Research On Defect Nondestructive Testing System Based On Sheargraphy

Shearography is an optical nondestructive testing method with the advantages of full field,non-contact,high precision and high sensitivity.It can directly measure the first derivative of the deformation or displacement of the measured object along the shear direction.It has been widely used in the non-destructive testing of delamination,debonding,cracking and other defects of materials used in aerospace,precision manufacturing and other industries.At present,in some special application fields,such as detection the special materials(mirror or smooth surface objects),multi-directional detection simultaneously and so on,further research and analysis are still needed.In this paper,the nondestructive testing system in these special fields is studied.The main research work includes the following contents:(1)The measurement principle and application fields of shearography are introduced,and the development status at home and abroad is studied and analyzed.The following phase processing methods are introduced,and the advantages,disadvantages and applicability of different phase extraction methods are compared.(2)The parameters of shearography based on spatial carrier are studied.The influence of the parameters,such as the shape of apertures,the relationship between aperture size and shearing amount,on the measurement is analyzed and verified by experiments.(3)Aiming at the problem that shearography can’t directly measure the object with the mirror surface,combined with the existing solutions,a measurement method of secondary scattering imaging based on the spatial carrier principle is proposed.The principle derivation and optical path optimization are explored to realize the dynamic and rapid detection of the defect of the object with the mirror surface.(4)In view of the problem that the single direction shearography system will result in the missing detection of directional defects,a multi-directional shearography system based on the spatial carrier principle is proposed.The system realizes the single multidirectional detection of the tested object,thus avoiding the missing detection of directional defects.