预应力过载对低周疲劳及da/dN的影响
THE EFFECTS OF PRESTRESSING OVERLOAD ON LOW CYCLE FATIGUE AND da/dN
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摘要: 研究了预拉伸应力过载对TC-11钛合金及GH33A高温合金的低周疲劳及da/dN的影响。证明在5×103~5×104低周疲劳寿命范围内,单边缺口试样的疲劳裂纹起始寿命Ni有明显提高,并可用经验表达式Sm(Nf/r)=C来估算,但对其裂纹扩展寿命Np的影响则并不显著。Abstract: The effects of prestressing overload on dow cycle fatigue and fatigue crack growth rates da/dN of titanium alloy TC-11 and Ni-base superalloy GH33A for gas turbine disks were investigated at room temperature and 633K. The experimental results show that the low cycle fatigue crack initiation life is increased by prestressing overload treatment within the range of low cycle fatigue life 5×103 to 5×104,but the effect of the prestressing overload on fatigue crack propagation life Np is not obvious. In addition, an empirical expression is formulated to estimate the fatigue life of side edge notched (SFN) specimen under prestressing overload as Sm(Nf/r) = c. When this expression is employed to estimate the fatigue life of a notched specimen prestressed, it is only necessary to know the conventional fatigue S-N curve.
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