Papers by Keyword: Fracture Criterion

Abstract: This paper describes finite element method analysis (FEM analysis), results of burring processing of large diameter steel pipe and fracture criterion in burring process of large diameter steel pipe. In this study, the pipe is the 150A SGP pipe with a diameter of 165.2 mm and a wall thickness of 5 mm. The pipe is used for a plant as a flow channel of gas and liquid. A burring process of pipe is generally for forming the branch. The burring process is achieved by drawing of die from prepared hole. And the branch pipe is welded to the formed pipe. This process has some problem. One is the forming limit of pipe, and the other is needed to machining the end surface to be welded. Therefore, in this study, the forming limit of SGP pipe was estimated by FEM analysis of burring process. The parameters used for criteria for forming limit are the maximum shear stress and the equivalent strain. As a result of comparing the analysis result and the experimental result, the forming limit of the 150A SGP pipe was estimated that the maximum shear stress is 350 MPa and the equivalent strain is around 0.8.

Abstract: The process of destruction of cylindrical samples under uniaxial tension is described taking into account changes in the geometry of the sample. An approach is formulated to determine the failure constants in the form of invariant characteristics based on standard mechanical tests under conditions of axisymmetric deformation.

Abstract: A numerical method to predict failure performance was developed for resistance spot welded AHSS (advanced high strength steel) sheets in this work and applied for a TRIP (transformation induced steel sheets) 980 sheet. For the numerical analysis, utilizing the numerical inverse calibration method, hardening data and fracture criteria were characterized for the base and the weld nugget based on the standard simple tension test and a newly designed miniature tension test, respectively. The characterized properties of the base and the weld nugget were then applied to analyze failure performance in the coupon tests of the lap-shear and U-shape tension tests carried out for welded sheets. The analysis was performed under the quasi-static condition in this early effort and showed reasonably good agreement with experiments both in failure modes and strength.

Abstract: The inclined surface cracks are under the mixed mode I,II,III loading conditions. Direct tension experiments of brittle materials with surface crack have been carried out. The crack growth process, fracture pattern and the initiation angle of the surface crack were attained. In order to analyze the mixed-mode fracture criterion of the surface crack in brittle materials stress intensity factor of the crack front of the surface crack was calculated based on the FRANC3d firstly. And then the minimum strain energy density criterion, the maximum circumferential stress criterion and the revised maximum circumferential stress criterion were used to calculate the initiation angle. The revised maximum circumferential stress criterion proved to be fit for the attained experimental results.

Abstract: Study on tensile fracture behavior of TiAl alloy by means of the macro fracture theory and micro dislocation block theory. A quantitative analysis method of micro crack nucleation and crack mechanism for TiAl alloy is performed with the help of the dislocation distribution model, and is based on the strain energy density theory and criterion, a crack criterion of TiAl alloy instability is established. The experimental results confirmed that the dislocation model and S criterion on tensile fracture behavior of TiAl alloys are effective.

Abstract: The problem of crack path stability along the interface between two orthotropic elastically dissimilar materials under the presence of in-plane residual stresses is analyzed using the concept of Finite Fracture Mechanics and matched asymptotic procedure. An energy based fracture criterion is introduced for this problem and it is investigated whether and how is the criterion for the prediction of crack kinking from the interface affected by residual stresses. The complex stress intensity factor and the T-stress characterizing the stress state at the crack tip are calculated both for the thermal (residual stresses) and mechanical loading using the two-state integral. The matched asymptotic procedure together with FEM is used to derive the change of the potential energy induced by the crack growth by crack increment of finite length.

Abstract: Finite element method is used to compute the factor of safety of jointed rock slope. The stability of jointed rock slope is simulated by using shear strength reduction approach. Mohr-Coulomb fracture criterion is used to evaluate the sticking or sliding state of jointed rock mass. The distribution of plastic zone at collapse state is determined. Numerical computational results show that the proposed procedure is effective to evaluate stability of jointed rock slope.

Abstract: The problem of crack deflection from the interface between two orthotropic materials is analyzed using the concept of Finite fracture mechanics and matched asymptotic procedure. A fracture criterion based on the energy approach is introduced for this problem. The main input for such criterion is the complex stress intensity factor calculated e.g. using the two-state integral. However for more precise predictions of the crack propagation also higher order terms of the asymptotic expansion are advisable to involve in the fracture criterion. To this end a T-stress term will be calculated and considered as the second input parameter. The matched asymptotic procedure together with FEM is used to derive the change of the potential energy induced by the incremental crack growth.

Abstract: The main defect in concrete and other brittle materials was the crack in the materials which would cause the structures brittle fracture. So it is very important to study the development of cracks in the concrete structure. This article researched the criterion of the shortest distance from the crack tip to the plastic zone edge for concrete and other brittle materials based on the least distance in plastic zone theories. The numerical example verified that the proposed criterion could solve the low stress brittle fracture phenomena in engineering better.

Abstract: Steel fiber concrete is a new-type composite material of excellent property with broad application formed by common concrete mixed with disorderly oriented short steel fiber. Main action of steel fiber is to prevent broadening of interior micro crack in concrete and restrict occurrence and growth of macro crack. Based on basic theory of concrete fracture mechanics, this treatise adopts four-point shearing sampling material to conduct experimental research, having obtained critical fracture curve of crack of composite mode I, II of steel fiber concrete, setting up experimental formula of fracture criterion, probing into difference between fracture toughness of steel fiber concrete and that of common concrete, and discussing application of maximum tension stress theory in steel fiber concrete.