Download or read book Numerical Approach for Predicting Fatigue Crack Growth in Residual Stress Bearing Bodies written by Jihwi Kim and published by . This book was released on 2015 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue failure in mechanical components is one of the main concerns of the aircraft industry, so compressive residual stress is often applied to the components because it is beneficial to improve resistance to fatigue by slowing down crack growth. As a result, residual stress has been included in fatigue crack growth prediction methods. To date, residual stress was usually combined with applied loads to affect the stress intensity factor (at the current crack size) in the fatigue crack growth prediction. However, crack face contact may occur due to compressive residual stress during fatigue crack growth, and the contact effect was barely included in the prediction. Crack face contact near the crack tip under cyclic loading due to plasticity or roughness, which is called fatigue crack closure, has been studied extensively because it has a significant effect on fatigue crack growth rate (FCGR), but little research has been conducted to understand the details of crack closure due to bulk residual stress fields.This work focuses on crack closure due to compressive residual stress in an elastic material with bulk residual stress, and emphasizes that the effect of bulk residual stresses on crack closure described here is an elastic effect, which distinguishes it from the more commonly discussed forms of closure. This work describes a means to forecast crack closure due to bulk residual stress fields and assesses schemes to account for its effects on fatigue crack growth. First, contact pressure between two opposing crack faces is quantified with modeling the problem of frictionless contact. In the modeling, a weight function for a specific geometry is used and the problem is solved using quadratic mathematical programming. Second, the contact pressure is included as a form of stress intensity factor to the fatigue crack growth prediction, and the new prediction method is suggested. The new prediction method is compared to the previous methods in the literature for specific geometries (a crack on compact tension coupons and a radial crack at a hole in a strip), applied loads and residual stress fields. Additionally, in order to support this work, weight functions for cracks at a hole were newly developed.
Download or read book Residual Stress Effects in Fatigue written by H. S. Reemsnyder and published by ASTM International. This book was released on 1982 with total page 244 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Predicting Fatigue Crack Growth in the Residual Stress Field of a Cold Worked Hole written by Jude H. Restis and published by . This book was released on 2007 with total page 13 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cold working of holes generates compressive residual stresses resulting in a significant fatigue life improvement over a non-cold worked hole. Current fatigue life prediction methods for cold worked holes are based on two-dimensional (2-D) linear superposition of stress intensity factor, K, solutions of the non-cold worked hole and the residual stresses. Such predictions have shown various levels of agreement with the overall fatigue life and have generally underpredicted the crack growth over the majority of life. An inverse process was used to generate K solutions for the residual stresses of two experimental data sets using AFGROW and the crack growth data from the experiments. The inverse K solutions were inconsistent with the residual stress distribution indicating that it contained mechanisms or features not inherent to the 2-D weight function method. The predicted fatigue life was found to be very sensitive to a ± 1 % variance in the inversely generated K solution. This sensitivity of the K method is a very important issue that must be addressed in the future. A 2-D FEA model indicated that the crack remained completely closed over a range of crack lengths despite experimental crack growth indicating that the model was not an accurate physical representation of the real crack. The results of this study combined with the significantly faster crack growth observed on the side of the hole corresponding to the entry side of the mandrel and the through thickness residual hoop stress variation show that the current methodology based on a 2-D assumptions is inadequate in predicting the fatigue crack growth from cold worked holes for the range of specimen thicknesses in this study. It is suggested that further research focus on incorporating the through thickness stress variance in a solution that predicts crack growth both in the radial and through thickness directions to capture the peculiar crack growth associated with cold working.
Download or read book Methods and Models for Predicting Fatigue Crack Growth Under Random Loading written by and published by ASTM International. This book was released on with total page 147 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Influence of Residual Stress on Fatigue Crack Growth written by James E. LaRue and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis discusses the analysis of fatigue crack growth in the presence of residual stresses to determine a suitable method for fatigue life predictions. In the research discussed herein, the prediction methodologies are compared to determine the most accurate prediction technique. Finite element analysis results are presented as well as laboratory test data. The validity of each methodology is addressed and future work is proposed.
Download or read book Fatigue Crack Growth written by Hans Albert Richard and published by Springer. This book was released on 2016-06-13 with total page 305 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book offers a concise introduction to fatigue crack growth, based on practical examples. It discusses the essential concepts of fracture mechanics, fatigue crack growth under constant and variable amplitude loading and the determination of the fracture-mechanical material parameters. The book also introduces the analytical and numerical simulation of fatigue crack growth as well as crack initiation. It concludes with a detailed description of several practical case studies and some exercises. The target group includes graduate students, researchers at universities and practicing engineers.
