Aplicações de pulsos codificados e novos arranjos ultrassônicos para concreto

Abstract

This work aims to expand the understanding of the application of ultrasound in cementitious materials through the study of classical arrangements and the evaluation of capacity of coded pulses as excitation signals with respect to conventional tional pure tones, in the measurement of the wavefront travel times. Additionally, from the literature review it was possible to group the main ultrasonic methods and to present a new method that allows improvement of these measurements in non-destructive contact ultrasound tests. Simulations were carried out, based on scenarios that approximated to masses and concretes, using the aforementioned excitation signals with a band of linear frequencies ranging from 20 kHz to 750 kHz and faced with pure tones of 50 kHz, 100 kHz, 300 kHz, 500 kHz, 700 kHz and 1000 kHz. Tests were also carried out on concrete samples to verify the lower resolution of the encoded pulses. Experiments on aluminum samples were used to validate the application of the new method and expressions developed to calculation of a combined re ection coeficient (CRC) and acoustic attenuation in low-loss means, which may provide standard contributions. Finally, from the results found, it was veri ed the superior capacity the use of coded pulses to obtain smaller relative errors (simulations) and standard deviations (experiments) in the determination of ultrasonic transit times. It was also proved through simulations and experiments the application of a new method and the determination of the CRC that allows better estimation in the determination attenuation of acoustic attenuation in low-loss media.