超声振动载荷下S06钢的长寿命疲劳性能

采用超声疲劳试验方法对新型沉淀硬化马氏体不锈钢S06钢在106~109周次范围的疲劳性能进行测定,结果表明:S06钢在循环周次大于107周次的范围仍然发生疲劳断裂,在106~109之间,应力寿命曲线持续下降,不存在疲劳极限,用107周次的条件疲劳极限来对S06钢长寿命构件进行无限寿命设计是不安全的.用载荷类型相同并且试样尺寸相近的高频疲劳试验方法对S06钢104~107周次的疲劳性能进行测定,将数据与超声疲劳试验结果进行对比发现:超声疲劳试验方法获得的S06钢的疲劳强度更高.用两种加载频率下106~107周次左右的试验数据拟合得到中值应力寿命曲线,根据应力寿命关系式中的疲劳强度系数的比值来对超声疲劳试验数据进行修正.在考虑了裂纹萌生机制和进行了频率影响修正的情况下,用线性异方差回归方法将超声疲劳试验数据拟合得到S06钢的长寿命P-S-N曲线,为长寿命构件的疲劳设计提供了基础.

Fatigue properties of S06 steel in long life regime under ultrasonic frequency

S06 steel is a new kind of precipitation-hardened stainless martensite steel. The fatigue properties between 10⁶~10⁹ cycles of S06 steel were tested with ultrasonic fatigue testing machine. Results show that fatigue failure takes place after 10⁷ cycles and an endurance limit does not exist for S06 steel. Fatigue design on infinite life criterion can-t be used for components made of this steel. High-cycle fatigue testing method with the same loading mode and approximate specimen dimension with that of ultrasonic fatigue tests was used to study the fatigue properties between 10⁴~10⁷ cycles. The results show that fatigue strength of S06 steel is higher with ultrasonic fatigue testing method. Ultrasonic fatigue testing data was amended by comparing the fatigue strength coefficient of Basquin formula. The P-S-N curves at 10⁶~10⁹ cycles of S06 steel considering cracking initiation mechanism and frequency effect were fit with linear variance regression analysis method and the curves can be used for fatigue design of engineering components with long lifetime.