Objective  This paper analyses the fatigue life of weld cracks in a large opening coaming with a conical shell under uniform pressure load.

  Methods  First, a finite element model of an underwater pressure-hull structure is built. Next, the peril point and its fatigue life are calculated using the structural strain method. Finally, the accuracy of the structural strain method used in the fatigue life evaluation of the underwater pressure-hull structure is verified through a comparison with the calculated results of the experimental data model.

  Results  The results show that the maximum structural stress is located at the weld of the coaming near the large end, which is the same as the appearance location of fatigue cracks in the experiment. The fatigue life calculated using the structural strain method shows good agreement with the experimental results, and the data of the model fatigue experiment is located in a narrow band of the master e-N curve. The normal structural stress is far greater than the shear structural stress at the peril point of the coaming weld.

  Conclusions  The structural strain method can effectively solve problems with the fatigue life of weld cracks in a large opening coaming with a conical shell. Under the load conditions of this paper, the initial crack at the peril point should be type one.