Application Research On Topology Optimization Method In Structural Design For Oil Tankers

In recent years,ship structural optimization technology has received more and more attention,and its main purpose is to reduce the weight of ship as much as possible on the premise of ensuring the structural strength.Nowadays the research on ship structural optimization mainly focuses on shape optimization and size optimization,but the application research of topology optimization method is not wide enough.The topology optimization method can find the optimal paths of the structure to transmit load and the optimal configuration to carry load on the premise of ensuring the design requirements,which is difficult for general optimization methods.There are still some optimization spaces for the steel weight of large oil tankers designed by China compared with that by Japan and Korea.Therefore,it is of great importance to adopt topological optimization technology in the lightweight design of oil tankers.So this paper carries out the following researchs on the application of topology optimization method in the structural design of oil tankers:(1)For the layout of pillars in the aft part of VLCC,design domain is set up depending on the design limitations,and two different optimization objective functions are selected for the multi-objective optimal design.The results of optimization show that this method is feasible,and the layout of ship pillars with better structural performance can be designed without much design experience.(2)Depending on new CSR or so-called CSR-H to confirm the load cases and boudary constraints of three cargo hold model with two longitudinal bulkheads,and the transverse web frame is selected as the topological optimization object.Relevant research work is carried out on the range of design domain,constraint conditions,relation between thickness of plate in design domain and stable topological configuration,the thickness of plate within double side and the web depth of the vertical web frame on the longitudinal bulkhead,finally some suggestions are put forward by analyzing the optimization results.(3)For the problem of many structural optimization load cases,a complete set of cases screening criteria has been proposed.Through this standard,the representative load cases as well as the weight coefficient can be obtained.When the weight coefficient is set,not only the traditional strength factor is considered,but also the probability of load case is also included,so that the weight coefficient of each load case is more accurate.(4)Compromise programming method is adopted in the objective function to avoid sick optimization results to occur in multi-cases optimization.Based on the the topological optimization calculation of the transverse web under multi-case,reasonable and valid topological form is obtained.The optimization results demonstrate that the topological configuration of transverse web frame can be obtained effectively by the method in this paper,and has certain reference significance for the structural optimization design of other ships.(5)In order to obtain the suboptimal form of the transverse web frame,the original design domain is modified to artificially hinder the appearance of the optimal topological results,and then a reasonable suboptimal structure of the transverse web fame is obtained.The optimization results demonstrate that the topology optimization method described in this paper has wide application value in hull structure design.