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周国林 谭国焕
,李启光,Tsui Y

岩石力学与工程学报 , 2001,
Abstract: Based on the observation and modeling of localized deformation and failure for rock with the shear failure mode, a new strength criterion is proposed. This criterion takes the characteristics of the non-homogeneous and localized failure of rock into account. It accounts for the size effect of rock in the shear failure mode.

GAO Hong,ZHENG Yingren,FENG Xiating,

岩石力学与工程学报 , 2007,
Abstract: Yield and failure are two different conceptions,and they are two different steps in the deformation processes of materials.In the stress space,the failure surface of perfect plastic materials keeps unchangeable.In the strain space,however,with the constant size of failure surface,its center location moves with the increase of plastic deformation.So the traditional criteria built in the stress space cannot determine whether the material is destroyed.On the contrary,the criteria built in the strain space can properly deal with the problem.The strain criterion for ductile shear failure based on the maximum principal shear strain is established.On the basis of triaxial compression test results of normally consolidated saturated clay,the development laws of stress and volume strain(drained)or pore water pressure(undrained)with strain are analyzed;and the results of numerical simulation with ANSYS are in consistent with the test results.So it is rational to take the shear strain of initial critical state as the limit failure strain.The formulas of the maximum principal shear strain are deduced;and the calculation cases for several commonly used yield criteria are presented.

Xu Zhiwei,Zhang Jingde,Li Yuzhong,Wang Chunjin,

岩石力学与工程学报 , 1998,
Abstract: The principle, testing process f and data interpretation of single point method are outlined. The principle and criterion to determine shear strength of rocks are proposed with single point method. Comparison of testing results is made between single point method and multipoint method, and the differences are very small. The single point method is a novel testing method to determine shear strength of rocks in practice.
Measuring cosmic shear with the ring statistics  [PDF]
Tim Eifler,Peter Schneider,Elisabeth Krause
Physics , 2009, DOI: 10.1051/0004-6361/200912888
Abstract: Commonly used methods to decompose E- and B-modes in cosmic shear, namely the aperture mass dispersion and the E/B-mode shear correlation function, suffer from incomplete knowledge of the two-point correlation function (2PCF) on very small and/or very large scales. The ring statistics, the most recently developed cosmic shear measure, improves on this issue and is able to decompose E- and B-modes using a 2PCF measured on a finite interval. First, we improve on the ring statistics' filter function with respect to the signal-to-noise ratio. Second, we examine the ability of the ring statistics to constrain cosmology and compare the results to cosmological constraints obtained with the aperture mass dispersion. Third, we use the ring statistics to measure a cosmic shear signal from CFHTLS (Canada-France-Hawaii Telescope Legacy Survey) data. We consider a scale-dependent filter function for the ring statistics which improves its signal-to-noise ratio. In addition, we show that there exist filter functions which decompose E- and B-modes using a finite range of 2PCFs (EB-statistics) and have higher S/N ratio than the ring statistics. However, we find that data points of the latter are significantly less correlated than data points of the aperture mass dispersion and the EB-statistics. As a consequence the ring statistics is an ideal tool to identify remaining systematics accurately as a function of angular scale. We use the 2PCF of the latest CFHTLS analysis and therefrom calculate the ring statistics and its error bars.
Elastic-plastic solutions of bilinear strain-hardening tunnel and pile cavity based on tri-shear failure criterion

