Showing papers on "Paris' law published in 2010"
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 paper, a microstructure-sensitive extreme value statistical framework was proposed to quantify the effects of interactions between various micro-structure attributes on fatigue life in the HCF regime.
178 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
15 Nov 2010-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the authors investigated the fracture toughness of LRMed Inconel 625 compact tension specimens of thickness 12 and 25mm and found that fracture toughness values were in the range of about 200-255kJ/m 2.
Abstract: Fatigue crack growth and fracture toughness characteristics of laser rapid manufactured (LRMed) Inconel 625 compact tension specimens of thickness 12 and 25 mm were investigated. Fatigue crack propagation in all the specimens investigated in the stress intensity range (Δ K ) of 14–38 MPa√m, exhibited stage II crack growth in Paris’ regime with nearly same slopes of crack growth per cycle versus Δ K plot. Fatigue crack growth rates in the LRMed specimens of present study were found to be lower than the reported values for wrought Inconel 625 in the Δ K range of 14–24 MPa√m and above this range they tended to coincide. X-ray diffraction patterns of the fractured surfaces revealed that the crack propagated along the growth direction of the specimens which was predominantly along the (1 1 1) plane. The fracture toughness values ( J 0.2 ) for LRMed Inconel 625 specimens were found to be in the range of about 200–255 kJ/m 2 . The LRMed specimens exhibited stable crack growth during the J -integral test.
111 citations
TL;DR: In this paper, microstructural changes and cyclic deformation characteristics of friction-stir-welded 7075 Al alloy were evaluated and two low-hardness zones (LHZs) between the TMAZ and the heat-affected zone (HAZ) were observed, with the width decreasing with increasing welding speed.
Abstract: Microstructural changes and cyclic deformation characteristics of friction-stir-welded 7075 Al alloy were evaluated. Friction stir welding (FSW) resulted in significant grain refinement and dissolution of η′ (Mg(Zn,Al,Cu)2) precipitates in the nugget zone (NZ), but Mg3Cr2Al18 dispersoids remained nearly unchanged. In the thermomechanically affected zone (TMAZ), a high density of dislocations was observed and some dislocations were pinned, exhibiting a characteristic Orowan mechanism of dislocation bowing. Two low-hardness zones (LHZs) between the TMAZ and the heat-affected zone (HAZ) were observed, with the width decreasing with increasing welding speed. Cyclic hardening and fatigue life increased with increasing welding speed from 100 to 400 mm/min, but were only weakly dependent on the rotational rate between 800 and 1200 rpm. The cyclic hardening of the friction-stir-welded joints exhibiting a two-stage character was significantly stronger than that of the base metal (BM) and the energy dissipated per cycle decreased with decreasing strain amplitude and increasing number of cycles. Fatigue failure occurred in the LHZs at a lower welding speed and in the NZ at a higher welding speed. Fatigue cracks initiated from the specimen surface or near-surface defects in the friction-stir-welded joints, and the initiation site exhibited characteristic intergranular cracking. Crack propagation was characterized by typical fatigue striations along with secondary cracks.
102 citations
TL;DR: In this article, the authors developed a framework for computationally modeling microstructurally small fatigue crack growth in AA 7075-T651 (Bozek et al. 2008 Modelling Simul. Mater. Sci. 16 065007).
Abstract: The objective of this paper is to develop further a framework for computationally modeling microstructurally small fatigue crack growth in AA 7075-T651 (Bozek et al 2008 Modelling Simul. Mater. Sci. 16 065007). The focus is on the nucleation event, when a crack extends from within a second-phase particle into a surrounding grain, since this has been observed to be an initiating mechanism for fatigue crack growth in this alloy. It is hypothesized that nucleation can be predicted by computing a non-local nucleation metric near the crack front. The hypothesis is tested by employing a combination of experimentation and finite element modeling in which various slip-based and energy-based nucleation metrics are tested for validity, where each metric is derived from a continuum crystal plasticity formulation. To investigate each metric, a non-local procedure is developed for the calculation of nucleation metrics in the neighborhood of a crack front. Initially, an idealized baseline model consisting of a single grain containing a semi-ellipsoidal surface particle is studied to investigate the dependence of each nucleation metric on lattice orientation, number of load cycles and non-local regularization method. This is followed by a comparison of experimental observations and computational results for microstructural models constructed by replicating the observed microstructural geometry near second-phase particles in fatigue specimens. It is found that orientation strongly influences the direction of slip localization and, as a result, influences the nucleation mechanism. Also, the baseline models, replication models and past experimental observation consistently suggest that a set of particular grain orientations is most likely to nucleate fatigue cracks. It is found that a continuum crystal plasticity model and a non-local nucleation metric can be used to predict the nucleation event in AA 7075-T651. However, nucleation metric threshold values that correspond to various nucleation governing mechanisms must be calibrated.
98 citations
TL;DR: In this paper, a mechanism-based model is developed to describe the time and temperature dependent cyclic plasticity and damage of cast iron materials, which is a combination of a viscoplastic model with kinematic hardening and a porous plasticity model.
98 citations
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.
90 citations
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.
90 citations
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.
88 citations
TL;DR: In this paper, the fatigue-crack-growth-rate data generated in the threshold and near-threshold regimes on two aluminum alloys (T651, T7351), a titanium alloy (Ti-6Al-4V β-STOA), a high-strength 4340 steel and a nickel-based superalloy (Inconel-718) using compression precracking constant-amplitude (CPCA), compression pre-racking load-reduction (CPLR), and the ASTM E-647 load reduction (LR
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 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 paper, the authors exploit synchrotron radiation to report very high spatial resolution two-dimensional elastic strain and stress maps at maximum and minimum loading measured under plane strain during a normal fatigue cycle, as well as during and after a 100% overload event, in ultra-fine grained AA5091 aluminium alloy.
