Stress Intensity Factors for Embedded, Surface, and Corner Cracks in Finite-Thickness Plates Subjected to Tensile Loading (original) (raw)
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Frattura ed Integrità Strutturale
Non-singular terms in the series expansion of the elastic crack-tip stress fields, commonly referred to as the T-stress. The T-stress is as an additional stress field characterizing parameter to stress intensity factor (K) in the analysis of cracked bodies. T-stress is used as an important constraint parameter in the fracture analysis. In this investigation, three-dimensional finite element analyses have been conducted to compute the elastic T-stress considering a single edge notched tensile (SENT) specimen with varied thickness and a/W ratio. The results indicate that the T-stress depends on the specimen thickness and significantly varies along the crackfront from surface to centre of the specimen. The T-stress results obtained in the present analysis together with corresponding K I values can be used for analysis of constraint effects in a fracture specimen.
ESTIMATION OF STRESS INTENSITY FACTOR (SIF) ON CRACK COMPONENT BY USING FINITE ELEMENT ANALYSIS
Theoretical solutions are available for idealized cases such as Infinite flat plate with edge crack, central crack etc. However main limitation of these theoretical solutions is they are very restrictive and while analyzing a normal component, a lot of assumptions go into it. Finite Element Analysis on the other hand provides good tool to determine Stress Intensity Factor. Cracks generally initiate at geometric discontinuities (such as notches, holes, weld toes, voids etc.) that induce large stress (stress concentration). Since crack growth is related to the effective stress intensity factor (SIF) which is at crack tip, the evaluation of Stress Intensity Factors. The present work would aim to fulfill this gap and generate more information thereby increased understanding on fracture behavior in 3D Components. Finite element analysis has been performed to support the results on fracture parameters like Location and Size of Cracks and results has been compared with available theoretical solutions. It is concluded that magnitude of critical Stress Intensity Factor can be used as a fracture criterion for thin Plates. Same procedure has been adapted for Analysis of connecting rod to find Stress Intensity Factor at various lengths of crack
Stress intensity factors and weight functions for a corner crack in a finite thickness plate
Engineering Fracture Mechanics
The failure of cracked components is governed by the stresses in the vicinity of the crack tip. The singular stress contribution is characterised by the stress intensity factor K. Stress intensity factors depend on the geometry of the component and on the special loading conditions (tension, bending, thermal stresses,...). A procedure for their determination is the weight function technique where the weight functions are only dependent on the crack geometry. Stress intensity factors and weight functions are reported for many practical problems in handbooks. In this report new solutions for stress intensity factors and weight functions are compiled in form of tables or approximate relations.
The Effect of the Size and Position of the Crack on the Normalized Stress Intensity Factor
Algerian Journal of Renewable Energy and Sustainable Development
In this work, finite element method was used to determine the normalized stress intensity factors for different configurations. For this, a 2-D numerical analysis with elastic behavior was undertaken in pure I mode. This simulation was carried out using a numerical calculation code. On the basis of the numerical results obtained from the different models treated, there is a good correlation between the nodal displacement extrapolation method (DEM) and the energy method based on the Rice integral (J) to evaluate the normalized stress intensity factors and this for different crack lengths. For each configuration, the increase in the crack size causes an amplification of normalized intensity stresses fators.
Theoretical and Applied Fracture Mechanics, 2020
This paper presents the application of the weight function method for calculating the stress intensity factors for high aspect ratio semi-elliptical surface cracks in finite thickness plate subjected to arbitrary two-dimensional stress fields. Based on the formulation initially proposed by Wang and Glinka (2009), an extended 2D weight function for surface cracks with aspect ratio 1.0 ≤ a/c ≤ 8.0 is developed. The unknown coefficients in the formulation can be determined from reference stress intensity factors which are obtained by finite element analysis with the J-integral method. The effectiveness of the proposed weight functions have been verified by comparing the stress intensity factors available in the literatures and those obtained from FEM for several linear and nonlinear two-dimensional stress distributions, indicating a good accuracy. The present results complement the application range of 2D weight functions for low-aspect-ratio cracks, 0.0 < a/c ≤ 1.0, developed by the previous researchers.
Variation of crack-opening stresses in three-dimensions: finite thickness plate
Theoretical and Applied Fracture Mechanics, 1991
Crack growth and closure behavior of a center cracked finite thickness plate subjected to constant amplitude cyclic load is investigated by means of a three-dimensional elastic-plastic finite-element analysis. Results are obtained for initial half crack length c i to half plate thickness t ratios of Ci//l = 3.891 and 1.465 which shall be referred to, respectively, as thin and thick plate. A constant amplitude load with R = Smin/Sma x = 0.1 and Smax/O 0 = 0.25 is applied, where S stands for the stress amplitude and o 0 the effective yield stress. Crack closure for the thinner plate is found to be largest at and near the free plate surface and to decrease toward the interior during the unloading portion of cyclic loading. The closure pattern stabilizes at the interior and exterior regions, respectively, for ci/t = 3.981 at 0.34Sma x and 0.56Sma× and for ci/t =1.465 at 0.26Sma~ and 0.46Sm~ ~. A load-reduced displacement technique was used to determine crack-opening stresses at specified locations in the plate from the displacements calculated after the 7th cycle (using unloading and reloading portions of cyclic loading). All locations were on the plate exterior surface and were located behind the crack tip and at the centerline of the crack. The opening stresses at the specified points as certain percentage of the maximum stress amplitude were obtained.
Stress intensity factors for cracks in structures under different boundary conditions
Engineering Fracture Mechanics, 1990
In calculating stress intensity factor solutions for standard cases, the weight function and superposition technique have been used extensively. These solutions although valid for simple specimens present a problem in the case of statically indeterminate structures. The work described in this paper investigates the effect of boundary conditions on the stress intensity factor solution for an edge cracked plate, edge cracked ring and a surface cracked plate using the finite element technique.
2012
The study is a preliminary effort which investigates the effect of variations of crack geometry on the stress concentration factor on a simple thin plate subjected to a constant, uniform, uniaxial tensile load. The geometry of the central crack is varied to produce rectangular models ranging from circular, elliptical to sharp cracks. Due to symmetry, the models are reduced to quarter symmetric, meshed and refined at the edges of the cracks for clearer, detailed analysis and solution accuracy. Finally, a uniform pressure is applied at the top and the model is constrained with symmetric boundary conditions at the left and bottom. These numerical results are compared to those obtained from analytic fracture mechanics procedures and are found to be consistent.
International Journal of Pressure Vessels and Piping, 2011
Normalized mixed-mode stress intensity factor equations are presented for deflected and inclined circular surface and corner cracks in finite-thickness plates under uniform remote tensile loading. The equations are obtained by performing non-linear regression analyses on the data from previous numerical solutions based on three-dimensional enriched finite elements. In the equations, the effects of deflection/inclination angles and plate thickness on mixed-mode stress intensity factors are included. The comparisons of normalized stress intensity factors from the equations with those of the finite element analyses show good agreement. Thus, it is concluded that, as a reasonable approximation, the presented equations can be used to assess stress intensity factors and fracture conditions of mixed-mode circular surface and corner cracks in finite-thickness plates.