共查询到17条相似文献，搜索用时 156 毫秒
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本文采用边界元法研究了半空间中一近表面裂纹对SH波的散射问题,导出了以裂纹张开位移为未知函数的边界积分方程,针对边界积分方程高阶奇异性的特点,运用降低奇异性的方法,计算了裂纹边界面的裂纹张开位移、半空间表面的散射位移、裂纹尖端的动态应力强度因子。给出的算例表明,本文的方法不仅计算量小,而且有较好的精度。 相似文献
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研究了断裂面分形特征的力学特征，同时研究了自相似和自仿射分形裂纹尖端附近应力和应变的奇异性结构，讨论了二维和三维固体中分形裂纹的3种经典断裂型式和第四种断裂型式。发现分形断裂力学中有6种断裂型式。同时，结果表明J积分与路径有关。阐明了文献中提出修改的、且被证明与路径无关的，积分仅局部与路径无关，而且没有物理意义。可以推测，分形，积分应当是单位裂纹扩展分形测度的势能释放率。我们计算了某些应变硬化材料中分形裂纹应力知应变奇异性的幂。结果显示，分形裂纹尖端的应力和应变比光滑裂纹的应力和应变有较弱的奇异性。 相似文献
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本文利用数值模拟方法对 2种典型地震断层系进行了研究。首次引入利用所有裂纹面上裂纹张开位移 ( COD)数据计算应力强度因子和应力场的方法 ,提高了计算精度。本文对此方法进行了验证 ,利用边界元算法获得 COD数据 ,将全裂纹面上的 COD数据代入公式 ,拟合出应力强度因子和应力场。此方法后处理少、可靠性好、计算时间也相应较短 ,且易于操作实现 ,适用范围较广。在上述工作的基础上 ,本文利用此算法讨论了 2种典型的平面双等长裂纹系问题。第一种是平面共线剪切双裂纹 ,主要讨论了这种非单一裂纹在外力作用下的相互作用 ,定量给出了裂… 相似文献
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在隧道的施工和运营中,隧道衬砌不可避免会产生裂纹。裂纹和地震荷载的相互作用将加剧隧道的破坏,因此研究带裂纹隧道衬砌地震荷载作用下的破坏具有重要的意义。为了证明本文二维有限元数值模拟计算结果的正确性,首先用相互作用积分的方法计算动载作用下的静态裂纹,并与解析解进行比对,发现二者的吻合性很好。计算结果表明相互作用积分法可以用来精确地计算动载作用下带裂纹结构的动应力强度因子。用这种经过验证的方法来计算带裂纹重载铁路隧道衬砌的动应力强度因子和动承载力安全系数,可以看出在地震荷载作用下,I型裂纹的动应力强度因子在隧道结构的安全中起控制作用。当裂纹的长度大于某特定值时,隧道处于很危险的状态。 相似文献
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本文研究了抗震工程所关心的三维空间中共面周期裂纹阵与正入射S波的相互作用问题。导出了以裂纹张开位移为未知量的奇异积分方程组,详细研究了散射波的特征。当裂纹面为矩形时,对反射系数进行了数值计算,并求得了动态应力强度因子沿裂纹周界的分布,结果的可靠性由能量平衡关系及与二维问题的极限状态的比较得以初步验证。 相似文献
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岩石破裂时电磁辐射的机理研究 总被引：21，自引：6，他引：21
本文提出了岩石破裂时的电磁辐射是裂纹尖端电荷随着裂纹加速扩展运动所产生的假说.应用断裂力学方法推导了岩石破裂时初始裂纹长度与裂纹扩展加速度的关系,并计算了其速度和加速度值.根据破裂岩石的电子发射理论,解释了裂纹尖端带电荷的现象.利用岩石在单轴压缩致裂过程中记录到的近场电磁辐射的实验结果,计算了裂纹扩展时裂纹尖端的电荷量和远场电磁辐射强度.通过对电磁辐射波谱分析的研究,得到岩石破裂时电磁辐射频率上限的估计值.最后对岩石破裂时出现的声光电磁现象在理论上作了统一的定性的解释. 相似文献
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Crack widths and rock temperatures were monitored on an andestic bedrock cliff in the summit area of the Daisetsu Mountains, Hokkaido, northern Japan. Sequential data recorded the gradual widening of a crack to the point of critical crack extension, which resulted in catastrophic rock breakage. The data indicate that a combination of liquid water in?ltration into crack tip and subsequent freezing is the most signi?cant factor contributing to critical crack extension. The recorded sub‐critical crack movements involved a number of minor crack extensions and contractions, the timing of which correlates well with the magnitude of the reconstructed thermal stresses at the crack tip derived from thermal deformation of the plate‐shaped rock fragment. Larger crack extensions occurred when stress at the crack tip exceeded a threshold value, possibly re?ecting the control of rock fracture mechanics by which cracks are thought to propagate when the stress intensity factor at the crack tip exceeds the threshold values for stress corrosion cracking and the fracture toughness of the material. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
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近年来,人们越来越多地注意到地震发生前所存在着的地温增高的各种异常现象.本文以这些异常现象为根据,试图探讨地热变化与地震孕育的关系.文章假定,无限弹性介质中含有椭圆盘状断层面,并以此断层面为热通道.考虑在压应力作用下,温度为 x,y 的线性函数分布在此通道内,根据线弹性断裂力学观点,借助断裂力学中三维问题的解法,求出了断层面边缘附近的应力场和应力强度因子.结果表明,热应力有千巴的量级,并较定量地讨论了热应力大小与介质线膨胀系数的关系.最后简要地讨论了介质线膨胀系数的变化对地震孕育的影响. 相似文献
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—In order to investigate the effects of injected water in hydraulic fracturing, experiments were conducted on cubic granite
specimens, comparing fracturings induced by conventional water injection with those induced by pressurization of a urethane
sleeve, thereby realizing "hydraulic fracturing" without the use of fracturing fluid. In both experiments, a shear type mechanism
was found to be dominant in fault plane solutions of AE events. However, in the case of water injection, cracks extended rapidly
with large drops in hole water pressure and bursts of AE, whereas in pressurization by the urethane sleeve, cracks extended
stepwise with no such large drops in hole pressure and no bursts of AE. The difference in crack extension in the two experiments
can be analyzed by comparing relations between crack length and stress intensity factor of mode I at a crack tip. The observation