- , 2018,
Abstract: 将隧道和桩孔简化为厚壁圆筒,基于三剪强度准则和双线性强化模型,考虑材料的应变强化和中间主应力效应,推导了厚壁圆筒在均匀内外压作用下的弹塑性极限解,并给出恒定外压条件下塑性区半径与内压的关系式,分析了强化模量系数、半径比、中间主应力与材料强度拉压异性对厚壁圆筒弹塑性极限解的影响规律。研究结果表明:所得弹塑性极限解克服了Tresca屈服准则与Mises屈服准则未考虑拉压异性,Tresca屈服准则与Mohr-Coulomb屈服准则未考虑中间主应力与双剪强度理论极限解存在滑移面突变现象的不足; 弹塑性极限解均随半径比与中间主应力影响系数的增大而增大,随拉压强度比的增大而减小,外压对极限内压的影响程度随着拉压强度比的增大而减小; 当强化模量系数为0.1、半径比为2时,考虑强化效应的塑性极限内压比不考虑时相对增大10%以上,随着半径比增大到4,塑性极限内压比不考虑强化效应时相对增大38%以上,强化效应影响更加明显,故对于存在应变强化效应的材料,采用双线性强化模型的分析结果更接近工程实际; 当不考虑中间主应力与应变强化时,土体的极限扩孔压力弹塑性极限解与Vesic解相差在0.02%以内,当考虑了土体的中间主应力和应变强化效应后,塑性区半径与内半径比为10时,弹塑性极限解分别是Vesic解的1.06、1.81倍,因此,基于Vesic解的极限扩孔压力过于保守。
Tunnel and pile cavity were simplified as thick-walled cylinders, the effects of strain hardening and intermediate principal stress were considered, the elastic-plastic limit solution of thick-walled cylinder under uniform internal and external pressures was deduced based on the tri-shear failure criterion and the bilinear strain-hardening model, the relationship of internal pressure and elastic-plastic radius under constant external pressure was given, and the effects of many parameters on the limit solution of thick-walled cylinder were discussed, including strengthening modulus, radius ratio, intermediate principal stress and material strength heterogeneity of tension and compression. Research result shows that the proposed solution can overcome the deficiencies of material strength heterogeneity of tension and compression ignored by Tresca and Mises yield criteria, the intermediate principal stress ignored by Tresca and Mohr-Coulomb yield criteria, as well as the abrupt changing phenomenon of slip plane in twin shear strength theory. The limit solution increases with the radius ratio and the intermediate principal stress coefficient, but decreases with the tension-compression strength ratio. The effect of external pressure on the limit internal pressure decreases with the tension-compression strength ratio. Compared with no considering strengthening modulus, when the strengthening modulus is 0.1 and the radius ratio is 2, the plastic limit internal pressure increases by more than 10%. When the radius ratio increases to 4, the plastic limit internal pressure increases by more than 38%, so the strengthening effect is more obvious. Obviously, for the material with strain hardening effect, the result analyzed by the bilinear strain-hardening model is closer to the engineering practices. When the intermediate principal stress and the strain hardening are not considered, the differences of limit expansion soil pressures calculated by the proposed solution are within 0.02%
Optimization of laminates subjected to failure criterion  [PDF]
E. Kormaníková,Ilija Mamuzi?
Metalurgija , 2011,
Abstract: The paper is aimed on laminate optimization subjected to maximum strain criterion. The optimization problem is based on the use of continuous design variables. The thicknesses of layers with the known orientation are used as design variables. The optimization problem with strain constraints are formulated to minimize the laminate weight. The design of the final thickness is rounded off to integer multiples of the commercially available layer thickness.
The Effect of Scale Direct Shear Test on the Strength Parameters of Clayey Sand in Isfahan City, Iran  [PDF]
R. Dadkhah,M. Ghafoori,R. Ajalloeian,G.R. Lashkaripour
Journal of Applied Sciences , 2010,
Abstract: The direct shear test measures shear strength parameters of soils and other particulate materials. In this study the effects of box size on the strength parameters of soil is studied in Isfahan city area. The soil samples are classified as SC according to the unified soil classification system. The samples were well graded with dry density ranges in the between 1.67 and 1.82 g cm-3. The tests on the shear strength properties of SC soils were carried out by using large, medium and small scale direct shear equipment with shear box dimensions of 60, 100 and 300 mm. The undistributed samples, having almost the same properties, were tested in three square shear boxes of varying sizes. Forty five sets (each set with three samples) of direct shear tests at a constant rate of 1 mm min-1 were performed to study the influence size of the shear boxes and soil density on the strength parameters. The results show the effect of scale on the test. The large and medium scale direct shear produces a higher cohesion and lower friction angle compared with the results of the small-scale direct shear test. The tests indicate that the friction angle and cohesion increase when soil density in each of the three boxes increases. Therefore, these observations suggest that strength parameters are controlled by the scaling effect and physical properties of the soil. The present study also shows the relationship between the shear strength parameters of small and large scale direct shear tests.
A simple beam model for the shear failure of interfaces  [PDF]
F. Raischel,F. Kun,H. J. Herrmann
Physics , 2005, DOI: 10.1103/PhysRevE.72.046126
Abstract: We propose a novel model for the shear failure of a glued interface between two solid blocks. We model the interface as an array of elastic beams which experience stretching and bending under shear load and break if the two deformation modes exceed randomly distributed breaking thresholds. The two breaking modes can be independent or combined in the form of a von Mises type breaking criterion. Assuming global load sharing following the beam breaking, we obtain analytically the macroscopic constitutive behavior of the system and describe the microscopic process of the progressive failure of the interface. We work out an efficient simulation technique which allows for the study of large systems. The limiting case of very localized interaction of surface elements is explored by computer simulations.
The Lesser Role of Shear in Star Formation: Insight from the Galactic Ring Survey  [PDF]
Sami Dib,George Helou,Toby Moore,James Urquhart,Ali Dariush
Physics , 2012, DOI: 10.1088/0004-637X/758/2/125
Abstract: We analyse the role played by shear in regulating star formation in the Galaxy on the scale of individual molecular clouds. The clouds are selected from the 13^CO J=1-0 line of the Galactic Ring Survey. For each cloud, we estimate the shear parameter which describes the ability of density perturbations to grow within the cloud. We find that for almost all molecular clouds considered, there is no evidence that shear is playing a significant role in opposing the effects of self-gravity. We also find that the shear parameter of the clouds does not depend on their position in the Galaxy. Furthermore, we find no correlations between the shear parameter of the clouds with several indicators of their star formation activity. No significant correlation is found between the shear parameter and the star formation efficiency of the clouds which is measured using the ratio of the massive young stellar objects luminosities, measured in the Red MSX survey, to the cloud mass. There are also no significant correlations between the shear parameter and the fraction of their mass that is found in denser clumps which is a proxy for their clump formation efficiency, nor with their level of fragmentation expressed in the number of clumps per unit mass. Our results strongly suggest that shear is playing only a minor role in affecting the rates and efficiencies at which molecular clouds convert their gas into dense cores and thereafter into stars.
Ring-Driven Shear Thickening in Wormlike Micelles?  [PDF]
M. E. Cates,S. J. Candau
Physics , 2001, DOI: 10.1209/epl/i2001-00359-2
Abstract: The shear-thickening behaviour of wormlike micelles, at concentrations just below overlap, remains unexplained. In some cases it has recently been confirmed that very slow relaxations must be present even in the quiescent state -- for example, the shear thickening properties can depend on earlier thermal cycling. We present a speculative scenario based on the presence, just below the (apparent) overlap threshold, of large rings whose linking and delinking kinetics control the shear thickening process. Equilibration between rings and open chains in turn controls the slow relaxations.
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