Showing papers on "Crack closure published in 2010"
TL;DR: In this paper, the role of microstructural features such as grain size, texture, porosity, non-metallic inclusion in the fatigue crack initiation process and the manners by which these micro-structural effects affect the shape of the stress-life curves are examined.
363 citations
TL;DR: In this article, an overview of some of the applications of DIC for crack tip characterisation such as K, T-stress and crack tip opening angle (CTOA) measurements as well as data obtained from 3D measurements of a propagating crack.
206 citations
TL;DR: In this paper, a three-dimensional extended finite element method (X-FEM) coupled with a narrow band fast marching method (FMM) is developed and implemented in the Abaqus finite element package for curvilinear fatigue crack growth and life prediction analysis of metallic structures.
186 citations
TL;DR: In this article, a theoretical equation for stress corrosion crack growth rate of austenitic alloys in high temperature water is reformulated based on crack tip asymptotic fields and crack tip transient oxidation kinetics.
142 citations
TL;DR: A comprehensive picture is provided of how remotely applied forces drive material failure in the most fundamental of fracture states: straight, rapidly moving cracks by using a brittle neo-Hookean material.
Abstract: In a stressed body, crack propagation is the main vehicle for material failure. Cracks create large stress amplification at their tips, leading to large material deformation. The material response within this highly deformed region will determine its mode of failure. Despite its great importance, we have only a limited knowledge of the structure of this region, because it is generally experimentally intractable. By using a brittle neo-Hookean material, we overcame this barrier and performed direct and precise measurements of the near-tip structure of rapid cracks. These experiments reveal a hierarchy of linear and nonlinear elastic zones through which energy is transported before being dissipated at a crack's tip. This result provides a comprehensive picture of how remotely applied forces drive material failure in the most fundamental of fracture states: straight, rapidly moving cracks.
137 citations
TL;DR: In this article, the authors investigated the effect of hydrogen on fatigue crack growth behavior, including the measurement of the hydrogen content in various materials such as low-carbon, Cr-Mo and stainless steels.
137 citations
TL;DR: In this article, the authors show that external hydrogen reduces tensile ductility more than internal hydrogen, while with internal hydrogen surface cracking is largely absent, thus preempting hydrogen-assisted crack propagation from the surface.
130 citations
TL;DR: In this article, a philosophy of employing computational simulation to establish relations between remote loading conditions and microstructure-scale slip behavior in terms of Fatigue Indicator Parameters (FIPs) as a function of stress amplitude, stress state and micro-structure, featuring calibration of mean experimental responses for known microstructures.
128 citations
TL;DR: In this article, a series of Vickers indentation and counting of cracks around the indentation was used to measure the crack initiation in various commercial glass compositions, and the authors found that the crack resistance of glass does not have clear relationship with hardness, fracture toughness, nor "brittleness" which is a ratio of the hardness to the fracture toughness.
Abstract: Crack initiation in various commercial glass compositions was investigated by measuring “crack resistance”, which is determined by a series of Vickers indentation and counting of cracks around the indentation. The crack resistance of glass does not have clear relationship with hardness, fracture toughness, nor “brittleness” which is a ratio of the hardness to the fracture toughness. However, the crack resistance has a strong relationship with densification. Glass experiencing larger densification around the indentation shows higher crack resistance. Densification is assumed to reduce residual stress around the indentation, resulting in an increase in the crack resistance.
128 citations
TL;DR: In this article, the initial stages of fatigue crack formation in the commercial aluminum alloy 7075-T651 were studied under moderately high fatigue loads in a scanning electron microscope, and the experimental conditions were designed to mimic the behavior of fastener holes in the lower wing covers of military attack aircraft, thus the loading parameters were such that local plasticity was expected.
117 citations
TL;DR: In this paper, an acoustic emission (AE) system was used to study the damage behavior of some Australian black coal samples subjected to uniaxial compression, and the results showed that sorption of CO 2 can cause a reduction in strength of the coal samples when tested under uniaaxial compression.
