The phenomenon of plasticityinduced crack closure is. The fatigue crack closure models discussed above fundamentally assume plasticity induced crack closure picc as the only mechanism of closure. Many researchers have proposed finite element analyses simulating plasticityinduced fatigue crack closure, considering different twodimensional throughthickness cracked configurations under planestrain or planestress conditions. Plasticity induced crack closure and constraint effects due to finite plate thickness are both fundamental aspects in the mechanics of fatigue cracks. An evaluation of the plasticityinduced crackclosure concept. The premature contact of crack surfaces attributable to the neartip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure picc, has long been focused. Plasticity induced crack closure in middlecrack tension. Plasticity and asperityinduced fatigue crack closure under. In the high loading ratio fatigue crack growth experiment the effect of plasticityinduced crack closure is inhibited croft et al.
On the basis of the lack of a thickness effect and an insensitivity to r in the absence of closure it is concluded that plasticity induced closure plays a relatively minor role in affecting the rate of fatigue crack propagation with the exception of overload effects. Abstract numerical studies played a major role in the current understanding of plasticity induced crack closure picc, however it is well known that the numerical models simplify the reality by considering discrete crack propagations, relatively high fatigue crack growth rates, sharp cracks and that propagation occurs at a welldefined load. Fatigue 2010 an analytical model of plasticity induced crack closure f. Apr 11, 20 the premature contact of crack surfaces attributable to the neartip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure picc, has long been focused as supposedly controlling factor of fatigue crack growth fcg. Pdf role of plasticityinduced crack closure in fatigue. He measured a crack closure load of about 40% pmax. Feb 01, 2017 for the explanation of the plasticity. In plasticity induced crack closure, the crack growth is governed by the effective stress intensity range. An evaluation of the plasticityinduced crackclosure. Abstract the change in cyclic plastic deformation at a fatigue crack tip as a function of crack extension and the variation in the crack closure are. Nasa langley research center hampton, virginia usa abstract an assessment of the plasticity induced crack closure concept is made, in light of some of the questions that have been raised on the validity of the concept, and the. Separating plasticityinduced closure and residual stress. Specimen compliance curves turned out to be nonlinear merely by virtue of plasticity with no contribution of crack closure.
Elbers results, and suggested that crack closure might account for the delay in crack extension due to an overload cycle, and also might reduce the ingress of a corrosive environment to the crack tip, hence reducing the corrosion fatigue effect. Influences of plasticityinduced crack closure on fatigue crack healing of carbon steel with heat treatment. Dynamic analysis of plasticityinduced fatigue crack closure. Influences of plasticity induced crack closure on fatigue crack healing of carbon steel with heat treatment. Department of mechanical and design engineering, university of portsmouth, anglesea building, anglesea road, portsmouth, po1 3dj, uk. Plasticityinduced crack closure is due to the accumulation of residual plastic deformation along the crack surfaces as the crack tip advances. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Finitedeformation elastoplastic analyses of cracks subjected to mode i cyclic loadings at various load ranges and ratios, as well as with an overload, are presented focusing the evolutions of the near tip deformations. Roughnessinduced crack closure is promoted by small plastic zone. Citeseerx plasticityinduced fatigue crack closure in high. Plasticity induced crack closure under plane stress and plane strain conditions require, in principle, a different explanation. Plasticity and asperityinduced fatigue crack closure. Simulations discarded the supposed mechanism of plasticity induced crack closure picc via outofplane stretching of material elements fillingin the crack and coming in contact at unloading.
Finite element simulations of crack growth have been extensively used to investigate plasticityinduced closure. Investigation of plasticityinduced fatigue crack closure. Welding strongly affects the material by the process of heating and subsequent cooling as well as by the fusion of additional filler material, resulting in inhomogeneous materials. Mar 23, 2012 a series of experiments has been carried out to determine why some alloys display plasticity induced fatigue crack closure pifcc, whereas other alloys display roughness induced crack closure rifcc. Apr 02, 2014 fatigue crack growth tests conducted on planesided, shallowcracked ct specimens provide the necessary data against which crack closure effects on fatigue crack growth behavior can be assessed. Roughnessinduced crack closure arises due to the roughness of the fracture surface near threshold stress intensity. The phenomenon of plasticity induced crack closure is associated with the development of residual plastically deformed material on the flanks of an advancing fatigue crack the degree of plasticity at the crack tip is influenced by the level of material constraint. So, this paper will present a fatigue crack propagation 3d model based on a calculation of the stress intensity factors based on an interpolation of the stresses, while taking into account the influence of the plasticity induced crack closure.
Numerical simulation of plasticityinduced fatigue crack. On the distinction between plasticity and roughness. Researches have achieved the knowledge of the different causes of the problem. May 01, 2008 read numerical simulation of plasticity induced fatigue crack closure with emphasis on the crack growth scheme. It is shown that the applied mode ii can either increase or decrease the effective. Plasticityinduced crack closure picc has long been focused as supposedly controlling factor of fatigue crack growth fcg. Roughness induced crack closure arises due to the roughness of the fracture surface near threshold stress intensity. Roughness induced crack closure is promoted by small plastic zone. A parameter for quantitative analysis of plasticity induced. In this study, the influences of plasticity induced crack closure on healing were evaluated by obtaining the crack opening load during the pre crack introduction and evaluating the fatigue crack propagation characteristics before and after the healing heat treatment, using compact tension specimens made of carbon steel with different test.
Role of plasticityinduced crack closure in fatigue crack. The premature contact of crack surfaces attributable to the neartip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced crack closure picc, has long been focused as supposedly controlling factor of fatigue crack growth fcg. The role of plasticityinduced crack closure and residual stressstrain on crack retardation after occurrence of overload has been. Influences of plasticityinduced crack closure on fatigue. A few models for plasticity induced crack closure have been. The influence of plasticityinduced crack closure on creep.
