Research On Deformation Measurement Method Of Structure Part Based On Curvature Distributed Sensing

In mechanical processing,such as the base,guide rail and other large structural parts of heavy-duty CNC machine tools are prone to bending deformation after being loaded due to their own structural constraints,which results in changes in the linearity of both sides of the structural surface,and ultimately affects the processing accuracy of the parts.In the process,curvature as the most intuitive deformation parameter,realtime monitoring and timely analysis of structural health status,not only can advance the maintenance and adjustment of the equipment,but also the continuous processing can be ensured to improve production efficiency.Compared with other electrical sensors,fiber Bragg grating(FBG)plays an important role in health monitoring of large structural parts because of its unique material and good mechanical properties.However,FBG also has some shortcomings in practical applications,such as low sensitivity,cross-sensitivity of stress and temperature,which makes it difficult to improve these problems.In order to avoid these defects of FBG used alone and achieve the purpose of curvature measurement,this paper designed a FBG composite curvature sensor for curvature measurement of structural parts,and measured the surface curvature of beam-type structural parts in a distributed method.Finally,the surface curve of the base beam is reconstructed and validated.The specific content of this paper can be divided into composite curvature sensor design,structural surface curvature algorithm research and experimental verification.When designing FBG composite curvature sensor,firstly,the appropriate packaging model is selected according to FBG principle,and then compared with the traditional curvature measurement theory,a new distributed strain measurement method is proposed to measure the surface curvature of structural parts.This method can avoid the biggest difficulty of finding the position of the neutral layer of structural parts.At the same time,the temperature compensation theory is introduced,and the influence of the temperature on the FBG is measured by two FBGs.After the sensor structure model is established,the parameters of the sensor's elastomer are optimized by analyzing the strain transfer law.Finally,the dynamic characteristics,static characteristics and temperature characteristics of the sensor are analyzed by simulation and experiment to evaluate the performance.When researching the surface curvature algorithm of structural parts,the model of the surface plate is simplified by analyzing the influence factors of the deformation curvature of structural parts.Then the corresponding boundary relations are found according to different boundary constraints.The basic equation of structural parts is established in rectangular coordinate system and the surface deflection equation is derived.Finally,the recursive algorithm of strain curvature is obtained through the simulation analysis of structural deformation.In the final experiment process,the relevant parameters of the composite curvature sensor are determined firstly.After the elastomer is processed,the FBG package is unified and the related parameters of the composite sensor are calibrated.Then the curvature of the beam structure is monitored through a reasonable measurement scheme,and finally the performance of the composite sensor and the reconstruction method were evaluated by analyzing the experimental results.