J-INTEGRAL FOR A 3-D INTERFACE CRACK CONFIGURATION IN WELDS OF DISSIMILAR STEELS

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4201-4206
Author(s):  
KYONG-HO CHANG ◽  
CHIN-HYUNG LEE
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Interface Crack ◽  
Three Dimensional ◽  
Crack Tip ◽  
J Integral ◽  
Residual Stress Field ◽  
Crack Configuration ◽  
Dissimilar Steels ◽  
Path Independence

In this study, path-independent values of the J-integral in the finite element context for an arbitrary three-dimensional interface crack configuration in welds of dissimilar steels are presented. For the fracture mechanics analysis of an interface crack in welds of dissimilar steels, residual stress analysis and fracture analysis must be performed sequentially. In the analysis of cracked bodies containing residual stress, the usual domain integral formation results in path-dependent values of the J-integral. And unlike cracks in homogeneous materials, an interface crack in welds of dissimilar steels always induces both opening and shearing modes of stress in the vicinity of the crack tip. Therefore, this paper discusses modifications of the conventional J-integral that yield path independence in the presence of residual stress and the total J values which can characterize the severity of an interface crack tip in welds of dissimilar steels. A finite element method which can evaluate the J-integral for an interface crack in three-dimensional residual stress bearing bodies is developed using the modified J-integral definition and total J values. The situation when residual stresses only are present is studied as is the case when mechanical stresses are applied in conjunction with a residual stress field.

Numerical Calculation of Residual Stress Corrected J-Integral Using ABAQUS

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Stress Effect ◽  
J Integral ◽  
Residual Stress Field ◽  
Path Independence ◽  
Residual Stress Effect ◽  
Senb Specimen

Residual stresses exist in welded structures due to thermal stresses. Without temperature change, large plastic deformation can result in “cold” residual stresses in a wrinkle or dent in a metallic pipe. For a crack in residual stress field, residual stresses might have strong effect on fracture parameter, the J-integral. In order to ensure its path-independence, different correction methods have been developed in consideration of residual stress effect. Recently, the finite element commercial software ABAQUS adopted one of the correction methods, and is able to calculate the residual stress corrected J-integral. A brief review is first given to the J-integral definition, the conditions of path-independence or path-dependence, and the modifications to consider the residual stress effect. A modified single edge-notched bend (SENB) specimen is then used, and a numerical procedure is developed for ABAQUS to evaluate the path-independence of the residual stress corrected J-integral. Detailed elastic-plastic finite element analyses are performed for the SENB specimen in three-point bending. The residual stress field, crack-tip stress field, and J-integral with and without consideration of residual stresses are discussed.

Crack Tip Behaviour in Residual Stress Field: Finite Element Modelling and Neutron Diffraction Measurements

2011 ◽  
Author(s):  
H. Dai ◽  
J. F. Kelleher ◽  
P. J. Withers
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Intensity ◽  
Crack Closure ◽  
Finite Element Modelling ◽  
Applied Load ◽  
Crack Tip ◽  
J Integral ◽  
Residual Stress Field ◽  
Element Modelling

Simple analyses of fracture and fatigue often make use of the stress intensity at a crack tip or the J-integral surrounding it. However, there is no universally accepted method of including the effect of residual stress in these values, even though the qualitative effect of residual stress on crack growth is well known. In this work, we create a cracked compact tension C(T) specimen with a residual stress field that affects the crack tip behaviour, in particular by altering the level of expected crack closure. Neutron diffraction measurements under in situ applied loading reveal strain distributions consistent with an increased level of closure when the crack tip is in a state of compressive residual stress. Through finite element modelling of the samples studied, we show that the residual stress in these samples redistributes as the crack grows, which changes the level of crack closure for any given crack length and applied load. As crack closure is often considered in fatigue analysis by deriving an ‘effective’ stress intensity based on the applied load needed to overcome the closure and open the crack, the model is used to compare this approach with numerical calculations of the J-integral for different crack lengths.

Determination of Path-Independent J-Integral for Cracks in Residual Stress Fields Using Finite Element Method

2015 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Residual Stresses ◽  
Stress Effect ◽  
J Integral ◽  
Residual Stress Field ◽  
Crack Tip Field ◽  
Path Independence ◽  
Residual Stress Effect ◽  
Senb Specimen

“Hot” residual stresses exist in metal welds due to welding thermal stresses, and “cold” residual stresses occur in mechanical damaged metallic pipes due to large plastic deformation. For a crack in ether a hot or cold residual stress field, residual stresses might have a strong effect on the crack-tip field and the fracture parameter, J-integral. To consider the effect of residual stresses and to ensure the path-independence of J, different correction methods have been developed over the years. Recently, the finite element analysis (FEA) commercial software ABAQUS adopted one of correction methods for determining the residual stress corrected J-integral. This paper intends to evaluate this new function of ABAQUS and to see if the residual stress corrected J-integral is path-independent. A brief review is first given to the J-integral definition, the conditions of J-integral path-independence or dependence, and the modifications of J-integral to consider the residual stress effect. A modified single edge-notched bend (SENB) specimen is then adopted, and a FEA numerical procedure is developed and used in the numerical tests to evaluate the path-independence of the residual stress corrected J-integral using ABAQUS. Detailed elastic-plastic FEA calculations are carried out for the modified SENB specimen in three-point bending. The residual stress field, crack-tip field, and J-integral with and without consideration of the residual stress effect are determined and discussed.

