两级交变载荷下船体结构典型节点疲劳试验研究

江海直达船属于浅吃水大型宽船,往复航经江段和海段,其疲劳问题不容忽视。将江段和海段载荷简化为小和大2级交变载荷,选取较为典型的船底纵骨贯穿横舱壁节点,通过对比试验探讨2级交变载荷对该船疲劳寿命的影响。试验结果表明,在试验工况下,变幅载荷中的大载荷是导致裂纹扩展的主要因素,小载荷的参与会降低大载荷作用下裂纹扩展的速率。采用等效应力法对变幅载荷下节点的疲劳寿命进行评估,发现采用Miner准则所得结果偏保守,采用均方根法所得结果偏危险,采用修正的Miner准则所得结果精度较高,推荐采用该方法评估2级交变载荷下船体结构典型节点的疲劳寿命。

Fatigue Experimental Study of Typical Welded Joints under repeated two-step loading for Hull Structure

The new generation River-Sea-Going Ship has the characteristics of shallow draft and wide breadth and navigation area should go through river and sea repeatedly. Its fatigue problem can not be ignored. In this paper, the river-sea loads are simplified into low-high amplitude loads, choosing one of the typical joints of the ship: longitudinal through transverse bulkhead joints of ship bottom, and comparative studies were made to discuss the effect of the repeated two-step loading on fatigue life of it. The test results show that under the experimental conditions of this study, the large load in the variable amplitude load is the main factor causing crack growth, and the participation of small load will restrain the crack growth rate. The equivalent stress method was used to evaluate the variable amplitude life, the Miner cumulative damage theory is conservative, the root mean square method is dangerous. The modified Miner criterion has higher accuracy and is recommended to evaluate the fatigue life of typical ship structure joints under the repeated two-step loading.