| As the leading direction of the future development of new energy industry,offshore wind power is the one of the important ways to build a green technology innovation system and promote the revolution of energy production and consumption.Furthermore abundant offshore wind energy sources provide favorable conditions for the large-scale development of wind power in China.In fact,the existing offshore wind farm project planning and construction has trends of development from near and far,from shallow to deep,from fixed to floating.Wind power technology is maturing,and the installed capacity of offshore wind power is growing rapidly,but the period of transportation,hoisting and maintenance of ships,some collisions with wind turbines occur frequently,resulting in damage or even collapse of offshore wind turbines;Dense shipping routes increase the risk of collision between ships and wind turbines,which greatly threatens the efficient and high-quality development of the industry.It can be seen that there are still many problems in the structural protection measures of offshore wind turbines that need further study.The traditional protective device mainly refers to the anti-collision design of marine engineering platform and lacks the equipment that can adapt to the inherent mechanical characteristics of offshore wind turbine foundation.Therefore,the paper based on the theory of nonlinear dynamics,combined with the internal and external dynamics method,using LS-DYNA to simulate the fender of tripod foundation of offshore wind turbine during ship collision,Designing the opening structure in the traditional fender to optimize the relevant single-hole design parameters and introduce the multi-porous Cartesian fractal feature with a multi-target genetic algorithm,further study of the power response of fenders of different structures and materials,and explore its optimal collision resistance and damage.The main works are as follows:1.Based on traditional ring solid protection design,this paper designs a single fender through putting the hollow hole in its internal form and makes the comparative analysis with and without opening fender into resistance and dynamic responses to explore the collision under the action of main factors influencing single-hole fender anti-collision performance and optimization method,respectively from two aspects of the relative angle and outer diameter of the hole.Firstly,the impact contact force,internal energy absorption,stress and strain and the acceleration of the tower top of the wind turbine are analyzed by finite element simulation under 19 relative angles of the hole.The results show that the comprehensive anti-collision protection effect is obvious when the relative angle of the hole is 20°.Secondly,based on setting the outer diameter of different holes of 0.5 m,0.6 m and 0.7 m,the paper contrastive analyzed the dynamic response and top acceleration of the fender.The results show that the protection device had better anti-collision characteristics when the outer diameter was 0.7 m.Finally,this paper further based on Kriging approximation model and the multi-objective genetic optimization algorithm,conducted the minimum collision force and maximum internal energy absorption index design optimization of single-hole fender,to obtain the optimal parameter configuration,structure and properties.The results show that the inner hole diameter size is 0.658 m,relative angle is 0.22° fender collision resistance ability of the optimal.2.The paper is based on the optimized design of single hole,and further introduce into porous ring structure of fractal geometry with the existing design fractal fender,through constructing descartes circle for fractal structure to realize fractal fender by tangent circle theorem and under the same size and same quality of different fractal orders of collision resistance were analyzed.Firstly,compared with the fender of different orders in volume,the contact force reduction ratio of the first-order fractal structure is 3.93% at most;In the condition of the same mass,the first-order fractal structure weakens the collision force by 12.94%,and the internal energy and stress-strain capacity are better than the second-order and third-order structures.Secondly,the first-order fractal geometry is especially effective in improving the anti-collision performance of fenders,while the second-order fractal is poor in contact force,internal energy and stress and strain;The interaction between elastic and plastic deformation of fractal holes is the main reason for the instability of impact resistance under different orders.Finally,the increase of the mass of the fender has positive significance for improving the anti-collision performance,but the response effect of the fractal structure to the acceleration of the top of the tower is significantly weaker than that of the solid structure when it meets the acceleration standard of the wind turbine nacelle.3.Based on the above analysis,it can be seen that the resistance of fractal structural protection device is good,so the impact of collision resistance is further explored in different material structural models..The paper make some researches with three kind of constitutive model Aluminum foam,Mooney-Rivlin and Ogden model in fender,by using the method of collision kinematics analytic and numerical and transformation of energy dissipation to do an analysis of the collision speed and deep,contact force and the stress strain relationship.Firsly,the numerical analysis method combined with collision energy dissipation experience formula is suitable for evaluating protective device of energy dissipation;the aluminum foam was obviously deformed during the collision process,and the plastic deformation area was larger than that of Mooney-Rivlin and Ogden,and its energy absorption characteristics were enhanced to a certain extent.Secondly,In the actual collision process,Mooney-Rivlin and Ogden are both rubber materials,and their internal energy dissipation rate is higher than that of Aluminum foam,but their super elastic effect causes the energy to quickly spread to the tower foundation and the external steel shell,and part of the ship collision force is transferred to the tower foundation.Finally,the elastoplastic change process of the outer steel shell and the core material of the protective device was analyzed,it can be known that the plastic deformation energy absorption invariance has an effect on the collision energy absorption,and the anti-collision protection ability of aluminum foam fender is the best. |
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