Search results for " Crack growth"
showing 7 items of 7 documents
Fatigue crack growth through particulate clusters in polycarbonate material
2011
The interaction of a crack with a perfectly bonded inclusion or a cluster of inclusions in polycarbonate matrix was investigated through both numerical simulations and fatigue tests. Stress intensity factors (K(I)) were evaluated by boundary element method for several particle sizes, position and finally for inclusion cluster as a precursor study for the experiments. The numerical simulation has shown the crack tendency to circumvent the inclusions with consequential reduction of the growth rate. Fatigue crack growth tests were carried out on several particle-filled specimens at constant value of the applied stress intensity factor range (Delta K(Iapp)) highlighting the crack delay due to t…
Fatigue crack growth in 2024-T351 Friction Stir Welded Joints: longitudinal residual stresses and microstructural effects
2009
Abstract The role of longitudinal residual stress on propagation of fatigue cracks was examined in friction stir welds produced in 2024-T351 aluminum alloy. Fatigue crack growth rate was obtained through constant Δ K Iapp tests for notches at different distances from the weld centerline. Subsequently, crack growth was correlated to weld residual stress measured by the cut-compliance method. It was found that residual stresses correspond to low crack growth rates outside the weld zone during fatigue loading. Once in the weld zone, the crack growth was affected by microstructural and hardness changes. Furthermore, weld residual stresses were mechanically relieved and effects on crack propagat…
Empirical model for stress ratio effect on fatigue delamination growth rate in composite laminates
2004
An empirical model is proposed for the stress ratio effect on the fatigue delamination growth rate in composite laminates under single-mode loading, intending to provide a simple and accurate description tool in engineering application. The model is based on heuristic considerations of damage accumulation ahead of the crack. Linear cumulative assumption is used for damage estimation. Comparison of the prediction based on the proposed model with the test results for different carbon, glass, and alumina fibre-reinforced composites at several stress ratios shows reasonable agreement.
Fatigue delamination experiments on GFRP and CFRP specimens under single and mixed fracture modes
2011
This paper deals with the experimental analysis of the delamination phenomena in composite materials under different loading conditions. Quasi-static and fatigue tests are performed on specimens made of glass-fibre (GFRP) and carbon-fibre (CFRP) reinforced plastic. In particular, experiments have been carried out under single fracture modes I and II (using standard DCB and ENF test configurations) and mixed modes I+II (using the MMB test configuration) with several mode mixtures. Results obtained for the two materials have been compared paying attention on the relationship between the parameters that describe the fatigue behaviour and the mode mixture acting during the crack propagation. © …
Dual Boundary Element Method for fatigue crack growth: implementation of the Richard’s criterion
2013
A new criterion for fatigue crack growth, whose accuracy was previously tested in the literature with the Finite Element Method, is here adopted with a Dual Boundary Element formulation. The fatigue crack growth of an elliptical inclined crack, embedded in a three dimensional cylindrical bar, is analyzed. In this way in addition to the propagation angle estimated by the Sih’s criterion, it is possible to take into account a twist propagation angle. The two propagation criteria are compared in terms of shape of the propagated crack and in terms of SIFs along the crack front. The efficiency of the Dual Boundary Element Method in this study is highlighted.
Training Deep Neural Networks with Novel Metaheuristic Algorithms for Fatigue Crack Growth Prediction in Aluminum Aircraft Alloys
2022
Fatigue cracks are a major defect in metal alloys, and specifically, their study poses defect evaluation challenges in aluminum aircraft alloys. Existing inline inspection tools exhibit measurement uncertainties. The physical-based methods for crack growth prediction utilize stress analysis models and the crack growth model governed by Paris’ law. These models, when utilized for long-term crack growth prediction, yield sub-optimum solutions and pose several technical limitations to the prediction problems. The metaheuristic optimization algorithms in this study have been conducted in accordance with neural networks to accurately forecast the crack growth rates in aluminum alloys. Through ex…
A model for predicting the mixed-mode fatigue crack growth in a bonded joint
2013
Bonded joints are highly sensitive to the presence of defects and to the degradation phenomena, and this aspect represents the primary obstacle to their use in different structural engineering applications. Delamination in a bonded joint represents, in fact, one of the primary, most common and insidious causes of damage. In this paper, a numerical–experimental study on the crack propagation along the adhesive layer of a bonded joint specimen is carried out. Experimental study is focused on the evaluation of the damage modalities of a bonded joint when the specimens are subject to fatigue load. Experimental tests are compared with the results of several numerical analysis performed in ANSYS …