The question of selecting the pitch of an ultrasonic antenna arrays in order to obtain the maximal signalto-structural noise ratio is considered. The ordinary mode of a linear antenna array, in which ...one of its elements radiates a signal and the other receives a signal, as well as the synthetic aperture mode, and the SAFT-C mode, in which each element in turn radiates a signal and the others receive the signal, are described. It is shown that the SAFT-C mode produces a four-fold increase in the signal-to-structural noise ratio from that achieved in the other modes.
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.
The limitations of using the sonic echo method for evaluating the integrity of driven concrete piles with near-surface flaws are examined. Criteria for detecting pile flaws in a compact region are ...obtained. It is shown that it is possible to use the multiplicative impact-echo method for determining the length of a pile with a near-zone flaw.
The possibility of the effective use of the kinetic indentation method in combination with the acoustic emission method for evaluating the fracture toughness of titanium nitride hardening coatings is ...shown. It is established that the occurrence of the first jog on the loading line of the kinetic indentation diagram in “load–indentor displacement–time” coordinates is due to the formation of the first crack in the coating and practically coincides in time with the occurrence of the acoustic emission impulse with an increased energy value. This permits a more accurate and substantiated determination of the critical load, indentation depth of the indentor, and hardness at which the first visible ring crack forms around the impression on the coating surface.
A reference-free method is considered for concurrent measurement of the speed of ultrasonic vibrations and the thickness of concrete constructional products with ultrasonic antenna arrays that use ...the “focusing to a plane” algorithm.
Problems that arise in ultraacoustic contactless testing of articles across a nonresonant air gap are considered. Results of the development of high-efficiency, wideband, low-frequency, ultraacoustic ...piezoelectric transducers for contactless testing of articles made of composite materials are presented.
It is shown that in order to improve the accuracy of measuring the speed of ultrasonic vibrations in cast-iron products by echo-pulse method, one should use noise-immune space-time echosignal ...processing methods that improve signal–to–pattern-noise ratio. Signal parameters should also be adapted for characteristics of the test object. Requirements for the choice of probing-signal parameters have been established as well as optimum displacement step of a double-crystal transducer. The value of the speed of ultrasound at a time moment that precedes the destruction of cast-iron mold has been determined.
It is shown that during ultrasonic control of products that are made of materials with a complex structure (cast iron, concrete, and bronze) the use of ultrasonic signals with a wavelength that is ...comparable to the sizes of the acoustic irregularities in a material induces the combined reflection of an ultrasonic probing signal from structural irregularities, which masks the reflections from the initial defects of the product. The combined reflected signal is correlated with the probing signal; in ultrasonic defectoscopy of products it has to be considered as interference that masks the echo signals from the initial defects of the product. At the same time, it provides information on the structural state of a studied material. In this work we consider the model of a complex material with a random structural irregularity distribution, for which the statistical characteristics of the combined reflected signal, viz., the density of the structural-noise probability, dispersion, and energy spectrum, are determined. We propose a new method for defining the structural state of a complex material by analyzing the statistical characteristics (energy spectrum and dispersion) of the structural noise.
The experimental results on the analysis of the statistical characteristics of the structural noise are discussed for cast-iron products, allowing the structural state to be detected and monitored during their operation.
It has been shown that in order to increase the sensitivity of ultrasonic noncontact shadow testing of products made of polymer composite materials (PCMs), it is necessary, along with the well-known ...techniques (increasing the amplitude of the probing signal, using radio technical signal processing methods, employing highly sensitive electroacoustic transducers), to optimize the parameters of noncontact testing. Criteria have been established for choosing air gaps between the emitting transducer and the test object and between the test object and the receiving transducer, as well as criteria for choosing the duration of probing signals. Methods for increasing the reliability of testing the border regions of small-thickness PCM products are proposed. The results of automatic noncontact scanning of PCM products in the shadow mode using an adaptive measuring complex that allows the testing parameters to be adapted to each new tested product are presented.
It is shown that when large products with a complex structure with a high integral attenuation of ultrasound are tested, it is expedient to use different electronic signal-processing methods ...(storage, normalization, and synchronous detection) that allow one to increase the thickness-measurement accuracy of vermicular cast iron products with complex structures and poor surfaces; when large polymer composite products with a high integral attenuation of ultrasonic signals are tested these methods allow one to not only increase the signal-to-noise ratio but the measurement accuracy of the bottom signal. It is possible to fully apply different electronic signal-processing methods if a multifunctional software–hardware measuring system that we designed is used, which is capable of selecting the optimum set of signal-processing methods for each new product.
