Issue 37

Y. Wang et alii, Frattura ed Integrità Strutturale, 37 (2016) 241-248; DOI: 10.3221/IGF-ESIS.37.32 243 BS CYCLE COUNTING METHOD annantine and Socie [13] have proposed a method based on the critical plane concept and the rainflow cycle counting method. This method makes use of a major channel and some auxiliary channels. For those materials whose fatigue breakage is shear governed, the major channel is the shear strain history. For those materials characterised by a Mode I dominated cracking behaviour, the major channel is the normal strain history. The rainflow cycle counting method is used to post-process the master channel. The normal stress signal is the auxiliary channel for FS criterion. The schematic of BS cycle counting method is shown in Fig.1. Figure 1 : Schematic of BS cycle counting method. E XPERIMENTAL EVALUATIONS number of experimental data were selected from the technical literature [19, 20] to check the accuracy of the considered procedures in estimating multiaxial fatigue lifetime. The summary of the static and fatigue properties of the investigated materials are reported in Tabs. 1 and 2. When the material constants listed in Tabs. 1 and 2 were not directly available in the original sources, they were estimated as follows [1]: 3 ' ' f f   ; f f '3 '   ; b b 0  ; c c 0  The required stress component was calculated from the strain load histories being provided by using the model proposed by Jiang and Sehitoglu [21, 22]. The hardening effect under non-proportional loading was taken into account by making the following assumption [1]: K25.1 'K NP    ; 'n 'n NP  Material Ref. E (GPa) G (GPa)  y (MPa) k in FS S45C [19] 186 70.6 496 1 1050 QT steel [20] 203 81 1009 0.6 304L stainless steel [20] 195 77 208 0.15 Table 1: Static properties of the investigated materials B A