Test MethodExperimental study on stress intensity factor for an axial crack in a PMMA cylindrical shell

In the paper, the stress intensity factor (SIF) for an axial crack in a polymethyl methacrylate (PMMA) cylindrical shell is studied using the optical caustic method. First, the optical analysis of transmitted caustics is proposed based on the geometry conditions of PMMA cylindrical shell. Then, the governing equations that are related to the caustic measurements and the elastic stress fields at an axial crack tip in the cylindrical shell are derived in terms of the SIF, material constant, shell radius and shell thickness. Finally, the characteristics of stress singularity for mode I edge crack in the PMMA cylindrical shell specimen with different crack length, shell thickness and shell radius are experimentally investigated using the caustic method under three-point-bend loading, also the SIF obtained from the caustic measurement shows a good agreement with finite element results.