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一、前言界限应力强度因子幅度△K_(th)是材料疲劳裂纹扩张特性的一个重要参数。当外加应力强度幅度△K小于△K_(th)时裂纹不再发生扩张,并处于一稳定状态。因此如果将受有高周疲劳的结构设计成在裂纹尖端处的△K<△_(th),则带缺陷的结构就不会因受交变载荷发生疲劳裂纹扩展了。电站汽轮机转子每分钟旋转3000次,每年旋转1.5×10~9次,因此必须保证汽轮机转子在高速度旋转时在自重引起的交变载荷下,缺陷处的△K小于△K_(th)。为此必须准确
First, the preface Boundary stress intensity factor range △ K_ (th) is an important parameter fatigue crack propagation properties. When the applied stress intensity range △ K is less than △ K th (th), the crack no longer expands and is in a steady state. Therefore, if the structure subjected to high cycle fatigue is designed to have △ K <△ _ (th) at the tip of the crack, the flawed structure will not expand due to fatigue crack under alternating load. The steam turbine rotor rotates 3000 times per minute and rotates 1.5 × 10 ~ 9 times per year. Therefore, it is necessary to ensure that the △ K of the defect is less than △ K th (th) under the alternating load caused by self-weight of the turbine rotor at high speed. This must be accurate