Objectives Permanent dent defects induced by the impact of high falling objects on ship hull decks exert a significant influence on the ultimate strength of deck stiffened plates. Most existing studies apply simplified impact-induced dents as additional initial deformation defects to stiffened plates models, followed by nonlinear finite element analysis for ultimate strength evaluation. To deeply consider the actual impact process of high falling objects, the true damage morphology and residual stress after impact, and their influence on the ultimate strength of deck stiffened plates, it is necessary to conduct further research.
Methods In this study, the explicit dynamic method was first adopted, with the Cowper-Symonds material constitutive model employed to simulate the impact process of high falling objects on a deck stiffened plate, thereby obtaining the plastic damage characteristics and residual stresses distribution of the stiffened plate after impact. Subsequently, nonlinear finite element analysis was conducted to evaluate the ultimate strength of the stiffened plate with impact-induced damage. Specifically, the damage formation process of the stiffened plate under impact, as well as the effects of impact mass, impact position, and dent-induced residual stresses on the ultimate strength, were discussed in detail.
Results The results indicate that the degree of permanent damage deformation varies with different impact positions and tends to aggravate with the increase of falling object mass. Dents caused by high falling object impacts reduce the ultimate strength of stiffened plates, and the strength reduction can reach 29.8% for the worst case.
Conclusions Ultimate strength of the stiffened plate will decrease with the increase of the mass of the falling object. And, the plastic deformation and residual stress caused by dent damage are the important factors leading to the decline of the ultimate strength.
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