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991.
Flexural tests are sometimes used for the evaluation of fatigue and fracture properties, especially for thin cross sections
such as plate material where compact tension speciments cannot be used, or where material thicness is limited in the direction
required for data generation. The method is also useful for evaluation of crack closure provided the force transfer occurs
correctly. This paper shows how the influence of incorrect test fixture supports, which are outside the standard testing arrangement
for such test specimens, can affect the force-displacement curves as evidenced using the backface strain method. The results
show that incorrect test fixture supports may cause deviations in the force-displacement trace as an artifact of the testing
conditions. This effect can severely influence crack closure measurements. The effect was also modeled with finite element
analysis. 相似文献
992.
Summary Experimental, theoretical and numerical investigations show that crack kinking and crack branching can be observed and simulated
in brittle solids and in the fast dynamical propagation of quasi-brittle fractures. The present study shows that kinking and
branching may also occur in the quasi-static regime when an isotrophic or equi-biaxial tensile state of stress arises at the
tip of a cohesive crack, and may represent alternative itineraries (i.e. path bifurcation) of the fracture process. Specific
reference is made to the common but meaningful case of the three-point-bending test. Various numerical techniques apt to capture
the above occurrence are comparatively presented, and the influence of path bifurcation on the overall behaviour of the specimen
is discussed.
Received 8 October 1997; accepted for publication 22 January 1998 相似文献
993.
The plane stability problem for a rectangular, linearly elastic, isotropic plate with a central crack is solved. The dependence of the critical load on the crack length is studied using exact (the three-dimensional linearized theory of stability of elastic bodies) and approximate (beam approximation) approaches. The results produced by the beam approach are evaluated.Translated from Prikladnaya Mekhanika, Vol. 40, No. 11, pp. 117–126, November 2004.This revised version was published online in April 2005 with a corrected cover date. 相似文献
994.
C. FOND R. SCHIRRER 《宁波大学学报(理工版)》2003,16(4):367-372
采用冲击改性的高聚物对材料的断裂能在近瑞利波速Cr时减小的断裂行为进行了研究.设计了基于条带几何形状的实验装置用以探索这些高聚物在快速裂纹传播(RCP)时的脆性行为.发现沿着橡胶增韧聚甲基丙烯酸甲酯(RT-PMMA)的整个试样,尽管有的出现裂纹分叉甚至裂纹俘获静止,其宏观裂纹速度几乎恒定.当材料行为趋于加速裂纹时,临近Cr时断裂能减少,而当由于分叉使力学惯性效应趋于限制裂纹传播速率时,宏观裂纹速度稳定在大约αmb=0.6
Cr,其是RT-PMMA的宏观裂纹分叉速度.因此,对这种材料在宏观裂纹分叉速度时,实验断裂表面能及断裂表面韧性没有单一值.实际上,其宏观断裂表面能值随着失稳形态数目或无效裂纹分叉而增加. 相似文献
995.
The effects of pressure on the fracture properties of a rubbery particulate composite are studied. The results indicate elevated
fracture toughness values and lower crack growth rates relative to ambient pressure conditions. The regression method employed
for determining toughness establishes a minimum thickness requirement for application of linear elastic fracture mechanics
concepts. Also, it is demonstrated that single edge notched tension specimens can be successfully used to predict the fracture
initiation of specimens with semielliptical surface cracks. 相似文献
996.
Fracture phenomena at the debond tip of partially bonded bimaterial half-planes subjected to concentrated normal forces, couples, and uniform tension are considered. The crack initiation conditions are described by the stress distribution before the initiation and the energy release rate of the crack immediately after the initiation. The debond development conditions are described by the stress distribution and the energy release rate of the debond before its initiation. When both the crack and the debond have chances to occur, or when cracks can arise in both the materials, the fracture phenomena are predicted by comparing the ratio of energy release rates and the ratio of fracture toughnesses. 相似文献
997.
Hou Mishan 《Acta Mechanica Solida Sinica》1999,12(1):83-90
The coupled elastic and electric fields for anisotropic piezoelectric materials with electrically permeable cracks are analyzed
by using Stroh formula in anisotropic elasticity. It is shown from the solution that the tangent component of the electric
field strength and the normal component of the electric displacement along the faces of cracks are all constants, and the
electric field intensity and electric displacement have the singularity of type (1/2) at the crack tip. The energy release
rate for crack propagation depends on both the stress intensity factor and material constants. The electric field intensity
and electric displacement inside electrically permeable cracks are all constants. 相似文献
998.
Using a sub-regional boundary element method, an algorithm for the two-dimensional elastic bodies with a closed crack loaded
by a moving contact elastic body is proposed. Since the extent and status of the contact surface of two elastic bodies and
the crack within the body are all not known in advance, a double iterative contact algorithm is used. The BEM program for
solving the closed crack problems is developed, some numerical examples are calculated, and the results of the center crack
cases are shown to be in good agreement with the analytical solution in the classical fracture mechanics. In the condition
of friction and non-friction, some coupling computational results of the SIF for the closed crack, with different angles and
loaded by a moving contact elastic body, are also obtained by a numerical computation.
The project supported by the National Natural Science Foundation of China (10172053) and NJTU Foundation of China (PD-157) 相似文献
999.
The problems of finite bimaterial plates, bearing uniform tension, compact tension and three point bending, are studied by
using the eigenfunction expansion variation method (EEVM). And interfacial stress intensity factors (SIFs) are determined.
The SIFs varying with shear modulus μ and Poisson's ratios ν of both materials are discussed. 相似文献
1000.
给出载流无限大薄板在形成半无限长裂纹的瞬间,尖端附近的温度和应力的具体表达式。通过算例表明:在电流所产生的焦耳热源的作用下,裂尖区域处的温度将瞬时升高,并伴有压应力的产生,从而可达到阻裂纹扩展的目的。 相似文献