Download or read book Prediction of Crack Growth Rate and Load Interaction Effects Using Damage Accumulation Model written by Virender Goswami and published by . This book was released on 2004 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Probabilistic Prediction of Crack Growth Based on Creep Fatigue Damage Accumulation Mechanism written by Zhigang Wei and published by . This book was released on 2011 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this paper a deterministic creep/fatigue accumulation model from simple sequential and repetitive creep and fatigue crack growth mechanisms for creep-brittle materials is developed. In the model the maximum stress intensity factor and stress intensity factor range can be used to describe, respectively, the creep and fatigue crack growth behaviors. The probabilistic behavior of the combined creep-fatigue can be calculated by direct integration of a joint log-normal probability density function or other methods. The Monte Carlo simulation method is used in this paper to analyze the probabilistic behavior of the derived deterministic creep-fatigue model and to estimate the reliability of a creep-fatigue correlation as introduced by the uncertainties in both creep and fatigue lives. Predicted results from this new crack growth method are compared with the bi-linear creep-fatigue interaction models as adopted by ASME Code Case N-47 and API579/ASME FFS, and the results are discussed.
Download or read book Random Spectrum Fatigue Crack Life Predictions With Or Without Considering Load Interactions written by M. Szamossi and published by . This book was released on 1981 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The validity of using constant amplitude crack growth rate data for the prediction of fatigue crack growth behavior and lives of center-cracked tension (CCT) specimens under random spectrum loadings was assessed. Analytical predictions obtained from the EFFGRO computer program were the results from two different approaches. One approach did not account for the load interaction effects to the fatigue crack growth, while the other approach considered both the tensile overload retardation and the compressive load acceleration effects as well as the reduction of overload retardation effect caused by the compressive load immediately following the tensile overload. This paper describes the fatigue crack growth rate equation, the load interaction model, the numerical procedure, and the cycle counting technique used in the EFFGRO program. Results from other studies, including the sensitivity of the overload shut-off ratio, the crack growth rate constants determination procedure, and the range-pair counting effects to the prediction accuracies, are also presented.
Download or read book Fatigue Behavior Under Multiaxial Stress States Including Notch Effects and Variable Amplitude Loading written by Nicholas R. Gates and published by . This book was released on 2016 with total page 747 pages. Available in PDF, EPUB and Kindle. Book excerpt: The central objective of the research performed in this study was to be able to better understand and predict fatigue crack initiation and growth from stress concentrations subjected to complex service loading histories. As such, major areas of focus were related to the understanding and modeling of material deformation behavior, fatigue damage quantification, notch effects, cycle counting, damage accumulation, and crack growth behavior under multiaxial nominal loading conditions. To support the analytical work, a wide variety of deformation and fatigue tests were also performed using tubular and plate specimens made from 2024-T3 aluminum alloy, with and without the inclusion of a circular through-thickness hole. However, the analysis procedures implemented were meant to be general in nature, and applicable to a wide variety of materials and component geometries. As a result, experimental data from literature were also used, when appropriate, to supplement the findings of various analyses. Popular approaches currently used for multiaxial fatigue life analysis are based on the idea of computing an equivalent stress/strain quantity through the extension of static yield criteria. This equivalent stress/strain is then considered to be equal, in terms of fatigue damage, to a uniaxial loading of the same magnitude. However, it has often been shown, and was shown again in this study, that although equivalent stress- and strain-based analysis approaches may work well in certain situations, they lack a general robustness and offer little room for improvement. More advanced analysis techniques, on the other hand, provide an opportunity to more accurately account for various aspects of the fatigue failure process under both constant and variable amplitude loading conditions. As a result, such techniques were of primary interest in the investigations performed. By implementing more advanced life prediction methodologies, both the overall accuracy and the correlation of fatigue life predictions were found to improve for all loading conditions considered in this study. The quantification of multiaxial fatigue damage was identified as being a key area of improvement, where the shear-based Fatemi-Socie (FS) critical plane damage parameter was shown to correlate all fully-reversed constant amplitude fatigue data relatively well. Additionally, a proposed modification to the FS parameter was found to result in improved life predictions in the presence of high tensile mean stress and for different ratios of nominal shear to axial stress. For notched specimens, improvements were also gained through the use of more robust notch deformation and stress gradient models. Theory of Critical Distances (TCD) approaches, together with pseudo stress-based plasticity modeling techniques for local stress-strain