The dependence of acoustic emission behavior on prior fatigue loading history

Fatigue cracks are a major concern for aging metallic structures, as they can cause unexpected catastrophic failure. They often occur on hidden surfaces, e.g., under paint and rust or the interface between two structural layers, which makes visual detection difficult. Acoustic Emission (AE) is passive nondestructive evaluation (NDE) method that measures initiation progression of defects when structure continuously monitored. While using this method, has been successfully applied to monolithic composite fatigue life related cumulative AE count. However, if after crack initiated, relationship count may not be applicable. In paper, dependence behavior prior loading history studied modified compact tension specimens. The count, correlation plots, waveform characteristics shown dependent conditions in addition coupling state. Relative behaviors sensors trends illustrated by being independent discontinuities.