Crack size, hammer stroke frequency and rotary speed influence the drilling string fatigue life involve, in which the crack size and stroke frequency were two major factors.

影响钻柱疲劳寿命的因素包括钻柱裂纹尺寸、空气锤冲击频率、转盘转速等，而空气锤冲击频率与裂纹尺寸是影响钻柱疲劳寿命的两大主要因素。

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"Each wave is like a hammer stroke beating on a sea wall which starts to make it crack and then we have to repair it, " she says.

BBC: Legacy of Britain's great flood