A fracture mechanics interpretation of acoustic emission results

The examination of the crack growth processes during thermal shock experiments performed with a corrosive medium on a cladded nozzle of the HDR-RPV was carried out by an acoustic emission and analysis system, that is able to automatically identify acoustic emission events as crack growth or as other processes (such as crack friction). This classification is based on a statistical model that considers different signal parameters (rise time, endurance, energy of the signal) for each acoustic event. More often, additional signal parameters are the position and time of starting. Using an evaluation system it is possible to pick out the events with certain parameters, using many different combinations, and plot and compare them against other results obtained from measurements or calculations. In this way the acoustic emission location method is confirmed by a general comparison with a nondestructive test result. This paper demonstrates that current ideas on fracture mechanics processes are only possible through the use of acoustic emission testing, through a powerful evaluation and presentation system for the measured results which include acoustic emission, and not least through the simulation of the real-life conditions found in a nuclear pover station (HDR).