and analysis indicate that existence of fracturing fluid like water helps initiated cracks to extend rapidly and widely in
hydraulic fracturing in actual HDR fields.
Received September 12, 1996, accepted January 24, 1997 相似文献
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Application of caustic method to determining stress intensity factor of compressive shear crack 总被引：1，自引：0，他引：1
Introduction The caustics method has been introduced into seismology in recent years and preliminary in- vestigation indicates that it is effective to study the compressive stress (strain) of transparent sam- ples such as plexiglass (XU et al, 2001, 2002; Xu et al, 2000, 2002; XIONG et al, 2000, 2002). Especially, as a seismological concept, earthquake nuclei, becomes clearer according to the caustic shadow, which combines plastic area, nucleation area and crack concentration area together … 相似文献
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A numerical procedure for evaluation of the fracture process of gravity dams during strong earthquakes is presented. The BEM is used to discretize the dam reservoir system including the crack surfaces, and stress intensity factors at the crack tip are employed in a stage by stage procedure which simulates the crack extension. For each stage of constant crack length the mode superposition technique is applied; this is made possible by simulating the impact process of crack closing by a load pulse applied at the contact points which permits the structural stiffness to be assumed unchanged. To verify the proposed procedure, a cantilever beam model structure made of gypsum was tested on a shaking table. Good correlation with the numerical results was obtained, from which it is concluded that the procedure can be employed for evaluation of the crack propagation process in concrete structures subjected to dynamic loadings. 相似文献
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Summary The predetermination of the trajectory of a tensile crack induced at the tip of a stress-free fault plane (open slit, in two dimensional approximation) was investigated. Both the primary field of the tensile component of principal stress and the primary field of the strain energy density factor were computed and compared with the trajectory of the subsequent tensile crack. It was found that it is not the field of the strain energy density factor, but the field of the tensile component of principal stress which determines the trajectory of the tensile crack. Moreover, this field is responsible for the trajectory of the tensile crack not only in its seismoactive phase of its development, but also in the following aseismic stage characterized by slow stable growth. 相似文献
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Bogusław M. Domański 《Acta Geophysica》2010,58(2):174-194
The singular integral equations method makes it possible to determine a general analytical solution to the problem of a crack
subjected to any stresses, including singular ones. The singularity of stresses means that they tend to infinity in the concentration
point. In exponential functions describing this relationship, the exponent characterizes the stress curvature growth. Also
the energy released by crack opening can be described by a simple analytical formula. The problem is solvable for an exponent
greater than −1. The class of all the cracks subject to stresses that exponentially grow to one of the crack ends is divided
into three sub-classes. One of these embraces most of crack types, also Griffith’s. The remaining two are a source of microcracks
in an elastic medium. The onset of such a stress concentration gives rise to a microcrack which cancels the stress singularity
up to that with the exponent of −1/2, ensuring a strong stability of the medium. An analysis of the nucleation of such cracks
brought about a concept of elastic field rupture without destruction of interatomic bonds, which has implications relating
to the conductivity of metals. A general formula for the crack energy singles out a special crack of unit length, whose energy
is constant and independent of stress concentration. 相似文献