In situ study of nano-cracking in multilayered magnetic tapes under monotonic and fatigue loading using an AFM.

Atomic force microscopy (AFM) techniques are increasingly used for tribological studies of engineering surfaces on micro- to nano-scales. In situ surface characterization of local deformation of materials and thin coatings helps to develop a better understanding of failure mechanisms. In this study, an AFM-based technique has been developed for in situ monitoring of nano-crack formation and progression under fatigue loading. To conduct monotonic and fatigue loading tests, a tensile stage is used to mount samples on the AFM base and the same area on the sample surface is scanned intermittently during the loading process. Crack growth under monotonic and fatigue loading for multilayered magnetic tapes is studied and a crack growth mechanism for metallic magnetic tapes under monotonic loading is proposed. Fatigue strength for the metallic magnetic tapes is measured and a mathematical model based on theory of elasticity for fatigue life prediction is developed.