Study on critical condition of damage mode of local grillage structure under near-field underwater explosion

The rapid prediction of damage to underwater explosion-damaged ship plate structures is a crucial element in the assessment of ship impact damage. In this paper, we address the challenge of rapidly predicting the damage mode of plate and frame structures subjected to underwater explosions. We begin by establishing that the shock wave load of an underwater explosion can be modeled as a rectangular pulse, based on the effective impulse of action and the characteristics of the target structure. We then delve into the mechanical criteria governing the different damage modes, employing the equivalent theory of plate and frame. The critical condition of the dimensionless damage mode of the local plate and frame structure of the ship is deduced by the dimensional analysis method based on the mechanical criterion of damage mode. In this paper, an integrated approach combining experimental and numerical research methods is employed. Firstly, an analysis of the damage modes of the light plate structure is conducted. The experimental data, numerical data, and theoretical calculation data based on the critical discriminant condition of the dimensionless damage mode are compared. The accuracy and reliability of the numerical method and the critical discriminant condition of the dimensionless damage mode are validated. A series of numerical simulations were conducted on the plate and stiffened plate structure of a ship, and the validity of the critical discriminant conditions of the dimensionless damage mode is confirmed. In conjunction with the underwater explosion impact factor, an engineering estimation method for the damage of the local plate structure of the ship is developed ultimately.