How can fatigue crack growth be correctly characterized in presence of significant plastic deformation. A simple method for measuring tearing energy of nicked rubber strips. Numerical simulation of fatigue crack growth rate and crack. Fatigue crack propagation is by far the most important failure mechanism.
Some examples indicated that such a fate has caught up the jintegral which is. This paper provides a method for addressing surface crack growth in railway wheels, taking into account rail and brake blocks effects. In mixedmode crack growth calculations using fe, three methods are generally used to compute the stress intensity factors along the generally curved crack path. Fatigue crack propagation under complex loading in arbitrary 2d. Although other researchers 10 found that delta j integral still maintains its path independence under cyclic loadings, nevertheless, it is a considerable issue how to use delta j integral correctly in fatigue crack growth simulations. Calculating crack growth life based on the nasgro crack growth mathematical model without or with the generalized willemborg retardation model, once the stress intensity factor curves are calculated at the crack propagation phase. J integral correlation with fatigue crack growth rates was comparable to the ak correlation. In this software, without using the remeshing technique, effect of crack tip plasticity in fatigue crack growth life was analyzed. In the linear portion of the crack growth curvestage ii, the crack growth rate. Elasticplastic fracture mechanics famufsu college of. The jintegral is a widely applied fracture mechanics parameter relating to the energy release associated with crack growth and is a measure of the deformation intensity at the crack tip.
Some systems may be designed to allow for some crack growth before repair and replacement. Dtd handbook analysis of damage growth crack growth. It was indicated that retardation effect by excessive loading beyond smallscale yielding could be quantitatively evaluated using the jwheeler model. The jintegral, as originally proposed by rice, is a pathindependent contour integral which may be used to characterise. The strain energy density w, appearing in equation 2. J is the range of the cyclic jintegral, f is a function of the jintegral.
The cyclic jintegral as a criterion for fatigue crack growthj. An integral formulation of twoparameter fatigue crack growth. Dtdhandbook afgrow air force growth fracture mechanics. A study of plane stress fracture in the largescale plastic yielding regime. Jan 10, 2011 the modified wheeler model using jintegral range. A set of experiments were performed using specimens made from a 7475t7351 aluminium alloy plate. Introduce holes or crack stop drill holes in the structure and accounting of such modifications. Dtd handbook residual strength failure criteria crack. J, has been proposed for the prediction of retardation effect on crack growth after excessive loading. Crack tip opening displacement ctod parameter jintegral parameter jic and j resistance curve testing similitude under elasticplastic conditions day two introduction to fatigue crack growth lecture, discussion, and examples similitude in fatigue empirical crack growth equations.
It is related to the energy release associated with crack growth and is a measure of the intensity of deformation at a notch or crack tip, especially for nonlinear materials. Stp590 mechanics of crack growth astm international. Effect fracture resistance on retardation of crack growth. Load sequence effects and mixedmode fatigue crack growth. Quantitative evaluation of fatigue crack growth retardation. The constitutive equation under the lowcycle fatigue lcf was discussed, and a twodimensional 2d model for simulating fatigue crack extension was put forward in order to propose a new cyclic jintegral. Some examples indicated that such a fate has caught up the j integral which is widely used in rateindependent quasistatic fracture analysis to characterise the energy release rate associated with crack growth. By tracking crack opening displacements, it was further possible to convert j integral results into mode i and mode ii stress intensity factors. A new basis for the application of the jintegral for cyclically loaded. Thus creep crack growth was sensitive to microstructure whereas fatigue crack growth was not, excluding environmental effects. Fatigue crack growth during gross plasticity and the j integral. Crack growth evaluation methods have been experimentally investigated in several studies by applying seismic response load to cracked pipes 18.
The analysis procedure for crackgrowth prediction requires the following steps. Stage ii crack growth and overall life prediction, metallurgical and materials transactions a, 48, 4, 1641, 2017. Fracture mechanics, damage and fatigue non linear fracture. Rice, who showed that an energetic contour path integral called j was independent of the path around a crack. Application of the j integral to the initiation of crack extension in a titanium 6al4v alloy. In this paper the stress intensity factors for 2d cracked structural components have been derived using j integral approach. Jun 28, 2002 jiaxi zhao, weixing chen, mengshan yu, karina chevil, reg eadie, jenny been, greg van boven, richard kania and sean keane, crack growth modeling and life prediction of pipeline steels exposed to nearneutral ph environments. Fracture mechanics, damage and fatigue non linear fracture mechanics.
These studies have yielded several important findings, including applicability of the j integral value for crack growth beyond the ssy condition. Numerical aspects of the pathdependence of the jintegral in. Jintegral and cyclic plasticity approach to fatigue and fracture of. The severest restriction for j results from the assumed existence of a strain. Calculation of jintegral and stress intensity factors using. The constitutive equation under the lowcycle fatigue lcf was discussed, and a twodimensional 2d model for simulating fatigue crack extension was put forward in order to propose a new cyclic j integral. In this model, the fatigue crack propagation behavior is governed by the temporal crack tip state including the current applied load and the physical condition due to the previous load sequence. Jintegral tests indicate the resistance of a material to crack propagation under a steady tensile deformation.
