基于小样本数据的构件疲劳破坏全寿命区S-N曲线

摘要

The applicability of traditional S-N curve in fatigue failure life cycle of component was not strong.The high cycle fatigue tests of HRB400 high strength steel bars connected by flash butt welding were carried out based on single point method,and a series of small sample data were got.Accordingly,double-logarithmic double-dogleg S-N curve was studied and proposed which was suitable for the fatigue failure life cycle of component.The improved Chauvenet criterion was proposed to select the test data of the first segment of dogleg line,and then the equation for the first segment was obtained according to a linear regression principle.Based on the gradient obtained by three-parameter exponential function curve and the fatigue strength determined by staircase method of the second segment,the equation for the second segment was worked out.Double-logarithmic double-dogleg S-N curve suitable for the fatigue failure life cycle of component was obtained by the simultaneous equations of two segments.On this basis,the calculation method considering dependability and reliability was further studied and proposed for double-logarithmic double-dogleg S-N curve suitable for the fatigue failure life cycle of component.%针对传统S-N曲线在构件疲劳破坏全寿命区适用性不强的问题,采用单点试验法对闪光对焊连接的HRB400高强钢筋标准试件进行高周疲劳试验,得到一系列小样本数据;然后基于小样本数据研究并提出适用于构件疲劳破坏全寿命区的双对数双折线S-N曲线.利用提出的改进肖维奈准则对第1段折线的试验数据进行取舍,然后根据一元线性回归原理得到第1段折线的方程;基于三参数幂函数曲线得到第2段折线的斜率和升降法确定的疲劳强度,求得第2段折线的方程;将2段折线方程联立,得到适用于构件疲劳破坏全寿命区的双对数双折线S-N方程.在此基础上,进一步研究并提出考虑置信度和可靠度条件下适用于构件疲劳破坏全寿命区的双对数双折线S-N曲线的计算方法.