Research On Materials Failure Model And Crashworthiness Application Of Offshore Wind Turbine Support Structure

Since the world oil crisis in the 1970s,wind energy has received widespread attention as a renewable and clean energy source.Compared with onshore wind power,the marine environment is complex and may be subjected to a variety of random loads such as wind,waves,currents,and sea ice.In addition,as the wind farm approaches the navigation channel,the probability of collision with the ship increases.The ship collision process is a dynamic response process in which the impacted object is subjected to a large impact load in a short time and has a series of highly complex nonlinear problems.In addition to the deformation damage of the impacted object and the impactor itself,this nonlinear process also includes the fluid movement around the ship,the rigid motion of the impactor and the impacted object.In this paper,the internal dynamics of the collision process between ship and offshore wind turbine is studied by finite element method,and the stress distribution,impact force-impact curve,energy conversion curve and other data of wind turbine in the impact process are obtained.By analyzing the calculated results,conclusions with certain value are acquired.In this paper,the Gurson-Tvergaard-Needleman damage model is used to describe the ductile fracture process of NVA low carbon steel,and the combination of Swift and Voce equations is used to describe the stress-strain relationship of the material before and after the necking occur.A new method for predicting the critical pore volume fraction f_c is proposed,which reduces the uncertainty of the GTN damage model parameter determination process and improves the accuracy of numerical simulation calculation.In addition,the mechanical properties and damage parameters of the model are determined by uniaxial tensile test.The accuracy of the proposed theory and selected parameters is verified by the side-structure collision test,which laid a theoretical foundation for this paper.Based on the material failure model,the research on the crashworthiness of offshore wind turbines is carried out.The finite element software LS-DYNA is used to simulate two collision scenarios,namely a140,000-ton shuttle tanker with different initial velocity lateral impact target wind turbine single pile structure,and a LNG ship bow forward impact the single pile structure of the offshore wind turbine.Through numerical simulation,the deformation damage characteristics of the ship and wind turbine,the relationships between the collision force and penetration,the energy conversion curves and the time history curves of the velocity or the penetration are obtained.In addition,the influence of the soil on the structure during the impact process is discussed.The concentrating mass method is used to study the interaction between soil and structure,that is,the soil around the underground part is regarded as the equivalent spring-mass-damping system,and the equivalent soil spring stiffness is calculated by the"m"method.According to the numerical simulation results,the influence of foundation soil on the impact process is obtained.