Method And Application Of In-plane Strain Measurement Based On Speckle Digital Image Correlation

In recent years, digital image correlation method has become a striking modern opticalmeasuring method in the field of mechanics testing, and has been paved the way of extendedapplication. Since2007, In-plane strain measurement technology, which is based on digitalimage correlation (DIC) method, is widely used in various disciplines like mechanics ofmaterials, bio-mechanics, fracture mechanics, micro nanometer strain measurement, themacroscopic size of deformation measurement, performance testing of new materials and soon.Measurement based on the DIC method has many advantages like non-contact, full fieldmeasurements, wide application, high precision, simple collection of raw data, lowmeasurement requirements, and being easy to realize automation of the entire measuringsystem. With the advent of high-resolution microscope, it can be used to measure the micronand even nanoscale deformation, making its application more widely.Based on the domestic and international researches in this area, this thesis analyzes theinfluence of various experimental factors and external interferences on the calculationaccuracy of digital image correlation method in simulation and practical experiment in orderto obtain the reliable basis to improve the accuracy. Finally this method is applied to theflexible hinge’s displacement measuring and force sensing.This thesis emphasizes on the studying of measuring precision under different conditionsin simulation and practical experiments. First the relationships of ideally speckle and thecorrelation accuracy are analyzed using numerical simulations to generate speckle patterns.Then the method is validated in practical experiment based on the results of the simulationanalysis. The actual parameter value of the method to result in the best calculation accuracywas obtained. After analyzing the causes of various errors, some effective suggestions in themeasurement are proposed to eliminate or inhibit the errors. Finally, this method is applied tothe force measuring using the flexible hinges. The relationships of the hinge’s displacementand loading force could be obtained by using digital image correlation method, then the compliant structural vison-based force sensor can be build up. The experimental results showthat the vision-based force sensor is quite useful and has good accuracy.