TL;DR: In this article, the initiation of crack growth under a combination of opening and anti-plane shearing mode loading is considered, and it is shown that such cracks do not grow through a continuous evolution of the crack surface.
Abstract: The initiation of crack growth under a combination of opening and anti-plane shearing mode loading is considered in this paper. It is shown that such cracks do not grow through a continuous evolution of the crack surface. Rather, an abrupt fragmentation or segmentation of the crack front is generated. Through experimental observations and a theoretical model, we postulate a relationship between the scale of the fragmentation and the mode mix.
TL;DR: In this paper, a solution to the problem of a plane-strain fluid-driven crack propagation in elastic permeable rock with resistance to fracture is presented, restricted to the case of zero lag between the fluid front and the fracture tip, where the fluid flow takes place mostly inside the crack toward the large-time response when most of the injected fluid is leaking from the crack into the surrounding rock.
Abstract: A solution to the problem of a plane-strain fluid-driven crack propagation in elastic permeable rock with resistance to fracture is presented. The fracture is driven by injection of an incompressible Newtonian fluid at a constant rate. The solution, restricted to the case of zero lag between the fluid front and the fracture tip, evolves from the early-time regime when the fluid flow takes place mostly inside the crack toward the large-time response when most of the injected fluid is leaking from the crack into the surrounding rock. This transition further depends on a time-invariant partitioning between the energy expanded to overcome the rock fracture toughness and the energy dissipated in the viscous fluid flow in the fracture. A numerical approach is used to compute the solution for the normalized crack length and crack opening and net-fluid pressure profiles as a function of two dimensionless parameters: the leak-off/storage evolution parameter and the toughness/viscosity number. Relation of this solution to the various available asymptotic solutions is discussed. Obtained mapping of the solution onto the problem parametric space has a potential to simplify the tasks of design, modeling, and data inversion for hydraulic fracturing treatments and laboratory experiments.
TL;DR: In this article, the effect of corrosion on the gigacycle fatigue strength of a martensitic-bainitic hot-rolled steel used for manufacturing offshore mooring chains for petroleum platforms was studied.
TL;DR: In this paper, the effect of constraint induced by the crack depth on creep crack-tip stress field in compact tension (CT) specimens is examined by finite element analysis, and the effects of creep deformation and damage on the Hutchinson-Rice-Rosengren (HRR) singularity stress field are discussed.
TL;DR: In this paper, the effect of localized corrosion on fatigue cracking of 7075-T6511 was established using crack surface marker-band analysis and a fracture mechanics model, showing that substantial reduction of fatigue life due to EXCO solution L-S surface pre-corrosion is nearly independent of exposure time after initial sharp degradation, scaling with the evolution of pit-cluster size and initial stress intensity range with exposure time.
TL;DR: In this article, the effect of surface hardening by shot peening on electrochemical stability and corrosion fatigue properties of high-strength aluminium alloy 7075-T651 in the corrosive environment of a chloride solution was investigated.
TL;DR: In this article, a crack-closure system for cementitious materials using shrinkable polymer tendons is presented, which is achieved by thermally activating the shrinkage mechanism of the restrainable tendons after the material has undergone initial curing.
TL;DR: In this paper, the authors analyzed the fatigue crack propagation behavior of a magnesium single crystal using molecular dynamics simulation and found that the growth rate of fatigue crack decreasing with increasing strain rate.
TL;DR: In this article, the authors presented an antenna sensor that is capable of monitoring the growth of fatigue cracks with a sub-millimeter resolution using microstrip patch antenna theory, where the resonant frequencies of a dual-frequency patch antenna are inversely proportional to the electrical lengths of corresponding antenna radiation modes.
