Nondestructive Testing Of Materials Based On Speckle Shearing Interferometry

Speckle interferometry has entered into the digital era in recent years,as a result,digital shearing speckle pattern interferometry(DSSPI)emerged.It is a non-destructive testing(NDT)technique,which is especially suitable for defect detection in thin plate materials,for its simple structure,low requirements for the measurement environment,no reference objects needed,non contact and other advantages.But to the best of our knowledge,we have not found the research of DSSPI system starts from theory aspect.In this thesis,the research starts from the finite element analysis software ANSYS,using MATLAB for the speckle image process,and the experiment system is established based on the theory research.The integrated DSSPI experiment system has been used for the flaw detection and analysis of aluminum plate and composite plate.The main content is as follows:1.MATLAB and finite element analysis software ANSYS were used to simulate the influence of PZT displacement error on defect detection in DSSPI.The simulation experiment referred to the performance of P-841.10 Pizeo actuator and E-709.SRG Pizeo controller manufactured by PI.Company.Through a series of simulations obtained at different defect size,defect depth,defect location and loading intensity,the displacement error of PZT's influence on defect detection were discussed.The conclusions can provide some useful guidance to the actual experiment.2.Design,build and integrate a set of digital speckle detection system based on Michelson interferometer.In this system,PZT is used as a phase shift device.The shear volume is decided bythe angles between the two mirrors.In the image acquisition part,a set of software is developed for simultaneous control of PZT displacement and CCD image acquisition.The software can accurately set the exposure and phase shift,shift in speckle mode and interferogram mode to observe the interference fringes in real time,which can facilitate the load applying.3.Apply the integrated DSSPI system for aluminum plate defect detection with variable size and depth.The simulation results reveals the feasibility that the holes from the back can simulate the internal hole flaws.In the contrast experiment with/ without flaws,defects in the experiment are “enlarged” by subtracting the unwrapping phase images with/without flaws.The method has high identification degree and can be used for the quality inspection of materials in mass production.In the experiments with variable defect size and depth,through analyzing the phase diagram and the two-dimensional phase curve,it is found that the effect of flaw depth on defect detection is larger than the flaw size.Even if the defect size is large enough,the defect can not be detected effectively if the defect depth is too large.This provides a basis for future material testing.4.Apply the integrated DSSPI system for defect detection of composite plates.The two test samples are resin and carbon fiber composite plate with force process.It is unknown that whether the two plates contain defects after shock.By analyzing the phase diagram of the wrapped phase diagram,one composite plate is found to have more than one defect.The other piece of composite plate,whose surface looks smooth,contains one defect.The test results show that the DSSPI system we built can be used for the composite material surface and shadow surface defect detection.In this paper,from the theory to the experimental research work,a lot of useful experiment data and research experience has been accumulated for the digital speckle shearing speckle interference system,which laid a good foundation for the future application.