Volume 18, Issue 6 (November 1990)
Imaging Short Fatigue Cracks with the Gel Electrode
A new non-destructive inspection tool is described for tracking and recording crack growth in test coupons and structural components. The current state of development of this device, the gel electrode, is reviewed. This hand-held inspection probe can image surface fatigue cracks in iron, titanium, magnesium, and aluminum alloys. Fatigue cracks only ∼10−2 mm long can be detected, a sensitivity which surpasses that of commercially available techniques by a factor of 100. Images of short fatigue cracks are shown for each of the above alloy systems. The examples are selected to illustrate the good visibility and repeatability of the images, as is required to monitor crack growth. Included are quantitative measurements of the growth kinetics of a short (10−1 to 1 mm) crack in a prototype component.