Consideration of runouts on the evaluation of fatigue experiments

SN曲线的确定是一个复杂的数学随机问题。对于钢结构和相关扇区，用基于试验的SN曲线的脂肪表来估算疲劳载荷下缺口细节的寿命。这是由基于线性Basquin模型的高周疲劳状态下的疲劳试验评估确定的。这个模型的缺点是，它不能在非常高的周期范围内提供外推，因为它也不能遇到跳动。这导致了对耐力极限的不安全估计，以及关于高负荷循环的结构设计的不确定性，例如风能转换器。卡斯蒂略和费尔南德斯-坎特利的模型是基于威布尔分布的，并在非焊接疲劳细节研究项目中得到了实验验证。它描述了从有限寿命疲劳到超高周疲劳的SN曲线。此外，它还提供了将跳动包括在疲劳试验评估中的可能性，以及对具有更大应力范围的跳动的重新测试。该模型在碳钢焊接接头和奥氏体钢焊接接头上的适用性有待进一步研究。

The determination of SN-curves is a complex mathematical and stochastic problem. With steel structures and related sectors the estimation of lifetime of a fatigue loaded notch detail is done with FAT-tables, which are based on experimentally based SN-curves. These are determined by the evaluation of fatigue tests in the high cycle fatigue regime based on a linear Basquin model. The shortcoming of this model is, that it does not provide the extrapolation in the very high cycle regime as also cannot encounter runouts. This results in an unsafe estimation of the endurance limit as also in uncertainities concerning the design of constructions for high load cycles, such as wind energy converters. The model of Castillo and Fernández-Canteli is based on a Weibull-distribution and is experimentally verified within the resarch project for unwelded fatigue details. It describes the SN-curve from finite life fatigue up to the ultra high cycle fatigue. In addition, it provides the possibilty to include runouts within the evaluation of fatigue tests as also the retesting of a runout with an increased stress range. The applicability of this model on welded connections of carbon steels as also austenitic steels should be further investigated in the research project.