Abstract: Fatigue cracking is one of the most common failure modes of various load-bearing structures. Even though sensors of many different types have been developed for crack detection, very few can monitor crack growth with a high sensitivity. This paper presents an antenna sensor that is capable of monitoring the growth of fatigue cracks with a sub-millimeter resolution. According to microstrip patch antenna theory, the resonant frequencies of a dual-frequency patch antenna are inversely proportional to the electrical lengths of the corresponding antenna radiation modes. The presence of a crack in the ground plane or the elongation of the antenna patch due to crack opening increases the electric length, thereby causing a shift in its corresponding resonant frequency. As a result, crack propagation and opening can be monitored from the resonant frequency shifts of the patch antenna. The patch antenna's capability of monitoring crack growth was validated using fatigue testing of a compact tension specimen. The specimen preparation, sensor fabrication, and experimental procedure are presented. The experimental results demonstrated that the corresponding resonant frequency of the antenna sensor shifted linearly with crack growth. On average, 1 mm crack growth caused the antenna frequency to shift by 22.1 MHz. The orientation of the crack and the effect of crack closure on the resonant frequencies of the antenna sensor are also discussed.
TL;DR: In this paper, numerical analyses based on the finite element (FE) method and remeshing techniques have been employed in order to develop a damage tolerance approach to be used for the design of aeroengines shaft components.
15 Apr 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the twin density in the plastic zone of compact tension (CT) specimens is very low, leading to the conclusion that the deformation mechanisms depend drastically on the loading conditions.
Abstract: The crack growth behavior of a high-manganese austenitic steel, which exhibits the twinning-induced plasticity (TWIP) effect, was investigated under positive stress ratios. An experimental study making use of miniature compact tension (CT) specimens and thorough microstructural analyses including transmission electron microscopy and fracture analyses demonstrated that the microstructural evolution in the plastic zone of the fatigued TWIP CT specimens is substantially different as compared to the monotonic plastic deformation case. Specifically, the twin density in the plastic zone of the CT specimens is very low, leading to the conclusion that the deformation mechanisms depend drastically on the loading conditions. The absence of twinning under cyclic loading in the plastic zone of the CT specimens indicates that even large accumulated plastic strains are not sufficient to cause substantial twinning in the TWIP steel. This lack of hardening preserves the ductile character of the TWIP steel in the plastic zone ahead of the crack tip and provides for a crack growth rate in the Paris regime lower than reported for other high strength steels.
TL;DR: In this article, a five times improvement in fatigue life of an investment cast Al-7Si-0.6mg hypoeutectic alloy was reported due to the closure of casting porosities.
TL;DR: In this paper, the microporosity and mechanism of fatigue damage formation and growth were invested using X-ray computed tomography and scanning electron microscopy, and the variations in the fracture surfaces according to three fatigue damage evolution stages: fatigue crack formation (incubation), microstructurally/physically small cracks, and long cracks.
TL;DR: In this article, a typical fracture surface with a fine concavo-convex pattern called "ODA" was discovered for very high cycle fatigue (VHCF) of high strength steel.
TL;DR: In this article, the authors examined the influence of microstructure on the crack growth behavior in high temperature titanium alloys and made a focus on the concept that the fracture mechanisms in these alloys are governed by the slip process taking place within the crack tip region.
TL;DR: The existence or non-existence of fatigue crack growth thresholds is of practical importance and scientific interest, as is knowledge of the stresses enabling crack formation at the surface and the interior of a specimen as discussed by the authors.
TL;DR: In this article, a new fatigue crack growth formulation at the small time scale is proposed, which is fundamentally different from the classical reversal-based fatigue analysis and is based on the incremental crack growth at any time instant within a cycle.
TL;DR: In this article, the number of cycles to crack initiation is estimated by using the Paris law and the surface temperature of the sample during the test of the test sample, which can be used to follow crack propagation.
TL;DR: In this paper, the authors investigated the role of cyclic plastic deformation at the crack tip in the growth of fatigue-cracks in nickel and copper single crystals and polycrystals, including single crystals, bicrystals, and poly-crystals.