The high-strength steel in Figure 7-20 is subjected to a stress alternating at 200 revolutions per minute between 600 MPa and 200 MPa (both tension). Calculate the growth rate of a surface crack when it reaches a length of 0.2 mm in both m/ cycle and m/s. Assume that f = 1.0.

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Crack growth rate (m/cycle) 10-10 10-11 10-12 10-13 10-14 10-15 1 1 1 1 Power law behavior = C(AK)" dN No crack growth Rapid unstable crack growth Slow crack growth 0.8 Stress-intensity factor range AK (MPa √m) 0.4 100