An ultrasound wave measurement technique suitable for large compact-sized (where measured thickness is comparable with other dimensions) concrete structures is described. The technique is based on ...ultrasonic bulk wave velocity measurement Cl. The Cl value is determined
by the correlation method: correlation is established between the experimental spectral responses of a real sample and the series spectral responses of a finite element model calculated with different model ultrasonic velocity parameter values Cmod.j. To increase the accuracy of
the velocity measurement the multiplicative correlation method is used: cross-correlation is calculated between the spectral response curves obtained at different points on the sample and the spectral response curves of the finite element model calculated for the same points of the model.
It is shown that ultrasonic adaptive antenna arrays that are able to take the shape of a nonplanar surface of the tested product should be used for ultrasonic tomography of concrete building ...structures with a nonstandard surface configuration. It is also necessary to use adaptive methods of ultrasonic tomography allowing one to simultaneously determine the coordinates of defects and the speed of ultrasonic vibrations in concrete and to adjust the parameters of the probing signals to the characteristics of concrete products.
WE consider a modernization of the echo method of ultrasonic flaw detection that uses one or several receiving transducers on the object’s lateral surface in addition to the array of transducers ...contacting with the working (front) surface of the object. This method of array arranging can substantially improve the resolution and, in the case of using an antenna array on the lateral surface of the object, obtain additional information for imaging the internal structure of the object. In order to obtain the potential resolution, an ultrawideband probing signal with a Gaussian envelope is used in combination with a novel signal processing algorithm that includes summation, one-sided clipping, and multiplication of recorded signals. Some practical recommendations are given in the paper. Potential resolution in various directions has been assessed.
The need for zero drift and accurate object pose estimation is very common in today's industry. Implementing optical measurement system allows to overcome certain problems, that are inherent to ...inertial navigation systems (INS). These problems include size and weight of high accuracy systems of the type and zero drift, low dynamic range. Method, described in this article is based on the fiducial markers recognition. The markers were located on investigated object, their positions were estimated on four images, captured by four digital cameras, connected to the PC. The Results, obtained by four cameras, were processed by developed algorithm, allowing to conduct pose estimation with an accuracy of 0.2 degrees in 3 degrees of freedom.
It was noted that in most ultrasonic tomographs for concrete products, tomograms are constructed based on the velocity of body (longitudinal, transverse) ultrasonic waves, calculated from the easily ...measured velocity of surface waves. However, in engineering structures exposed to climatic or other impacts, the state of the concrete structure can vary greatly from its surface to its depth, leading to errors in determining the body ultrasound velocity and, consequently, to inaccuracies in displaying defects in the structure and product dimensions. In order to improve defect location accuracy, a new reference-free method has been proposed for measuring the speed of ultrasound in the volume of large-sized engineering structures. The method employs ultrasonic antenna arrays that take advantage of the “focusing to a point” algorithm when constructing tomograms, provided that a point reflector (e.g., an access hole) is present in the product.
We consider ultrasound tomography of concrete building structures containing defects arranged at large angles to the antenna array (AA). In oblique sounding of such building units made of ...complex-structured concrete, the influence of pattern noise (PN) increases due to the effect of negative cross-correlation of PN signals on adjacent AA transducers. It has been shown that the optimum (providing the maximum signal–to–pattern-noise ratio) antenna-array pitch for oblique sounding should be (0.35–0.4)
. It is shown that, in the tomography of inside corners at the junction of two walls, it is advisable to use either two separate antenna arrays, designed for oblique sounding of building structures, located on different sides of a corner wall junction or a single antenna array consisting of two linear AAs combined into one antenna in order to more efficiently extract useful signals from PN and increase the angular resolution.
The results of using ultrasonic broadband complex-modulated signals to increase the accuracy of measurements of the velocity of ultrasound waves in the acoustic testing of concrete products are ...presented. It is shown that it is possible to employ signals with linear frequency modulation to analyze the structure of concrete from the attenuation of the ultrasonic signals.
Pattern-noise (PN) that occurs due to combined reflection of an ultrasonic probing signal from acoustic inhomogeneities in the material structure is an interference that conceals echo-signals from ...flaws. The most efficient method for extracting echo-signals from PN is multichannel spacetime signal processing (STSP). Different inspection purposes dictate different configurations of STSP schemes with the parameters that are determined by PN correlation characteristics. A theoretical model has been used to determine mutual PN correlation characteristics for the main types of transducers. The theoretical results have been confirmed experimentally.
The influence of phased array (PA) pitch on signal/pattern-noise ratio when probing objects with inhomogeneous structure by low-aperture transducers of transverse acoustic waves is considered. A ...saturation phenomenon has been discovered for small PA pitches. The phenomenon is due to the influence of positive cross correlation between pattern-noise instances at neighboring receiving transducers. The optimum PA pitch has been determined to be approximately 0.5 of the wavelength when probing the object area across the PA and 0.4 of the wavelength when probing areas at the side of the PA. Experimental research has been carried out and proved the validity of the theoretical results.
A method of measurement of the velocity of ultrasonic vibrations in structural units made of concrete by means of ultrasonic phased antenna arrays without the use of samples is described. In the ...methods signals are processed by means of a plane focusing algorithm designed for the detection of reflecting planes. Results of measurements of the velocity of ultrasound in concrete are presented.
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