Ultrasound propagation in non-metallic materials

摘要

This paper presents results concerning the ultrasound waves propagation in concrete andbricks. In the field of non-destructive evaluation of concrete, the ultrasonic wave velocity isusually measured and utilized to predict or correlate the strength of concrete. The impact-echomethod is a technique for flaw detection in concrete based on stress wave propagation. Atransient stress pulse is introduced into a test object by a mechanical impact generator on theconcrete element surface. By this test method we can determine ultrasonic pulse velocity,propagated in concrete specimen. A device generates low frequency pulses and measures thetime taken for pulses to pass between the two transducers placed at the end of the specimenbeing tested. It meets the testing standard BS1881: Part 203; ASTMC597. The equipment has apulse generator, an ultrasonic emitting transducer and a sensitive receiver piezoceramictransducer. The piezoceramic emitting transducer is excited by electrical pulses of high voltageamplitude, and converts the electrical signal in mechanical vibrations, which propagate inconcrete specimen. The piezoceramic sensor output signal is displayed on the memory digitaloscilloscope, type TDS 3023, Tektronix, USA. Also, by signal graphic representation analysisin time and frequency can be determined the attenuation coefficient of the pulse in concrete. Inthe specialty literature we can find tables with experimental material parameter values fordifferent type of concrete. Therefore, we are able to compare our experimental results withknown concrete parameters.