On the use of hot-spot stresses, effective notch stresses and the Point Method to estimate lifetime of inclined welds subjected to uniaxial fatigue loading

• Published in: International journal of fatigue 2018-12, Vol.117, p.432-449
• Main Authors: Al Zamzami, Ibrahim, Susmel, Luca
• Format: Article
• Language: English
• Subjects: Critical distance; Effectiveness; Estimates; Experiments; Fatigue strength; Fillet welds; Hot-spot stress; Inclined welds; Load; Local stress; Materials fatigue; Nominal stress; Seams; Stress analysis; Validation studies; Welded joints
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2018.08.032

•Uniaxially loaded inclined welds can be designed via multiaxial fatigue approaches.•The MWCM is accurate in estimating lifetime of uniaxially loaded inclined welds.•The proposed approach can be used to assess both toe and root failures. The present paper addresses the problem of estimating fatigue strength of welded joints when the weld seams are inclined with respect to the direction of the applied cyclic force. From a fatigue design point of view, the main complexity lies in the fact that, with this particular welded geometries, although the applied loading is uniaxial, accurate fatigue assessment can be performed provided that the degree of multiaxiality of the nominal/structural/local stress states at the weld toes/roots is modelled effectively. To this end, in the present investigation the Modified Wöhler Curve Method (MWCM) is attempted to be used to assess the fatigue strength of steel joints with inclined welds by using this multiaxial fatigue criterion in conjunction with nominal stresses, hot-spot stresses, effective notch stresses, and the Theory of Critical Distances (TCD). A large number of experimental results taken from the literature and generated by testing inclined fillet welds was used to check the accuracy and reliability of the MWCM applied along with these different ways of determining the relevant stress states. The results obtained from this validation exercise demonstrate that the MWCM returns satisfactory estimates when it is used to assess fatigue strength in the presence of inclined welds, with this holding true independently of the specific stress analysis strategy being adopted.