Design Of Dynamic Defect Detection System For Laser Shearing Speckle Interferometry

Digital laser shearing speckle interferometry is a branch of digital speckle interferometry technology,which can directly measure the deformation gradient,so as to realize the real-time and dynamic defect detection of industrial product structural specimens.In particular,composite materials are widely used in aviation,aerospace,weapons,ships and other military structural components,and there are different types of defects in composite materials,such as porosity,fluidity,cracking,delamination and debonding,which will reduce the service life of equipment or endanger the use of safety,affecting the performance of equipment.The current analysis on composite material defects exist multiple detection methods,but a lot of deficiencies,based on the traditional method of composite material defects detected detected damage type single,low defect detection rate,slow detection speed lead to can't real-time analysis defect status,unable to determine the dynamic change analysis of defects and other issues,put forward a kind of contact of the whole,high sensitivity,fast,and test the laser shearing speckle interference optical measurement method,and set up the corresponding optical measurement system,realize the defect of real-time and dynamic testing.The main research work of this paper has the following points:1.In this paper,the basic theory of laser shearing speckle interferometry for the measurement of composite material defects is presented,and the basic principle and application range of time and space phase-shift techniques are analyzed,which provides a theoretical basis for the subsequent phase extraction process.The influence of the relative parameters in the spatial phase shift method on the experimental results is explored,and the measures to improve the quality of the phase diagram are proposed,and the value of the influence parameters is verified by experiments.2.According to the mode of introducing carrier frequency,the principle of shearing speckle interference with single carrier frequency and multiple carrier frequency is described respectively.The test device was improved into a cage structure system,and the speckle pattern was collected and processed in real time by the laser speckle interferometry software,and the measured objects were verified by experiments.In order to improve the contrast and unwrapping accuracy of the fringe in the phase image,an GRA-NLM algorithm based on grey correlation analysis and a fast Fourier cosine transform unwrapping algorithm were proposed to prevent excessive useless noise from the phase image wrapping and image inversion in the later phase diagram.3.Thermal loading and vacuum loading were used to detect the defects of composite materials,and the results of the two loading methods were analyzed.The maximum detection rate of defects was 87%,which realized the full field of view and dynamic measurement of composite materials.In order to solve the problem of missing detection of special defects in defect interference system,a two-way testing method with two carriers was proposed.In order to observe the dynamic change process of the defect obviously,the original speckle pattern obtained from the test was filtered and then processed with pseudo color,so that the defect location and the micron scale shape variable could be accurately measured.