Multi-challenge aspects in fatigue due to the combined occurrence of multiaxiality, variable amplitude loading, and size effects

Abstract

ABSTRACT. The three major issues which contribute to uncertainties in fatigue life estimations are the limited transferability of material data obtained in a laboratory for describing the fatigue behavior of components, the lack of damage accumulation rules to realistically take into account the effects of various load sequences, and the uncertainty in the assessment of multiaxial stress states. The three issues contribute to life prediction errors in a balanced way. Some modeling effort was spent in joining solution proposals in a unifying short crack model. The actual state is presented in the paper together with some ideas for further improvement as well as simplification for promoting the model's acceptance in practical applications.

Report of Committee III.2: Fatigue and fracture

“…Different assessment concepts; fatigue damage criteria and corresponding resistance curves, accounting for endurance and mechanism contributions, have been developed over time and reviewed, including recent contributions (Fricke, 2003, Radaj et al, 2006, Hobbacher, 2009, Radaj et al, 2009a, Radaj et al, 2009b, Rizzo, 2011, Fricke, 2015, Radaj, 2015, Vormwald, 2015, Hobbacher, 2016, Lotsberg, 2016, proposed to be classified (Den Besten, 2019) according to ( Figure 2):…”

“…The effectiveness of common equivalent stress-and strain-based fatigue damage criteria have been evaluated and areas of improvement have been discussed. Mixed-mode hypotheses, sequence-and size effects are considered to be most important and require further investigation, as well as the development of simplified procedures in order to reduce computation time (Vormwald, 2015).…”

Fatigue of weld ends under combined in- and out-of-phase multiaxial loading

“…Many research activities have been initiated during the last years for the investigation of fatigue design of multiaxially loaded welded joints [9][10][11]. Vormwald [12] explored in the event of variable amplitude loading conditions a list of challenges have to be considered. Nevertheless, the case of weld ends under such loading is not sufficiently explored yet.…”

Linear Elastic Fracture Mechanics Analysis of Fatigue Crack Growth Under Complex Loading Using the Digital Image Correlation Technique

“…One of the problems in mixed-mode loading to be yet fully understood is to predict crack grow direction [20,51,53]. Nonetheless, the problem of crack kinking and equivalent SIF already has several postulated criteria.…”

“…Although some indications [73,80], it is still open which condition leads to either normal or shear stress driven fatigue crack growth, respectively [82]. For cases for which the Schöllmann et al hypothesis is valid, the FCG prediction requires to take all influencing phenomena into account which have impact on the crack tip fields [25,53].…”