In this thesis, an automated system with high precision has been developed to perform fatigue crack growth tests under constant effective stress intensity factor range $ΔK_{eff}$. The system has been developed to measure in real time the crack length by using the unloading elastic compliance method and the crack opening load by using the compliance offset method or unloading compliance offset method. The performance of the automated system developed in this study was verified through a series of fatigue crack growth tests under constant amplitude loading.
The system consists of two personal computers, an analog electrical subtraction circuit, and the application software used to integrate the whole system.
In this thesis, constant $ΔK_{eff}$ crack growth tests on a M(T) specimen of 2024-T351 aluminum alloy are performed and it is observed that fatigue crack growth rates can be well expressed in terms of the effective stress intensity factor range $ΔK_{eff}$.
Besides, the automated system developed in this study can be efficiently applied for automation of various fatigue crack growth tests including short crack growth studies.
