A New Crack Growth Test System and Its Application to K-Controlled Fatigue Crack Growth Tests at Elevated Temperatures

Abstract

A new automated crack growth test system with the aid of an image processing technique was developed. This system consists of a mechanical stage with a CCD camera, an image processing unit and a personal computer. A CCD camera with an image guide scope was used to monitor the microscopic image of a crack tip. This image around the crack tip was processed and analyzed by using a template-scanning technique to make a real-time recognition of the crack tip. The crack length was determined from the detected crack tip location. The crack growth rate and stress intensity factor were also calculated and recorded on a magnetic medium. This system was widely applicable to various fracture mechanics tests with no limitations in sample shape, environment and so on. Several K-controlled fatigue crack growth tests both at room and elevated temperatures were conducted to demonstrate the reliability, performance and precision of this system.