二种岩石断裂韧度试样测试的稳定性分析

本文分析了 ISRM 采纳的两种具有人字形切槽的试样在测试过程中裂纹扩展的稳定性问题,计算了它们在不同加载条件和试验机刚度时各自的稳定性因子;指出对岩石等一类脆性材料,加载方式和试验机刚度对测试的稳定性有很大的影响;说明了这两种试样在稳定性方面的差异,并指出它们在稳定性上明显地优于普通直裂纹试样.     

切槽爆破中切槽角的研究

切槽爆破技术是作者在岩石断裂力学理论和大理石矿实际开采要求的基础上提出的。这个技术的关键是采用带V型槽口的炮孔。本文从理论上论证了采用V型槽口炮孔的合理性,并着重研究了V型槽口角,给出了最佳V型槽口角的大小。文中附有某大理石矿采用V型槽口炮孔爆破切割大理石的现场照片及试验数据,切割效果是令人满意的。     

碳纤维增强混凝土缺口梁承载力试验研究

利用纤维薄板对混凝土构件进行加固或修补以提高其承载能力及延长使用寿命是一种新的先进补强方法。本文通过改变试件的缺口高度（α0）和纤维薄板长度（LX）,对素混凝土以及碳纤维薄板增强混凝土三点弯曲缺口梁试件进行对比试验研究,探讨两种梁的破坏机理及其极限承载力。试验及分析结果表明,采用碳纤维薄板外贴在梁的底部可提高梁 的整体刚度和强度,抑制混凝土中裂缝的扩展,改变梁的破坏模式,并大大提高其极限承载能力（可提高1．7－6．9倍）。     

Measurement and modeling of stress concentration around a circular notch

When designing composite materials, the presence of stress concentration at locations such as circular nothces is unavoidable. Such locations in structural elements arise from joints required to form a structure. The stress concentration, observed around the notch, is quantified by the stress concentration factorK. This quantity is normally calculated analytically and/or numerically and is an important design parameter. In this work, the experimental technique of remote laser Raman microscopy is used for the in situ measurement ofK in Kevlar 49 fiber/epoxy composite plates containing a circular hole. The results obtained by this technique are compared with those calculated analytically and by finite element analysis. Both analytical and numerical methods underestimate the experimental results for maximumK by approximately 10 percent, which is considered reasonable within experimental error. In addition, very good agreement between analytical and experimental data is obtained for the decay of the stress concentration factor as a function of distance from the edge of the hole. The numerical results, however, overestimate the decayK with distance from the notch boundary and only converge at relatively large distances.B. P. Arjyal has obtained his PhD from the Materials Department, Queen Mary & Westfield College, University of London, London, E1 4NS, United Kingdom.     

橡胶楔体与刚性缺口接触大变形分析

利用Ｋｕｏｗｌｅｓ与Ｓｔｅｒｎｂｅｒｇ提出的非线性弹性大变形应变能函数,对橡胶楔体与刚性缺口接触问题进行大变形渐近分析,推导了楔体尖端场的渐近方程,得到楔体尖端附近的应力应变场及应力的奇异性指数与橡胶楔体角度、刚性缺口角度及材料常数有关的表达式;楔尖附近同一半径上应力分量为常数,同时,利用非线性有限元理论编制了大变形有限元程序,考虑楔体尖端与缺口接触边界条件,计算得到了与分析解一致的结论,当缺口角     

Electronic transport properties on V-shaped-notched zigzag graphene nanoribbons junctions

Using nonequilibrium Green?s functions in combination with the density functional theory, the spin-dependent electronic transport properties on V-shaped notched zigzag-edged graphene nanoribbons junctions have been calculated. The results show that the electronic transport properties are strongly depending on the type of notch and the symmetry of ribbon. The spin-filter phenomenon and negative differential resistance behaviors can be observed. A physical analysis of these results is given.     

Large eddy simulation of turbulent premixed and stratified combustion using flame surface density model coupled with tabulation method

Large eddy simulations (LESs) are performed to investigate the Cambridge premixed and stratified flames, SwB1 and SwB5, respectively. The flame surface density (FSD) model incorporated with two different wrinkling factor models, i.e., the Muppala and Charlette2 wrinkling factor models, is used to describe combustion/turbulence interaction, and the flamelet generated manifolds (FGM) method is employed to determine major scalars. This coupled sub-grid scale (SGS) combustion model is named as the FSD-FGM model. The FGM method can provide the detailed species in the flame which cannot be obtained from the origin FSD model. The LES results show that the FSD-FGM model has the ability of describing flame propagation, especially for stratified flames. The Charlette2 wrinkling factor model performs better than the Muppala wrinkling factor model in predicting the flame surface area change by the turbulence. The combustion characteristics are analyzed in detail by the flame index and probability distributions of the equivalence ratio and the orientation angle, which confirms that for the investigated stratified flame, the dominant combustion modes in the upstream and downstream regions are the premixed mode and the back-supported mode, respectively.     

The expression of stress and strain at the tip of three-dimensional notch

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