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71.
72.
The solution of a screw dislocation under time-harmonic condition is obtained in an infinite isotropic plane by means of the Fourier transform method. The stress components reveal the familiar Cauchy singularity at the location of dislocation. The solution is employed to derive integral equations for a plane weakened by cracks and cavities. Cavities are considered as closed curved cracks without singularity. Several examples are solved and the stress intensity factor of cracks and hoop stress on cavities are obtained. 相似文献
73.
An in-depth investigation is made on the problem of an arc-shaped interface insulating crack in a three-phase concentric circular
cylindrical piezoelectric composite constitutive model. An exact solution in series form is derived by employing the complex
variable method. In addition, the distribution of physical quantities such as stresses, strains, electric displacements and
electric fields in the whole field and along the interface is also presented. Explicit expressions for crack opening displacement,
jump in electric potential on the crack surface and the electro-elastic field intensity factors at the crack tips are obtained.
Specific calculations demonstrate that the convergence of the series form solution is satisfactory and that the outer phase
(composite phase) will exert a significant effect on the electro-mechanical coupling response of the composite system. Owing
to the fact that stresses and electric displacements still possess conventional inverse square root singularities, the oscillating
singularities near the crack tip under plane strain conditions will be absent and, as a result, no unphysical interpenetration
phenomenon of the two crack surfaces will occur. In conclusion, the elastic solution obtained is also based on a solid physical
foundation.
Project supported by the National Natural Science Foundation of China (No.59635140), and the Doctorate Foundation of Xi'an
Jiaotong University. 相似文献
74.
The crack tip fields of stress, strain and damage for concrete under both antiplane shear and plane strain conditions are investigated based on the damage model proposed by Mazars and Lemaitre [2]. The structures of near tip fields obtained are similar to those for an elastic-perfectly-plastic material. It has been found that damage boundaries can not be determined by the near-tip analysis due to the discontinuities of stresses on the damage boundaries induced by the damage model used in the present paper.The Project is Supported by National Natural Science Fundation of China. 相似文献
75.
Saqlain Abbas Fucai Li Zulkarnain Abbas Taufeeq Ur Rehman Abbasi Xiaotong Tu Riffat Asim Pasha 《声与振动》2021,55(1):1-18
Structural health monitoring (SHM) is recognized as an efficient tool to interpret the reliability of a wide variety of infrastructures. To identify the structural abnormality by utilizing the electromechanical coupling property of piezoelectric transducers, the electromechanical impedance (EMI) approach is preferred. However, in real-time SHM applications, the monitored structure is exposed to several varying environmental and operating conditions (EOCs). The previous study has recognized the temperature variations as one of the serious EOCs that affect the optimal performance of the damage inspection process. In this framework, an experimental setup is developed in current research to identify the presence of fatigue crack in stainless steel (304) beam using EMI approach and estimate the effect of temperature variations on the electrical impedance of the piezoelectric sensors. A regular series of experiments are executed in a controlled temperature environment (25°C–160°C) using 202 V1 Constant Temperature Drying Oven Chamber (Q/TBXR20-2005). It has been observed that the dielectric constant ε33T which is recognized as the temperature-dependent constant of PZT sensor has sufficiently influenced the electrical impedance signature. Moreover, the effective frequency shift (EFS) approach is optimized in term of significant temperature compensation for the current impedance signature of PZT sensor relative to the reference signature at the extended frequency bandwidth of the developed measurement system with better outcomes as compared to the previous literature work. Hence, the current study also deals efficiently with the critical issue of the width of the frequency band for temperature compensation based on the frequency shift in SHM. The results of the experimental study demonstrate that the proposed methodology is qualified for the damage inspection in real-time monitoring applications under the temperature variations. It is capable to exclude one of the major reasons of false fault diagnosis by compensating the consequence of elevated temperature at extended frequency bandwidth in SHM. 相似文献
76.
Molecular dynamics simulations of dopant effectson lattice trapping of cracks in Ni matrix
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Shulan Liu 《中国物理 B》2021,30(11):116107-116107
Molecular dynamic analysis was performed on pure and doped (by Re, Ru, Co or W) Ni at 300 K using the embedded-atom-method (EAM) potentials to understand the crack formation of the doped Ni matrix in the (010)[001] orientation. When Ni was doped with Re, Ru, and W, the matrix demonstrated increased lattice trapping limits and, as a result, improved the mechanical properties. Consequently, this prevented the bond breakage at the crack tips and promoted crack healing. The average atomic and surface energy values increased when Re, Ru, and W were added. Analysis of these energy increase helped us to understand the influence these elements had on the lattice trapping limits. The fracture strength of the Ni matrix at 300 K increased because of the formation of the stronger Ni-Re, Ni-Ru, and Ni-W bonds. At the same time, doping the Ni matrix with Co did not demonstrate any strengthening effects because of the formation of Co-Ni bonds, which are weaker than the Ni-Ni bonds. Out of all dopants tested in this work, Ni doping with W showed the best results. 相似文献
77.
超奇异积分方程方法的理论分析已在本文的第I部分中给出,这一部分是经的数值方法,及用此方法求解的若干典型的平片裂纹问题。 相似文献
78.
给定寿命下的焊趾疲劳裂纹深度尺寸分析 总被引:1,自引:0,他引:1
本文提供并用统计方法研究了焊趾疲劳裂纹扩展的N~α曲线族,给出了联系给定裂纹尺寸下的疲劳分布,给定疲劳寿命下的裂纹尺寸分布以及随机初始条件的概率相容条件。研究表明,给定寿命下的焊趾疲劳裂纹深度尺寸α服从分布Ф[(μ(a)-logN)/σ(a)]。 相似文献
79.
Fractal modeling of the rugged crack geometry is considered for the stable and dynamic fracture mechanics characterizing the morphology of a fracture surface and the influence of its growth. It is shown that the fractal dimension has a strong influence on the rising of the R-curve in brittle materials. For the unstable Griffith–Mott’s approach or dynamical crack growth the fractal dimension has a strong influence on the velocity limit of the crack growth. It is also shown that the limit of crack velocity lowers with increasing surface ruggedness (higher fractal dimension D = 2 − H) explaining the intangibility of the Rayleigh wave velocity by the cracks. 相似文献
80.
磁粉法检测表面裂纹概率曲线的测定 总被引:1,自引:0,他引:1
本文介绍了利用实物零件测定裂纹检出概率的方法,并作出了用磁粉法检测表面裂纹的检测概率曲线,为大型构件检测周期的确定提供了可靠数据,为结构损伤容限设计,可靠性设计提供了重要的依据。 相似文献