Crack growth detection and monitoring using broadband acoustic emission techniques

This paper will provide an overview of an approach that will autonomously detect and monitor crack growth in aircraft structure. Present day computer technologies make it possible to put a small computer and sensor system on an aircraft to monitor structural health at locations that are difficult and costly to inspect through more traditional techniques. The health of the monitored locations can be determined by the end user through normal operations (Standard Flight Data Recorder download), thereby providing a significant reduction in scheduled maintenance requirements. All types of aircraft suffer from structural cracking. Even though the location of the crack can often he predicted, the inspections required are costly, often requiring significant structural disassembly. Sometimes there is an unacceptable level of uncertainty in NDI results, leading to more frequent inspections and even greater costs due to prematurely replaced structure. Broadband Acoustic Emission (BAE) systems have demonstrated the capability to detect crack growth in structure. Such a system can autonomously monitor aircraft structure during operation and provide information necessary to detect crack growth, determine the source location and monitor crack growth without disassembly. This paper will present an overview of the BAE approach to crack monitoring. Results from proof-of-concept testing will he included with comparisons to BAE waveform analysis results. Conclusions, system requirements and a preliminary design of the electronics and software necessary for an aircraft crack monitoring flight, system will also be presented.