Angled Crack Problem Research Articles

Crack growth path prediction for the angled cracked plate using higher order terms of Williams series expansion

A B S T R A C T The amount of damage induced by brittle fracture of cracked bodies depends considerably on the path of fractures. Therefore, prediction of the trajectory of fracture using suitable theoretical fracture criteria is very important for cracked structures. In this paper, using higher-order terms of Williams's series expansion and the maximum tangential stress criterion, the mixed mode I/II crack growth path of an angled crack plate subjected to biaxial far field loading is investigated theoretically. To evaluate the accuracy of the theoretical results, they are compared with the experimentally reported trajectories for the angled crack plate specimen. It is shown that by taking into account the higher order terms of the Williams series expansion a very good agreement is observed between the experimental and theoretical mixed mode fracture paths in the angled crack problem. It was also observed that the theoretically determined initial angle of crack growth is consistent with the experimental results. }}

Investigation of Fatigue Crack Propagation in Line Pipes Containing an Angled Surface Flaw

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In the present paper, an investigation of fatigue crack initiation and propagation in line pipes containing an inclined surface crack is presented. The inclined angle of the surface crack with respect to the axis of loading varies between 0deg and 90deg. Based on the concept of the effective stress intensity factor range Δkeff, the rate of fatigue crack propagation db∕dN is postulated to be a function of the effective strain energy density factor range ΔSeff. This concept is applied to predict the crack growth due to fatigue loading. Furthermore, the threshold condition for nongrowth of the initial crack was established and assessed based on the experimental data.

Fatigue fracture criteria and microstructures of magnesium alloy plates

Due to its close proximity to realistic conditions in engineering structures the angled crack problem has been given special attention in the recent years by fracture mechanics investigators. In this study, experimental and theoretical investigations were conducted to characterize the fatigue crack propagation in rectangular AM60B magnesium alloy plates containing an inclined through crack. The inclined angle of the crack with respect to the axis of loading was varied between 0° and 90°. The von Mises yield criterion is applied to define the plastic zone, instead of assuming a circular shape plastic zone with a constant radius. The commonly employed fracture criterion, the minimum strain energy density criterion, is modified by adopting the von Mises elasto-plastic boundary. The threshold condition of fracture is also established based on the experimental data. Finally, the influence of material microstructures on fatigue crack growth is assessed using the scanning electron microscope (SEM).

An improved model for predicting the crack size and plasticity dependence of fatigue crack propagation

The angled crack problem has been given special attention in the recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In this paper, an investigation of fatigue crack propagation in rectangular steel plates containing an inclined surface crack is presented. The inclined angle of the crack with respect to the axis of loading varied between 0° and 90°. During the fatigue tests, the growth of the fatigue crack was monitored using the AC potential drop technique. A series of modification factors, which allow accurate sizing of such defects, is recommended. Paris power law is normalized and adopted for data analysis. Subsequently, this concept is applied to predict crack growth due to fatigue loads. The results obtained are compared with those obtained using the commonly employed fracture criterion and the experimental data.

Fatigue life prediction of the plates with an inclined surface crack

The angled crack problem has been given special attention in recent years by fracture mechanics investigators due to its close proximity to realistic conditions in engineering structures. In this paper, an investigation of fatigue crack propagation in rectangular aluminum alloy plates containing an inclined surface crack is presented. The inclined angle of the crack with respect to the axis of loading varied between 0° and 90°. During the fatigue tests, the growth of the fatigue crack was monitored using the AC potential drop technique. Based on the concept of the effective stress intensity factor range, Δ k eff, an effective strain energy density factor range, Δ S eff, is proposed in the present study. The rate of fatigue crack propagation, d b/d N, is then postulated to be a function of the effective stress intensity factor range, Δ k eff, and thus the effective strain energy density factor range, Δ S eff. Subsequently, this concept is applied to predict crack growth due to fatigue loads.

Mixed mode crack propagation studied by the Yeh-Stratton criterion

The angled crack problem is examined with the Yeh-Stratton criterion in the form of the maximum principal stress theory of isotropic materials. The angle of fracture and the fracture load as a function of a crack angle are computed for simple uniaxial, biaxial and in-plane shear loadings. The predictions are compared with experimental data. The two-dimensional crack tip stresses for a general loading case are obtained by the principle of superposition.

The Mixed Mode Fracture Analysis of Unidirectional Composites

The generalized Yeh-Stratton criterion is applied to an angled crack prob lem of unidirectional fibrous composites with a crack oriented in the fiber direction under uniaxial tensile load. The fracture stresses and the fracture angles are computed, and the predictions are compared with the available experimental data.