Numerical Study of Welding Sequence on the Residual Stress Field in a Thick-Walled Tee Joint

2011 ◽  
Vol 219-220 ◽  
pp. 1211-1214
Author(s):  
Wei Jiang
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Numerical Study ◽  
Three Dimensional ◽  
Element Model ◽  
Residual Stress Field ◽  
Factors Affecting ◽  
Welding Sequence ◽  
Welding Sequences ◽  
Three Dimensional Finite Element

Finite element simulation is an efficient method for studying factors affecting weld-induced residual stress distributions. In this paper, a validated three-dimensional finite element model consisting of sequentially coupled thermal and structural analyses was developed. Three possible symmetrical welding sequences, i.e. one-welder, two-welder and four-welder sequence, which were perceived to generate the least distortion in actual welding circumstances, were proposed and their influences on the residual stress fields in a thick-walled tee joint were investigated. Appropriate conclusions and recommendations regarding welding sequences are presented.

Three Dimensional Finite Element Analysis of a Split-Sleeve Cold Expansion Process

2009 ◽  
Vol 131 (3) ◽  
Author(s):  
S. Ismonov ◽  
S. R. Daniewicz ◽  
J. C. Newman ◽  
M. R. Hill ◽  
M. R. Urban
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Residual Stress Field ◽  
Expansion Process ◽  
Element Analysis ◽  
Cold Expansion ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

A cold expansion process is used to prolong the fatigue life of a structure under cyclic loadings. The process produces a beneficial compressive residual stress zone in the hole vicinity, which retards the initiation and propagation of the crack at the hole edge. In this study, a three-dimensional finite element model of the split-sleeve cold expansion process was developed to predict the resulting residual stress field. A thin rectangular aluminum sheet with a centrally located hole was considered. A rigid mandrel and an elastic steel split sleeve were explicitly modeled with the appropriate contact elements at the interfaces between the mandrel, the sleeve, and the hole. Geometrical and material nonlinearities were included. The simulation results were compared with experimental measurements of the residual stress. The influence of friction and the prescribed boundary conditions for the sheet were studied. Differences between the split-sleeve- and the non-split-sleeve model solutions are discussed.

A Comparison of 2D and 3D Fracture Assessments in the Presence of Residual Stresses

2007 ◽  
Author(s):  
Simon J. Lewis ◽  
Christopher E. Truman ◽  
David J. Smith
Keyword(s):  
Residual Stress ◽  
Stress Field ◽  
Structural Integrity ◽  
Three Dimensional ◽  
External Loading ◽  
Assessment Procedure ◽  
J Integral ◽  
Residual Stress Field ◽  
Fracture Parameters ◽  
Three Dimensional Simulations

This paper presents an investigation into the effects of an initial residual stress field on fracture parameters, calculated via an energy-type integral method, in two and three-dimensional simulations. A residual stress field was introduced into a modified single edge notched bend, SEN(B), specimen using an in-plane compression procedure, such that a crack introduced into the specimen experienced opening displacement, even in the absence of external loading. J integral calculation was undertaken using standard two-dimensional area formulations and pointwise three-dimensional formulations, as well as using modified two- and three-dimensional routines developed to provide path independence in the presence of initial strain fields and non-monotonic plastic loading. The paper will describe the application of these modified J-integral techniques and use the results to re-interpret experimental fracture test data obtained from a set of A533B ferritic steel SEN(B) specimens. The implications for structural integrity assessments in the presence of residual stress fields, as well as the calculation route chosen for determination of fracture parameters, were explored in the context of the R6 assessment procedure. In particular, the different levels of conservatism in the assessments resulting from two- and three-dimensional simulations will be highlighted.

Effects of Finite Strains and Residual Stresses on Path Independence of the J-Integral for Ductile Cracks

2017 ◽  
Author(s):  
Xian-Kui Zhu ◽  
Tom McGaughy
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Driving Force ◽  
Path Dependence ◽  
New Technology ◽  
Finite Strains ◽  
J Integral ◽  
Residual Stress Field ◽  
Path Independence ◽  
Major Factors

Large plastic deformation and residual stresses exist in mechanical damages to pipelines. If a crack occurs in the damages, residual stresses will affect mechanics behavior of the crack and path independence of the J-integral, and so the J-integral may lose capacity to describe fracture driving force. This paper theoretically investigates basic conditions required for the path independence of the J-integral and major factors affecting the path independence, including the incremental plasticity, finite strains and residual stresses. Residual stress modified J-integrals are then introduced for ensuring the path independence. With use of a notched beam, detailed elastic-plastic finite element analyses are performed in terms of the incremental plasticity for a crack subject to three-point bending. The path dependence of the J-integral due to the three major factors is then evaluated. Numerical results show that the residual stress modified J-integral is path-independent, and able to describe the fracture driving force for ductile cracks in a residual stress field. This provides a new technology to assess pipeline integrity for cracks coupling residual stresses.

