The Research On Shape Optimization Of Ship Local Structures

Some typical joints such as hatch corners,brackets and openings are often placed in areas where the hull structure crosses or the shape is abrupt,the phenomenon of stress concentration is obvious,and the damage of the structures occur frequently.Shape optimization of these structures has always been studied.At the same time,the Common Structure rules(HCSR)issued by IACS has been in force.HCSR has made many changes in various aspects such as load,strength calculation,analysis and evaluation methods,and the strength requirements of the above partial structures have been further improved.At present,the research on the shape optimization of local structure based on direct calculation of HCSR was very limited,and the corresponding optimization design basis was few.In this paper,the shape optimization of the three kinds of local structures have been studied including hatch corner,bracket and opening.The main research contents include the following aspects.(1)The principle and application method of PCL language were studied.The stable and efficient parametric modeling program was developed based on PCL language and finite element modeling method for hatch corners,brackets and openings.According to the given design parameters,an accurate and high-quality local structural finite element model can be automatically established on the original fine mesh structure,which provides a modeling tool for structural shape optimization.(2)The mathematical model of shape optimization was established.Based on the Isight optimization platform,two efficient global optimization algorithms were selected to build an integrated system of shape optimization.The system has strong versatility and can be applied to various forms of local Structures' optimization work.(3)The three-chamber finite model was adopted,and the shape control parameters were selected as the design variables.The descriptive requirements for the hatch corners and the direct calculation requirements of the yield strength in the HCSR rules were selected as the constraints,and the local structure weight and stress were concentrated.The optimization were carried out by two optimization algorithms,Multi-Island Genetic Algorithm and Simulated Annealing.To improve the efficiency,the screening method to determine the critical conditions and the most dangerous conditions were given.(4)The principle of the sub-model was studied.Taking the optimization of hatch corner as an example,the selection method of the sub-model range and the method for model boundary constraint and loading ways were given.Then,the stress of the submodel were compared with the results in the entire model so as to verify the accuracy of the submodel method.Finally,the shape optimization of hatch corners,brackets and openings were carried out respectively based on the sub-model method.