡稳定性、变形与运动过程进行分析,最后得到稳定平衡状态下圆环横截面上的内力最大值。 相似文献
60.
In conjunction with the homogenization theory and the finite element method, the mathematical models for designing the corss-section
of composite shafts by maximizing the torsion rigidity are developed in this paper. To obtain the extremal torsion rigidity,
both the cross-section of the macro scale shaft and the representative microstructure of the composite material are optimized
using the new models. The micro scale computational model addresses the problem of finding the periodic microstructures with
extreme shear moduli. The optimal microstructure obtained with the new model and the homogenization method can be used to
improve and optimize natural or artificial materials. In order to be more practical for engineering applications, cellular
materials rather than ranked materials are used in the optimal process in the existence of optimal bounds for the elastic
properties. Moreover, the macro scale model is proposed to optimize the cross-section of the torsional shaft based on the
tailared composites. The validating optimal results show that the models are very effective in obtaining composites with extreme
elastic properties, and the cross-section of the composite shaft with the extremal torsion rigidity.
The project supported by the National Natural Science Foundation of China (10172078 and 10102018) 相似文献