Download or read book Influence of Residual Stress on the Initiation of Fatigue Cracks at Welded Piping Joints written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Fatigue failures of small bore piping systems have historically occurred in nuclear power plants, resulting in unanticipated plant downtime and substantial financial loss. These failures have been reported with increasing frequency over the past 20 years and have motivated the research described in this thesis. Recent research at North Carolina State University (NCSU) pointed to the strain ratcheting response of the welded joint as a probable reason for fatigue failure and indicated that welding residual stresses might be responsible for inducing this strain ratcheting response. It was the primary objective in this investigation to determine what happens to residual stresses at the welded piping joint under the application of low-cycle fatigue loading and to understand how residual stresses induce strain ratcheting and thus affect the fatigue life of the welded joint. In order to achieve stated objectives, a systematic set of residual stress measurements and low-cycle fatigue tests was conducted. Initial residual stresses near the weld toe of six welded piping specimens were measured using the technique of x-ray diffraction. The specimens were then loaded in low-cycle fatigue to intermediate points in their fatigue lives and residual stresses were measured again. Strain response data near the weld toe was gathered throughout specimen fatigue life. Residual stress data and recorded strain responses in fatigue prompted conclusions concerning the role of residual stresses in inducing strain ratcheting which were verified by additional material level experiments. Initial residual stress measurements obtained from the welded specimens revealed that residual stresses near the weld toe--the location of fatigue crack initiation and final failure--were compressive in the overwhelming majority of measurement cases. It is widely accepted that compressive residual stresses are beneficial in fatigue. However, in this set of experiments, it was observed that compressive.
Download or read book Influence of Residual Stress on the Initiation of Fatigue Cracks at Welded Piping Joints written by Abigail Elaine Humphreys and published by . This book was released on 2004 with total page 129 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: Fatigue, Welded Piping Joints, Residual Stress, Ratcheting.
Download or read book Influence of Residual Stress on Fatigue Failure of Welded Joints written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation makes an effort to understand the influence of residual stresses on the fatigue failure of butt- and socket-welded piping joints. In order to achieve this goal, this study develops experimental fatigue failure data and a numerical scheme for the analysis of these data. A set of low-cycle fatigue tests of welded piping joints in the cantilever setup is conducted. A new observation made in these tests is that the recorded strains near the weld toe ratchet continuously, which results in the initiation of fatigue crack(s). Comparison of these ratcheting responses with those from the cyclic pipe bending and material ratcheting experiments indicates that the residual stresses at the welded joints may not relax to zero after a few inelastic cycles, as assumed in the fatigue design methods. This observation is further supported by the symmetric strain response (no ratcheting) at the mid-pipe length, which is located away from the welded joint. At this location, there are no residual stresses to induce ratcheting. It is also observed that the fatigue cracks in all experiments occurred at the weld toe location where the ratcheting strain is the largest. This indicates that the fatigue life of materials is reduced in the presence of ratcheting. There are several observations made in the tests that need further exploration. Ratcheting in the tests occurs under displacement-controlled loading cycles, which seems kinematically inadmissible. The recorded load responses demonstrate cyclic softening for stainless steel, which is known as a cyclically hardening material. It is also observed that the socket-weld which is fabricated using the quarter-circumferential welding method has a longer fatigue life than the one which is fabricated using the full-circumferential welding method. Also, the socket-weld with four weld passes has longer fatigue life than the socket-weld with three weld passes. This study with its limited time and resource could not explore these iss.
Download or read book Welding Deformation and Residual Stress Prevention written by Ninshu Ma and published by Elsevier. This book was released on 2012-04-26 with total page 313 pages. Available in PDF, EPUB and Kindle. Book excerpt: Generally, welding produces welding deformation and residual stress in the products, which influences the quality and performance of the products. Although many engineers and researchers have made great effort how to control these incidents, they have still remained unresolved. Welding Deformation and Residual Stress Prevention provides a unique computational approach to the prediction of the effects of deformation and residual stress on materials. The goal is to provide engineers and designers with the ability to create their own computational system for predicting and possibly avoiding the problem altogether. - The basic theories including "theory of elastic-plastic analysis" and "inherent strain theory" , and analysis procedures are described using a simple three-bar model - Online simulation software to perform basic analysis on welding mechanics - Examples of strategic methods and procedures are illustrated to have solved various welding-related problems encountered in the process of construction - Appendices present data bases for welding residual stresses, temperature dependent material properties, etc.
