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51.
This paper presents a boundary element method (BEM) procedure for a linear elastic fracture mechanics analysis in two‐dimensional anisotropic bimaterials. In this formulation, a displacement integral equation is only collocated on the uncracked boundary, and a traction integral equation is only collocated on one side of the crack surface. A fundamental solution (Green's function) for anisotropic bimaterials is also derived and implemented into the boundary integral formulation so that except for the interfacial crack part, the discretization along the interface can be avoided. A special crack‐tip element is introduced to capture the exact crack‐tip behavior. A computer program using FORTRAN has been developed to effectively calculate the stress intensity factors of an anisotropic bimaterial. This BEM program has been verified to have a good accuracy with previous studies. In addition, a central cracked bimaterial Brazilian specimen constituting cement and gypsum is prepared to conduct the Brazilian test under diametral loading. The result shows that the numerical analysis can predict relatively well the direction of crack initiation and the path of crack propagation. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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Microdiamond and graphite occur in quartzofeldspathic rocks (saidenbachites) of the central Erzgebirge in Saxony. Zircon from such rocks contains not only relatively high but also variable amounts of early formed graphite and later crystallized diamond, however no carbonate. Six purified zircon concentrates were analysed by mass spectrometry for δ13C(PDB) values which were between −24 and −33‰. The carbon inclusions resulted in C contents of the concentrates as high as 0.5 wt%. It is hypothesized that the observed δ13C signature results from organic material in the sedimentary protoliths of the saidenbachites probably deposited not earlier than Mid‐Devonian. This material was transformed to graphite during early metamorphism and subsequently to diamond after an anatectic event at great depths (>150 km). During these processes, the δ13C signature of the carbon did not (significantly) change. 相似文献
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商丹断裂带作为扬子板块与华北板块的缝合带,在秦岭造山带中占据重要的地位。对其进行精细的构造研究,是了解扬子板块与华北板块相互作用过程的关键。研究工作在商丹断裂带东段展开,对该带进行了详细的野外观察、显微构造观察、糜棱岩化过程中温度的估算、有限应变测量、差异应力的计算以及糜棱岩化过程中运动学涡度的计算。变形温压条件指示糜棱岩形成于中-高绿片岩相到低角闪岩相变质条件。差异应力计算结果指示商丹带具备大型构造动力特征。涡度分析表明该断裂带的变形以纯剪切作用占据主导作用,但包含有简单剪切的分量,从而证明了扬子板块与华北板块之间具有以碰撞挤压为主的斜向汇聚方式。 相似文献
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小秦岭地区太华群锆石U-Pb年龄及华北克拉通南缘地壳演化 总被引:4,自引:0,他引:4
以小秦岭地区太华群二长片麻岩为研究对象,分析其地球化学、锆石U-Pb年龄和Hf同位素特征。地球化学分析显示其原岩为高钾钙碱性花岗质岩石,稀土元素总含量较高(229×10-6),轻、重稀土元素分馏明显(w(La)N/w(Yb)N=45.39),有明显的Eu负异常(0.43)。原始地幔标准化微量元素蛛网图显示其富集Rb、Ba、Th、U等大离子亲石元素和亏损Nb、Ta、Sr、P、Ti等高场强元素。锆石U-Pb定年结果显示,其原岩的形成时代为古元古代早期(2.47Ga)。锆石Hf同位素分析结果显示:初始N(176 Hf)/N(177 Hf)值变化范围很小,为0.281 284~0.281 328,εHf(t)值均为正值(0.93~5.18);二阶段Hf模式年龄为2.70~2.89Ga,新生地壳(现代岛弧火山)Hf模式年龄为2.54~2.73Ga,接近于锆石结晶年龄(2.47Ga),指示华北克拉通南缘在这一时期有明显的新生地壳生长。华北克拉通南缘在新太古代早期(2.7~2.9Ga)、新太古代晚期—古元古代早期(2.2~2.5Ga)和古元古代中期(1.8~2.1Ga)有3期重要的构造热事件。新太古代早期及晚期有明显的新生地壳生长(εHf(t)0),新太古代晚期—古元古代早期和古元古代中期的岩浆活动有明显的新生地壳生长,同时还伴随有古老地壳物质的再循环和改造(εHf(t)0或εHf(t)0)。 相似文献
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Natural Hazards - Tsunamis occur not only in marine settings but also in lacustrine environments. Most of the lacustrine tsunamis are caused by seismically- or aseismically-triggered mass... 相似文献
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WANG Pu-jun HOU Qi-jun SHU Ping HUANG Yu-long GUO Zhen-hua LI Jin-long College of Earth Sciences Jilin University Changchun Jilin China Jilin Petroleum Company Songyuan Jilin China Daqing Petroleum Company Daqing HeiLongjiang China 《东北亚地学研究》2005,(Z1)
Volcanic rocks of the late Mesozoic are very important reservoirs for the commercial natural gases including hydrocarbon, carbon dioxide and rare gases in the northern Songliao Basin. The reservoir volcanic rocks include rhyolite, andesite, trachyte, basalt and tuff. Facies of the volcanic rocks can be classified into 5 categories and 15 special types. Porosity and permeability of the volcanic reservoirs are facies-controlled. Commercial reservoirs were commonly found among the following volcanic subfacies: volcanic neck (I1) , underground-explosive breccia (I3), pyroclastic-bearing lava flow (II3), upper effusive (III3) and inner extrusive ones (IV1). The best volcanic reservoirs are generally evolved in the interbedded explosive and effusive volcanics. Rhyolites show in general better reservoir features than other types of rocks do. 相似文献
60.
A comparison has been made between the predictions of the theory for radial variations of both Alfvénic fluctuations and solar wind proton temperatures proposed by Tu (1987, 1988) and the statistical results of hourly averaged plasma and magnetic field data observed by Helios 1 and 2 from launch through 1980 for different solar wind speed regimes. The comparison shows that for speed ranges between 500–800 km s-1, the radial variation of the proton temperature between 0.3 and 1 AU can be explained by heating from the cascade energy determined by the radial variation of the total variance of magnetic field vector. The explanation of the radial variations of both temperature and the total variance of magnetic fields for speed ranges less than 400 km s -1 is less clear.This project was supported by National Natural Science Foundation of China for Tu's part of the work. 相似文献