Investigating the Effects of Locks on the Fracture Force and Stress Intensity Using Experimental Photoelasticity.

Most of the engineering materials are faced with fracture phenomenon that needs to be controlled. There are several methods for controlling crack growth such as hole technique, using locks etc. In order to predict crack growth, stress intensity factor can be conducted as a useful tool. In this paper, the photoelasticity method is conducted as an experimental stress analysis tool in order to calculate the stress intensity factor (SIF). The investigations were conducted to find the effects of holes and locks on the fracture resistance and the SIF. This research is specially focused on the crack stitch as a unique technique to control crack propagation. In this technique, holes of locks are drilled close to each other in rows perpendicular to the crack then keys are inserted into the holes. Three batches including six different edge crack samples of polymethyl methacrylate rectangular plates were used for fracture tests. In the present study, the effects of locks in various geometries were investigated on the SIF. The results were obtained using a polariscope and the tensile load was applied to the specimens on the mode fracture (I) strength; then, the fracture forces were measured. The results showed that the samples with lock and hole have more fracture strength and thus their SIF decreases in comparison with the lock-less or hole-less samples. [ABSTRACT FROM AUTHOR]