scholarly journals The study of redistribution in residual stresses during fatigue crack growth

2021 ◽  
Vol 15 (4) ◽  
pp. 8565-8579
Author(s):  
Mohammad Noghabi ◽  
I. Sattari-far ◽  
H. Hosseini Toudeshky
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Residual Stresses ◽  
Crack Growth ◽  
Crack Tip ◽  
Side Surface ◽  
Fatigue Loading ◽  
Compact Tension ◽  
Fracture Parameter ◽  
Residual Stress Field

Numerical and experimental study was conducted on fatigue crack growth (FCG) of metallic components to investigate the redistribution of mechanical residual stresses during FCG. To this end, the compact tension specimens of an aluminium alloy were used. In addition, mechanical residual stresses were introduced near the crack tip by applying compressive and tensile loads, followed by visually observing the side-surface of the specimens to estimate the crack growth length. In the numerical simulation, cyclic J-integral was used as the crack growth fracture parameter and a good agreement was observed between the numerical and experimental results. The results of the finite element method demonstrated a clear redistribution of mechanical residual stresses during FCG. After a few cycles, the residual stress field around the crack tip reached a lower magnitude value confined in a smaller zone, although this zone was stable during the remaining fatigue process. Finally, present study evaluated the effect of stress ratio, load amplitude, and initial residual stresses level on the redistribution of residual stresses. It was observed that the residual stresses are mainly released during the first steps of fatigue loading.

scholarly journals Influence of Grain Boundary on the Fatigue Crack Growth of 7050-T7451 Aluminum Alloy Based on Small Time Scale Method

2016 ◽  
Vol 2016 ◽  
pp. 1-7 ◽  
Author(s):  
Weihan Wang ◽  
Weifang Zhang ◽  
Hongxun Wang ◽  
Xiaoliang Fang ◽  
Xiaobei Liang
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundary ◽  
Crack Growth ◽  
Time Scale ◽  
Crack Tip ◽  
Fatigue Loading ◽  
Small Time ◽  
Scale Method

Based on the small time scale method, the influence of grain boundary on the fatigue crack growth of 7050-T7451 has been investigated. The interaction between fatigue crack and grain boundary was investigated by in situ SEM testing. Results showed that the fatigue crack growth will be retarded by grain boundary when the angle between fatigue crack and grain boundary is greater than 90 degrees. Mechanism analysis showed that the fatigue crack tip would not be able to open until the loading reached the 55% of maximum load, and the fatigue crack had been closed completely before the loading was not reduced to the minimum value, which led to the crack growth retardation. When the 7050-T7451 aluminum alloy suffered from fatigue loading with constant amplitude, a behavior of unstable fatigue crack growth could be observed often, and results indicated that the bridge linked mechanism led to the behavior. The grain boundary was prone to fracture during fatigue loading, and it became the best path for the fatigue crack growth. The fatigue crack tip would be connected with fractured grain boundary eventually, which led to the fast crack growth in different loading stage.

Quantification and Prediction of Residual Stresses in Creep Crack Growth Specimens

2014 ◽  
Vol 777 ◽  
pp. 25-30 ◽  
Author(s):  
Ali Mehmanparast ◽  
Catrin M. Davies ◽  
Kamran Nikbin
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Growth ◽  
Creep Crack Growth ◽  
Crack Tip ◽  
Creep Damage ◽  
Compact Tension ◽  
Life Assessment ◽  
Creep Crack ◽  
Fatigue Crack Growth Test

An important issue to be considered in the life assessment of power plant components is the effects of prior creep damage on subsequent fatigue crack growth and fracture behavior. To examine these effects, creep damage has been introduced into 316H stainless steel material by interrupting creep crack growth (CCG) tests on compact tension, C(T), specimens at 550 °C. During the CCG tests, the specimen is loaded in tension, crept and unloaded after a small amount of crack extension. This process introduces compressive residual stress fields at the crack tip, which may subsequently affect the fatigue crack growth test results. In this work, neutron diffraction (ND) measurements have been conducted on interrupted CCG test specimens, which contain creep damage local to the crack tip, and the results are compared to predictions obtained from finite element (FE) simulations. Reasonable agreement has been found between the FE predictions and ND measurements.

