桁架臂K型管接头寿命评估方法的对比分析与研究

Comparative analysis on fatigue life assessment for tubular K-joints of truss booms

以国外通用疲劳设计标准ABS,DNV,BS7608,ASME,IIW等为依据,总结对比了起重机桁架臂K型管接头疲劳评估的方法.通过对比可知,国外标准中没有给出名义应力法对应的SN曲线,热点应力法成为其疲劳寿命评估的主要方法.ABS,DNV,BS7608标准中推荐的表面外推热点应力法与提供的管接头S-N曲线基本一致;ASME中给出的网格不敏感结构热点应力法即Battelle结构应力法也适用于管接头.同规格K型管接头在5种不同网格大小下的有限元应力计算结果的对比表明:相对于ABS,DNV,BS7608标准中的外推热点应力法,ASME标准中的Battelle结构应力法对网格有更强的适应性.

Based on such fatigue design standards as ABS, DNV, BS7608 and ASME, the fatigue assessment on crane truss boom is postulated.Due that the S-N curves of nominal stress are not included in fatigue design standardsfor complex tubular K-joints, the hot-spot stress method is employed.Accordingly, the extrapolation-based hot spot stress method is proposed with consistent S-N curves in ABS, DNV and BS7608.By referencing to a new hot-spot stress method called Battelle structural stress method in ASME, it is found that the Battelle structural stress method is more mesh-insensitive by verifying five mesh finite element models.Compared with ABS, DNV and BS7608, this approach is less conservative to fatigue life assessment.