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 paper, it was shown that the residual stresses arising from the shot peening process can affect the rate of crack growth, and the results showed that the growth rates of the cracks were more affected by the tensile core than by the compressive surface stresses.
TL;DR: In this paper, a general methodology is proposed for fatigue-life prediction using crack growth analysis, based on a critical plane-based multiaxial fatigue damage model and the Equivalent Initial Flaw Size (EIFS) concept.
TL;DR: In this paper, the effects of weld microstructure and residual stress distribution on the fatigue crack growth rate of stainless steel narrow gap welds were investigated, and the results showed that strength was greater in the inner weld than outer weld region.
TL;DR: In this article, a procedure to predict fatigue crack growth in bonded joints is developed in this work within the framework of cohesive zone modelling and finite element analysis, where the idea is to link the fatigue damage rate in the cohesive elements to the macroscopic crack growth rate through a damage homogenisation criterion.
Abstract: A procedure to predict fatigue crack growth in bonded joints is developed in this work within the framework of cohesive zone modelling and finite element analysis. The idea is to link the fatigue damage rate in the cohesive elements to the macroscopic crack growth rate through a damage homogenisation criterion. In this way, the experimental crack growth rate is related directly to damage evolution in the cohesive zone, that is, no additional parameters have to be tuned beside the quasi-static cohesive zone parameters. The procedure was implemented in the ABAQUS finite element software using the USDFLD subroutine. In order to evaluate the crack growth rate automatically, the strain energy release rate (crack driving force) was calculated and updated automatically within the subroutine. Mode I and Mode II loading cases have been dealt with and the implementation for Mixed Mode I/II is under way.
TL;DR: In this paper, the evolution of the residual stresses in a MIG-welded 2024-T3 aluminium alloy M(T) specimen during in situ fatigue crack growth at constant load amplitude has been measured with neutron diffraction.
TL;DR: In this paper, a testing setup to determine stress-strain curves of hard metals under static and cyclic uniaxial compression and tension loading was developed, where the investigated hard metal grades varied in WC grain size and Co-binder content ranging from 0.2 to 1.3μm.
TL;DR: In this article, the authors deal with the mechanism of fatigue crack growth in natural rubber submitted to severe relaxing loading conditions and explain why the striation shape evolves from triangular to lamellar during crack propagation.
Abstract: This paper deals with the mechanism of fatigue crack growth in natural rubber submitted to severe relaxing loading conditions. In one mechanical cycle under such loading conditions, the high level of stress at the crack tip engenders high crystallinity, which halts crack growth in the plane perpendicular to the loading direction. Consequently, the crack bifurcates. Then the fracture surfaces tear, slide and relax simultaneously along a highly crystallized crack tip to form striations. The higher the stress level, the lower the crack growth in the plane perpendicular to the loading direction and the greater the bifurcation phenomenon. This explains why the striation shape evolves from triangular to lamellar during crack propagation.
TL;DR: In this paper, a new methodology is described for in situ characterization of fatigue damage accumulation using nonlinear ultrasonic measurements via analysis of the feedback signal of a closed-loop ultrasonic fatigue system.
TL;DR: In this article, the authors investigated the 3D fatigue crack growth behavior of two anti-symmetric "bird wing" cracks, initiated from the two crack front corner points of a notched shaft undergoing torsion.
TL;DR: In this paper, the dependence of fatigue properties on the different size scale microstructural inclusions of a cast A356 aluminum alloy in order to quantify the structure-property relations was examined, and the results clearly showed that the maximum pore size, NND of gas pores, and DCS all can influence the fatigue life.
Abstract: We examine the dependence of fatigue properties on the different size scale microstructural inclusions of a cast A356 aluminum alloy in order to quantify the structure-property relations. Scanning electron microscopy (SEM) analysis was performed on fatigue specimens that included three different dendrite cell sizes (DCSs). Where past studies have focused upon DCSs or pore size effects on fatigue life, this study includes other metrics such as nearest neighbor distance (NND) of inclusions, inclusion distance to the free surface, and inclusion type (porosity or oxides). The present study is necessary to separate the effects of numerous microstructural inclusions that have a confounding effect on the fatigue life. The results clearly showed that the maximum pore size (MPS), NND of gas pores, and DCS all can influence the fatigue life. These conclusions are presumed to be typical of other cast alloys with similar second-phase constituents and inclusions. As such, the inclusion-property relations of this work were employed in a microstructure-based fatigue model operating on the crack incubation and MSC with good results.
TL;DR: It is demonstrated that a modulated structure is generated in a nanocrystalline Ni-Fe alloy under cyclic deformation and substantial grain coarsening and loss of growth twins are observed in the path of fatigue cracks, while the grains away from the cracks remain largely unaffected.
Abstract: Theoretical modeling suggests that the grain size remains unchanged during fatigue crack growth in nanocrystalline metals. Here we demonstrate that a modulated structure is generated in a nanocrystalline Ni-Fe alloy under cyclic deformation. Substantial grain coarsening and loss of growth twins are observed in the path of fatigue cracks, while the grains away from the cracks remain largely unaffected. Statistical analyses suggest that the grain coarsening is realized through the grain lattice rotation and coalescence and the loss of growth twins may be related to the detwinning process near crack tip.
TL;DR: In this article, the growth of interacting surface cracks was simulated by using the S-version finite element method, in which a local detailed finite element mesh (local model) is superposed on a coarse finite element model (global model) representing the global structure.