Preliminary study of the influence of low temperatures on tuning conditions of the Lamb waves in aluminium plates for Structure Health Monitoring.

The method of Lamb waves to detect defects in aerospace structures is already known in research environments for its benefits, using an inexpensive equipment. The major benefits are: accurate determination of location and size of the defects in material and the fact that it is a non destructive method. For experiments are used aluminum plates that are willing piezoelectric exciters as follows: a piezoelectric actuator placed on a point on the plate will excite that point and the signal will be received by a piezoelectric receiver placed on another point from the plate. By interpreting the shape, phase and amplitude of the received signal we can determine the shape and location of the defect. The excitation signal frequency should be previously known by determining the amplitude in a frequency band set between 10-800 kHz, for the plate without defects, which is called the tuning procedure. Due to the fact that the structures will work also on flight condition temperature as on high altitude or in space, it is necessary to check how these extremelly low temperatures influence the defect detection. For this purpose the first step is to determine how the temperature variation affects the tunning results. As preliminary study the first step of the tunning procedure has been performed at different low temperature down to - 70°C. [ABSTRACT FROM AUTHOR]