Digital image correlation of brittle materials based on ultrashort pulse laser imaging

Abstract

Based on the extremely narrow half-height width (FWHM) characteristics of ultrashort pulsed lasers, a DIC imaging technique that can realize picosecond time resolution is proposed by combining the traditional digital image correlation (DIC) technique with it. This method can solve the problems of blurring and dragging of scattering images caused by the sudden crack initiation and fast crack expansion in the fracture process of brittle materials. The crack opening displacement (COD) and the full-field displacement of the sample at the instant of cracking of brittle materials can also be obtained. In addition, the error in spatial resolution of the traditional DIC technique using a continuous light source can be greatly reduced by using this method. In this paper, this method is used to record the tip displacement field of a tuff sample containing a type I prefabricated crack under semicircular disk three-point bending (SCB) experimental conditions. The experimental results show that the recording of crack extension behavior on the order of picoseconds can be achieved using this method, and the key parameters of fracture of brittle materials are calculated more accurately.