Optimizing Ultrasonic Forgings Inspection by combining Pulse-Compression technique and multi-frequency AVG analysis

Rizwan, Muhammad Khalid; University of Perugia; Italy

Rizwan, M.K.; University of Perugia; Italy
Senni, L.; University of Perugia; Italy
Laureti, S.; University of Perugia; Italy
Burrascano, P.; University of Perugia; Italy
Ricci, M.; University of Calabria; Italy

ID: ECNDT-0586-2018
Download: PDF
Session: Ultrasonic Inspection 1
Room: G2
Date: 2018-06-13
Time: 09:00 - 09:20

Ultrasonic pulse-echo NDT combined with AVG – Distance Gain Size – analysis is still the main method used for the inspection of forgings such as shafts or discs. Such method allows the inspection to be carried out in most of the cases assuring the necessary sensitivity and defect detection capability. However, when samples characterized by large dimensions and/or high attenuation are considered, the maximum Signal-to-Noise Ratio level achievable with standard pulse-echo presents major limitations due to the contextual action of the geometrical aperture of the ultrasound beam and of the physical attenuation of the beam energy during the propagation. To face this issue, the application of the pulse compression technique to the ultrasonic inspection of forgings was proposed by some of the present authors in combination with the use of broadband ultrasonic transducers and broadband chirp excitation signal. Here we extend the method by applying to pulse-compression data a specific multi-frequency AVG analysis that allows the evaluation of the sample as various samples simultaneously. The results of this analysis are compared with those of the standard single-frequency AVG method on a forging having known defects. It is show that the AVG analysis works fine with pulse-compression data collected by using a separated transmitter and receiver transducer. Moreover, narrowband analysis and broadband analysis provide almost identical results, but the latter allows the inspection frequency to be optimized with the use of a single transducer pair.