疲劳强度
在规定循环次数 N 下，50% 的疲劳试验试样发生失效时的应力（Shigley，第 161 页）。疲劳强度受许多因素影响（参见疲劳）。
Fatigue strength
The stress at which 50% of fatigue test samples will have failed at a specified number of cycles N (Shigley, p. 161). The fatigue strength is affected by many factors (see fatigue).