Issue 37

Y. Wang et alii, Frattura ed Integrità Strutturale, 37 (2016) 241-248; DOI: 10.3221/IGF-ESIS.37.32 241 Focussed on Multiaxial Fatigue and Fracture Estimation of fatigue lifetime for selected metallic materials under multiaxial variable amplitude loading Yingyu Wang Key Laboratory of Fundamental Science for National Defense-Advanced Design Technology of Flight Vehicle, Nanjing University of Aeronautics and Astronautics, Nanjing, 210016, China yywang@nuaa.edu.cn Luca Susmel Department of Civil and Structural Engineering, the University of Sheffield, Sheffield S1 3JD, UK l.susmel@sheffield.ac.uk A BSTRACT . This paper initially investigates the accuracy of two methods, i.e., the Maximum Variance Method (MVM) and the Maximum Damage Method (MDM), in predicting the orientation of the crack initiation plane in three different metallic materials subjected to multiaxial variable amplitude loading. According to the validation exercise being performed, the use of both the MVM and the MDM resulted in a satisfactory level of accuracy for selected three metals. Subsequently, three procedures to estimate the fatigue lifetime of metals undergoing multiaxial variable amplitude loading were assessed quantitatively. Procedure A was based on the MDM applied along with Fatemi-Socie’s (FS) criterion, Bannantine-Socie’s (BS) cycle counting method and Miner’s linear rule. Procedure B was based on the MVM, FS criterion, BS cycle counting method and Miner’s linear rule. Procedure C involved the MVM, the Modified Manson Coffin Curve Method (MMCCM), the classical rainflow cycle counting method and Miner’s linear rule. The results show that the usage of these three design procedures resulted in satisfactory predictions for the materials being considered, with estimates falling within an error band of three. K EYWORDS . Multiaxial fatigue; Variable amplitude loading; Critical plane; Life prediction. I NTRODUCTION ince the beginning of the last century, devising a sound method to estimate the fatigue lifetime of a component subjected to variable amplitude (VA) multiaxial loading has been the goal of numerous experimental/theoretical investigations. There are four aspects that need to be considered to estimate fatigue lifetime under multiaxial variable amplitude fatigue loading, i.e., the cyclic stress-strain model, the cycle counting method, the damage model and the damage accumulation model. [1] In addition, also the following aspects should be considered under multiaxial variable amplitude load histories: determining the orientation of the critical plane and calculating the amplitude and mean value of the stress/strain components relative to the critical plane. [2] S