Research On Crashworthiness Of Titanium Alloy Pressure Cylindrical Structure

With the rapid development of the world economy today,energy issues have become one of the important factors restricting economic development.Traditional land resources are becoming more and more difficult to meet human needs.The ocean is not only rich in fish resources,but also rich in oil and gas resources.Therefore,mankind has strengthened the development and utilization of it.As one of the important tools for human understanding and exploiting the ocean,the submersible vehicle plays a vital role.Thus the development of the submersible vehicle,in recent years under the unremitting efforts of scientific researchers,is quite rapid.However,the submersible vehicle will encounter various unexpected accidents during the work,in which collisions are the most common accidents during submersible navigation.The reserve buoyancy of the submersible is very small,and the external hydrostatic pressure will have a great influence on the whole structure when it works underwater.So once there’s a collision,large hydrostatic pressures will quickly collapse the pressure resisting structure,which may cause bigger casualties.Based on the above reasons,the crashworthiness of the fore and midship parts of the pressure-resistant cylinder structure is studied in this thesis,and the bearing capacity of the midship part under the condition of large depth is discussed.The main research work of this thesis is as follows:(1)To give a conclusion of the key technology of nonlinear finite element software used.To determine the solution method,contact mode and hourglass control method used in the simulation.And thus to determine the material parameters,element types,mesh size of the pressure-resistant cylindrical structure model,and establish related models.(2)In view of the collision of the pressure-resistant cylindrical structure bow,three different shapes of ram heads were selected according to the actual situation,and the impact of the shape of the ram,the collision angle,and the collision speed on the impact resistance of the pressure-resistant cylindrical structure bow was studied on the water surface.Carry out underwater collision research to explore the influence of hydrostatic pressure on the collision resistance of the pressure-resistant cylindrical structure bow.Through research,it is found that the response of the pressure-resistant cylindrical structure under impact is mainly related to the collision contact area.(3)Aiming at the collision of the pressure-resistant cylindrical structure amidships,the collision between the steel submersible and the titanium alloy pressure-resistant cylindrical structure is simulated underwater.Exploring the impact of collision angle,collision speed and hydrostatic pressure on the crashworthiness of the pressure-resistant cylindrical structure midway through research,it is found that under high hydrostatic pressure,the pressure-resistant cylindrical structure has an initial internal energy before the collision.Hydrostatic pressure will also have a greater impact on structural damage.(4)The strength of the pressure-resistant cylindrical structure used in this thesis is calculated according to relevant theories,and the theoretical maximum depth is determined,which is compared with the finite element simulation results.When submerged,most of the material’s properties are used to resist hydrostatic pressure,while some of the material’s properties are retained to resist external forces.And to make sure how much impact the remaining part can bare and to provide alternative options to enhance the local strength of the pressure-resistant cylindrical structure,the collision was simulated by changing the parameter of kinetic energy.