Russian Journal of Nondestructive Testing最新文献

This paper presents an ultrasonic-guided wave technique for measuring the fluid level using a helical waveguide sensor. The torsional T(0, 1), longitudinal L(0, 1), and flexural F(1, 1) modes were propagated concurrently in the waveguide (WG) utilizing through-transmission (TT) and pulse-echo (PE) approaches. We used a stainless-steel wire to make the helical sensor, and both dead ends of the sensor were connected to the shear transducer at 45° orientations to transmit and receive all three modes using TT and PE techniques simultaneously. Experiments were performed with various fluids (glycerin, water, and petrol) to determine the level (0.5 to 100 mm). The amplitude of all three modes decreased because of wave leakage when the sensor portion (helical) was inside the liquid medium. The fluid level was measured based on the sensor’s reflection factor due to the amplitude drop of each wave mode. Multiple experiments (T1, T2, T3) were performed to ensure the sensor’s repeatability. Also, the micro-fluid level was measured at every 0.5 mm depth increment using Fast Fourier Transform (FFT) of F(1, 1) mode using PE and TT concepts. Finally, the F(1, 1) mode provides better level sensitivity than other wave modes. This technique can especially be used in hazardous or inaccessible regions of interest to simultaneously monitor fluid levels and temperature in oil industries and nuclear power plants.

The methodology of joint application of acoustic emission diagnostics (AED), vibration-based diagnostics (VBD), and videotaping for monitoring the load-bearing capacity of polymer composite material (PCM) specimens during compression tests is considered. Test specimens cut from a composite panel were divided into five groups of two specimens each. Before the compression test, the specimens of the second group were subjected to an impact with an energy of 50 J, the third group, with 70 J, the fourth group, with 90 J, and the fifth group, with 110 J. Assessment of the state of damage of the specimens during compression was carried out using AED, VBD, and video recording. The obtained results confirmed the high efficiency of the complex application of these methods. Their joint application allowed us not only to monitor the level of bearing capacity of the specimens in the loading mode, but also to trace the sequence of mechanisms of evolution of multilayer carbon fiber-reinforced plastic fracture in compression at the stage of ultimate deformation of the material.

The article presents the results of acoustic emission testing of an aircraft wing box made of composite material ACM 102 130 C UD. The load was changed in steps of 10% of its maximum value. Before loading, the control zones consisting of four piezoelectric acoustic emission transducers were calibrated. In order to reduce the influence of anisotropy and design features of the wing box on the errors in defect location, a new technique consisting of analytical and tabular methods was developed. In the analytical method, the coordinates of defects were calculated using three sensors of a piezoantenna, and the location error included random and systematic components. Inaccurate determination of the difference in the times of signal arrival at the sensors of the piezoantenna was the main source of the random component of the error. The complexity of the design influenced the appearance of a systematic error. At the same time, the features of the test object hampered the rectilinear propagation of sound waves. When using the tabular method, the wing box structure was divided into a number of zones and the matrix of correspondence between the difference in signal arrival times and the coordinates of the selected cells was calculated. It was shown that the number of signals localized using the tabular method is bigger than that using the analytical method. Practical application of the developed location method showed that the average value of the reduced error decreased twofold when calculating the (X)-coordinate and sixfold when calculating the (Y)-coordinate. This made it possible to reduce location errors associated with the location of the calibration points on the structure. If the location error of signals exceeded the permissible value determined by the cell size, they were excluded from further consideration as nonlocalized.

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 multiple reflection method, based on measuring the velocities of longitudinal and transverse waves propagating along the rod diameter of the spring, is used to evaluate the nonuniformity of acoustic properties. Specially designed pass-through electromagnetic–acoustic transducers of transverse waves of axial polarization and transducers of longitudinal waves on the basis of flexible piezoelectric 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 based on the results of wave velocity measurements. It was established that the nonuniformity of acoustic and elastic properties along the length of the bar differs for automotive and railway springs. A linear variation of acoustic and elastic properties along the length of the coiled wire was observed in the railway spring (from one end to the other), caused by the technology of high-temperature mechanical processing. In the barrel-shaped automotive spring, a nonlinear variation occurs along the length of the coiled wire, correlating with the coil diameter and the formation of residual stresses.

The growing demand for carbon fiber reinforced polymer (CFRP) pipes in industry and their susceptibility to impact damage have led to great focus on damage detection in these structures. This paper proposes a method for detecting impact damage in CFRP pipes using low-power ultrasonic thermography with sweep excitation. The bottom of ultrasonic transducer was designed into a curved surface to improve its coupling to the composite pipes. In accordance with the attributes of local defect resonance (LDR), the frequency band was ascertained by analyzing the displacement spectrum at the site of impact damage. The LDR frequencies were further validated from the thermal responses of ultrasonic thermography inspection and finite element analysis of the specimen eigenfrequencies. Finally, the method was used to detect various impact damage on CFRP pipes. Since the LDR frequency at the defect is covered by the frequency range of the narrowband sweep excitation, impact damages can be efficiently activated, resulting in an obvious temperature rise.

