Study On Static Characteristic Of A Wind Turbine Blade With Digital Image Correlation Method

Wind turbine blade is the most important,expensive and easily damaged part of wind turbine.It is extremely critical to ensure that wind turbine blades have good working performance,and very urgent and necessary to carry out timely wind turbine blade structural characteristic testing research including the one under static loads.At present,domestic wind turbine blade static property testing researchs are not complete enough,most of which are under uniaxial static loads,and lack of biaxial load loads.The measured values is likely to be less than the design values in the blade practical work condition.In addition,domestic wind turbine blade static tests mainly use strain sensors or displacement sensors,a contact measurement method.Sensor installation layout is complex,and cannot be used multiple times,which is not conducive to compose the whole full-size structural testing procedure.And testing result accuracy is not high.Especially,these sensors can only measure wind turbine blade local structural deformations,not full-field 3D static properties.And wind turbine blade crucial structural response informations(such as extreme values)are not available.There is currently a lack of wind turbine blade biaxial static properties with finite element analysis.Most researchers use solid or entity units modeling wind turbine blade,which not only makes model analysis complex,but also consumes too much time,and needs a lot of tedious corrections.Wind turbine blade material properties are difficult to obtain exactly,which difficultly ensure model calculation accuracy.In order to solve these problems or deficiencies,the thesis has done wind turbine blade static characteristic experimental research with digital image correlation technique to find out wind turbine blade full-field 3D deformations induced by biaxial(flapwise direction and edgewise direction)static loads.Then software ANSYS was used to analysis wind turbine blade static characteristics under biaxial loading,in order to explore the feasibility of finite element analysis method applied to wind turbine blade static characteristic analysis.The wind turbine blade static characteristics anlysis has been carried out.At first,the thesis has tested the full-scale 3D deformations of a wind turbine blade under single-/dual-axis static loads with digital image correlation technique.This technique has non-contact,full-field,three-dimension,few test environmental requirements,testing process simple to learn,high precision,and other advantages,and is a reliable engineeringmeasurement technique.Domestic digital image correlation technique still not complete applied to characteristic testing of wind turbine blades started lately.3D deformation regulations and the mechanical behaviors of wind turbine blade under uniaxial/biaxial loads on the basis of experimental phenomena and data anlysis,which of 3D deformations of wind turbine blade induced by biaxial loads are the thesis breakthrough point,have been obtained,exploring a technique suitable for wind turbine blade non-contact full-field 3D deformation testing more applicable to practical engineering researchs in order to solve the disadvantages of traditional measurement methods in the tangent and discrete ways,and then further finding out the deformation regulations of wind turbine blade under biaxial loading,and comparing deformations induced by single-with dual-axis static loads to observe whether the differences between the two is apparent,and examine the necessity of biaxial static loading test and verify the feasibility of digital image correlation technique applied to wind turbine blade property testing.The research will play an important role in safety monitoring,design and manufacture,testing and certification of wind turbine blades.The finite element analysis for wind turbine blade static characteristics has been carried out.Firstly,for modeling blade in the method of solid model input,which can greatly reduce time-consuming,a suitable wind turbine blade airfoil was selected in accordance with the structural shape of the blade;the selected blade airfoil data were extracted from the software Profili;geometric transformations of 2D coordinates of points on all foliosines or splines along the wind turbine blade spanwise direction were made in order to obtain the 3D coordinates of these points;all 3D coordinates of each foliosine were input into the software Pro/E for the establishment of the solid model of the wind turbine blade;then the solid model was imported into the finite element simulation software ANSYS to create the blade finite element model.Material property data used in this thesis result from the actual sample testing in order to ensure the reliability of its accuracy.Then the finite element analysis for the static properties of the finite element model has been carried out to acquire the full-scale 3D deformations of the blade under biaxial loads,which are similar to actual occured stress distributions around the blade cross sections in the wind turbine blade operation process.Finally,the 3D deformation data by finite element analysys with by experimental testing have been compared to verify the applied feasibility of finite element analysis in the blade static testing,and acquire a reasonable and effective finite element model.The researchs in this thesis can provide technical support for finite element model amendment and modal and fatigue finite element analysis of wind turbine blades in the future.