13th International Conference on Fracture June 16–21, 2013, Beijing, China -7- da/dN [mm/cycle] Stress intensity factor range ΔK / MPa・m1/2 FSW panel Δσ=75 MPa FSW panel Δσ=50 MPa Base metal Δσ=50 MPa Weld line of FSW Δσ =50 MPa 10-6 10-5 10-4 10-3 10-2 10-1 5 10 60 Weld line of FSW =75 MPa Crack growth rate da/dN /mm/cycle 2.1 times 2.3 times under the same FSW condition. Therefore, residual stress of all specimens is identical. So, in the case of = 25 MPa, the effect of residual stress is relatively high. This means the acceleration and deceleration of crack growth rate for that situation is also high. Figure 8. da/dN-K curves for different external stress
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