基于固有耗散理论和计算模型, 对FV520B钢的高周疲劳性能进行了较为系统的实验研究. 结果表明, 随着施加的交变应力幅的增大, FV520B钢的固有耗散也不断增大. 其变化规律的拐点对应于固有耗散产生机制的转变, 从单纯地由材料微结构的可逆运动(位错线在强钉扎点之间的摆动)引起, 到由材料微结构的可逆运动和不可逆运动(永久滑移的产生、强钉扎点的脱钉以及位错的增殖)共同引起. 并且, 固有耗散拐点的应力幅值就是导致材料疲劳损伤累积的临界应力幅值, 即疲劳极限. 另外, 实验还表明, FV520B钢在等幅交变应力下具有相对稳定的损伤演化速率, 且损伤演化速率由应力幅值决定, 与加载次序无关; 每一周加载造成的疲劳损伤也不受加载频率的影响. 当FV520B钢在疲劳过程中累积的与微结构不可逆演化相关的固有耗散部分达到一个临界值时, 材料即发生疲劳断裂, 且这个临界值是一个与加载历史无关的材料常数.

Systemic experimental research was carried out on high-cycle fatigue behavior of FV520B steel based on the theory and calculation model of intrinsic dissipation. The experiment results show that the intrinsic dissipation of FV520B steel increases with the increase of the applied stress amplitude. Generally, the inflection point of intrinsic dissipation corresponds to the transition of the generation mechanism of intrinsic dissipation: from the reversible motion of the microstructure (the swing of dislocation lines between strong pinning points) to the combined effects of the reversible and irreversible motion of the microstructure (the generation of permanent slip, the unpinning from strong points and the multiplication of dislocation). And the stress amplitude corresponding to the inflection point is just the critical stress value inducing fatigue damage accumulation. Moreover, the results also indicate that FV520B steel subjected to constant stress amplitude keeps a relatively steady rate related to the applied stress amplitude and independent of the loading sequences. Additionally, the loading frequency has no effect on the fatigue damage per loading cycle. Fatigue failure will occur once the amount of the intrinsic dissipation, due to the irreversible motion of the microstructure, accumulates to a threshold value. And the energy threshold is found to be independent of the loading history.