13th International Conference on Fracture June 16–21, 2013, Beijing, China The macro morphology of the turbine component is shown in Figure 6. It can be seen that crack propagates at the second mortise tooth of the leading edge of the disc. The SEM observations provide further information for understanding the interaction of HCF and LCF. The examination of fracture surfaces shows that fatigue cracks initiate from many positions in Figure 7(a), and there are obvious wide fatigue striations in the crack initiated region (see Figure 7(b), which indicates that stress resulting in crack initiation is large due to LCF loading. The crack propagation area of the fracture surface is dominated by transgranular mode and many thin fatigue striations emerged in Figure 7(c). This implies that HCF loading controls the crack growth. At the same time, oxidation features can be observed at the crack propagation region, as shown in Figure 7(d). The SEM observations reveal that high frequency vibration stress greatly affects the crack growth under HLCCF loading. Thus the effect of HCF damage on LCF damage should be considered for turbine attachments. Figure 6. Macro morphology of the turbine component (a) (b) (c) (d) -5-
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