Residual stresses induced by laser shock peening in the near-surface layer in AISI 316Ti austenitic stainless steel specimen were measured by ultrasonic technique using critically refracted longitudinal waves. The results of ultrasonic measurements were compared with the results obtained by hole drilling method. The values of the residual stresses induced by laser shock peening, the initial residual stresses in the rolled sheet, and the yield strength of the material were compared. The thermal stability of laser-induced residual stresses after annealing the specimen for 5 h at the temperature of (200^circ {text{C}}) and reannealing for 5 h at the temperature of (280^circ {text{C}}) was investigated. The results of study were analyzed taking into account the accepted assumptions, limitations, and uncertainties. The structure near the untreated and laser-treated surface was studied using optical and scanning electron microscopes. The directions of further studies for the development of nondestructive technique for ultrasonic evaluation of residual stresses induced by laser shock peening of the surface were proposed.

Single-crystal silicon wafers play a key role in photovoltaic technology and microelectronics manufacturing due to their good semiconductor characteristics. In order to meet the demand of high-tech industries, the production technology of silicon wafer is supposed to meet the high-precision standard, and if the micro-cracks produced during grinding are not detected on time, the yield of a useful product will be reduced. In order to achieve more efficient detection of micro-cracks in silicon wafers, a scanning laser thermal nondestructive testing system was developed. Using the pseudo static matrix reconstruction algorithm, the experimental data has been converted into static images to provide easier defect detection and evaluation. The influence of geometric characteristics (length, width and depth) of micro-cracks and laser excitation power on surface temperature signals in the laser scanning tests has been studied. The image enhancement techniques, such as linear gray scale transformation, basic function transformation and histogram equalization have been compared. The effectiveness of using super-pixel segmentation, dual threshold segmentation, iterative threshold segmentation and UNet3+ network for improving micro-crack detection efficiency has been explored. Common segmentation techniques have not proven to be useful in the image enhancement because of the presence of noise. Better results in image segmentation have been achieved by using a UNet3+ network, which ensured identification accuracy of about 90% in the segmentation of micro-crack defects.

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 lateral super-resolution of reflectors, various methods are used: maximum entropy method, Bernoulli–Gaussian 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 lateral super-resolution of DFA-images. The performance of the proposed method is confirmed by model experiments.

The objective of this paper is to study the feasibility of detection and characterization of damage in glass fiber composite laminated plates using S₀ Lamb waves. The characterization of this waves is first clarified experimentally by plotting these dispersion curves and their attenuation. The aim of the second part of this work is to investigate the use of the S₀ Lamb waves for the detection of damages. The influence of parameters such as the damage size and position in thickness was studied. It has been found experimentally, that the amplitude of S₀ Lamb waves decreases with a time shift and its frequency spectrum changes in the presence of damage. The rate of those changes is related to the increase in defect size and the damage location.

This study has considered free and forced vibration analysis of a cracked Timoshenko beam exposed to a moving mass. It considers both analytical and finite element (FE) methods to analyse the vibration response of a simply supported beam carrying a moving mass and suffering from an open crack. Timoshenko beam theory has deliberated to investigate the dynamic behavior of a discretely simply supported beam with including shear deformation and rotational inertia under various configurations of open crack and moving mass conditions. The beam was divided into two segments, which obeyed the Timoshenko beam theory and the crack was modeled by a torsional spring with local elasticity at the connecting region of the two segments. The governing equations of the beam transverse vibration were solved based on Hamilton’s principle, and the obtained results are validated with previously published works, including numerical and experimental works. The effect of crack depth (CD) and crack location (CL) with the amount and speed of the moving mass on the dynamic response of the beam have been investigated, where the presence of the crack plays a key role in both free vibration characteristics and dynamic response of the Timoshenko beam. Hence, more nonlinearity and higher deflection in the dynamic behavior have perceived at CL = 0.5 and CD > 0.3 h. The obtained natural frequencies are generally decreased with increasing CD, in which significant drop in the 1st and 3rd natural frequencies have been identified when the crack is located at the mid-span of the beam. A frequency-domain representation under various mode excitations of moving load has evaluated to indicate the presence of the crack within the Timoshenko beam. Hence, the evaluation of frequency domain and dynamic deflection can be sensitive to indicate the presence of the crack and its severity.