Abstract
In this paper, we summarize the magnetic and electromagnetic non-destructive testing techniques and devices based on the magnetostrictive delay line principle. Three main techniques are presented. The first is based on surface crack and defect detection on ferromagnetic surfaces by measuring the corresponding magnetic anomaly distribution. The second is the measurement of eddy currents generated around the cracks and defects on a magnetic or non-magnetic metallic surface. The third technique is measuring the surface magnetic permeability of ferromagnetic substances. Finally, the methods of measuring the properties of magnetostrictive ribbons and cylinders used as MDLs, such as magnetoelastic performance and longitudinal sound velocity as well as their uniformity measurements are also discussed.