共查询到14条相似文献,搜索用时 93 毫秒
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六方金属在疲劳过程中的位错组态演化──兼论位错理论和协同论在材料强度学中的应用 总被引:2,自引:0,他引:2
简述了位错理论发展及在中国传播的历史、位错理论的应用领域、金属中常见的位错组态;介绍了协同论在位错研究中的应用,并据此分析讨论了在钛、锆等六方金属中所获得的某些实验结果。 相似文献
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利用积分变换技术,结合Copson方法,研究了含直线型对称裂纹的一维六方压电准晶对SH波的散射问题。通过求解对偶积分方程,得到声子场、相位子场应力、位移及电场电位移分量的解析解。定义了裂纹尖端应力强度因子及电位移强度因子,给出了电非渗透性条件下应力强度因子及电位移强度因子的解析解。此研究结果对压电准晶材料的工程应用有一定的理论价值。 相似文献
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梯度纳米结构金属力学性能、变形机理和多尺度计算研究进展 总被引:1,自引:0,他引:1
近年来,梯度纳米结构金属因其优越的力学性能和独特的塑性变形机理受到广泛关注,已成为材料与力学学科的热点和前沿.论文首先介绍梯度纳米结构金属的强度、塑性、加工硬化和抗疲劳等核心力学性能,以及晶粒长大、塑性应变梯度和几何必需位错等塑性变形机理及其力学研究.其次介绍梯度纳米结构金属的多尺度计算与模拟研究.最后讨论梯度纳米结构金属研究领域存在的挑战. 相似文献
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《International Journal of Solids and Structures》2006,43(6):1787-1817
A second strain gradient elasticity theory is proposed based on first and second gradients of the strain tensor. Such a theory is an extension of first strain gradient elasticity with double stresses. In particular, the strain energy depends on the strain tensor and on the first and second gradient terms of it. Using a simplified but straightforward version of this gradient theory, we can connect it with a static version of Eringen’s nonlocal elasticity. For the first time, it is used to study a screw dislocation and an edge dislocation in second strain gradient elasticity. By means of this second gradient theory it is possible to eliminate both strain and stress singularities. Another important result is that we obtain nonsingular expressions for the force stresses, double stresses and triple stresses produced by a straight screw dislocation and a straight edge dislocation. The components of the force stresses and of the triple stresses have maximum values near the dislocation line and are zero there. On the other hand, the double stresses have maximum values at the dislocation line. The main feature is that it is possible to eliminate all unphysical singularities of physical fields, e.g., dislocation density tensor and elastic bend-twist tensor which are still singular in the first strain gradient elasticity. 相似文献
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This article is concerned with the development of a discrete theory of crystal elasticity and dislocations in crystals. The theory is founded upon suitable adaptations to crystal lattices of elements of algebraic topology and differential calculus such as chain complexes and homology groups, differential forms and operators, and a theory of integration of forms. In particular, we define the lattice complex of a number of commonly encountered lattices, including body-centered cubic and face-centered cubic lattices. We show that material frame indifference naturally leads to discrete notions of stress and strain in lattices. Lattice defects such as dislocations are introduced by means of locally lattice-invariant (but globally incompatible) eigendeformations. The geometrical framework affords discrete analogs of fundamental objects and relations of the theory of linear elastic dislocations, such as the dislocation density tensor, the equation of conservation of Burgers vector, Kröner's relation and Mura's formula for the stored energy. We additionally supply conditions for the existence of equilibrium displacement fields; we show that linear elasticity is recovered as the Γ-limit of harmonic lattice statics as the lattice parameter becomes vanishingly small; we compute the Γ-limit of dilute dislocation distributions of dislocations; and we show that the theory of continuously distributed linear elastic dislocations is recovered as the Γ-limit of the stored energy as the lattice parameter and Burgers vectors become vanishingly small. 相似文献
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A material body with smoothly distributed microstructure can be seen geometrically as a fibre bundle. Within this very general framework, we show that a theory of continuous distributions of dislocations can be formulated and specialized to particular applications, both old and new. 相似文献
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S. P. Kiselev 《Journal of Applied Mechanics and Technical Physics》2004,45(4):567-571
Formulas for calculating internal stresses in a material, generated by continuously distributed dislocations, are found on the basis of the gauge theory of defects. It is shown that internal stresses are selfbalanced and satisfy the equilibrium equations and boundary conditions in the absence of external loads. 相似文献
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S. Cleja-Ţigoiu 《Archive of Applied Mechanics (Ingenieur Archiv)》2014,84(9-11):1293-1306
The paper deals with elasto-plastic models for crystalline materials with defects, dislocations coupled with disclinations. The behaviour of the material is described with respect to an anholonomic configuration, endowed with a non-Riemannian geometric structure. The geometry of the material structure is generated by the plastic distortion, which is an incompatible second-order tensor, and by the so-called plastic connection which is metric compatible, with respect to the metric tensor associated with the plastic distortion. The free energy function is dependent on the second-order elastic deformation and on the state of defects. The tensorial measure of the defects is considered to be the Cartan torsion of the plastic connection and the disclination tensor. When we restrict to small elastic and plastic distortions, the measures of the incompatibility as well as the dislocation densities reduced to the classical ones in the linear elasticity. The constitutive equations for macroforces and the evolution equations for the plastic distortion and disclination tensor are provided to be compatible with the free energy imbalance principle. 相似文献