Papers by Keyword: Failure Criterion

Abstract: Abstract: The nouniformity of rock and soil materials and differences of boundary conditions caused the differentiation of stress field, together with the elastic-plastic characteristics of sliding zone material control the progressive unstable failure process. In this paper, The analysis of engineering example shows that the mechanical criterion is reasonable to judge the state of progressive slope evolution.

Abstract: In Four-column limb lattice jib structure system as the research object, considering the structure and mechanical characteristics, combining with the allowable stress method, from the failure mode of static strength, stiffness, overall stability and local stability to build lattice jib structure system reliability failure criterion. Based on the influence of parameter perturbation calculation of four-column limb lattice jib structure system, get the length of the jib, lifting weight, jib elevation, hoisting load bearing point offset, the proportion of wind environment on the influence of different failure modes and failure change law, as the main failure mode of the decision to provide the basis and methods.

Abstract: Based on the micro-structure, a mosaic model was established to obtain the stresses distribution of the C/C composite beam subjected to bending load. Then a subroutine for failure analysis was introduced to calculate the failure index of the composite beam. A corresponding laminate model was used to validate the calculation of the mosaic model. The results indicated that the method combining micro stresses and macro failure criterion was suitable for strength analysis of composite structure, which could be used in guiding the design of composite.

Abstract: The unstable failure of rock and soil slope was a progressive evolution process from local failure to total failure. The no-uniformity of rock and soil materials and differences of boundary conditions caused the discrepancy of stress field, together with the elastic-plastic characteristics of the sliding zone which controls the progressive unstable failure process. In this paper, any point of slop sliding zone was taken for the research object. On basis of limit slice method, the mechanical condition of slice was considered as a plane strain problem. According to Mohr-Coulomb linear failure criterion the stress state of a point is obtained with selecting stress function to establish the mechanical criterion of progressive slope failure. The analysis of engineering example shows that the mechanical criterion is reasonable to estimate the state of progressive slope evolution.

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.

Abstract: Biaxial compression tests are performed on 450mm*450mm*450mm cubic specimens of big aggregate concrete at five kinds of stress ratios,0:-1, -0.25:-1, -0.5:-1, -0.75:-1 and-1:-1 after exposure to freeze-thaw cycles of 50, 100, 150, 200, 250 and 300 times by employing a large static-dynamic true triaxial machine. Failure modes of the specimens are observed and described. The two principally static compressive strengths are measured. Based on the test data, the influences of the freeze-thaw cycles and stress ratios on the biaxial strengths of big aggregate concrete after exposure to freeze-thaw are analyzed respectively. The relationships between the ultimate compressive strength and freeze-thaw cycles, stress ratios are given respectively. The unified failure criterion with consideration of the influence of freeze-thaw cycles and stress ratios is proposed, which provides the experimental and theoretical foundations for strength analysis of big aggregate concrete structures subject to complex loads in cold environment. Key words: big aggregate concrete; freeze-thaw cycle; stress ratio; biaxial compressive strength; failure criterion

Abstract: Quasi-static method originated from the safety evaluation of structural engineering under earthquake. Compared with the time history analysis method, quasi-static calculation is simple and quick, and gradually applied in the analysis of slope stability. This article combined quasi-static method with three-dimensional finite difference method (FLAC3D), and applied it in the seismic stability study of a slope. The slope has a convex shape. Two tunnel anchorages and four bridge foundations built in central of it bearing bridge load, so it is a typical bearing slope. This article put forward a numerical calculation failure criterion to the slop of this type by calculating and analyzing the stress, displacement and plastic zone distribution characteristics when it under earthquake, and gave out the slopes seismic safety coefficient. The research results of this paper can provide a useful reference for the similar projects.

Abstract: In the actual structure, the concrete materials are mainly in multi-axial stress state. Because of the rapid development of concrete structures and the continuous improvement of structural engineering analysis theory, engineers have put forward higher requirements for concrete performance under multi-axial stress research. Based on stress space, this paper studies strength failure criterion of concrete, analyzed its limitations, and proposed concrete strength failure criterion research directions. It plays a strong practical role in scientific research.

Abstract: Microneedle, as a novel way for transdermal drug delivery, due to its painless and minimally invasive, has recently attracted much attention. The present study investigated skin deformation and failure due to insertion by a single microneedle with nonlinear finite element method. The finite element model considered multilayered, non-linear and hyperelastic properties of the skin, and tissue failure was phenomenologically described by an effective stress failure criterion. The deformation and failure of skin and the force displacement behaviour of the microneedle are discussed. The numerical results show a good agreement with the reported experimental data. The performed study provided novel insights into skin failure due to insertion of microneedle, and provided useful information with which to optimise the microneedle design.

Abstract: The paper establishes the forming limit diagrams (FLDs) for QSTE340 seamed tube hydroforming and the mother sheet metal forming by numerical approach and experimental approach. A novel experimental approach is proposed to evaluate the formability for tube hydroforming under biaxial stretching through elliptical bulging.Then the Nakazima and three types of tube hydroforming tests are simulated with finite element (FE) program LS-DYNA. The failure criterion of thickness gradient criterion (TGC) is introduced. The FLDs for seamed tube hydroforming and the mother sheet metal forming are constructed. The comparison of results based on TGC with experimental data shows the TGC is an appropriate one to determine the onset of localized necking. Finally, the differences and relationships between the FLDs for the seamed tube hydroforming and the mother sheet metal forming are discussed.