The Research On Attenuation And Randomness Of Ultrasound Propagating In Concrete

Ultrasonic testing technology is a commonly used detection technology in biomedical engineering(BME)and industrial non-destructive testing(NDT),which can detect hidden lesions and defects without invading the measured object.Domestic and foreign scholars have carried out fruitful research in the field of ultrasonic imaging algorithms,and developed imaging algorithms such as ultrasound tomography(CT),phased array focusing,synthetic aperture focusing(SAFT),and composite plane wave imaging.However,in the field of concrete ultrasonic NDT,the application of ultrasonic algorithms faces special problems,such as the coupling problem between ultrasonic transducer and concrete surface,the penetration limit of ultrasound in concrete,the problem of acoustic scattering in concrete,sound beam directivity problems in concrete,etc.The particularity of these problems stems from the heterogeneity of concrete materials and the large scale of concrete structures.The object of BME ultrasonic detection is biological tissue.The depth of the detected area is only about ten centimeters.Therefore,high frequency sound waves of several megahertz can be used,and the imaging resolution is in millimeters level.The object of industrial NDT is mostly metal.Apart from polycrystalline metals,the scattering effect of general metal media on acoustic waves is much smaller than that of concrete media.At present,there are few studies on the influence of the properties of concrete materials on the application of ultrasonic NDT technology.Based on the above problems,this paper studies the attenuation behavior of ultrasonic propagation in concrete materials and the statistical randomness of ultrasonic signals,mainly carrying out the following work.:(1)The acoustic attenuation coefficient and attenuation rate coefficient in the frequency range of 50 kHz~140 kHz were experimentally measured by ultrasonic transducer embedded in concrete,and the contribution of sound field diffusion attenuation and material attenuation to total attenuation was studied respectively;Variability of sound velocity,amplitude,and frequency spectrum in the frequency range of 50 kHz to 140 kHz;(2)The ultrasonic simulation method of concrete based on Field II and random aggregate model was proposed and validated.The maximum particle size and volume ratio of concrete aggregate were analyzed by echoed signals.(3)The compactness of compound concrete materials was detected by ultrasonic transmission technology,and the detection method of judging the compactness with sound velocity and spectral center frequency was validated.