estimation, resulted in better correlation of multiaxial fatigue data when compared to traditional approaches such as Neuber's rule with fatigue notch factor. Since damage parameters containing both stress and strain terms, such as the FS parameter, are able to reflect changes in fatigue damage due to transient material hardening behavior, this issue was also investigated with respect to its impact on variable amplitude life predictions. In order to ensure that material deformation behavior was properly accounted for, stress-strain predictions based on an Armstrong-Frederick-Chaboche style cyclic plasticity model were first compared to results from deformation tests performed under a variety of complex multiaxial loading conditions. The model was simplified based on the assumption of Masing material behavior, and a new transient hardening formulation was proposed so that all modeling parameters could be determined from a relatively limited amount of experimental data. Overall, model predictions were found to agree fairly well with experimental results for all loading histories considered. Finally, in order to evaluate life prediction procedures under realistic loading conditions, variable amplitude fatigue tests were performed using axial, torsion, and combined axial-torsion loading histories derived from recorded flight test data on the lower wing skin area of a military patrol aircraft (tension-dominated). While negligible improvements in life predictions were obtained through the consideration of transient material deformation behavior for these histories, crack initiation definition was found to have a slightly larger impact on prediction accuracy. As a result, when performing analyses using the modified FS damage parameter, transient stress-strain response, and a 0.2 mm crack initiation definition, nearly all variable amplitude fatigue lives, for un-notched and notched specimens, were predicted within a factor of 3 of experimental results. However, variable amplitude life predictions were still more non-conservative than those observed for constant amplitude loading conditions. Although there are numerous factors which could have contributed to this non-conservative tendency, it was determined that some of the error may have resulted from inaccuracies in life prediction curves, the modeling of material deformation behavior, the consideration of normal-shear stress/strain interaction effects, and/or linear versus nonlinear damage accumulation. In addition to crack initiation, fatigue crack growth behavior was also of interest for all tests performed in this study. Constant amplitude crack growth in notched specimens was observed to be a primarily mode I process, while cracks in un-notched specimens were observed to propagate on maximum shear planes, maximum tensile planes, or a combination of both. Specialized tests performed using precracked tubular specimens indicated that the preferred growth mode was dependent on friction and roughness induced closure effects at the crack interface. As a result, a simple model was proposed to account for frictional attenuation based on the idea that crack face interaction reduces the effective stress intensity factor (SIF) by allowing a portion of the nominally applied loading to be transferred through the crack interface. Crack path/branching, growth life, and growth rate predictions based on the proposed model were all shown to agree relatively well with the experimentally observed trends for all loading conditions considered. For notched specimen fatigue tests, although crack growth was observed to be mode I-dominated, constant amplitude crack growth rates under multiaxial nominal stress states were observed to be higher than those for uniaxial loading at the same SIF range. While T-stress corrections were able to account for this difference in some cases, growth rates for pure torsion loading still had the tendency to be higher than those for uniaxial loading. Additionally, using short crack models to account for stress concentration and initial crack geometry effects was found to improve growth rate correlations in the notch affected zone. For 90° out-of-phase loading conditions, small crack growth appeared to have been dominated by the mode I loading from the axial component of the applied stress, but as cracks grew, they turned, and mode I SIF range alone was unable to successfully correlate crack growth rate data. Finally, for variable amplitude crack growth, two state-of-the-art analysis models, UniGrow and FASTRAN, were used to predict crack growth behavior for the notched specimens tested in this study. UniGrow is based on the idea that residual stress distributions surrounding the crack tip are responsible for causing load sequence effects, while FASTRAN attributes these effects to varying degrees of plasticity induced closure in the crack wake. While both models were able to predict nearly all uniaxial constant amplitude crack growth lives within a factor of 3 of experimental results, they both produced conservative predictions under uniaxial variable amplitude loading conditions. For variable amplitude torsion and combined axial-torsion crack growth, however, the degree of conservatism in these predictions was found to reduce. This was attributed to an increase in experimental growth rates due to multiaxial stress states effects, which are not accounted for in either UniGrow or FASTRAN. By comparing differences in crack growth life between tests performed using full and edited versions of the same loading history, it was found that FASTRAN was generally better able to account for the effects of small cycles and/or changes in loading history profile. Additionally, initial crack geometry assumptions were found to have a fairly significant impact on analysis results for the specimen geometry considered in this study.
