A Dual-Imaging Framework for Simultaneous Measurements of Short and Long Crack Initiation and Propagation in Metallic Materials

Abstract This paper presents a dual-imaging methodology to investigate fatigue crack initiation & propagation along the lateral and transverse directions in Al7075 flat specimens having a one-sided V-notch. The framework consists of a confocal and a digital microscope. The confocal microscope can detect the short crack initiation at a length-scale of 3 micron while the digital microscope has the capability of reliably measuring cracks at a scale of 0.5 millimeter. The apparatus provides a unique advantage of detecting short crack initiation due to the presence of surface defects without any significant restrictions on maximum specimen size and maximum loading or frequency.