Papers by Keyword: Crack-Tip Field

Abstract: Multi-parameter fracture mechanics concept has been applied to investigate crack behavior under mixed-mode loading, particularly in a semi-circular bending disc. The so-called Williams’ series expansion is used for the crack-tip stress field approximation. It has been shown that application of the generalized fracture mechanics concept can be crucial for materials with specific fracture behavior, such as elastic-plastic or quasi-brittle one, when fracture occurs not only in the very vicinity of the crack tip, but also in a more distant surrounding. Then, considering the higher-order terms of the Williams’ expansion in fracture criteria can be helpful. The attention is devoted to the analysis of the influence of various distances between the supports during the three-point bending test on the results of the further crack propagation direction.

Abstract: A mixed-mode geometry has been chosen in order to investigate crack propagation through the specimen. There exist several criteria for estimation of the crack path, and this work enriches the concept by application of multi-parameter fracture mechanics. Particularly, the classical MTS criterion is presented in its generalized form when several initial terms of the so-called Williams series expansion are used for the tangential stress approximation. The results obtained show that the generalized approach can be important in some special cases, when the criterion shall be applied in a larger distance from the crack tip.

Abstract: The stress intensity factor and the T-stress describing the near-crack-tip fields for selected specimen shapes of a test geometry based on wedge splitting and three point bending tests with several variants of boundary conditions are computed using finite element software ANSYS. The test configuration in question is expected to be a convenient alternative to classical fracture tests (especially the tensile ones) for investigation of the quasi-brittle fracture of building materials, when low constraint is requested. These specimens are investigated within the framework of two-parameter fracture mechanics; near-crack-tip stress field parameters are determined and compared with those of the wedge splitting test due to their shape similarity. The sensitivity of the values of these parameters to the boundary conditions is also shown. Suitable choice of the shape of the specimens is discussed.

Abstract: The mechanical behaviors of super-elastic shape memory alloy are formulated based on Auricchios constitutive model. The finite element simulation method for the mechanical behaviors of super-elastic shape memory alloy using the software of ANSYS is introduced. The mechanical behaviors near crack-tip in a shape memory alloy plate with one inclining crack are numerically simulated by finite element method. Results show that the software of ANSYS can simulate the mechanical behaviors of shape memory alloy with crack effectively.

Abstract: The crack problem of power functionally graded spherical shell with Reissners effect is studied. Based on the Reissners theory, the governing equation of power functionally graded spherical shell is given. The eigen-solution of the crack tip field is obtained by using the asymptotic expansion method. The result is similar to Williams solution for homogeneous material.

Abstract: Reissner’s plate bending fracture theory with consideration of transverse shear deformation effects is adopted for the crack problem of power-law functionally graded materials (FGMs) plates. Assume that the crack is parallel to the material property gradient. By applying the asymptotic expansion method, the crack-tip higher order asymptotic fields which are similar to Williams’ solutions of homogeneous materials are obtained.

Abstract: This paper focuses on the thermo-mechanical behaviors of the shape memory alloy board with a crack and under the torsion load. A stress field equation from mechanics of elasticity is used to describe the stress distribution around the crack tip in the shape memory alloy board. A martensitic phase transition equation is supposed to predict the martensitic phase transition behaviors of the field near the crack tip in the shape memory alloy board. The martensitic phase transition zones near the crack tip in the shape memory alloy board under the torsion load are numerically described based on the stress field equation and martensitic phase transition equation at various temperatures. Results show that the stress field equation and martensitic phase transition equation can predict the thermo-mechanical behaviors of the shape memory alloy board with a crack and under the torsion load effectively.

Abstract: The Reissner’s plate bending theory with consideration of transverse shear deformation effects is adopted to study the fundamental fracture problem in functionally graded materials (FGMs) plates for a crack perpendicular to material gradient. The crack-tip higher order asymptotic fields of FGMs plates are obtained by the asymptotic expansion method. This study has fundamental significance as Williams’ solution.

Abstract: Natural fiber reinforced composites have become excellent candidates for automotive applications and civil engineering facilities. The design procedures will require precisely evaluating the toughness of the materials, which demand accurate measurements of strain or displacement that are difficult to obtain for ductile materials. The primary objectives of this paper were to develop reliable experimental approaches which can effectively evaluate the fracture behaviors of random short natural fiber reinforced polypropylene (PP) composites. The digital image correlation method (DICM) was applied to compute the deformation fields around the crack tip of a compact-tension specimen in a process of loading. An experimental and numerical hybrid method was used to describe the fracture behaviors of the composites. The relationship between the micro-structure of random fibers and the macroscopic mechanical properties of the composites can also be understood.

Abstract: The stress and strain field near the tip of Mode I growing crack in materials under creep conditions is examined. The case of the effective stress equal to zero is considered. The asymptotic equations for the crack of the crack tip field are derived and solved numerically. It is concluded that the rates of stress and strain posses the r^δ-1 singularity near the tip crack, and the stresses remain finite at the crack tip.