中文摘要：

对承受疲劳载荷的海洋平台K型管节点首先进行了静力测试,确定了沿着焊缝的热应力区的应力分布及热应力区最大应力点的位置,从而判断裂纹产生的位置;然后通过专用测试设备提供循环疲劳载荷,用ACPD（Alternating Current Potential Drop,即交流电流势能落差法）技术检测裂纹的产生和增长过程,得到裂纹最深点,用S-N曲线估算其疲劳寿命。对已有裂纹的K型管节点,用应力强度因子估计其剩余寿命。同时用测试的结果验证了S-N的准确性和可靠性。

英文摘要：

　A large full-scale tubular K-joint specimen under cyclic load was tested in this study.Before fatigue test,static test was carried out to determine the hot spot stress（HSS） distribution along the weld toe of the K-joint sepcimen and locate the position of the peak HSS.Thus,the position of the surface crack initiation is determined.During the fatigue test,a specially designed test rig was used to provide constant amplitude cyclic load.The technique called Alternating current potential drop（ACPD） technique was used to monitor the crack initiation and development in the fatigue test.From the test results,the development of the deepest point of the surface crack can be obtained and shapes of the surface crack during different stages were obtained.In the prediction of the fatigue life of a tubular K-joint,S-N curve is frequently used.For cracked tubular K-joints,stress intensity factors（SIFs） are used to estimate the remaining life of such joints.In this study,through comparing with the S-N curves,the fatigue test results were used to verify the accuracy and reliability of S-N curve method.From the test results,the SIFs of the K-joint specimen are also obtained for using Paris＇ equation.