石油钻柱的失效80 %以上都为疲劳破坏，这与钻柱在弯曲和扭转组合下的交变应力有关。
The fatigue rupture made up 80 percent of the total petroleum drillstring failures, which is related to the flexural-torsional alternate stress acted on drillstring.
拉伸强度呈下降趋势，而拉伸断裂伸长率以及冲击韧性则呈先增大后减小的变化趋势，弯曲性能对温湿度交变的环境不敏感。
Tensile strength decreased, while the tensile break extension percentage increased first and then decreased, flexural properties was not sensible to the changing humiture.
它既受、交变的拉压应力、又受弯曲应力。
Itsubject, alternating the tension pression stress, the bending stress.
它既受、交变的拉压应力、又受弯曲应力。
Itsubject, alternating the tension pression stress, the bending stress.
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