Pdf effect fracture resistance on retardation of crack growth. The jintegral is widely accepted as a fracture mechanics parameter for both linear and nonlinear material response. The crack growth retardation effect in filletwelded steel joints subjected to periodic overloads has been investigated by garwood and maddox. The effect in the welded joints was weaker than in the nonwelded material. Jintegral evaluation massachusetts institute of technology. Crack propagation an overview sciencedirect topics. Aug 10, 2015 read effect fracture resistance on retardation of crack growth, international journal of structural integrity on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. The jintegral represents a way to calculate the strain energy release rate, or work energy per.
When the above conditions are not satisfied, j becomes path dependent and does not relates to any physical quantities 3. Crack growth evaluation for cracked stainless and carbon. Crack growth equations are used to predict the crack size starting from a given initial flaw and are typically based on experimental data obtained from constant amplitude fatigue tests. In order to improve the limitation of fracture mechanicsbased models, besides the predictions of the moderate fatigue crack growth rates at the paris regime and the high fatigue crack growth rates at the high stress intensity. Fundamentals of damage tolerance afgrow air force growth. An increasing number of the offshore structures in the north sea are being operated in a life extension phase, which means that their original design life has been exceeded. The j integral is widely accepted as a fracture mechanics parameter for both linear and nonlinear material response. Pdf jintegral and fatigue life computations in the incremental. The j integral approach in elasticplastic fatigue crack propagation. The themes of fracture mechanics analysis which continue to be dominant interests in this book are applications to elasticplastic fracture through j integral methods, instability and material property analysis through rcurve methods, fatigue crack growth phenomena and life estimation, creep cracking analysis, and applications of fracture. A cohesive xfem model for simulating fatigue crack growth.
In addition, the phenomenon of fatigue retardation was explained through the. For loading symmetry about the crack axis xaxis, the results of the integration on paths 01, 12 and 23 are equal to the integrations on paths 67, 56 and 45, respectively. The method is aimed at simulating fatigue crack growth as well as crack growth retardation due to an overload. This paper addresses presetting of the fracture toughness k r based on j integral j q according to astm1820 in the fastran retardation model. J integral resistance curve testing and evaluation. A cyclic cohesive zone model is applied to characterize the fatigue crack growth behavior of a in718 superalloy which is frequently used in aerospace components. The theoretical concept of j integral was developed in 1967 by g. Application of a cohesive zone model for simulating fatigue. Corrosion pitting and environmentally assisted small crack growth. The critical role of pitting in crack nucleation in power generation, aerospace, and oil and gas applications stimulated considerable effort to understand and to model quantitatively the different stages of damage development, including pit initiation, pit growth, the transition from a pit to a crack and subsequent growth of the crack 38.
Moreover, crack retardation effects compromise even more the computational. In this work, a numerical method is pursued based on a cohesive zone model czm. The j integral represents a way to calculate the strain energy release rate, or work per unit fracture surface area, in a material. Jp0 plastic part of the jintegral without crack growth correction.
The definition, primary characteristics, physical interpretations and numerical evaluation of the new parameter were investigated in detail. Thermoplastic j integral calculation for a semielliptical. Creep and fatigue crack growth in several cast superalloys. Determination of fracture mechanics parameters using fem and. However, some researchers 11, 12 have pointed out that j integral is invalid upon unloading. In this case, fatigue crack growth analysis is key to safe operation of the system. It was indicated that retardation effect by excessive loading beyond smallscale yielding could be quantitatively evaluated using the j wheeler model. The j integral was developed because of the difficulties involved in computing the stress close to a crack in a nonlinear elastic or elasticplastic material.
Establish a stress history and mission mix section 5. Investigation on evaluation method based on j integral for. New cyclic j integral for lowcycle fatigue crack growth. Hovever, this technique may be complex in the case of the fatigue growth of general cracks. Rice 166 also showed that the value of the j integral represents the energy release rate for the planar crack growth. Plasticity effects were considered by using three methods. Calculated results for crack growth rates were compared with experimental data in literature.
Nonlinear measures as the jintegral and the crack tip opening dis placement. Difficulties in estimating crack tip plasticity under largescale yielding conditions, led wilhem 1974 to an alternate failure criterion based on the j integral rice, 1968. One of the earliest crack growth equations based on the stress intensity factor range of a load cycle is the pariserdogan equation. Jexp is questionable, since it presumes, like the classical jintegral, deformation theory of plasticity, which is not applicable for cyclic loading and crack extension. These studies have yielded several important findings, including applicability of the jintegral value for crack growth beyond the ssy condition. The jintegral is equal to the strain energy release rate for a crack in a body subjected to. A wellknown approach is to apply the experimental cyclic jintegral. J integral is defined as it can be shown that j is path independent and represents energy release rate for a material where is a.
1399 9 983 621 41 957 909 1426 266 282 695 1486 1189 1536 8 575 865 15 712 399 1444 1509 988 1396 356 998 978 1469 770 369 911 1133 63 114 782 522 927 1158 1104 260 1437 961 369 368 530 1349