چكيده به لاتين
In recent years, non destructive testing methods, especially ultrasonic methods, have been used in connection with the inspection of railway lines. For this reason, in this project, we will design an optimal probe for detecting rail defects so that specifications such as the type of piezoelectric material, matching layers, backing layer, bonding, electrode and couplant material suitable of rail characteristics.
To do this, we first obtain the acoustic impedance equivalent of two piezoelectric heads, which is of PMN-PT type, using the transmission line model and the KLM model. Then, by genetic algorithm, we obtain the acoustic impedance of the backing and matching layers in such a way that this equivalent impedance has its best state in terms of size and phase, as well as the quality coefficient and insertion loss. We repeat these steps for probes with different number of matching layers.
The simulation results show that the two layer probe is suitable for railways, which is made of austenitic stainless steel SUS316 with a density of about 8000 Kg/m3 and 46.58 MRayl acoustic impedance. The acoustic impedance of the backing, first and second matching layers of this probe is about 20, 2 and 43 MRayl, respectively. Thus, for the backing layer, we use aluminum 1100 alloy with a density of 2745 Kg/m3 and an acoustic impedance of 17.1 MRayl. Also, for the first matching layer, we use polycarbonate with a density of 1185 Kg/m3 and a acoustic impedance of 2.71 MRayl, and for second matching layer use alumina ceramics with a density of about 10846 Kg/m3 and a acoustic impedance of 43 MRayl.
