变幅载荷作用下焊接接头疲劳寿命预测方法

Fatigue life prediction of weld-joints under variable amplitude fatigue loads

船舶与海洋结构物在其服役过程中受到波浪等载荷的交变作用而引起结构的疲劳损伤。检测结果表明船舶及海洋结构的疲劳热点部位大多数是在构件相互连接的焊缝焊趾处。因此,研究典型接头表面裂纹应力强度因子统一计算方法以及变幅载荷作用下表面裂纹扩展规律对船舶与海洋结构物的寿命预测是十分重要的。本文讨论了裂纹闭合及开口比的计算,在Newman有效应力强度因子计算方法的基础上,提出了考虑因素更全面的有效应力强度因子幅计算式以及变幅载荷作用下船舶与海洋结构物典型焊接接头疲劳裂纹扩展寿命预测模型。

Fatigue damage of ship and ocean engineering structures will caused by fluctuation loadings, such as wave loading, during their service time. Most of the fatigue cracks in ship and platform structures can be traced to the connected welded toes. It's very important to study the unified SIF (Stress Intensity Factor) calculation of typical weld joints and the crack propagation law under variable fatigue loading and consequently put forward the fatigue life prediction method of ship and ocean structures. In this paper, the crack closure and the calculation of crack opening ratio were discussed. Based on Newman's effective stress intensity factor range calculation equation, a unified effective stress intensity factor range calculation equation for surface cracked structures subjected to variable amplitude fatigue loading was put forward. The SIFs of surface cracked structures including plate, butt weld joints, T joints and cruciform joints can be estimate by a set of simplified equations. These procedures can be used to predict the fatigue life of ship and ocean engineering structures subjected variable amplitude fluctuation loads.