Pseudo-shakedown in the collision mechanics of ships

The pseudo-shakedown phenomenon in the collision mechanics of ships is investigated both theoretically and experimentally. An energy criterion, which can be used to judge the pseudo-shakedown state of structures is postulated. The energy criterion is applied to the analysis of pseudo-shakedown of ship plates under repeated mass impacts. An illustrative example and experimental results are given. According to the analysis, it is found that, for the axially restrained ship plate with repeated dynamic loads, the elastic strain energy absorbed in the structure increases with that of the plastic deformation of the structure. The structure will reach a pseudo-shakedown state when the maximal elastic strain energy to be absorbed in the deformed structure is equal to or larger than the external work of the dynamic load in magnitude. This postulation has been confirmed by the experimental results of repeated mass impact on a fully clamped plate.