Defektoskopiâ

The digital focusing aperture (DFA) method is widely used to image reflectors during ultrasonic inspection. The reliability of inspection is determined by the quality of the DFA image — resolution and signal-to-noise ratio. To achieve super-resolution of echo signals, which will lead to radial super-resolution of CFA-image of reflectors, various methods are used: maximum entropy method, Bernoulli—Gauss deconvolution, Lucy—Richardson deconvolution, methods of recognition with compression (CS), methods of construction of autoregressive models of signals, etc. To apply these methods, we need to know the impulse response of the ultrasonic inspection system. It can be measured, but you can use methods of “blind” deconvolution, which are used in image and signal processing. For example: the method of eliminating camera blur at its random displacement, maximum correlated kurtosis deconvolution (MCKD), cepstral analysis, etc. In this paper, a cepstral analysis method for super-resolution or for obtaining information about the impulse response of the system is considered to construct an AR spectrum model to obtain the radial super-resolution of CFA images. The performance of the proposed method is confirmed by model experiments.

The paper is devoted to the investigation of the acoustic and elastic properties of automotive and railway springs manufactured by cold coiling and high-temperature machining, respectively. The mirror-shadow method of multiple reflections based on measuring the velocities of longitudinal and transverse waves propagating along the rod diameter of the spring is used to evaluate the non-uniformity of the acoustic properties. Specially designed pass-through electromagnetic-acoustic transducers of transverse waves of axial polarisation and transducers of longitudinal waves on the basis of flexible piezo film of polyvinylidene fluoride provide multiple reflection of volume waves along the cross-section of the coiled coil of the spring. The elasticity, shear moduli and Poisson’s ratio are calculated from the results of wave velocity measurements. It was established that the non-uniformity of acoustic and elastic properties along the length of the bar differs for automotive and railway springs. It was found that there are differences in the non-uniformity of acoustic and elastic properties along the length of the coiled bar for automotive and railway springs.

An infrared diagnostic of the scale of turbulence in the front of a natural fire is presented, as well as a comparison with the scale of turbulence in the air near the combustion source for a model grassland and crown fire. An analysis of the flame of a grassland fire reveals smaller turbulence scales than the flame of a crown fire. A fire-induced atmospheric turbulence at a height of 10 m is observed with the corresponding frequency of air temperature pulsation (0.1-6 Hz for a steppe fire and 0.1-3 Hz for a crown fire). The values of the structural functions of refractive index and temperature fluctuations are significantly higher than the background values and can be used for remote fire detection.

The article belongs to the flaw detection stories section and contains fragments of the author’s memories about the formation and development of domestic thermal control.