Atomistic modelling of fatigue crack growth and dislocation structuring in FCC crystals

2006 ◽  
Vol 462 (2076) ◽  
pp. 3707-3731 ◽  
Author(s):  
G.P Potirniche ◽  
M.F Horstemeyer ◽  
P.M Gullett ◽  
B Jelinek
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Grain Boundaries ◽  
Crack Growth ◽  
Growth Rates ◽  
Main Crack ◽  
Crack Tip ◽  
Fatigue Loading ◽  
Crack Plane ◽  
Small Cracks

Fatigue damage in face-centred cubic crystals by dislocation substructuring and crack growth was computationally simulated at the atomic scale. Single-crystal copper specimens with approximately 200 000 atoms and an initial crack were subjected to fatigue loading with a constant strain amplitude of ϵ max =0.01 and a load ratio of R = ϵ min / ϵ max =0.75. Cyclic plastic deformation around the crack tip is the main influencing factor for the propagation mechanisms of nanocracks. The main crack-propagation mechanisms occurred either by void nucleation in the high-density region near the crack tip or by fatigue cleavage of the atomic bonds in the crack plane. Fatigue crack growth at grain boundaries was also studied. For high misorientation angle grain boundaries, the crack path deviated while moving from one grain to another. For low crystal misorientations, the crack did not experience any significant out-of-plane deviation. For a large crystal misorientation, voids were observed to nucleate at grain boundaries in front of the crack tip and link back with the main crack. During fatigue loading, dislocation substructures were observed to develop throughout the atomic lattices. Fatigue crack growth rates for nanocracks were computed and compared with growth rates published in the literature for microstructurally small cracks (micron range) and long cracks (millimetre range). The computed growth rates for nanocracks were comparable with those for small cracks at the same stress intensity ranges and they propagated below the threshold for long cracks.

On the Stress Intensity Factor of Cracks in Residual Stress Field

2007 ◽  
Vol 353-358 ◽  
pp. 1078-1081
Author(s):  
Liang Wang ◽  
Ya Zhi Li ◽  
Hong Su
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Stress Intensity ◽  
Fatigue Crack Growth ◽  
Stress Field ◽  
Residual Stresses ◽  
Weight Function ◽  
Crack Growth ◽  
Function Technique ◽  
Residual Stress Field

The use of weight function technique in fatigue crack growth subjected to external cyclic loading and residual stress field has been questioned by several researchers in that the technique is unable to account for the residual stress redistribution during the crack growth. In this paper a center cracked tension specimen containing residual stresses was analyzed by finite element method. The crack growth was simulated by releasing the nodes ahead of crack tip in stepwise and the stress intensity factors induced by residual stresses at different crack lengths were estimated. The results from the numerical analysis are identical to the weight function solution, which demonstrates that the weight function technique can be used for the fatigue crack growth analysis in residual stress field, unless the residual stress distribution is disturbed by the plastic yield.

Fatigue Crack Growth Modeling in Stiffened Panels Considering Residual Stress Effects

2010 ◽  
Vol 636-637 ◽  
pp. 1172-1177 ◽  
Author(s):  
Sérgio M.O. Tavares ◽  
Valentin Richter-Trummer ◽  
Pedro Miguel Guimarães Pires Moreira ◽  
Paulo Manuel Salgado Tavares de Castro
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Growth ◽  
Initial Crack ◽  
Residual Stress Field ◽  
Stiffened Panels ◽  
Stiffened Structures

A model to determine Stress Intensity Factors (SIFs) and simulate the fatigue crack growth in stiffened structures taking into consideration residual stresses is presented in this paper. The stress field required to estimate the SIF was calculated using the Finite Element Method (FEM) considering the residual stress as an initial condition. The residual stress field redistribution as a function of crack growth is taken into account using the Abaqus software. Specimens without and with residual stresses, resulting from different welding techniques, were considered for the present study. The residual stress fields can significantly deteriorate or improve the fatigue life of the structure, depending upon the location of the initial crack; consequently these effects should be analyzed and modelled in order to better understand the consequences of the application of the considered manufacturing processes.