Download or read book The Influence of Residual Stress on Fatigue Crack Growth written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis discusses the analysis of fatigue crack growth in the presence of residual stresses to determine a suitable method for fatigue life predictions. In the research discussed herein, the prediction methodologies are compared to determine the most accurate prediction technique. Finite element analysis results are presented as well as laboratory test data. The validity of each methodology is addressed and future work is proposed.
Download or read book Analysis of Fatigue Crack Growth and Residual Stress written by Shakhrukh Ismonov and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part of this dissertation employs a three-dimensional elastic-plastic finite element model of straight-through crack growth to correlate four well-known methodologies characterizing fatigue crack closure. The compliance offset and the adjusted compliance ratio (ACR) are experimental methods, whereas the node displacement and the contact stress methods are numerical approaches. Evolutions of crack closure from all four methodologies are compared for a numerical model of a single edge-cracked tension specimen subjected to different levels of constant amplitude cyclic loading. In the second part, a detailed two dimensional stress analysis is conducted for a single pin-joint under plane stress conditions. This study investigates the influence of material nonlinearity, friction, and pre-existing residual stresses from cold-working process on the local radial and hoop stress levels around the pin-loaded hole. Next, the beneficial influence of cold working process is quantified by computing the Mode I stress intensity factors K[subscript I] for a single radial crack emanating from a side of a loaded hole. Two different loading configurations are considered: (a) an open hole in tension, (b) a pin-loaded hole. The stress intensity factors are computed using the J integral solutions and the weight functions specific to the crack configuration. The reductions in K[subscript I] values due to different levels of cold-working process are presented for a range of crack lengths. The final part of the research involves a numerical investigation of an on-line crack compliance technique that is used for experimental measurements of residual stress fields along the crack growth path. A finite rectangular sheet is considered with a single crack emanating from a side of a central hole. The residual stress field is introduced around the hole by cold-working simulation. As part of validation, the normalized residual stress intensity factors computed using the on-line crack compliance technique are compared with those from the J-integral approach for the case of elastic crack growth. The influence of crack tip plasticity on the performance of the on-line crack compliance technique is studied by comparing the solutions of the elastic and elastic-plastic crack growth models.
Download or read book Fatigue Damage Crack Growth and Life Prediction written by F. Ellyin and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 484 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue failure is a multi-stage process. It begins with the initiation of cracks, and with continued cyclic loading the cracks propagate, finally leading to the rupture of a component or specimen. The demarcation between the above stages is not well-defined. Depending upon the scale of interest, the variation may span three orders of magnitude. For example, to a material scientist an initiated crack may be of the order of a micron, whereas for an engineer it can be of the order of a millimetre. It is not surprising therefore to see that investigation of the fatigue process has followed different paths depending upon the scale of phenomenon under investigation. Interest in the study of fatigue failure increased with the advent of industrial ization. Because of the urgent need to design against fatigue failure, early investiga tors focused on prototype testing and proposed failure criteria similar to design formulae. Thus, a methodology developed whereby the fatigue theories were proposed based on experimental observations, albeit at times with limited scope. This type of phenomenological approach progressed rapidly during the past four decades as closed-loop testing machines became available.
Download or read book Analytical and Experimental Methods for Residual Stress Effects in Fatigue written by Robert L. Champoux and published by ASTM International. This book was released on 1988 with total page 141 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Residual Stress Effects on Fatigue Life Via the Stress Intensity Parameter K written by Jeffrey L. Roberts and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Residual stresses are known to have a significant effect on fatigue crack propagation and thus fatigue life. These effects have generally been quantified through an empirical approach, lending little help in the quantitative prediction of such effects. The weight function method has been used as a quantitative predictor, but its use neglects residual stress redistribution, treating the residual stress as a constant during crack growth. At least three different behaviors contribute to the redistribution of residual stress. First, the residual stress behind the crack tip is reduced to a negligible level as soon as the crack tip passes. Second, the residual stress tends to redistribute away from the crack tip with crack growth, and third, crack growth results in an overall relaxation of residual stress. An alternative method for predicting the effect of a residual stress distribution on fatigue crack growth is herein developed. The stress intensity factor due to residual stress, K[subscript res], is characterized as the change in crack driving force due to the presence of the residual stress. This crack driving force, being the derivative of a potential, is found through superposition of an applied stress and a residual stress, and subsequent manipulation of finite element strain energy and nodal displacement results. Finite element modeling is carried out using a spatial distribution of non-uniform thermal expansion coefficients and a unit temperature load to simulate the desired residual stress. Crack growth is then achieved through use of a node release algorithm which sequentially removes nodal displacement constraint. The complete stress distribution, nodal displacements and internal strain energy are captured for each increment of crack growth, and from this information, knowledge of the stress intensity factor as a function of crack length is derived. Results of the K[subscript res] calculations are used in a fatigue crack growth model to predict fatigue lives. The fatigue life model involves step by step analysis of crack growth increment based on knowledge of stress intensity factors resulting from applied and residual stress. The qualitative effects of residual stress predicted by this model agree with documented empirical results which show that compressive residual stress increases fatigue life, while tensile residual stress decreases fatigue life. Two solutions for K[subscript res] are possible, depending on the choice of load-control or displacement-control modeling. Use of displacement-control, or fixed displacement loading, minimizes redistribution of residual stress and, under net tensile loading, tends to lead to more conservative fatigue life predictions. Load-control modeling, not having the same displacement constraint, allows more relaxation of the residual stress and tends to provide the more non-conservative life estimates. Three residual stress patterns, two due to welding and one to shot peening, are also investigated. K[subscript res] solutions for each residual stress are developed, and fatigue life predictions made.
