Optimization For The Natural Frequency And Weight Of Laminated Composite Rudder

With the scramble for the rights and interests of the sea in many countries on the world,the military modernization construction has been in a state of chasing each other,resulting in the vigorous development of the maritime power of various countries,in which advanced ships are the main research and construction targets of those countries.The rudder equipment is also one of the main research objects in many countries.Compared with the traditional steel rudder,advanced composite rudder structure has attracted more and more countries to invest in R & D because of its good vibration characteristics and excellent acoustic performance.Therefore,it is very important to optimize the natural frequency and weight of the composite rudder.In this paper,a kind of NACA0025 composite rudder is designed on the basis of reference to relevant literatures,and the optimization design method of composite rudder is discussed.The main contents of the thesis include the following aspects:Firstly,based on the research status and design methods of composite rudder at home and abroad,the finite element simulation model of NACA0025 composite rudder is established by using ABAQUS finite element software,and the first three modal modes and natural frequencies are extracted.Secondly,by using the method of grouping and comparing,the initial skeleton layout is optimized to 8 reinforcement bars in both horizontal and vertical directions.On this basis,using Isight optimization software to integrate Abaqus,using gradient algorithm NLPQL and LSGRG,with the weighted sum of the previous third-order natural frequency as the design objective,the thickness of horizontal and vertical stiffeners is optimized.The influence of reinforcement thickness on the front three natural frequencies is analyzed.Thirdly,based on the above work,the composite skin was optimized by gradient algorithm and multi-island genetic algorithm(MIGA),respectively.The design is divided into two plans.The first is a simple method and the second is a more widely used one.The results show that although there are some differences between the two,each has its own advantages.The first scheme takes a shorter time cost,but there is some difference between the optimized solution and the optimal solution.The second scheme takes more time,but the result is closer to the optimal solution.Finally,the method of surrogate model was used,with the natural frequencies and the weight of the rudder as the optimization objectives.Through the data comparison method a RBF model was accepted.After trained well,the composite rudder is replaced by the surrogate model.Then an optimization algorithm NSGA-II was used to find the Pareto front.After that,several typical design points were selected to import the real model to calculate the real responses.The research content of this paper can be used for reference for the optimization design of composite rudder based on gradient algorithm,genetic algorithm and surrogate model method.And the influences of the design variables summarized in the optimization processes on the optimization objectives have certain reference value for the design of composite rudder.