Study of Crack Extension Effects on a Weld-Induced Residual Stress Field

2013 ◽  
Author(s):  
Jeong K. Hong ◽  
Thomas P. Forte
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Service Life ◽  
Stress Field ◽  
Residual Stresses ◽  
Crack Growth ◽  
Crack Extension ◽  
Growth Analysis ◽  
Crack Tip ◽  
Residual Stress Field

For many applications, welding is the best manufacturing process for joining two separate components. However, the welding process with its highly localized heating and cooling results in the residual stresses both along the surface and through the thickness of the joint. These residual stresses will affect the rate of growth of a fatigue crack as it propagates through the joint and therefore will affect the service life. Therefore, service life predictions must consider the residual stresses as well as their redistribution that occurs as the crack grows. Analytical approaches to assess fitness-for-service such as API 579 are available to evaluate the effect of weld-induced residual stresses. However, current industry practices calculate stress intensity factors (SIFs) for fracture and fatigue crack growth life estimates without considering the redistribution of the residual stresses as the crack propagates, and thus tend to be very conservative. In this paper, Battelle’s weld residual stress modeling methods are combined with a procedure for calculating the SIF using local crack tip displacements that accounts for the redistribution of the residual stresses due to crack extension. In addition, the finite element model used to determine the weld residual stresses is also used to determine the SIF. Therefore, the complete mechanical response to the welding, including residual stress, deformed geometry, elastic and plastic strains, etc. are available for the crack growth analysis. This new unified procedure is demonstrated for simple joints and is compared to a “simplified” crack growth analysis that uses stress mapping. The unified procedure clearly characterizes mixed mode crack behavior at the crack tip. In this paper the procedure is presented in terms of how the crack affects the weld-induced residual stress field; it is equally well suited for practical design use to assess structural integrity in the presence of a weld-induced residual stress field with or without external service loading.

Residual Strain Distribution around a Fatigue-Crack Tip Determined by Neutron Diffraction

2012 ◽  
Vol 706-709 ◽  
pp. 1685-1689
Author(s):  
E Wen Huang ◽  
Kuan Wei Li ◽  
Soo Yeol Lee ◽  
Wan Chuck Woo ◽  
Yi Shiun Ding ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Neutron Diffraction ◽  
Crack Growth ◽  
Residual Strain ◽  
Crack Tip ◽  
Compact Tension ◽  
Compact Tension Specimen ◽  
304L Stainless Steel ◽  
Crack Growth Mechanism

An analysis of residual stress, one of the contributory factors to the crack tip driving force, is extremely important to probe the fatigue crack growth mechanism and to further develop the life prediction methodology. Since fatigue crack growth is governed by crack-tip plasticity and crack closure in the wake of the crack tip, the investigation of residual stain/stress field in both behind and in front of the crack tip is crucial. In the current work, a 304L stainless steel compact-tension specimen is pre-cracked under constant-amplitude cyclic loading. Neutron diffraction is employed to directly measure the three orthogonal residual strain fields with 1-mm spatial resolution as a function of distance from the crack tip. The mapping results show that the three orthogonal residual-strain distributions around the crack tip depend on the stress multiaxiality, not following a single Poisson relationship to each axis.

