Optimization of a Stiffener to Stop a Propagating Crack

Abstract

The purpose of this paper is to demonstrate an application of dynamic photoelasticity to crack-arrestor effects on a brittle fracture propagation in order to extend the life of a precracked plate.

The experimental work is achieved with the help of a high-speed Cranz-Schardin camera which provides 24 pictures of the dynamic event. For each of these, the stress-intensity factor is determined with a method based on the finite series expansion of the components of the stress tensor. This approach which offers the possibility to process data far from the crack-tip, avoids the imprecisions inherent to measurements made in the near crack-tip zone. The analysis of data, with the use of a least squares minimization procedure, takes into account the general configuration of the isochromatic patterns.

The tested specimens are single edge notched plates in araldite B. The stiffeners which act to reduce the crack opening displacement, are separate from the structure along the path of crack propagation and bonded to it at their ends. The effectiveness of these crack-arrestors is discussed in terms of the variations of the stress-intensity factor and in terms of significant parameters (crack-arrestor dimensions, crack propagation speed).