Download or read book Fatigue Crack Growth Thresholds Endurance Limits and Design written by J. C. Newman and published by ASTM International. This book was released on 2000 with total page 436 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Contains 24 papers from the November, 1998 symposium of the same name, sponsored by the ASTM Committee E8 on Fatigue and Fracture, and presented by Newman and Piascik (both of the NASA Langley Research Center). The papers focus on such areas as fatigue-crack growth threshold mechanisms, loading and specimen-type effects, analyses of fatigue-crack-growth-threshold behavior, and applications of threshold concepts and endurance limits to aerospace and structural materials. Annotation copyrighted by Book News, Inc., Portland, OR.
Download or read book Fatigue Crack Growth Under Residual Stresses Around Holes written by Ramesh Nagaralu and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressive residual stresses induced by tensile overloads, compressive under loads, or by a cold-expansion process in specimens containing a circular hole and their influence on subsequent fatigue crack growth in aluminum alloys are studied. The finite element method is used to calculate residual stresses. The superposition method, which uses crack-tip stress intensity factors for cases involving remote loading and residual stresses, is used to calculate crack growth life for three kinds of tests from the literature: (1) fatigue of a circular hole specimen after an overload or under load, (2) single crack growing from a circular hole after a severe tensile overload, and (3) single crack growing from a circular hole after cold-working, reaming and notching. All specimens were subjected to subsequent constant amplitude loading. The superposition method worked fairly well for most cases, but tended to over predict fatigue life for small cracks and for cracks growing under residual stresses, which produce compressive (maximum and minimum) stress intensity factors.
Download or read book Fatigue Crack Growth Under Residual Stresses Around Holes written by and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Compressive residual stresses induced by tensile overloads, compressive under loads, or by a cold-expansion process in specimens containing a circular hole and their influence on subsequent fatigue crack growth in aluminum alloys are studied. The finite element method is used to calculate residual stresses. The superposition method, which uses crack-tip stress intensity factors for cases involving remote loading and residual stresses, is used to calculate crack growth life for three kinds of tests from the literature: (1) fatigue of a circular hole specimen after an overload or under load, (2) single crack growing from a circular hole after a severe tensile overload, and (3) single crack growing from a circular hole after cold-working, reaming and notching. All specimens were subjected to subsequent constant amplitude loading. The superposition method worked fairly well for most cases, but tended to over predict fatigue life for small cracks and for cracks growing under residual stresses, which produce compressive (maximum and minimum) stress intensity factors.
Download or read book Mechanics of Fatigue Crack Closure written by Wolf Elber and published by ASTM International. This book was released on 1988 with total page 671 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Residual Stress and Its Effects on Fatigue and Fracture written by Anastasius Youtsos and published by Springer Science & Business Media. This book was released on 2007-05-20 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: The contents of this book have been grouped into three topic areas covering theoretical /numerical and experimental analyses of residual stress and its effects on fatigue and fracture. It details recent advances on its title topics by leading European experts and contains theoretical/numerical studies of high value backed by sound experimental data. It also provides experimental studies based on novel and verifiable testing methods.
Download or read book Part Through Crack Fatigue Life Prediction written by J. B. Chang and published by ASTM International. This book was released on 1979 with total page 232 pages. Available in PDF, EPUB and Kindle. Book excerpt:
