PSI - Issue 42

Paulo Mendes et al. / Procedia Structural Integrity 42 (2022) 1752–1761 1753 Paulo Mendes, Rita Dantas, José A.F.O Correia, Nicholas Fantuzzi, Abílio M.P. Jesus / Structural Integrity Procedia 00 (2019) 000 – 000 Nomenclature ′ fatigue limit number of cycles to failure stress amplitude material constant ̂ mean value ̂ standard deviation probability of failure probability of survival stress range normalized number of cycles stress ratio FAT fatigue class ∆ detail category 1 − confidence level 1. Introduction S355 steel is currently used in fabrication of most wind turbine monopile support structures and offshore structures. A deep understanding of the mechanical properties of low-carbon mild steels at different strain and stress rates is crucial because these steels are the most commonly used in several fields, such as, automotive, aerospace, building construction as well as offshore structures. During the last decades, the influence of loading rates now was the subject of several experimental studies on the mechanical behavior of different grades of mild steels (E. Cadoni et al., 2016; Singh et al., 2008). In building constructions and offshore structures, a detailed knowledge of the material properties at high strain rates such as S355 steel is essential, for example, for the assessment of robustness where a collapse may be triggered by the failure of structural elements subjected to dynamic events (Ezio Cadoni et al., 2018). Fatigue is believed to be responsible for half of the failures of mechanical components and therefore understanding the fatigue behavior of S355 steel in welded connections is vital to ensure structural reliability and integrity. Several studies emerged to understand this behavior and consequently contribute to further knowledge in offshore structural reliability and provide researchers with the opportunity to contribute to the state of knowledge. Feng et al. (Feng & Qian, 2020) examined the low-cycle fatigue of circular hollow section (CHS) X-joints made of S355 steels, through a combined experimental and numerical investigation, assisted by non-destructive crack sizing methods, namely the Alternating Current Potential Drop and Ultrasonic Phased Array. Åstrand et al. (Åstrand et al., 2016) investigated different welding procedures for fatigue life improvement of the weld toe in cruciform joints made of S355 steel. Dantas et al. (Dantas et al., 2020) used the Susmel’s criterion to assess the multiaxial fatigue behavior of S355 steel in the high cycle region. The fatigue life of welded joints can be improved by modifying the weld toe geometry or by inducing beneficial compressive residual stresses in the weld. Solutions (Duncheva et al., 2015; Lesiuk et al., 2018; Lewandowski & Rozumek, 2016; Xin et al., 2021) were presented in order to enhance fatigue life of welded S355 steel and assessment of fatigue crack propagation and initiation. Jacob et al. (Jacob et al., 2017) and Xin et al. (Xin et al., 2021) applied the XFEM technique to predict the fatigue crack growth behavior in S355 structural steel using ABAQUS and ANSYS finite element software packages. Research works have been carried out for P-S-N curves estimation from small data sets, often involving complex data structures, by statistical methods, such as maximum likelihood method with a reference stress level (Ling & Pan, 1997), empirical Bayesian model (Guida & Penta, 2010), the random fatigue limit model (Pascual & Meeker, 1999), backwards statistical inference method (Xie et al., 2014), etc., driven by data analysis or physical models. The two parameter Weibull distribution is widely used to analyze fatigue experimental data (Mohabeddine et al., 2021; Pedrosa et al., 2020; Sakin & Ay, 2008), in reliability engineering (Bhardwaj et al., 2019; Huang & Dietrich, 2005) and elsewhere due to its versatility and relative simplicity, and it is characterized by its flexibility to establish reliable assessments. Several scientific investigations can also be found in literature (Castillo et al., 2006; Castillo & Fernández-Canteli, 2009; Engesvik & Moan, 1983)