Fatigue analysis of welded joints: state of development

The literature on fatigue analysis of welded joints is reviewed, considering mainly papers and books published during the past 10–15 years. After a short introduction, the different approaches for fatigue analyses are covered, i.e. the nominal stress approach, the structural or hot-spot stress approach, the notch stress and notch intensity approach, the notch strain approach and finally the crack propagation approach. Only seam-welded joints are considered, and not the behaviour of spot-welds, which is a very special field. Due to the vast amount of relevant literature, some specific areas are left for other reviews or only touched, i.e. fatigue testing and evaluation, fatigue loading and variable amplitude effects, environmental effects and fatigue reliability. r 2002 Elsevier Science Ltd. All rights reserved.

Review Fatigue analysis of welded joints: state of development

Fatigue cracking of welded railway bridges: A review

Crack growth resistance of MAG butt-welded joints of S355JR construction steel

T-welded joints are commonly employed in ship and ocean structures. The fatigue failure of structure components subjected to cyclic loading always occurs in T-welded joints because of the metallurgical differences, tensile residual stress fields and stress concentrations. The former researches about T-welded joints fatigue have in common that the boundary condition needs to be taken into account as an influencing parameter to predict the crack propagation during cyclic loading. In this paper, the crack growth behaviour in T-welded joint processed with Q345D steel (Pingxiang Iron & Steel Co., Ltd, Hukou, Jiangxi Province in China) under the fatigue loading was analysed via analytical model and verified via experiment. The results show that the influence of boundary condition should be considered in T-welded joint structure during crack propagation in weld toe area. The correction factor concerning the effect of boundary condition and modified Paris' equation was proposed according to the experimental results and verified by the following repeated experiments.

Experimental and analytical investigation of fatigue crack propagation of T‐welded joints considering the effect of boundary condition

The current procedures of fatigue design of ship structural components via application of S-N diagrams based on the test results of typified welded joints physically are not complete and may need in adjustment. The main base for discrepancies of actual and S-N-modeled fatigue behavior of structural details is formed by the fairly approximate following the principles of identity of material fatigue damage in fatigue assessment of structural details. The identity of fatigue damage in both, hull details and specimens may be limited by the initial phase of fatigue process, mostly within the stress concentration zone, specifically since the local conditions are assessed in fatigue analysis and in fatigue design of ship hull structures. To retain the current format of fatigue design a procedure of reduction of design S-N curves is developed considering the «informative part of fatigue process, completed with the adjustment which accounts for the possible mismatch in conditions for fatigue damage in laboratory specimens and structural details. The method is based on application of the local strain approach to fatigue assessment of both, the specimen and the detail. The adjustment suggests estimation of the ratio of fatigue lives of these and, respectively, correction of the reduced appropriate S-N diagram. The loading history of the detail comprises the feasible modes of loading and the service conditions, while the loading history of a specimen is related to the principal loading mode in a particular structure. A possible difference in fatigue properties of base-line specimen and structure materials may be considered.

A.K. Thayamballi

Papers

The similitude of fatigue damage principle: Application in S-N curves-based fatigue design