Plastic Response Of Ship Plates Under Single And Repeated Impacts

Plates and stiffened plates are main components of ship structures,which tend to be subjected to impact from other objects during the service period.For ice-class ships,the ship hull structures are frequently impacted by ice floes;For large ships and marine structures equipped with helicopter,the helicopter decks are subjected to the repeated loading and unloading caused by the helicopter wheels.In this paper,the experimental,numerical and theoretical methods are adopted to investigate the deformation modes and failure mechanisms of ship plates subjected to single and repeated impacts based on the above scenarios.The main contents are as follows:(1)Four groups of impact tests are conducted on plates and stiffened plates,in which the collision forces and deformation are monitored and eventually the relationship between collision force and deformation is obtained.The deformation profiles of ship plates are measured after each impact.According to deformation profiles,a kind of “Frustum-type” deformation mode is proposed,which provides the physical model for the deviation of theoretical formulas based on Rigid-plastic theory.(2)Numerical analysis is performed on plates and stiffened plates using finite element software ABAQUS,and the numerical results and experimental results are compared,and the reliability of finite element approach is verified.The model-building process using the ABAQUS and the set of relevant parameters are precisely introduced,which provide foundations in using numerical methods to analyze others numerical cases.(3)Rigid-plastic theory is adopted to conduct the theoretical analysis on plates and stiffened plates subjected to single and repeated impacts,and the theoretical results and experimental results are compared,and the accuracy of theoretical formulas in this paper is verified.According to the “Frustum-type” deformation mode proposed according to the test,theoretical predictions are made on the response of ship plates and stiffened plates under single and repeated impacts based on the Rigid-plastic theory.At the same time,parametric study are performed to analyze the influences of impact location,boundary conditions and load concentration on the structural responses.(4)The force-deformation curves and energy-deformation curves obtained from single impact and repeated impact are compared,respectively,to investigate the differences of the dynamic response between single impact scenario and repeated impact scenario.Based on Chapter III,finite element approach is adopted to analyze the influence of impact mass and impact velocity on the differences between single impact and repeated impact,which proves the feasibility of using single impact method to predict the dynamic response the of ship plates caused by complex repeated impacts.