Residual Stress Analysis of Tube Attachment Weld in Pressure Vessel Forging: Baseline FE Analysis and Sensitivity Studies

2005 ◽  
Author(s):  
N. A. Leggatt ◽  
R. J. Dennis ◽  
P. R. Hurrell
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Pressure Vessel ◽  
Three Dimensional ◽  
Wall Stress ◽  
Isotropic Hardening ◽  
Residual Stress Field ◽  
Element Analysis ◽  
Hardening Law ◽  
Sensitivity Studies

Full two and three-dimensional single or multi-pass weld simulations are now feasible and practical given the development of improved analysis tools (e.g. ABAQUS), and significantly greater computer power. This paper describes a finite element analysis undertaken to predict the as-welded residual stress field following the welding of a tube attachment weld inside a thick pressure vessel (PV) forging. The coupled thermal-mechanical analysis was performed using the finite element (FE) code ABAQUS, A heat source modelling tool was employed to calculate welding fluxes, which were read into ABAQUS via a user subroutine. The ‘block’ dumped approach was utilised in the 2D thermal analysis such that complete weld rings are deposited instantaneously. Heat inputs were based on the actual weld parameters and bead sizes. The predicted fusion depths matched well with those found in sectioned weld test pieces. 2D FE sensitivity studies were performed examining the effect of variations in a number of parameters (bead sequence, hardening law, inter-pass temperature and annealing temperature). The hardening law was changed from isotropic to kinematic to investigate the effect of material behaviour. Large weld residual tensile stresses were calculated with significant compressive stresses in the adjacent vessel wall. Stress results were generally insensitive in the tube and forging, indicating that the vessel constraint dominates over local welding conditions. Weld hoop stresses were overestimated partly due to the ‘tourniquet’ effect of depositing rings of weld metal and the isotropic hardening law assumed.

An Experimental Method to Measure Q-Parameter for Two Parameter Theory of Ductile Fracture

2003 ◽  
Author(s):  
Dong-Hak Kim ◽  
Jeong-Hyun Lee ◽  
Ki-Ju Kang
Keyword(s):  
Finite Element ◽  
Stress Field ◽  
Experimental Method ◽  
Plane Strain ◽  
Three Dimensional ◽  
Crack Tip ◽  
Image Correlation ◽  
J Integral ◽  
Q Value ◽  
Two Parameter

In the two parameter approaches, one of the second parameters, T-stress, Q and A2 is used together with J-integral to describe the constraint loss near the crack tip under large scale yielding states. Among the second parameters, Q seems to be most promising from a practical point of view because it applies for three-dimensional geometries. In order to determine the Q for a given geometry and load, however, three-dimensional elastic-plastic finite element analysis, which is time consuming and costly, has had to be performed so far. In this work an experimental method to measure Q-parameter insitu is described. The basic idea comes from the fact that side necking near a crack tip indicates the loss of stress triaxiality, which can be scaled by Q. From the out-of-plane displacement and the in-plane strain measured on the surface of side necking near the crack tip, stress field averaged through thickness is calculated and then Q is determined from the difference between the stress filed and the HRR field corresponding to the identical J-integral. To prove the validity, three-dimensional finite element simulation has been performed for a CT configuration with side-grooves. Q-value which was calculated directly from the near-tip stress field is compared with that determined by simulating the experimental procedure according to the proposed method, that is, the Q-value determined from the lateral displacement and the in-plane strain. Also, the effect of location where the displacement and strain are measured is explored. Moreover, an easy way for measuring the displacement and strain simultaneously is described. That is based on Stereoscopic Digital Photography and high resolution Digital Image Correlation (DIC) software, and can be performed along with conventional fracture tests. A case study for a CT specimen of ferritic steel is presented.

Multipass low-plasticity burnishing induced residual stresses: Three-dimensional elastic-plastic finite element modelling

2004 ◽  
Vol 218 (6) ◽  
pp. 663-668 ◽  
Author(s):  
W Zhuang ◽  
B Wicks
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Residual Stresses ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
Residual Stress Field ◽  
Moving Contact ◽  
Low Plasticity Burnishing

Low-plasticity burnishing (LPB) is a surface modification process involving complex cyclic plastic deformation that results in the development of a deep residual stress field. In order to achieve an optimal LPB-induced residual stress field for the geometry appropriate to the aircraft engine component, the key parameters of the LPB process, such as burnishing load, burnishing ball size and material properties, need to be determined. For this purpose, a three-dimensional non-linear moving contact finite element model is proposed to simulate the multipass LPB process and to predict the effects of those parameters on the resultant residual stress field. The material constitutive model used in the finite element analysis has been developed from the cyclic stress/strain response obtained from experimental measurements on the material. Prediction of the LPB-induced residual stresses by the finite element model appears to agree reasonably well with X-ray diffraction measurements.

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