BALRUE
- Paper number
IAC-08.C2.5.3
- Author
Mr. Jose Luis Buendia, Universidad Politécnica de Madrid, Spain
- Year
2008
- Abstract
Modern aircraft structures are composed of metallic and composite elements. These materials can experience damage during the service life of the aircraft. It is vital that the condition of the structural components is known. There are various methods of monitoring the structure. These can be labour intensive methods of manual inspection, that can involve long periods when the aircraft is taken out of service. The other end of the spectrum is Structural Health Monitoring where the structure is constantly monitored by an onboard system. This will help aircraft maintenance effort and weight saving. Acoustic Emission was the selected technology because its characteristics are drastically different than any other phenomena occurring in the aircraft, such as engine noise or aerodynamic noise. Additionally, the acoustic emission events are only generated when a structural damage has occurred. This alone permits avoiding false alarm and does therefore not require previous knowledge of damage history. The BALRUE system is one of the SHM systems. It works on the principal that when damage occurs in structures it emits high frequency sound waves called Acoustic Emissions (AE). These emissions are detected by piezoelectric sensors that are permanently attached to the aircraft structure. The sensors are attached to a BALRUE system box (DAU, Data Acquisition Unit) that stores the data detected by the sensors. The BALRUE DAU is capable of compressing the data that it records, and so can monitor a structure for a number of months with no user interaction with the system required. The data is downloaded from the BALRUE DAU to a PC. The data is analyzed by the BALRUE Data Analysis software. This is an intuitive piece of software that allows the user to see the results in various formats to allow full understanding of the location and severity of any damage. One of the most impressive and useful of these result formats is the location plot. These plots show graphically where the damage has occurred. This allows accurate location of damage that can be more closely examined using other NDT (Non-Destructive Testing) techniques. The sound waves from the source of the acoustic emission event take time to propagate through the structure. The further the sensor is situated from the source, the longer it will take for the sensor to sense the event. By measuring the difference in time that a sound wave takes to reach each sensor allows the system to calculate the location of the source. Therefore, no previous knowledge of damage location is needed. The sensors are typically 3 to 6 metres apart from each other, depending on the material, type and thickness as well as sensor redundancy factor.
- Abstract document
- Manuscript document
(absent)