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71.
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
72.
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
73.
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
74.
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
75.
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
76.
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
77.
A higher order asymptotic solution of near-tip field is studied for plane-atrain Mode-I quasi-static steady crack growth in
the incompressible (v=1/2) elastic perfectly-plastic media. The results show that the near-tip stress and strain are fully continuous, and the
strain possesses In (A/r) singularity at the crack tip. The expressions of the stress, strain and velocity in each region are also given.
The project supported by National Natural Science Foundation of China 相似文献
78.
研究了平面应变条件下幂硬化可压缩材料中定常扩展的Ⅰ型动态裂纹尖端应力应变奇异场.采用J2流动理论和场量直角坐标分量,得到了应力应变奇异性不同时的裂纹尖端渐近场,其中场量的角变化规律和理想弹塑性材料的完全相同 相似文献
79.
S. A. Nazarov M. Specovius-Neugebauer 《Journal of Applied Mechanics and Technical Physics》2006,47(5):714-723
An asymptotic formula is obtained for the total-energy increment during quasistatic growth of a semiin finite crack in an
anisotropic elastic plane under complex loading. It is assumed that the shear loads are much larger than the tearing loads.
The shape of the slightly curved crack was determined using the Griffith criterion in two versions: global and local. It is
shown, in particular, that the first version leads to an improbable result.
__________
Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 47, No. 5, pp. 119–130, September–October, 2006. 相似文献
80.