Download or read book Effect of residual stresses on the fatigue crack propagation in welded joints written by Nenad Gubeljak and published by . This book was released on 2005 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The effect of residual stress on the fatigue crack growth was investigated for cyclic tension. Three-point bend specimens were used with through thickness notches at the center line of the welded joint. The experiments were performed for different load amplitudes and load ratios under conditions of small-scale yielding. The influence of the residual stresses on fatigue crack growth was estimated by experimentally observed fatigue crack growth rate and measurement of residual stresses at the surface of specimen. This paper describes an approach taken in two models to estimate the residual stress effect on fatigue crack propagation and to predict remaining service life of a welded structure.
Download or read book Fracture and Fatigue of Welded Joints and Structures written by K Macdonald and published by Elsevier. This book was released on 2011-04-19 with total page 353 pages. Available in PDF, EPUB and Kindle. Book excerpt: The failure of any welded joint is at best inconvenient and at worst can lead to catastrophic accidents. Fracture and fatigue of welded joints and structures analyses the processes and causes of fracture and fatigue, focusing on how the failure of welded joints and structures can be predicted and minimised in the design process.Part one concentrates on analysing fracture of welded joints and structures, with chapters on constraint-based fracture mechanics for predicting joint failure, fracture assessment methods and the use of fracture mechanics in the fatigue analysis of welded joints. In part two, the emphasis shifts to fatigue, and chapters focus on a variety of aspects of fatigue analysis including assessment of local stresses in welded joints, fatigue design rules for welded structures, k-nodes for offshore structures and modelling residual stresses in predicting the service life of structures.With its distinguished editor and international team of contributors, Fracture and fatigue of welded joints and structures is an essential reference for mechanical, structural and welding engineers, as well as those in the academic sector with a research interest in the field. - Analyses the processes and causes of fracture and fatigue, focusing predicting and minimising the failure of welded joints in the design process - Assesses the fracture of welded joints and structure featuring constraint-based fracture mechanics for predicting joint failure - Explores specific considerations in fatigue analysis including the assessment of local stresses in welded joints and fatigue design rules for welded structures
Download or read book Influence of Residual Stress on the Predicted Fatigue Life of Weldments written by JD. Burk and published by . This book was released on 1982 with total page 11 pages. Available in PDF, EPUB and Kindle. Book excerpt: A model was developed that predicts the influence of residual stress and stress ratio on the total fatigue life of a weld. The total fatigue life of a weld was considered to be composed of both crack initiation and crack propagation. Weld toe residual stresses were considered to influence the crack initiation life but not the crack propagation life.
Download or read book Analysis of Welded Structures written by Koichi Masubuchi and published by Elsevier. This book was released on 2013-10-22 with total page 655 pages. Available in PDF, EPUB and Kindle. Book excerpt: Analysis of Welded Structures: Residual Stresses, Distortion, and their Consequences encompasses several topics related to design and fabrication of welded structures, particularly residual stresses and distortion, as well as their consequences. This book first introduces the subject by presenting the advantages and disadvantages of welded structures, as well as the historical overview of the topic and predicted trends. Then, this text considers residual stresses, heat flow, distortion, fracture toughness, and brittle and fatigue fractures of weldments. This selection concludes by discussing the effects of distortion and residual stresses on buckling strength of welded structures and effects of weld defects on service behavior. This book also provides supplementary discussions on some related and selected subjects. This text will be invaluable to metallurgists, welders, and students of metallurgy and welding.
