13th International Conference on Fracture June 16–21, 2013, Beijing, China -4- Auto-Montage micro-observation system by an inverted sequence method[10]. Thus, the information of short crack initiation and propagation, such as crack size, number, and angle, was obtained. 3. Results and Discussions 3.1. Comparison of Dominant Short Crack Growth Rate Inheriting the idea of effective short fatigue crack criterion[10-12], the relation curves between dominant short crack (DSC) growth rate, da/dN, and its size, a, with five different surface rolling times are shown in Figure 3. Following conclusions can be drawn: (a) (b) (c) (d) (e) Figure 3. Dominant short crack growth rate for each group of LZ50 axle steel specimens repair times for specimens are (a) f=0.0, (b) f=0.3, (c) f=0.5, (d) f=0.6, and (e) f=0.7 (1) During crack growth process, the growth rate decelerates once or twice clearly for all these five groups of specimens. If only the crack propagation after surface rolling is taken into
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