压弯组合应力下高强钢焊接板表面裂纹疲劳寿命计算

潜艇上浮下潜运动使得其耐压壳承受交变的外压载荷。潜艇耐压壳的疲劳热点为锥一柱过渡结构连接焊缝焊趾处，该处所受的应力特征为压弯组合应力。压弯组合应力下表面裂纹应力强度因子及其疲劳寿命的计算尚无报道。弄清楚压弯组合应力作用下带表面裂纹焊接板试件的疲劳特性对潜艇等结构的疲劳研究是必要的。文中提出用成一定角度的对接焊板试件和轴向加载获得压弯组合应力来模拟潜艇耐压壳锥一柱焊接结合区的应力特征的实验方法。用980高强钢作试件，研究焊趾处预制表面裂缝，并在压弯组合应力为特征的疲劳载荷作用下表面裂纹的疲劳行为。给出高强钢焊趾表面裂纹在压弯组合应力下应力强度因子及其疲劳寿命计算式。该结果可供海洋平台、压力容器及管道的某些受力特征为压弯组合应力的重要结构的疲劳设计时参考。

CALCULATION OF FATIGUE-LIFE OF SURFACE CRACKED HIGH-STRENGTH STEEL WELD PLATE SUBJECTED TO COMBINATION OF COMPRESSIVE AND BENDING STRESSES

The pressure of submarine is changing with its diving depth. One of the hot spot of fatigue failure of the submarine pressure shell is the weld toe of the cone-cylinder junction. The stresses in the area of the cone-cylinder junction of the cone-cylinder of submarine are compressing stress plus bending stress. The calculation method of SIF and fatigue life of surface crack which subjected to compressive and bending stresses have not been reported. It is useful, to have the knowledge of the fatigue property of the weld plates which subject compressing and bending stresses, for analyzing the fatigue of submarine structure. The experiment method of simulating the stress feature of weld structure of the cone-cylinder, by using the weld angle plate samples to get the compressing and bending combination stress with axial loading, has been put forward in this paper. The 980 high strength steel plate was used as the test sample material, and the samples were prefabricated surface arc shaped cracks at weld toe. The experiment on fatigue behavior of the surface crack that subjects compressing and bending stress has been performed. The formulae for calculating SIF and fatigue life of surface crack at weld toe of the high-strength steel under the combination stresses have been presented. The results obtained can be useful in fatigue design of other structures, which subject combination stresses of bending and compressing, such as some important structures of ocean platform and of pressure vessel.