Dynamic Optimization For Stiffened Plate Of Naval Vessel Based On Adaptive Evolutionary Strategy

The naval vessel will carry many loads such as main engine, propeller and wave force, which will excite nuisance vibration to some extent. As the main structural style of vessels, the dynamic characteristic of stiffened plate directly affect the comfortableness, safety, invisibility and even fight performance. Hence, the research on dynamic characteristic and further dynamic optimization has great significance for the engineering. To avoid resonance, this paper optimizes the dynamic characteristic by changing the plate thickness, type of stiffens, and gap between stiffens based on adaptive evolutionary strategy.This paper firstly discusses the finite element model based on Mindlin bending theory and spatial beam theory. To calculate nature frequency, the subspace iteration method is brought in. Then some common optimization methods are introduced, from which adaptive evolutionary strategy method is chosen for the following optimization. With the finite element theory and optimization theory, corresponding computer program is written in FORTRAN. Lastly, the program is used for the engineering practice. Typical stiffened plate such as deck and wide closed mast are chosen for optimization. The subjective function is weight. Design variables include plate thickness, stiffen type and gaps between stiffens are discrete. The constraint conditions are comprised of frequency forbidden zones which are designed according to forces produced by blade and multiple frequency of propeller and engine frequency. According to the optimization result, the weight of deck and wide closed mast is reduced a lot compared with original design plans. New design plans avoid resonance and obtain better dynamic performance.