Influence of mean stress on fatigue life of the austenitic stainless steel 316 L in air and light water environments (boiling water reactor/hydrogen water chemistry) at 288 °C was determined with a series of tests carried out in load-control mode. Fatigue life was found to increase with application of compressive and tensile mean stress in air and light water reactor environments. Secondary hardening was regarded as the main reason for this behavior. A modified Smith-Watson-Topper (SWT) model was considered to account for mean stress and was shown to predict fatigue life accurately in air and water environments. The reduction of fatigue life in water environment, determined with the SWT curves, was about 2.5. Observations of the end-of-life dislocation arrangements by transmission electron microscopy showed that the dislocation microstructure depends essentially on plastic strain amplitude, which in turn is strongly correlated to stress amplitude and mean stress. The microstructures were found consistent with those usually observed after strain-controlled experiments. At rather low plastic strain amplitudes, corduroy structure consisting of small dislocation loops was observed. Acting as significant obstacle to dislocation motion, corduroy structure affects overall dislocation mobility therefore contributing to notable secondary cyclic hardening.

通过在负荷控制模式下进行的一系列测试，确定了平均应力对288°C的空气和轻水环境（沸水反应堆/氢水化学）中奥氏体不锈钢316 L疲劳寿命的影响。发现在空气和轻水反应堆环境中，疲劳寿命随着压缩和拉伸平均应力的施加而增加。二次硬化被认为​​是造成这种现象的主要原因。修改后的Smith-Watson-Topper（SWT）模型被认为可以解决平均应力问题，并且可以准确预测空气和水环境下的疲劳寿命。通过SWT曲线确定的水环境中疲劳寿命的减少约为2.5。通过透射电子显微镜对寿命终止位错排列的观察表明，位错微观结构主要取决于塑性应变幅度，而塑性应变幅度又与应力幅度和平均应力密切相关。发现微观结构与应变控制实验后通常观察到的一致。在相当低的塑性应变幅度下，观察到由小的位错环组成的灯芯绒结构。灯芯绒结构是位错运动的重要障碍，它影响整体位错的流动性，因此有助于显着的二次循环硬化。发现微观结构与应变控制实验后通常观察到的一致。在相当低的塑性应变幅度下，观察到由小的位错环组成的灯芯绒结构。灯芯绒结构是位错运动的重要障碍，它影响整体位错的流动性，因此有助于显着的二次循环硬化。发现微观结构与应变控制实验后通常观察到的一致。在相当低的塑性应变幅度下，观察到由小的位错环组成的灯芯绒结构。灯芯绒结构是位错运动的重要障碍，它影响整体位错的流动性，因此有助于显着的二次循环硬化。