Fatigue Life Assessment of Fillet Welded Joint Considering the Relaxation and Redistribution of Residual Stresses

2004 ◽  
Author(s):  
Chang Doo Jang ◽  
Ha Cheol Song ◽  
Young Chun Jo
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Relaxation ◽  
Residual Stresses ◽  
Crack Propagation ◽  
Welded Joint ◽  
Life Assessment ◽  
Ship Structure ◽  
Fatigue Life Assessment ◽  
Plastic Analysis

This paper presents the fatigue life assessment procedure for the welded joint of ship structure. Test model is a boxing fillet specimen, the idealized welded joint model of longitudinal and transverse members in ship structure. Fatigue test was executed according to the 14-points S-N method of JSME, and experimental data were presented in the S-N curve based on HSS (Hot Spot Stress) approach. To define the fatigue life of crack initiation and crack propagation, S-N data for each length of crack were appraised. In this study, the new FE analysis algorithms for the estimation of residual stress relaxation due to external load and residual stress redistribution due to crack propagation were proposed to assess the effect of residual stresses on crack growth precisely. Initial welding residual stress field was obtained by thermal elasto-plastic analysis considering temperature dependent material properties, and the amount of residual stress relaxation and redistribution were assessed by subsequent elasto-plastic analysis. In the analysis of crack propagation, the SIF (Stress Intensity Factor) range was evaluated by 1/4-point displacement extrapolation method, and the effect of welding residual stresses on fatigue behaviors was considered by introducing the effective SIF concept. The test results of crack propagations were compared with the predicted data from the analysis.

Automated Fatigue Life Assessment for Welded Cruciform Joint Considering Welding Residual Stress

2005 ◽  
Vol 297-300 ◽  
pp. 2800-2805
Author(s):  
Tak Kee Lee ◽  
Chae Whan Rim ◽  
Seung Ho Han ◽  
Jong Han Lee
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Distribution ◽  
Rational Design ◽  
Welding Residual Stress ◽  
Life Assessment ◽  
Assessment Process ◽  
Automated System ◽  
Fatigue Life Assessment ◽  
Cruciform Joint

For a rational design of a welded joint, it is necessary to repeatedly assess the fatigue life of the joint with various dimensions and welding conditions. In this paper, an automated, repeatable/repetitive fatigue life assessment process for a welded cruciform joint was studied. The process consists of a structural analysis to obtain the stress distribution in the vicinity of the weldtoe, a thermal elasto-plastic analysis to determine the welding residual stress, and a fatigue life assessment based on the analyzed stress distribution and welding residual stress. With changes in design conditions including dimensions and/or welding heat input, the aforementioned tasks have to be performed. Using a commercial tool for system integration, automation of a repeated process for a welded cruciform joint based on 2D modeling was achieved. In this automated system, data exchanges between programs, regardless of whether they are commercial or in-house, work well, and parametric studies for optimal design can be performed.

scholarly journals Review on fatigue life assessment methods for welded joints in orthotropic steel decks of long-span bridges

2021 ◽  
Vol 1201 (1) ◽  
pp. 012036
Author(s):  
B Villoria ◽  
S C Siriwardane ◽  
H G Lemu
Keyword(s):  
Fatigue Life ◽  
Residual Stresses ◽  
Assessment Methods ◽  
Machine Learning Algorithms ◽  
Life Assessment ◽  
Steel Bridge ◽  
Long Span Bridges ◽  
Long Span ◽  
Fatigue Life Assessment ◽  
Orthotropic Steel Decks

Abstract Orthotropic Steel Decks have been used in long-span bridges for several decades because of their high capacity to weight ratio. However, many fatigue related issues have been reported. This paper provides an overview of the main existing fatigue prediction models and discusses their relevance for the fatigue life assessment of Orthotropic Steel Bridge Decks (OSBDs). Several case studies have proven the importance of considering the combined effect of wind and traffic loadings to estimate the fatigue life of long-span bridges. The importance of incorporating welding residual stresses is also well documented while it is often disregarded in design practices. Reliability-based fatigue assessment methods make it possible to quantify how the sources of uncertainty related to loading conditions, welding residual stresses or fabrication defects can affect the fatigue reliability of OSBDs. Monte Carlo simulations are often used to perform probabilistic analyses, but machine-learning algorithms are very promising and computationally efficient. The shortcomings of the Palmgren-Miner rule are discussed and the need for alternative damage accumulation indexes is clear. A number of conclusions are drawn from the analysis of fatigue tests conducted on OSBDs.

Master S-N Curve-Based Fatigue Life Assessment of Steel Bridges Using Finite Element Model and Field Monitoring Data

2018 ◽  
Vol 19 (01) ◽  
pp. 1940013 ◽  
Author(s):  
X. W. Ye ◽  
Y. H. Su ◽  
T. Jin ◽  
B. Chen ◽  
J. P. Han
Keyword(s):  
Finite Element ◽  
Fatigue Life ◽  
Welded Joint ◽  
Element Model ◽  
Field Monitoring ◽  
Life Assessment ◽  
Monitoring Data ◽  
Steel Bridge ◽  
Structural Stress ◽  
Fatigue Life Assessment

The accuracy of fatigue life assessment for the welded joint in a steel bridge is largely dependent on an appropriate [Formula: see text]-[Formula: see text] curve. In this paper, a master [Formula: see text]-[Formula: see text] curve-based fatigue life assessment approach for the welded joint with an open-rib in orthotropic steel bridge deck is proposed based on the finite element model (FEM) and field monitoring data from structural health monitoring (SHM) system. The case studies on fatigue life assessment by use of finite element analysis (FEA) for constant-amplitude cyclic loading mode and field monitoring data under variable-amplitude cyclic loading mode are addressed. In the case of FEA, the distribution of structural stress at fatigue-prone weld toe is achieved using 4-node shell element model and then transformed into equivalent structural stress by fracture mechanics theory. The fatigue life of the welded joint is estimated with a single master [Formula: see text]-[Formula: see text] curve in the form of equivalent structural stress range versus the cycles to failure. In the case of monitoring data-based fatigue life assessment, the daily history of structural stress at diaphragm to U-rib is derived from the raw strain data measured by the instrumented fiber Bragg grating (FBG) sensors and transformed into equivalent structural stress. The fatigue life of the investigated welded joint is calculated by cyclic counting method and Palmgren–Miner linear damage cumulative rule. The master [Formula: see text]-[Formula: see text] curve method provides an effective fatigue life assessment process, especially when the nominal stress is hard to be defined. A single master [Formula: see text]-[Formula: see text] curve will facilitate to solve the difficulty in choosing a proper [Formula: see text]-[Formula: see text] curve which is required in the traditional fatigue life assessment methods.

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