A131钢焊接接头安全疲劳寿命的实验研究

Experimental study of safety fatigue life of A131 steel welded joints

低温环境下焊接接头的安全疲劳寿命,是冬季海洋平台构件抗疲劳设计与可靠性评定的基础。利用概率统计的方法,得出了在小样本实验条件下,当疲劳寿命服从对数正态分布时安全寿命与中值实验寿命之间的关系。在PLG-300 kN高频疲劳试验机上,测定了在-25℃环境下海洋用钢(A131)焊接接头试样在5种不同应力水平下的疲劳寿命,并得出了其中值S-N曲线。利用对数疲劳寿命标准差的经验取值,得出了焊接接头对应一定置信度下不同安全概率的低温疲劳寿命表达式。结果表明,利用此关系式可以大大减少实验的样本数目。从低温疲劳实验的相关系数可以看出,用线性拟合来回归中值S-N曲线是成功的,而且根据不同的安全概率,可以计算出不同的安全疲劳寿命。

The safety fatigue life of welded joints at low temperatures is the basis of design against fatigue and rdiability estimation of offshore platform components in winter. Using the method of probability statistics, the relationship between safety life and experiment life was theoretically obtained at small-number specimen experimental conditions when the fatigue life obeys logarithmic normal distribution, At the temperature of - 25 ℃, the fatigue life of A131 welded joints used in off- shore structures was measured on PLG-300 kN high-frequency fatigue testing machine at five stress levels, and the S-N curve of welded joints was derived, By means of the experiential value of logarithmic fatigue life standard error, the safety fatigue life of welded joints was obtained at different safety probability with certain confidence level. The results show that the number of experimental specimen can be decreased greatly using the derived formula. It is successful to obtain the S-N curve by linear regression from the relative coefficient of low temperature fatigue experimental data. Different safety fatigue life can be estimated according to different safety probability.