| As an important support part of offshore wind turbine,the tower tube not only bears the effect of external load,but also suffers the influence of Marine environment corrosion.The two are coupled to each other,and the tower tube structure is more vulnerable to damage.In order to better grasp the corrosion law of the tower material and the change law of mechanical properties in the ocean environment,to provide a theoretical basis for the wind turbine tower structure optimization design.this paper uses ANSYS simulation software to carry out the load analysis of the tower.Using salt spray corrosion box and WDML-5 microcomputer controlled stress corrosion machine,corrosion loss calculation,XRD analysis,SEM observation,electrochemical test and other methods were used to analyze the corrosion law and mechanical properties of tower drum materials.The main contents and results are as follows:(1)The dry and wet acid salt spray test was used to simulate the coastal atmospheric environment and study the influence of Marine environment on the corrosion behavior of tower cylinder material Q345D for 24h,48h,72h,96h,168h,240h,360h and 480h.The results show that the corrosion weight loss of Q345D steel presents an increasing trend with the increase of corrosion period.Within 168h before corrosion,the corrosion weight loss was 8.701mg·cm-2,16.595mg·cm-2,28.431mg·cm-2,44.536mg·cm-2,respectively,and the corrosion rate was faster.When the corrosion time is 168h to 240h,the corrosion weight loss is 106.105mg·cm-2and148.736mg·cm-2respectively,and the corrosion rate slows down.After 360h corrosion,the weight loss was 363.734mg·cm-2and 576.343mg·cm-2respectively,and the corrosion rate began to increase slowly.(2)Based on DTU research on 10MW reference wind turbine,the stress condition of MW large offshore wind turbine tower drum during operation is studied.The basic material of DTU 10MW wind turbine S355 steel is defined as Q345D steel which is commonly used in domestic wind turbine tower drum by ANSYS simulation software,and the stress condition of the tower drum is analyzed under three working conditions.The results show that;Under the rated condition,the maximum stress and maximum displacement of the tower cylinder under the influence of load are111.65MPa and 123.27mm respectively.Under the cutting condition,the maximum stress and maximum displacement under the influence of load are 136.22MPa and750.75mm respectively.Under the ultimate condition,the maximum stress and maximum displacement under the influence of load are 29.21MPa and 94.11mm respectively.Therefore,under the cutting condition,the tower cylinder is most affected,and the maximum stress is less than the allowable stress of 313.64MPa and the maximum displacement is less than the allowable maximum deformation of 1.541m,which meets the requirements of strength check.According to the modal analysis,the first ten frequencies of the cylinder are not between 0.1-0.16Hz and 0.3-0.48Hz of the resonant frequencies of the impeller,and the first two frequencies are within the range of 0.16-0.3Hz,so they belong to the flexible tower.(3)Taking strain rate,temperature and salt spray environmental conditions as test factors and stress corrosion sensitivity index,elongation,reduction of section and fracture time as evaluation indexes,a three-factor and three-level orthogonal test was designed under the coupling action of corrosion and load to study the stress corrosion law of tower cylinder materials in Marine environment.The results show that a large number of cleavage surfaces appear at the rate of 3×10-7s-1,temperature of 50?and interval spray test,and the material has obvious stress corrosion sensitivity.At this time,the yield point and tensile strength of the material reach the minimum,which are 345.735MPa and 482.2MPa respectively.According to the coupling test of corrosion and load,a single tensile test after corrosion was designed to study the influence of Marine environment on the mechanical properties of the tower cylinder material.The results showed that:When the test condition is 3×10-7s-1and continuous spraying,the material property degradation of the tower cylinder is the fastest.In the corrosion and load coupling test,the test condition is 3×10-7s-1and the interval spraying,the material property degradation is the fastest.At this time,the lower yield point and tensile strength of the material reach the minimum,which are325.745MPa and 457.82MPa respectively.Compared with the second test,the tensile test after single corrosion has more serious effect on the material properties. |
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