Visualization method for stress-field evolution during rapid crack propagation using 3D printing and photoelastic testing techniques.

Quantitative visualization and characterization of stress-field evolution during fracture rapid growth is critical for understanding the mechanisms that govern the deformation and failure of solids in various engineering applications. However, the direct capture and accurate characterization of a rapidly-changing stress field during crack propagation remains a challenge. We report an experimental method to quantitatively visualize and characterize rapid evolution of the stress-field during crack propagation in a transparent disc model containing a penetrating fusiform crack. Three-dimensional (3D) printing technology and a stress-sensitive photopolymer resin were adopted to produce the disc model and to alleviate the residual processing stress that usually blurs the dynamic stress field due to overlap. A photoelastic testing system that synchronized a high-speed digital camera and a pulsed laser with a nanosecond full width at half maximum (FWHM) was used to capture the rapid evolution of the stress field in the vicinity of crack tips. The results show that the proposed method is suitable to directly visualize and quantitatively characterize the stress-field evolution during crack rapid propagation. It is proved that the crack propagation velocity is strongly governed by the stress field around the crack tips.