Study On The Invisible Light Imaging Based Digital Image Correlation Method

As a newly arisen deformation strain methodology,the digital image correlation method has been efficiently used in the research of material deformation behavior and engineering application because of its advantages such as full-field,non-contact,real-time and high precision.In general,the digital image correlation method is based on the visible-light imaging.With the progress of modern image sensors and the emergence of advanced experimental technology,many researchers have found that the invisible light imaging based digital image correlationmethod can provide richer and more in-depth information of material deformation behavior.When the digital image correlation method is adopted to correlate the infrared thermal images,we can obtain the strain field and thermal field simultaneously.Besides,when the digital image correlation method is used to correlate the images obtained by various microscopic imaging equipment,the deformation behavior and microstructure evolution of the material can be acquired at the micro-scale.Based on these points,this paper attempts to make some new progress in the application of the digital image correlation method and the corresponding works are as followed:(1)A new simultaneous assessment of the lagrangian strain and temperature fields by improved strategy is proposed.The methodology uses the infrared thermal image as the object of image registration,and only by a single infrared camera,the Lagrangian strain field and temperature field of the material can be obtained at the same time.The performance of the developed methodology is verified through a tensile test performed on a notched specimen,and the results show that it can precisely measure the strain field and temperature variation of a material point on the specimen surface.(2)The micro-scale deformation measurement technology based on the scanning electron microscopy images is studied.By this method,the image obtained by the scanning electron microscopy is used to be correlated by digital image correlation method,therefore,the displacement and strain fields can be acquired at the grain scale.The heterogeneous deformation characteristics of 316L stainless steel are observed in an in-situ manner during the uniaxial tensile test.