Research On The Measurement Of Out-of-Plane Deformation For Curved Objects With Digital Speckle Pattern Interferometry

The digital speckle pattern interferometry(DSPI)has proven to be a powerful tool widely used for the measurement of displacement/deformation,material properties,object shape,even temperature.Especially,as an interferometry-based technology,DSPI is widely recognized as a full-field,non-contact type deformation measurement technique with an accuracy of sub-micrometer.In the field of precision component processing and material stress-strain research,it is very important for the measurement of out-of-plane deformation,especially for the curved objects.DSPI technology has been widely applied in the measurements for planar objects.However,for objects with curved surfaces,it is difficult for DSPI to provide correct deformation measurement.This is because the sensitivity vector of deformation varies with the shape of the curved objects.In order to obtain the correct deformation of a curved surface,the shape should be known and included in the measurement.In this wok,we propose a simple DSPI technique for both shape and fast out-of-plane deformation measurement for curved objects undergoing out-of-plane deformations.The proposed DSPI technique adopts only one single DSPI setup and one single beam illumination.Therefore,both the setup configuration and operation is simple.Fourier transform method is utilized to evaluate the phase from interferograms in the proposed scheme,promoting fast performance further.In this paper,an error compensation method is proposed to correct the error associated with the spherical wave illumination.The experimental results prove the effectiveness of the method.In the experimental platform,we finished the system parameters such as beam deflection angle and incident light irradiation distance.According to the designed system parameters,we built an engineering prototype.A cylinder surface with arch height of 9 mm was measured by engineering prototype and the error of repeatability measurement was evaluated.Finally,a set of digital speckle interferometry system for measuring vibration and deformation is designed based on the static measurement optical path.The vibration modal analysis of standard thin-walled cylinder sample is completed by comsol.The design of thin-walled cylinder and excitation system was completed based on the result of finite element analysis.