Download or read book High Temperature Creep fatigue written by Ryuichi Ohtani and published by . This book was released on 1988 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Load Interactions on Crack Growth as Related to State of Stress and Crack Closure written by and published by . This book was released on 1985 with total page 26 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Design of Fatigue and Fracture Resistant Structures written by P. R. Abelkis and published by ASTM International. This book was released on 1982 with total page 500 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Experimental and Theoretical Analyses of the Load Sequence Effects on Fatigue Crack Growth Resistance written by and published by . This book was released on 2004 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Modeling of the fatigue crack propagation based on damage accumulation process ahead of the crack tip has been developed, which utilizes stress and strain distribution ahead of the crack tip, estimated using Rice and elastic solutions. The methodology is based on the use of both Kmax and DK as contributing parameters to the driving force and damage accumulation. Weight function approach has been adopted to determine the Kres profile. Load interaction and overload effects have been modeled by the effect of Kres on the Kmax and DK. The predictions of the present approach have been compared to experimental data and reasonable agreement has been found.
Download or read book Stochastic Crack Propagation with Applications to Durability and Damage Tolerance Analyses written by J. N. Yang and published by . This book was released on 1985 with total page 268 pages. Available in PDF, EPUB and Kindle. Book excerpt: Various stochastic models for fatigue crack propagation under either constant amplitude or spectrum loadings have been investigated. These models are based on the assumption that the crack growth rate is a lognormal random process, including the general lognormal random process, lognormal white noise process, lognormal random variable, and second moment approximations, such as Weibull, gamma, lognormal and Gaussian closure approximations. Extensive experimental data have been used for the correlation study with various stochastic models. These include fastener hole specimens under fighter or bomber spectrum laodings and center-cracked specimens under constant amplitude loads. The data sets for the fastener hole specimens cover adequately different loading conditions, environments, load transfers and crack size range. It is shown that the white noise process is definitely not a valid model for fatigue crack propagation.
Download or read book Improved Methods for Predicting Spectrum Loading Effects written by J. B. Chang and published by . This book was released on 1981 with total page 222 pages. Available in PDF, EPUB and Kindle. Book excerpt: This report presents the technical details of improved methods for predicting the load interaction effects on crack growth under flight spectrum loading developed in a research effort sponsored by the USAF. These include the cycle-by-cycle crack-growth prediction methods used in the detail design stage, the flight-by-flight crack-growth analysis method for individual aircraft tracking usage, and preliminary design trade-off studies.
Download or read book Multi parameter Yield Zone for Predicting Spectrum Crack Growth written by and published by . This book was released on 1980 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Prediction of Fatigue crack Growth Under Variableamplitude and Spectrum Loading Using a Closure Model written by and published by . This book was released on 1981 with total page 42 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue of Structures and Materials written by J. Schijve and published by Springer Science & Business Media. This book was released on 2008-12-16 with total page 627 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue of structures and materials covers a wide scope of different topics. The purpose of the present book is to explain these topics, to indicate how they can be analyzed, and how this can contribute to the designing of fatigue resistant structures and to prevent structural fatigue problems in service. Chapter 1 gives a general survey of the topic with brief comments on the signi?cance of the aspects involved. This serves as a kind of a program for the following chapters. The central issues in this book are predictions of fatigue properties and designing against fatigue. These objectives cannot be realized without a physical and mechanical understanding of all relevant conditions. In Chapter 2 the book starts with basic concepts of what happens in the material of a structure under cyclic loads. It illustrates the large number of variables which can affect fatigue properties and it provides the essential background knowledge for subsequent chapters. Different subjects are presented in the following main parts: • Basic chapters on fatigue properties and predictions (Chapters 2–8) • Load spectra and fatigue under variable-amplitude loading (Chapters 9–11) • Fatigue tests and scatter (Chapters 12 and 13) • Special fatigue conditions (Chapters 14–17) • Fatigue of joints and structures (Chapters 18–20) • Fiber-metal laminates (Chapter 21) Each chapter presents a discussion of a speci?c subject.
Download or read book Probabilistic Life Prediction of Structures Under Fatigue and Creep written by Hongyin Mao and published by . This book was released on 2002 with total page 157 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Damage in Composite Materials written by K. Reifsnider and published by ASTM International. This book was released on 1982 with total page 298 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Advances in Fatigue Lifetime Predictive Techniques written by Michael R. Mitchell and published by ASTM International. This book was released on 1992 with total page 495 pages. Available in PDF, EPUB and Kindle. Book excerpt: Twenty-seven papers from fatigue researchers and practitioners review in detail recent progress in the development of methods to predict fatigue performance of materials and structures and to assess the extent to which these new methods are finding their way into practice. The papers, from the ASTM
Download or read book Fracture at High Temperatures written by Hermann Riedel and published by Springer. This book was released on 2014-01-13 with total page 430 pages. Available in PDF, EPUB and Kindle. Book excerpt:
