Download or read book Evaluation of Linear Elastic Fracture Mechanics Predictions of One and Two dimensional Fatigue Crack Growth at Cold expanded Holes written by Daniel Haines Stuart and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work assesses the ability of linear elastic fracture mechanics (LEFM) with superposition to correlate the growth of one and two-dimensional fatigue cracks at cold-expanded open holes under constant amplitude loading. Care is taken in the work to accurately: control the test setup to ensure growth of a single crack, determine residual stress in the coupons, measure crack growth, determine the fatigue crack growth rate (FCGR), compute stress intensity factors, and correlate fatigue crack growth rate with stress intensity factor range [delta]K and stress ratio R. The work used long dog-bone coupons made from 2.03 mm and 4.83 mm thick 7075-T6 sheet having a gage section 38.1 mm wide, a centrally located 7.09 mm diameter hole, with through thickness notches for thin and corner notches for thick coupons. Quarter elliptical stress intensity factors are used for thick coupons while one-dimensional stress intensity factors are used for thin coupons. Residual stress due to cold expansion (CX) was measured using the contour method as a function of position on the crack plane and gave typical results. Measurements on multiple coupons showed "10% variability in residual stress. Crack growth behavior of multiple as-machined (AM) coupons (without CX) tested at R of 0.1 or 0.5 agreed with earlier results published in the literature for both one and two dimensional cracks. Crack growth behavior of multiple thin CX coupons tested at the same two applied stress ratios was consistent with predictions by linear superposition, with scatter in lifetime consistent with the observed 10% variability in residual stress. LEFM based on quarter elliptical models was found to be ineffective to predict crack growth in CX coupons because the quarter elliptical shape assumption is inaccurate. The work therefore demonstrates the ability of LEFM with superposition to accurately correlate the behavior of coupons with and without residual stresses for one-dimensional crack growth, and only for AM for two-dimensional crack growth.
Download or read book Proceedings of the 17th International Conference on New Trends in Fatigue and Fracture written by Ricardo R. Ambriz and published by Springer. This book was released on 2017-11-17 with total page 361 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents the proceedings of one of the major conferences in fatigue, fracture and structural integrity (NT2F). The papers are organized and divided in five different themes: fatigue and fracture mechanics of structures and advanced materials; fatigue and fracture in pressure vessels and pipelines: mechanical behavior and structural integrity of welded, bonded and bolted joints; residual stress and environmental effects on the fatigue behavior; and simulation methods, analytical and computation models in fatigue and fracture.
Download or read book An Evaluation of Crack Growth from Loaded Fastener Holes Treated with Cold expansion written by John Regis Minotti and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This work assesses the effects of residual stress, introduced via cold hole expansion (CX), on fatigue crack growth through clad 7075-T6 and 7075-T651 aluminum. This was done by comparing fatigue crack growth through samples without residual stress treatments (AM) to the crack growth through CX samples. Loaded hole and nested angle coupons were tested, representing an idealized loaded hole connection, and an actual splice joint used in rotorcraft assemblies, respectively. The effects of load interaction was evaluated through all sample configurations by comparing fatigue crack growth under constant amplitude sinusoidal loading and a variable amplitude load program. All loaded hole test data was compared to linear elastic fracture mechanics (LEFM) predictions of crack growth, which used superposition to combine the effects of applied and residual stress and the Modified Generalized Willenborg Model of crack closure. Nested angle crack growth was catalogued to support future lifing of nested angle samples and future development of crack growth models. Overall the LEFM approach provided good predictions of crack growth through AM and select CX loaded hole coupons under both load profiles. These results demonstrate the ability of LEFM with superposition to predict CX crack growth through loaded hole samples under constant amplitude and spectrum loading. Nested angle testing shows that current nested angle CX treatments do not affect fatigue performance, which is dominated by the influences of friction, contact and bending. Offered are techniques to quantify two-dimensional crack growth by photogrammetrically quantifying marker bands. Also addressed are test procedures necessary to achieve the desired one and two-dimensional crack growth in all samples, and to avoiding fretting failure.
Download or read book Residual Stress and Fatigue Crack Growth Modeling in Complex Geometry Using Eigenstrain written by Renan L. Ribeiro and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Residual stress (RS) from quenching is inherent in the production of key high-strength aluminum alloys (e.g., 7xxx series aluminum), as quenching is a step in the widely used precipitation hardening process. Some residual stress relief processes are available, but do not fully relieve the stress, especially in complex geometry (e.g., die forgings). It is well accepted that residual stress affects fatigue performance, and should be considered in structural design of critical components. residual stress can be measured by a variety of experimental techniques, but it is desirable to have modeling tools to predict residual stress more rapidly and efficiently. While nonlinear process models have been used with some success for prediction of quench-induced residual stress, they are very complex, time consuming, and typically require large amounts of experimental data specific to the problem being studied as input in the model. The eigenstrain method, on the other hand, uses linear elastic finite element (FE) models, and provides a useful alternative for modeling of quench-induced residual stress. Currently, no studies have been published in the literature using eigenstrain modeling in the context of quenching. As an extension to previous studies, this work seeks to evaluate eigenstrain models for prediction of quench-induced residual stress in finished parts given the residual stress in raw stock material, and subsequently the effects of residual stress in their fatigue performance. Chapter 1 provides an overview of residual stress, its importance for mechanical design, modeling of residual stress based on eigenstrain, and some applications of eigenstrain analysis for prediction of residual stress. A recent study evaluating eigenstrain models for prediction of residual stress from cold expansion of fastener holes is provided in Chapter 2. The results illustrate the capabilities of the method considering a new application. The model results are compared with contour method measurements, as well as a simplified elastic-plastic process model. Chapter 3 provides a benchmark fracture mechanics solution for a two-dimensional eigenstrain problem at the intersection of Linear Elastic Fracture Mechanics (LEFM) and residual stress analysis. Residual stress from quenching is studied in detail in Chapter 4, which includes an initial study considering a simple prismatic part removed from quenched aluminum bars, and a follow-on study with a more complex and representative part. Eigenstrain analysis is used for prediction of residual stress in the finished parts considering measured residual stress in the stock material (i.e., rectangular bars). Measurements of residual stress were performed in finished parts using the contour method and neutron diffraction method for the first study, and the contour method in the follow-on second study. Quantitative comparisons between measured and predicted residual stress are presented, and illustrate the abilities of the eigenstrain approach for prediction of quench-induced RS in finished parts. Overall, the eigenstrain models provide accurate predictions of residual stress for the simple prismatic parts. The second study, which considers more complex parts, shows mixed agreement between measurement and model results. Fatigue crack growth testing and modeling of complex parts with quench-induced RS (parts from Chapter 4, study 2) is presented in Chapter 5. Residual stress predicted by eigenstrain analysis and also measured by the contour method are used as input in fatigue crack growth simulations based on Multi-Point Fracture Mechanics (MPFM). Photogrammetry and the Direct Current Potential Drop (DCPD) method with incremental marker banding and quantitative fractography (QF) are used to measure crack growth as a function of cycles throughout the tests. A DCPD correlation is developed using a FE model to provide a relationship between measured voltage drop and crack area. The test results are compared with model results in detail. Overall, including the residual stress (measured or predicted) in the analyses improves fatigue crack growth prediction results significantly.
