Papers by Keyword: Failure Criterion

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Authors: Young Shin Lee, Hyun Soo Kim, Young Jin Choi, Jae Hoon Kim
Abstract: The laminated composite structures applied to the wing and the speed brake of an aircraft or the turbine blade of a compressor. These structures may be impacted by birds and hails during operation. They may also be impacted by drop of a tool during manufacture or repair. Unlike high velocity impact damage, which can be easily found by the naked eye, the damage due to low velocity impact may be difficult to detect. Damage which is not detected may cause failure of a structure and result in damage propagation. Growth of damage means reduction of stiffness on the structure. So, exact prediction of damage caused by a low velocity impact is very important in order to guard against sudden failure of the structure. In this study, modified delamination failure criterion has suggested in order to predict the failure behavior of a composite plate subjected to low-velocity impact. The criterion includes the assumption which is matrix cracking mode causes delamination failure. Predicted damage using supposed delamination criterion is similar to experiment results.
Authors: Bi Yong Li, Zhe Ming Zhu, Zhang Tao Zhou
Abstract: The existence of water affects the mechanical properties of cracked rock mass. Taking into account the friction generated by the crack closure, the stress intensity factor of the center cracked plate subjected to compression and seepage pressure was obtained through the theoretical analysis and numerical calculation of the boundary collocation method. The results show that crack tip stress intensity factor increases with the increasing of the seepage pressure, but decreases with the increasing of crack surface friction and the confining pressure. Finally a failure criterion for cracked rock mass under seepage pressure and confining pressure is developed.
Authors: Yu Tao Yan, Mai Yang, Zhi Li Sun, Li Fang Liu
Abstract: The formation and lubrication mechanism of boundary lubricating film were discussed. The boundary lubricating film includes adsorption film and chemical reaction film, and has respective temperature operating range. The adsorption film adsorbed in metal surface by Van-der Wads, and the parenchyma is the external friction between adsorption molecule layers. The chemical reaction film is made by the reaction between metal and extreme pressure additive in base oil, and the anti-wear capability is realized by the low-melting point eutectic alloy. The temperature is regarded as a judge criterion for failure of boundary lubrication. The failure model for boundary lubricating film is established. According to the failure model, the failure criterion proposed is effective by analysis of the spiral bevel gear using the finite element method. These results provide a basis for the application of boundary lubrication.
Authors: Huai Ning Ruan, Di Wang, J. W. Ju
Abstract: In designing earth structures, various kinds of complex soils and rocks are constantly encountered. These geomaterials exhibit heterogeneous, nonlinear, and anisotropic behavior. A failure criterion for such complicated materials is proposed. This model is highly comprehensive. It characterizes heterogeneity, nonlinearity, and anisotropy simultaneously in one equation. Many classical failure criteria employed in geomechanics and plasticity are its special cases. The material parameters in the proposed criterion may be determined from tests of unconfined compression, uniaxial tension, biaxial compression, and direct shear. The case study illustrates the potential of the proposed model in engineering application.
Authors: Wei Yu Wu, Guo Hua Liu
Abstract: A failure criteria basing on Drucker-Prager yield criterion for geomaterials is modified in terms of the inherent anisotropy of the friction angle and the dilation angle. To implement the model in a numerical way, the corresponding consistent return mapping algorithm is formulated and by dividing the scalar product of the stress rate and the strain rate into the deviatoric and spherical parts, the consistent elastoplastic tangent modulus matrix is obtained. Then, the codes are introduced into finite element software ABAQUS via the UMAT. An example has been presented illustrating influence of the anisotropic degree on the bearing capacity and the pattern of strain localization.
Authors: Xu Dan Dang, Shao Jie Shi, Yi Guo, Jun Xiao
Abstract: The finite element software was used to get the X-cor sandwich’s shear strength. During the shear strength analysis, the failure criterion and materials stiffness degradation rules fitting for the analysis of X-cor sandwich’s failure mechanism were proposed and the X-cor sandwich’s failure process and modes were also clarified. According to the failure criterion we used the elements with stiffness degradation and their distributions in the finite element model to simulate the types and propagation path of the failure and the failure mechanisms of X-cor sandwich under shear were explained. The finite element analysis indicates during the shear firstly the resin regions fail and then the multiple failure modes of Z-pin pull-out from the face-sheet, Z-pin shear off and Z-pin buckling all exist. The propagation paths of the failure elements are dispersive. By contrasting the finite element results and test results the values are consistent well and the error range is -10.4%~7.4%. The comparison results show that the failure criterion and stiffness degradation rules are reasonable and this method can be used to predict the X-cor sandwich’s shear strength.
Authors: Simona Coccia, Mario Como, Fabio di Carlo
Abstract: The research of a failure criterion for concrete under multi-axial stresses is a very important task because of the numerous civil engineering applications. Nowadays several concrete failure tests are available in literature and various criteria have been proposed. A multi-axial failure criterion for the concrete founded on a simple physical basis, has been proposed by one of the authors. In this paper a sharper foundation of this criterion is given. The hardened cement paste (hcp), the binder of all the aggregate particles, is responsible of the concrete strength. Consequently, a preliminary average evaluation of the stresses, occurring, when the concrete is loaded, into the various phases components, and particularly in the hcp, is necessary to analyse the failure. To that end, the paper revolves around the analysis of the thermal behaviour of the concrete at its early stage of setting. It is shown that the heat production during the cement hydration process, is responsible to produce clearances among the various particles and the surrounding hcp that, in turn, the consequent statically determined structure of the concrete. Validation of this result comes out by analysing the elastic moduli and the thermal expansion coefficients. The micro-macro failure condition of Como & Luciano thus receives a sounder physical basis.
Authors: Mu Yang, Jian Guo Liang, Wei Jun Yang
Abstract: Drying shrinkage loads are converted into the equivalent temperture,using the model of composite material mechanical analysised layer stresses and interlaminar stresses of the shear wall under the influence of temperture load stress,combined with wind load and weight ,acquired the thermal insulation layer’s stress effect under the combined effect. According the failure criterion of material and adhesive surface, to determined the cracking mechanism and crack control of aerated concrete thermal insulation layer.
Authors: Wan Zhen Wang, Yuan Jiang Chen, Fei Yi Chen
Abstract: Referring to an egg shaped yield function for geotechnical materials, a failure criterion for light-weight aggregate concrete is put forward, in which the tensile and compressive meridians are egg shaped curves and the failure envelopes in deviated plane is smooth elliptic curves. The suggested failure criteria could describe the failure characteristic of lightweight aggregate concrete at different stress state. The precision of the suggested egg shaped failure criteria is verified by comparing with experiment data of lightweight aggregate concrete.
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