The effect of high compressive loading on residual stresses and fatigue crack growth at cold expanded holes

2003 ◽  
Vol 38 (5) ◽  
pp. 419-427 ◽  
Author(s):  
D Stefanescu ◽  
M Dutta ◽  
D Q Wang ◽  
L Edwards ◽  
M. E Fitzpatrick
Keyword(s):  
Residual Stress ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Stress Distribution ◽  
Residual Stresses ◽  
Crack Growth ◽  
Compressive Loading ◽  
Residual Stress Distribution ◽  
Residual Stress Field ◽  
X Ray

The effect of monotonic compressive loading on the residual stresses developed at cold expanded fastener holes has been investigated using the neutron and X-ray diffraction techniques. Monotonic loading models the effect of the peak of a fatigue loading sequence experienced before a crack is initiated. It was found that the compressive loading significantly affected the residual stress distribution. A low load relaxed only the stresses near to the bore of the hole, whereas a larger load affected the stress distribution over a greater area. Residual stresses measured at the mandrel entrance face were more affected by the compressive loading than the residual stresses measured at the other segments of thickness. The comparison between the X-ray and neutron diffraction results showed that the techniques complemented each other well, enabling a three-dimensional residual stress distribution to be derived. This distribution was used for modelling the effect of compressive loading on fatigue crack growth, using a linear elastic fracture mechanics approach and assuming a stabilized residual stress field.

scholarly journals Study on the Influence of the Gurson–Tvergaard–Needleman Damage Model on the Fatigue Crack Growth Rate

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1183
Author(s):  
Edmundo R. Sérgio ◽  
Fernando V. Antunes ◽  
Diogo M. Neto ◽  
Micael F. Borges
Keyword(s):  
Growth Rate ◽  
Fatigue Crack ◽  
Crack Growth Rate ◽  
Fatigue Crack Growth ◽  
Plastic Strain ◽  
Crack Growth ◽  
Damage Model ◽  
Crack Tip ◽  
Strength Parameter ◽  
Stress Intensity Factor Range

The fatigue crack growth (FCG) process is usually accessed through the stress intensity factor range, ΔK, which has some limitations. The cumulative plastic strain at the crack tip has provided results in good agreement with the experimental observations. Also, it allows understanding the crack tip phenomena leading to FCG. Plastic deformation inevitably leads to micro-porosity occurrence and damage accumulation, which can be evaluated with a damage model, such as Gurson–Tvergaard–Needleman (GTN). This study aims to access the influence of the GTN parameters, related to growth and nucleation of micro-voids, on the predicted crack growth rate. The results show the connection between the porosity values and the crack closure level. Although the effect of the porosity on the plastic strain, the predicted effect of the initial porosity on the predicted crack growth rate is small. The sensitivity analysis identified the nucleation amplitude and Tvergaard’s loss of strength parameter as the main factors, whose variation leads to larger changes in the crack growth rate.

Finite Element Simulation of Stable Fatigue Crack Growth Using Critical CTOD Determined by Preliminary Finite Element Analysis

2014 ◽  
Vol 891-892 ◽  
pp. 1675-1680
Author(s):  
Seok Jae Chu ◽  
Cong Hao Liu
Keyword(s):  
Finite Element ◽  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Finite Element Simulation ◽  
Crack Growth ◽  
Crack Tip ◽  
Stress Intensity Factor Range ◽  
Crack Tip Opening Displacement ◽  
Element Analysis ◽  
Element Simulation

Finite element simulation of stable fatigue crack growth using critical crack tip opening displacement (CTOD) was done. In the preliminary finite element simulation without crack growth, the critical CTOD was determined by monitoring the ratio between the displacement increments at the nodes above the crack tip and behind the crack tip in the neighborhood of the crack tip. The critical CTOD was determined as the vertical displacement at the node on the crack surface just behind the crack tip at the maximum ratio. In the main finite element simulation with crack growth, the crack growth rate with respect to the effective stress intensity factor range considering crack closure yielded more consistent result. The exponents m in the Paris law were determined.

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