Automated real-time measurements of fatigue crack length and crack opening load using unloading elastic compliance method

Abstract

A system has been developed to measure crack length and crack opening load automatically in real time without changing any testing condition, by using an unloading elastic compliance method. The crack opening load is determined by a unique method using differential displacement signal data. The performance of the developed system was verified through constant-amplitude crack growth testing. The system is a very simple system, composed of a personal computer, an analogue electrical subtraction circuit, a stepping motor, a stepping motor driver, a PIO board and applications software. This system is expected to be utilized for measurements of crack length and crack opening load under random loading, short crack growth studies and effective stress intensity factor range Delta K-eff-controlled tests. (C) 1997 Elsevier Science Ltd.