scholarly journals An Energy-Based Approach for Fatigue Life Estimation of Welded Joints without Residual Stress through Thermal-Graphic Measurement

2019 ◽  
Vol 9 (3) ◽  
pp. 397 ◽  
Author(s):  
Chengji Mi ◽  
Wentai Li ◽  
Xuewen Xiao ◽  
Filippo Berto
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Welded Joints ◽  
Thermal Evolution ◽  
Surface Characteristics ◽  
Welding Residual Stress ◽  
Life Assessment ◽  
Linear Temperature ◽  
Fatigue Life Estimation ◽  
Intrinsic Dissipation

The traditional methodologies for fatigue life assessment of welded joints strongly depend on geometries and surface characteristics, as well as time. In this paper, an energy-based approach, independent of structures though thermal-graphic measurement, was presented to predict life expectancy of welded joints, via limited number of tests. In order to eliminate the thermal elastic effect caused by the welding residual stress, annealing was first conducted on welded specimens. Both monotonic and cyclic tests for welded joints were implemented. Then, based on the thermal evolution of welded joints measured by the quantitative thermo-graphic method, an energy-based approach, taking the linear temperature evolution and the intrinsic dissipation into account, was employed on the fatigue life prediction of flat butt-welded joints. The estimated results showed good agreement with the experimental ones, and the energy tolerance to failure E c for different stress amplitudes was found to be constant.

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 Effect of Welding Residual Stress on Along-Wind Fatigue Life of Welded Joints in Guyed Mast

2020 ◽  
Vol 2020 ◽  
pp. 1-12
Author(s):  
Weilian Qu ◽  
Min Wang ◽  
Qiang Zhou
Keyword(s):  
Residual Stress ◽  
Fatigue Life ◽  
Stress Field ◽  
Structural Steel ◽  
Welded Joints ◽  
Welded Joint ◽  
Welding Residual Stress ◽  
Wind Effect ◽  
Induced Stress ◽  
Guyed Mast

On the premise of only considering along-wind effect on guyed mast, the influence of welding residual stress on the fatigue life of welded joints is evaluated in this paper. Since the sum of residual stress and along-wind-induced dynamic stress exceeds the yield strength of structural steel, the effect of residual stress relaxation is included in the numerical analysis. The multiscale finite element analysis of guyed mast is developed in order to capture accurately stress field distribution of welded joint for the “welding-wind-induced” case in which both residual stress and along-wind-induced stress are taken into consideration, and the stress response characteristics at fatigue critical point of welded joints are pointed out. It is found that the “welding-wind-induced” stress field of welded joint can be approximately considered as multiaxial proportional loading state and hence the stress-based von Mises criterion can be adopted to evaluate the fatigue life of welded joints. Based on the S-N curve of stress fatigue life for welded specimens with structural steel commonly used in guyed masts, the fatigue damage of key welded joints is predicted, and as a consequence, the influence of welding residual stress on the fatigue life of welded joints is discussed.

scholarly journals Mapping of scatter in fatigue life assessment of welded structures—a round-robin study

2021 ◽  
Author(s):  
Gustav Hultgren ◽  
Mansoor Khurshid ◽  
Peter Haglund ◽  
Zuheir Barsoum
Keyword(s):  
Fatigue Life ◽  
Round Robin ◽  
Life Assessment ◽  
Fatigue Life Assessment ◽  
Fatigue Life Estimation ◽  
Box Structures ◽  
Load Carrying ◽  
Local Stresses ◽  
Sources Of Variation ◽  
Global And Local

AbstractA round-robin study has been carried out within a national project in Sweden with the addition of an international participant, where several industrial partners and universities are participating. The project aims to identify variation and sources of variation in welding production, map scatter in fatigue life estimation, and define and develop concepts to reduce these, in all steps of product development. The participating organisations were asked to carry out fatigue life assessment of welded box structures, which is a component in load-carrying structures. The estimations of fatigue life have also been compared with fatigue test results. Detailed drawings, loads and material data were also given to the participants. The participants were supposed to use assessment methods based on global and local stresses using the design codes or recommendations they currently use in-house. Differences were identified between both methods and participants using the same codes/recommendations. Applicability and conditions from the cases in the codes were also identified to be differently evaluated between the participants. It could be concluded that for the applied cases the nominal stress method often overestimated the fatigue life and had a high scatter in the estimations by different participants. The effective notch method is conservative in comparison to the life of tested components with little scatter between the results derived by the participants.

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