修正的古德曼应力图及许用安全系数

MODIFIED GOODMEN STRESS DIAGRAM FOR SUCKER RODS AND ALLOWABLE SAFETY CO EFFICIENT

研究 API RP11BR推荐的修正的古德曼应力图后得出 :该图的疲劳极限曲线是一条偏于安全的疲劳极限图线 ;对许用安全系数的计算表明 ,该图推荐的最大许用应力随交变应力中的交变分量的增大而减小 ,符合抽油杆对许用应力的要求 ,对应的许用安全系数符合常规疲劳设计的取值原则 ,是合理、科学的 ;建议将 API推荐图上的拉拉载荷安全工作区扩大到应力比 r<0～ - 1的拉压载荷工作区 ,以用于对抽油杆柱下部杆段的计算 ;当下部杆段的应力比 r<- 1时 ,建议以最小疲劳极限作为许用应力 ,其强度条件为 σmin≥ [σmin]。

This paper proved that the fatigue limit curve of the diagram is very safety by the study of the recommended-modified Goodmen-stres s diagram of the API RP 11BR.According to the calculation of its allowable safet y coefficient,the maximum allowable stress in the diagram was reduced with the i ncreasing of component of the alternating stresses,it met the requirement of the allowable stress of the sucker rod,and met the conventional principle of the fa tigue design.The paper suggested that the work range of the tensile safety of th e recommended API diagram be extended to the work range of the tensile-compress safety that the stress ratio r is less than 0～-1,so as to calculate the parame ters of the down section of the sucker rod.It was presented that the minimum fat igue limit was regarded as the allowable stress when the stress ratio r of the d own section of the sucker rod is less than -1,and its stress strength condition is σ_min≥.