Download or read book Applied mechanics reviews written by and published by . This book was released on 1948 with total page 400 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Evaluation of Fatigue Crack Growth and Fracture Properties of Cryogenic Model Materials written by and published by . This book was released on 2002 with total page 40 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Crack Growth Measurement and Data Analysis written by S. J. Hudak and published by ASTM International. This book was released on 1981 with total page 384 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 MT. Kokaly and published by . This book was released on 2005 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 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 Automatic Two dimensional Quasi static and Fatigue Crack Propagation Using the Boundary Element Method written by George Elbert Blandford and published by . This book was released on 1981 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Study of an On Line Crack Compliance Technique for Residual Stress Measurement Using 2D Finite Element Simulations of Fatigue Crack Growth written by S. Ismonov and published by . This book was released on 2012 with total page 21 pages. Available in PDF, EPUB and Kindle. Book excerpt: There are several methods available to measure residual stress fields present within a structural component. Recently a new so called on-line crack compliance technique has been proposed, which is based on linear elastic fracture mechanics. This experimental method uses incremental crack mouth opening displacements measured during fatigue crack growth testing to generate information on the existing residual stresses along the crack line. The present study employs two dimensional (2D) plane stress finite element simulations of fatigue crack growth from a cold worked hole to investigate the performance of this technique. Using the simulation results, the stress intensity factors due to the residual stress field normalized by the maximum applied stress intensity factor KIrs/KImax were obtained from the online crack compliance method. For validation, the J-integral approach was used to calculate KIrs/KImax values from fatigue crack growth simulations in an elastic material. The two methods generated nearly identical results. Fatigue crack growth was also simulated in an elastic-plastic material. Even though the stress intensity factor is not the appropriate crack tip characterizing technique for elastic-plastic material conditions, it is still investigated here to approximate the actual testing conditions, where plastic deformation near the crack tip is unavoidable. The KIrs/KImax solutions are presented for different cold work levels and applied loadings. Results indicate that the agreement between the elastic and elastic-plastic crack growth solutions is dependent on the maximum applied loading level, as might be expected.
Download or read book Fatigue in Mechanically Fastened Composite and Metallic Joints written by John M. Potter and published by ASTM International. This book was released on 1986 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1995 with total page 702 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fatigue Crack Growth written by Ping Tang and published by Nova Science Publishers. This book was released on 2012 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: In this book, the authors present current research in the study of the mechanisms, behaviour and analysis of fatigue crack growths. Topics discussed in this compilation include the unified fatigue crack growth rate model; practical tools for statistical fatigue design; probablistic algorithms performance evaluation and application in multi-fractured structures; three dimensional effects in the fracture mechanics of bi-dimensional specimens; fatigue crack propagation mechanism in porous open pore metal foams; lifetime predictions for short fatigue crack's initiation-propagation by basic mechanical properties; variable amplitude fatigue crack growth in selected aluminium alloys; fatigue threshold R-curves for analysis of short fatigue cracks; and multiaxial fatigue life prediction for lateral notched round bars made of high strength steel.
Download or read book Configurational Forces as Basic Concepts of Continuum Physics written by Morton E. Gurtin and published by Springer Science & Business Media. This book was released on 2008-01-20 with total page 248 pages. Available in PDF, EPUB and Kindle. Book excerpt: Included is a presentation of configurational forces within a classical context and a discussion of their use in areas as diverse as phase transitions and fracture.
Download or read book Linear and Nonlinear Crack Growth Using Boundary Elements written by Adrián Cisilino and published by Computational Mechanics. This book was released on 2000 with total page 216 pages. Available in PDF, EPUB and Kindle. Book excerpt: This text provides a three dimensional Boundary Element Method for the analysis of fatigue crack problems in both linear and nonlinear fracture mechanics. Special attention is devoted to the use of singular and near-singular integrals.
Download or read book Fatigue Crack Growth Under Spectrum Loads written by Ralph Ivan Stephens and published by ASTM International. This book was released on 1976 with total page 345 pages. Available in PDF, EPUB and Kindle. Book excerpt:
