Structural Condition Monitoring of Helicopter Components

Abstract

This paper will review the ongoing Structural Health Monitoring (SHM) work being done for the Aviation & Missile Research, Development, & Engineering Center (AMRDEC) Diagnostics and Prognostics Laboratory (DPL) located at the Redstone Arsenal in Huntsville, AL. The focus of DPL activities is to examine various techniques to enhance the diagnostic capability of Army aviation, ground, and missile systems. An area the DPL is involved in is structural health monitoring of critical structures of our aviation fleet. This work involves detecting and, in some cases, localizing damage on various air and rotor craft parts. Many of these applications are currently displayed as demonstrations in the DPL. Two laboratory demonstrations were developed to demonstrate the importance of optimizing sensor locations by comparing the results of a group of sensors that have been optimized to a group of twice as many sensors that had been heuristically placed. This is demonstrated on two very different parts; a Black Hawk drag beam tested in free-free boundary conditions and a Kiowa Warrior roof strap tested with many complex boundary conditions. The drag beam demonstration detects a simulated mass removal such as pitting or corrosion where as the roof strap demonstration detects simulated cracking and bolt loosening. Another demonstration involves detecting damage such as pitting and corrosion on an Apache tail rotor blade. Although the demonstration uses external sensors and actuators, the end goal would be to have the sensors and actuators integrated into the part during manufacturing. The correlation between the damage metric and corrosion are demonstrated on steel plates subjected to a salt fog chamber.