The premature contact of crack surfaces attributable to the neartip plastic deformations under cyclic loading, which is commonly referred to as plasticity induced. Different aspects have been investigated in detail, for example. The role of plasticity induced crack closure and residual stressstrain on crack retardation after occurrence of overload has been. For low load ratios, plasticityinduced crack closure affects fcgr immediately once the crack moves past the overload site. A series of experiments has been carried out to determine why some alloys display plasticityinduced fatigue crack closure pifcc, whereas. Creep and creepfatigue crack growth mechanisms in alloy709. The evolution of the stressstrain fields near a fatigue. The evolution of the stressstrain fields near a fatigue crack tip and plasticity.
Far fewer efforts have been directed toward the two dimensional problem. Finite element analysis is perhaps the most commonly used numerical method to model plasticity induced fatigue crack closure. Role of plasticityinduced crack closure in fatigue crack growth jesus toribio, viktor kharin university of salamanca, spain abstract. Finite element analysis of plasticity induced fatigue crack. Plasticityinduced crack closure is more prevalent in fatigue cracks under the planestress condition than those under planestrain condition due to differences in the cracktip plastic constraint. Overall, the present investigation provides additional support for estimation procedures of plasticity induced crack closure loads in fatigue. Fatigue crack propagation, plasticity induced crack closure, sensitivity analysis. Introduction fatigue of welds is a very complex phenomenon. Plasticityinduced crack closure under planestrain conditions in the. Finite element analysis of plasticity induced fatigue crack closure. Finite element simulations are performed to predict plasticity induced crack closure and creep fatigue crack growth rates in two heatresistant steels, the austenitic 20cr25ni alloy 709 and martensitic 9cr1mo modified 1cr9mo steels. Two stress intensity factors were examined at a stress ratio of 0.
A geometric model for fatigue crack closure induced by. To confirm that this is the case, in situ digital image correlation dic evaluation of crack opening was performed, and direct evidence of the lack of crack closure was obtained. Plasticityinduced crack closure an overview sciencedirect topics. Finite element simulations of crack growth have been extensively used to investigate plasticity induced closure. Jan 01, 2001 read behavior of plasticity induced crack closure and roughness induced crack closure in aluminum alloy, international journal of fatigue on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. On the distinction between plasticity and roughnessinduced. Plasticityinduced fatigue crack closure in highstrength. Special attention is devoted to the physical origin, the consequences for the experimental determination and the prediction of the effective crack driving force for fatigue crack propagation. Finite element analysis of plasticityinduced fatigue crack.
Finite element analysis of plasticity induced fatigue. Numerical simulation of plasticityinduced fatigue crack closure with emphasis. An analytical model of plasticity induced crack closure. A series of experiments has been carried out to determine why some alloys display plasticityinduced fatigue crack closure pifcc, whereas other alloys display roughnessinduced crack closure rifcc.
Experimental and numerical investigation of plasticity. Pdf role of plasticityinduced crack closure in fatigue crack growth. The phenomenon of plasticityinduced crack closure is associated with the development of residual plastically deformed material on the flanks of an advancing fatigue crack the degree of plasticity at the crack tip is influenced by the level of material constraint. The experiments included the determination of the crack opening levels as a. Zhao department of mechanical and design engineering, university of portsmouth, anglesea building, anglesea road, portsmouth, po1 3dj, uk. The results manifest the ambiguity of common justifications concerning fatigue crack closure fcc. Role of plasticityinduced crack closure in fatigue crack growth.
Plasticity and asperityinduced crack closure under mixedmode nonproportional loading are investigated, using numerical models. The aim of this thesis is to investigate plasticity induced fatigue crack closure from both modelling and experimental points of view. In contrast, crack closure is an effect that persists longer following ol. Experimental measurements of plasticityinduced crack closure related factors were made on the aluminum alloy 7091t7e69 using high resolution microscopy techniques. On the role of plasticityinduced fatigue crack closure in high. Such plasticityinduced closure, however, is most prevalent under essentially plane stress conditions,23 and yet recent studies on fatigue crack propagation at ultralow growth rates dadn crack closure mechanisms plasticity induced crack closure. On the modelling side combined analytical and numerical techniques and finite element analyses have been used to investigate 2d plane stress, 2d plane strain and 3d crack closure problems. Citeseerx plasticityinduced fatigue crack closure in. As well, the supposed origin of plasticity induced crack closure picc, which is habitually attributed to fillingin a crack with material stretched out of the crack plane behind the tip, is. Many researchers have proposed finite element analyses simulating plasticity induced fatigue crack closure, considering different twodimensional throughthickness cracked configurations under planestrain or planestress conditions. These models ignore the role of other known closure mechanisms like roughness induced crack closure ricc, oxide induced crack closure and transformation induced crack closure. Crack closure during fatigue crack propagation is a phenomenon widely investigated in the last years by experimental means.
Plasticity induced crack closure during fatigue crack. Two alloys were studied, the aluminum alloy 6061t6 pifcc and a steel of comparable yield strength, s25c rifcc. Plasticityinduced crack closure was first studied experimentally by elber, and is an inherent feature of the mechanics of fatigue crack growth. Although there exists other closure phenomena, such as roughness induced crack closure and oxide induced crack closure, they are often assumed to be secondary. For low load ratios, plasticity induced crack closure affects fcgr immediately once the crack moves past the overload site. Such plasticity induced closure, however, is most prevalent under essentially plane stress conditions,23 and yet recent studies on fatigue crack propagation at ultralow growth rates dadn fatigue crack growth ako, have clearly.
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