Download or read book Fatigue Fracture and Residual Stresses written by Sharif Rahman and published by . This book was released on 1998 with total page 552 pages. Available in PDF, EPUB and Kindle. Book excerpt: Fifty-one technical papers from the July 1998 Conference are organized into six sections which discuss probabilistic fracture mechanics, fracture of welds, finite elements and constraint effects on fracture, failure prediction, residual stresses, and pipe fracture. They present novel analytical and
Download or read book Influence of Seawater and Residual Stresses on Fatigue Crack Growth in C Mn Steel Weld Joints written by Leonardo Bertini and published by . This book was released on 1991 with total page 10 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Influence of Residual Stress and Heat Affected Zone on Fatigue Failure of Welded Piping Joints written by and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT CHENG, PEI-YUAN. Influence of Residual Stress and Heat Affected Zone on Fatigue Failure of Welded Piping Joints. (Under the direction of Dr. Tasnim Hassan.) In recent decades, some unexpected fatigue failure occurred in welded joint of metal structures under cyclic loading. In many cases, the cause for the failure could not be detected. A study at NC State University revealed that welding procedure could be one of the factors that was not appropriately considered in current design methodologies. The welding procedure can influence the strain response near weld toe in two ways: one is by generating residual stress, and the other is changing material properties in the heat affected zone (HAZ). It was the primary objective in this investigation to determine the influence of these two factors on strain response by conducting experiments and performing numerical simulations of welded piping joints. On experimental study a series of residual stress data were measured, using x-ray and neutron diffraction techniques, for welded piping joints. The measured results revealed that the initial maximum compressive residual stress of stainless steel piping joints is higher than the yield stress of base metal. Moreover, the axial residual stresses of stainless steel piping joints are mostly relaxed after 5 cycles. The change of mechanical material properties due to high temperature exposure was studied by conducting experiments on tubular specimens. It was obtained that some mechanical material properties changed after subjecting to high temperature cycles, and the changed material was correlated to the peak temperatures. A modified thermo-mechanical material heterogeneity model was then developed to improve the initial residual stress simulation at the weld toe. The heterogeneous material properties coupled with the Chaboche model were used for subsequent fatigue response simulation. Quarter-point elements were applied at the stress concentration locations. The analysis r.
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 Influence of Residual Stress and Heat Affected Zone on Fatigue Failure of Welded Piping Joints written by Pei-Yuan Cheng and published by . This book was released on 2009 with total page 120 pages. Available in PDF, EPUB and Kindle. Book excerpt: Keywords: FE simulation, residual stress, weld, piping joint.
Download or read book Effect of Residual Stresses on Fatigue Crack Growth in Steel Weldments Under Constant and Variable Amplitude Loads written by G. Glinka and published by . This book was released on 1979 with total page 17 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research deals with the effect of welding residual stresses on fatigue crack growth in medium strength low alloy steel weldments. Three kinds of flat specimens have been used--unwelded specimens, specimens with butt perpendicular welds, and specimens with butt longitudinal welds. Residual stress distributions were others in both kinds of welded specimens. All specimens were tested under constant and variable amplitude load with stress ratios R > 0. Forman's equation and Wheeler's model of crack retardation were used for theoretical analysis of fatigue crack growth under constant and variable amplitude load, respectively. The theoretical results were more realistic when effective stress ratio Reff and effective stress intensity range ?Keff, which compensated for residual stresses, were used. It was found that the tensile residual stresses increased the fatigue crack growth rate and compressive stresses reduced it. The lower the applied load, the higher the residual stress effect. This paper presents both experimental results and an analytical method of fatigue crack growth prediction in steel weldments on the basis of results obtained from parent material properties.
Download or read book Trends In Welding Research written by Stan A. David and published by ASM International. This book was released on 2006-01-01 with total page 1015 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Residual Stresses written by A. Niku-Lari and published by Elsevier. This book was released on 2014-05-17 with total page 587 pages. Available in PDF, EPUB and Kindle. Book excerpt: Residual Stresses presents a collection of articles that provides information regarding the use of surface treatment systems. It discusses the developments in the technology and application of surface treatment. It addresses the influence of minor stresses on the performance of materials. Some of the topics covered in the book are the introduction to self-equilibrating stresses existing in materials, the stresses that form as a consequence of welding, the stresses made by machining, and the mechanical generation of self-stresses. The analysis of the stresses caused by thermal and thermochemical surface treatments is covered. The minor stresses in composite materials are discussed. The text describes the stresses in uranium and uranium alloys. The Trepan or ring core method, centre-hole method, and Sach's method are presented. A chapter of the volume is devoted to the measurement of residual stresses. Another section of the book focuses on the application of shot peened plates to residual stress distribution. The book will provide useful information to mechanics, engineers, students, and researchers.
