The U.S. Naval Research Laboratory‘s optical sciences division has detected acoustic emissions from cracks in riveted lap joints with a new fiber laser-acoustic emission sensor during a demonstration for that technology.
Researchers inserted distributed feedback fiber laser acoustic emission sensors in riveted aluminum lap joints and measured acoustic emission for two hours over a bandwidth of 0.5 megahertz during the test, NRL said Wednesday.
The test also demonstrated that the sensors could fix low-level acoustic events generated by the so-called fretting from the riveted joint.
“Our research team has demonstrated the ability of this fiber laser technology to detect acoustic emission at ultrasonic frequencies from cracks generated in a simulated fatigue environment,” said Geoffrey Cranch, a research physicist for NRL’s optical sciences division.
“An automated, in-situ structural health monitoring system, capable of monitoring key structural parameters such as temperature, strain, impacts and cracks, and capable of reliably detecting damage well before reaching a critical level is needed to increase safety and readiness while lowering operational cost of Navy platforms.”
Based on the demonstration, the fiber laser sensor could also measure compromising impacts and operate with current fiber optic strain and temperature sensing systems to help fulfill operational safety requirements for an SHM system.