A new mixed mode fracture criterion: maximum tangential strain energy density criterion

In this paper, crack initiation is postulated to occur in the direction along which the tangential strain energy density factor possesses a maximum value and when it reaches a critical value in the angled crack problem. As a result of its examination, we can see that this criterion is able to be applied to this problem.

The solution of mixed-mode fracture problems using the boundary element method

Three methods of computing stress intensity factors from nodal values near the crack tip are compared for an angled crack problem using a double region boundary element method. Two methods are based on displacement and one on traction values. There is good agreement with published results obtained using a single region for the symmetric crack problem. The mixed-mode examples show that the traction method is accurate and is the least sensitive to local meshing. Accurate results may also be obtained using a one-point displacement method.

Second-order terms and strain energy density for the angled crack problem

The singular expansions for elastic stresses and displacements at a crack tip are incapable of describing some aspects of local behaviour adequately. In this paper we give the correct form of the next terms in the expansions for the angled crack problem. A formula using first and second order terms for the calculation of strain energy density is derived and is compared with exact solutions. The use of second order terms is shown to be essential (and sufficient) for the accurate determination of strain energy density. Examples are given which show that a minimum strain energy density may not exist and that this criterion may not agree with experimental values as well as the maximum tensile stress criterion.

Fracture under complex stress ? The angled crack problem

Fracture under complex stress ? The angled crack problem

On angled crack initiation under biaxial loading

The angled crack problem has been of growing interest to both designers and researchers for the prediction of the structural integrity of components under complex loading conditions. In the study of angled crack growth behaviour, it is invariably of interest to predict the initial crack growth direction θ0 and the fractures stress σc at which crack initiation occurs. In this paper the merits of the various proposed fracture criteria are reviewed. The biaxial loading effect on the parameter used in each criterion for the prediction of the fracture behaviour is studied. It is observed that the popular testing method employing uniaxial loading of a test specimen is inadequate to demonstrate the suitability of fracture criteria in the prediction of θ0 and σc. It is suggested that with the biaxial loading of a test specimen with an angled crack, a better appraisal of the fracture criteria can be obtained. The experimental results obtained in this study seem to support the maximum stress criteria for both uniaxial and biaxial loading conditions. Both tensions and compression biaxial loading effects have been considered.

A Further Examination on the Application of the Strain Energy Density Theory to the Angled Crack Problem

The strain energy density theory (the S-theory) has been examined. Two points that may lead to confusion have been discussed when the S-theory is employed in the study of the angled crack problem. Predictions for the biaxial tension configuration based on the S-theory compared with one based on the maximum strain criterion are presented. Use of the ratio of core region radius as a material parameter in the S-theory is also questioned.

Further studies of the maximum stress criterion on the angled crack problem

The maximum stress criterion for brittle fracture is examined and modified so that it may be applied to both the slit model and the elliptic model for a crack. Employing exact stress solutions, the present work then applies this criterion to a study of the angled crack problem for plates with a slit crack as well as those with an elliptic crack. Remarkable agreement is shown between predicted results and experimental data found in the literature for the direction of initial crack extension and the fracture strength.

On the maximum strain criterion—a new approach to the angled crack problem

The maximum-normal-strain theory for fracture is modified as a new approach to the study of the angled crack problem. Using this modified criterion and employing exact stress solutions, the present work presents predictions on the direction of initial crack extension and the fracture strength for plates containing a slit crack as well as those with an elliptic crack under uniform edge stresses. Good agreement is shown between the predicted results and experimental data found in the literature.

Further results on the angled crack problem

Panels of PMMA having edge cracks at an angle to applied load were tested in tension and bending. Direction of initial crack growth and load to failure were recorded. Stress analysis of each test configuration was performed, and the maximum hoop stress and minimum strain energy density criteria were used to predict failure data. Reasonable correlation between experiment and theory was realised, but with little basis for discriminating between the two failure criteria.

Discussion on ?fracture under complex stress?The angled crack problem?

Discussion on ?fracture under complex stress?The angled crack problem?

Further observations on the angled crack problem

Further observations on the angled crack problem

A note on the angled crack problem and the directional stability of cracks

A note on the angled crack problem and the directional stability of cracks

Fracture under complex stress — The angled crack problem

Experiments are described in which thin plates of polymethylmethacrylate were fractured with cracks set at various angles to an applied uniaxial stress. While there is substantial agreement with previous analytical predictions, it is shown that inclusion of the stress component parallel to the crack can improve the correlation between linear theory and experiment, using a critical stress at a critical distance interpretation of the stress intensity factor criterion.