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11.
采用光学显微镜和扫描电子显微镜等手段,对某轻型汽车40Cr后桥半轴断裂件的组织及断口特征进行了分析结果表明:半轴在调质处理时的淬火温度不够高,使其表层和心部组织中存在较多的铁素体相,造成了工件最终的硬度和疲劳强度不足,导致半轴在使用中发生扭转疲劳断裂. 相似文献
12.
Victor A. Kovtunenko 《Mathematical Methods in the Applied Sciences》2003,26(5):359-374
The 3D‐elasticity model of a solid with a plane crack under the stress‐free boundary conditions at the crack is considered. We investigate variations of a solution and of energy functionals with respect to perturbations of the crack front in the plane. The corresponding expansions at least up to the second‐order terms are obtained. The strong derivatives of the solution are constructed as an iterative solution of the same elasticity problem with specified right‐hand sides. Using the expansion of the potential and surface energy, we consider an approximate quadratic form for local shape optimization of the crack front defined by the Griffith criterion. To specify its properties, a procedure of discrete optimization is proposed, which reduces to a matrix variational inequality. At least for a small load we prove its solvability and find a quasi‐static model of the crack growth depending on the loading parameter. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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Arman Melkumyan 《Zeitschrift für Angewandte Mathematik und Physik (ZAMP)》2007,58(2):330-349
The problem of electric and acoustic waves diffraction by a half-plane crack in a transversal isotropic piezoelectric medium
is investigated. The crack is assumed to be electric permeable and free of tractions. The so-called “quasi-hyperbolic approximation”
[15] is adopted. Applying Laplace transformations and Wiener–Hopf technique a closed form solution is obtained. By the means
of Cagniard–de Hoop method a detailed dynamic full electroacoustic wavefield’s investigation is conducted. Mode conversion
between electric and acoustic waves, effect of electroacoustic head wave, Bleustein–Gulyaev surface wave and the wavefield
structure depending on the type of the incident wave (acoustic or electric) and its angle of incidence are analyzed in details.
The dynamic field intensity factors at the crack tip depending on the angle of incidence and on time are derived explicitly.
Numerical analysis is presented. 相似文献
15.
各向异性材料中共线刚性线夹杂的纵向剪切问题 总被引:8,自引:2,他引:6
本文研究各向异性材料中共线刚性线夹杂,(有时称作“硬裂纹”或“反裂纹”问题)的纵向剪切问题。利用复变函数方法,提出了一般问题的公式和某些实际重要问题的封闭形式解,考察了刚性线端点附近的应力分布.从本文解答的特殊情形,可以直接导出各向同性材料相应问题的公式和结果,包括某些已有的结果 ̄[7]. 相似文献
16.
This paper presents the applications of digital image correlation technique to the mesoscopic damage and fracture study of
some granular based composite materials including steelfiber reinforced concrete, sandstone and crystal-polymer composite.
The deformation fields of the composite materials resulted from stress localization were obtained by the correlation computation
of the surface images with loading steps and thus the related damage prediction and fracture parameters were evaluated. The
correlation searching could be performed either directly based on the gray levels of the digital images or from the wavelet
transform (WT) coefficients of the transform spectrum. The latter was developed by the authors and showed higher resolution
and sensitivity to the singularity detection. Because the displacement components came from the rough surfaces of the composite
materials without any coats of gratings or fringes of optical interferometry, both surface profiles and the deformation fields
of the composites were visualized which was helpful to compare each other to analyze the damage of those heterogeneous materials.
The project supported by the National Natural Science Foundation of China (10125211 and 10072002), the Scientific Committee
of Yunnan Province for the Program of Steel Fiber Reinforced Concrete, and the Institute of Chemical Materials, CAEP at Mianyang 相似文献
17.
Miyuki Harada Mitsuhiko Morimoto Mitsukazu Ochi 《Journal of Polymer Science.Polymer Physics》2003,41(11):1198-1209
A biphenol‐type epoxy resin, which had a mesogenic group in the backbone moiety, was modified with carboxy‐terminated butadiene acrylonitrile copolymer (CTBN) as a reactive elastomer, and its fracture toughness was measured. With the addition of CTBN, the fracture toughness of the biphenol‐type epoxy resin significantly increased and became significantly higher than that of a bisphenol A‐type epoxy resin modified with CTBN. The network chain orientation in the cured biphenol‐type epoxy resin system was clearly observed during the fracture process with polarized microscopy Fourier transform infrared measurements, although such a phenomenon was not observed in the bisphenol A‐type epoxy resin system. The high toughness of the cured biphenol‐type system was clearly due to the consumption of the mechanical energy by a large deformation of the matrix resin due to the orientation of the network chains during the fracture process. © 2003 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 41: 1198–1209, 2003 相似文献
18.
冲击载荷下剪切断裂研究 总被引:1,自引:0,他引:1
利用Hopkinson压杆技术对单边平行双裂纹试样倒向加载,在较大的加载率范围,对Ti6Al4V钛合金和40CrNiMoA两种材料的动态剪切断裂行为进行了研究.实验结果表明:存在两类韧性剪切断裂模式,即常规的韧性剪切型断裂和绝热剪切断裂.常规剪切型断裂模式的断裂韧性KⅡd随加载率的提高而增大,而绝热剪切型的断裂韧性KⅡd则随加载率的提高而减小,并且,当加载率增大至某一临界值时,常规的韧性剪切断裂模式将转变为绝热剪切断裂破坏模式. 相似文献
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20.
This study compared the fracture strength of Class II slot cavities restored with polymerizable restorative materials. Sixty, caries-free, posterior teeth were divided into five groups of 12 teeth. The Class II slot cavities were prepared. The teeth were restored with two packable composites (Filtek P60, Surefil), a microhybrid composite (Filtek Z250)and two ormocer (Definite, Admira). The restorations were then subjected to fracture resistance tests. The marginal ridges of the restorations were loaded at an angle of 13.5° to the long axis of the tooth in an Universal Testing Machine until failure. Analysis of mean forces indicated that, Filtek P60, Surefil and Filtek Z250 exhibited better performance than Definite and Admira. The tested resin composites differed in their mechanical properties. This study suggested that fracture behavior were highly influenced by the filler system. Overall, Filtek P60, Surefil, Filtek Z250, demonstrated good fracture resistance. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献