| In recent years,with the rapid development of technology and the development of the maritime economy,countries are paying more and more attention to maritime intelligent transportation.As an important part of this,unmanned boats are widely used in various tasks such as water patrol,communication relay,anti-terrorism and peacekeeping,and scientific research and survey.Unmanned boats are still mainly made of steel at this stage,but composite materials are gradually being used for lightweight reasons.However,due to the fast speed and weak structural stiffness of composite unmanned boats,a grounding accident will have a more serious impact on the hull structure.Although a lot of attention and research has been paid to the problem of ship collision resistance at home and abroad,most of them are limited to large ships and steel materials,and less research has been conducted on composite unmanned boats.Therefore,the comparative study of structural energy absorption and structural damage of composite unmanned boats under different stranding scenarios is of great significance.This paper takes steel and composite unmanned boats as research objects,and combines the non-linear finite element analysis software ABAQUS to conduct a comparative study on the structural damage characteristics of steel and composite unmanned boats under different stranding speeds and different reef types when the ship is hard stranded;the structural damage characteristics of steel and composite unmanned boats when the ship is soft stranded under different vertical stranding speeds and different stranding soil angles are studied.Based on the numerical calculation results of hard and soft grounding,the impact of different bow reinforcement structural solutions on the impact resistance of composite unmanned boats is analysed,and a composite bow structural form with better impact resistance under hard and soft grounding scenarios is obtained to provide reference for subsequent research.The main research work of this paper is as follows:(1)To systematically describe the non-linear finite element theory and the key techniques involved in the numerical simulation of ship grounding.The finite element control equations,finite element solution methods and techniques related to ship stranding simulation are analysed,the soil model used in the soft stranding process is studied in detail,and the macromechanical theory of composite single-ply and classical laminates is investigated to provide a theoretical basis for subsequent research;(2)Based on the theories related to ship stranding and composite materials,a numerical simulation study of the dynamic response of the reef type and stranding speed to the stranding process of steel and composite unmanned boats was carried out with the non-linear finite element software ABAQUS,to compare and analyse the collision damage forms and damage characteristics of the hull structures of composite and steel unmanned boats.To obtain the dynamic response characteristics of unmanned boats under different stranding speeds and different reef types;(3)Based on the theories related to ship stranding and composite materials,a numerical simulation study on the dynamic response of steel and composite unmanned boats to stranding process by combining the non-linear finite element software ABAQUS with the soil inclination and vertical stranding speed,and a comparative analysis of the collision form and damage characteristics of the hull structure of composite and steel unmanned boats To obtain the dynamic response characteristics of the composite unmanned boat under different vertical stranding speeds and different soil inclination angles;(4)Propose three types of reinforcement solutions for the bow structure of composite unmanned boats under stranding scenarios and analyse the effects of different reinforcement solutions on the crashworthiness of composite unmanned boats.To obtain the motion characteristics,stress distribution characteristics,displacement,stranding force and energy absorption of the composite unmanned boat under different strengthening structural forms,and to propose better composite boat bow impact resistance structural forms under soft and hard stranding. |
