Abstract
This paper presents how the frequency characteristics of AE sensors and threshold affect acoustic emission measurement. Static and fatigue tests of FRP reinforced by plain woven glass fabric were conducted. Three different types of AE sensors having different sensitivities with respect to frequency were used simultaneously to distinguish the difference of observed AE data. Following results are obtained from the test. 1. Threshold of AE system strongly affects observed AE data. Namely, observed AE under a certain threshold condition is different from that under another condition. This threshold dependence is due to the dead time and resolution time of AE measuring system. Total AE events and rate do not always increase as the threshold becomes lower. AE observation at a different threshold condition might derive different conclusions. 2. The frequency characteristics of AE sensors strongly affect the observed AE data as well as the threshold under a static loading while a rough tendency of total AE count record agrees with each other under a fatigue loading. The above results attract a strong attention that AE sensors must be carefully selected according to material AE nature taking the machine characteristics (i.e., dead time and so on) into consideration. It is quite difficult to compare the AE data obtained at a certain condition with the data obtained using different AE sensors or different condition.
