| Recently,the demand for materials performance has continued to increase,with the rapid upgrade of technologies in the complex applications in the fields of aerospace and equipment.The deformation measurement methods to investigate the mechanical properties of various materials and components with anisotropic properties or special structures,have been attracting increased attention.While the traditional contact measurement method couldn’t withstand the severe hightemperature environment,and measurement components might undergo thermal expansion during high-temperature measurement.The vision-based non-contact measurement methods,such as digital image correlation(DIC)and structured light metrology,has been widely used in complex applications and special scenes with the help of the advantages of non-contact,full-field measurement,high sensitivity,and wide application range.But various complex application and special scenarios have put forward higher requirements and more severe challenges to the noncontact deformation measurement methods.As regards the measurement requirements,the characteristics of the test objects,the dissertation are focusing on the topics including:investigation of DIC method and structured light method in large deformation measurement,high-temperature objects deformation measurement,and wind tunnel test as the main line,analyzing the problems such as the the image matching algorithm,the noise reduction methods,and the development of the vision-based measurement equipments.The solutions proposed to solve the existing problems,including:(1)For large deformation measurement application,a new dots pattern with randomly distributed dots and fixed size markers is proposed and a new Topologybased Matching Correlation(TMC)algorithm is presented.Experiments on simulated images and NBR tensile test under 260%length change were carried out.The results showed that the proposed method could avoid the problem of accumulative errors of the incremental DIC method.(2)For over-exposure imaging measurement application,a high dynamic range laser speckle high-temperature DIC method for measurements facing light source variation or exposure problems is proposed.The method has the ability to effectively eliminate the light source variation or exposure problems,and obtain high dynamic range laser speckle deformation images.Experiments of the 750℃superalloy material uniaxial tensile creep test were carried out.Compared with the original images,the quality of the HDR speckle images is significantly improved.The full-field deformation map is achieved.(3)For air disturbance measurement application,an in-situ non-contact measurement system for nozzle throat deformation in high-temperature gas heating via laser speckle DIC with wavelet smoothing of displacement field is proposed.Experiments on gas heating test of a nozzle sample made of carbon fiber high silica phenolic resin composites were carried out and the maximum sample temperature reached 1100℃.Experimental results show that compared with the air blade method,the proposed method has better denoising performance and can provide smoother displacement field for deformation evaluation in high-temperature environment.(4)For wind-tunnel high-temperature object in-situ 3D shape measurement application,an in-situ 3D shape observation and measurement method with singlecamera-DMD-projector system using structured laser light with adaptive speckle filtering is proposed.Experiments of in-situ 3D shape measurement of a blunt-head cylinder object were carried out in a 1MW plasma wind tunnel at the China Aerodynamics Research and Development Center(CARDC,China).The measured maximum temperature of the sample reached 1950℃.Diameter reconstruction error was 0.85%(0.17/20.03mm)compared with the average of measured results before and after experiments by a vernier caliper.In this dissertation,the proposed image matching algorithm,the noise reduction methods,and the development of the vision-based measurement equipments could also be employed to some advanced manufacturing applications such as high-temperature forging shape measurement. |
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