Dynamic Inelastic Behaviour of Ship Plates in Collision

[摘要] This thesis consists of eight chapters. In the first of these the literature on the structural aspects of ship collision is reviewed in terms of the specific topic in this field. Emphasis is placed on the structural response in collision in which several important aspects are addressed, such as, Minorsky's method, static and dynamic approach, impact force, dynamic effects and failure mode. Based on the Variational Finite Difference Method, a numerical model of dynamic inelastic response of plates impacted by a rigid knife indentor is developed in the second chapter. The numerical model includes the influence of finite transverse displacement, axial restraints, bending moments, material elasticity and strain hardening. The struck plate and rigid striker are coupled in the numerical simulation, with the deformation, strain, stress and impact force as output of the calculation. Chapter 3 presents the experimental investigation of clamped rectangular plates impacted by a knife edge indentor. A series of impact tests are conducted on aluminium and steel plates. The plate specimens are struck by a rigid knife edge indentor sliding down from a runway, and the impact loading is repeatedly applied to each plate until plate failure. Detailed experimental results are reported on impact and rebound velocities, permanent deformation, acceleration, dynamic strains and failure modes both for single impact and for repeated impacts. Different stages of plate failure are identified based on the dynamic strain recording. For the plate subjected to a number of identical impacts no pseudo-shakedown phenomenon is observed in the test. The influence of boundary conditions caused by in-plane sliding is also investigated. In chapter 4 the numerical approach proposed in chapter 2 is used to simulate the collision process of an aluminium plate impacted by a knife edge indentor. Numerical results provide a full picture of the response of the clamped rectangular plate under dynamic loading, giving information on the impact force, deformation, stress and strain history and distribution in the plate. Correlations are performed with the experimental results on the plate impact test described in chapter 3 as well as on the test of a small scale ship model which was conducted in the Department during 1981-1982. Very good agreement is reached. Parametric studies are made in chapter 5 on some important parameters for ship collision, such as mass and impact velocity of the striking bow, the length of vertical bow, the struck plate length and width, and plate thickness. As an application of the numerical work, critical speed for a longitudinally framed tanker struck by a rigid vertical bow is also investigated. Chapters 6 and 7 contain analytical solutions based on the Rigid Perfectly Plastic Method for single impact and repeated impacts respectively. An approximate theoretical procedure is developed to give the lower and upper bounds of the dynamic plastic solution to the impacted rectangular plate with finite deflections. The analytical solution obtained is compared with the experimental results and predictions of numerical program. It is found that no pseudo-shakedown occurs for the plate subjected to a number of identical impacts. Finally, conclusions and suggestions for further work are given in chapter 8.

[发布机构] University:University of Glasgow

[关键词] Naval engineering