Abstract
A mathematical model of defects of the inner surface of a ferromagnetic plate is presented. The model compares crack-type defects with wide-opening corrosion defects.
A mathematical model of defects of the inner surface of a ferromagnetic plate is presented. The model compares crack-type defects with wide-opening corrosion defects.
In this paper, a characterization study of concrete samples with ultrasonic surface waves at hundreds of kilohertz frequency range is presented. These waves are generated and received by using 0.5 MHz-nominal frequency transducers. This investigation therefore concerns the first centimeters in the nearby of the material surface. The study was applied to concrete specimens for which a compositional parameter which is the water-to-cement ratio (W/C) has been varied. The latter affects the density and porosity of the material and therefore its mechanical properties. In addition, the evolution of acoustic and mechanical parameters of the concrete during its curing period has been investigated. The acoustic velocity and attenuation parameters are determined by exploiting the time of flight and the amplitude of the received ultrasonic signals. This study shows that the variation of the water-to-cement ratio affects the velocity of propagation of the surface waves and also leads to a variation of the mechanical strength of the concrete. It concludes that there is a strong correlation between the strength of the concrete, the ultrasonic velocity, and the W/C ratio. The results obtained by the destructive evaluation, which provides a measurement of the compressive strength by mechanical crushing test, confirm those obtained by the non-destructive evaluation of concrete. The study shows that this type of non-destructive testing using ultrasonic surface waves is beneficial particularly when the concrete structure is only accessible from the surface or when the propagation of the bulk waves is perturbed by the presence of reinforcements.
We present the results of studying the influence of the geometric shape of the damper on its effectiveness and the overall efficiency of the emission–reception system. One of possible shapes for the damper is considered where it is a truncated cone with the generatrix tilted relative to the piezoelectric plate plane. A criterion for evaluating the efficiency of the damper operation is proposed. The study includes the results of computational-theoretical (using the finite element method) and experimental research on the influence of the tilt angle of the damper generatrix on the signal reflected from its rear part. The generatrix tilt angle at which the minimum of noise signal is achieved is determined. A study of the emission–reception system under load on the aquatic environment is carried out. A satisfactory agreement between the theoretical and experimental results is noted.
This paper introduces a method for measuring solute particle size in solution. The working principle of this method is to characterize the particle size by using the ultrasonic extended coupled phase model combined with the acoustic attenuation coefficient of the solution. In the ultrasonic detection of highly concentrated emulsion particles, the inter-particle interaction, namely the structural loss, becomes the main factor affecting the ultrasonic attenuation. In this study, micron-sized emulsions with 10, 15, and 20% concentration were experimentally detected by the extended coupled-phase model, and the inverse calculation of the particle size distribution was carried out using a differential evolutionary algorithm. The detection results showed an average error of 4.266% compared with those of laser particle sizer. The results show that ultrasonic detection based on the extended coupled phase model combined with differential evolution inversion algorithm can achieve accurate measurement of particle size distribution of emulsions with high concentration.
As a result of measurements carried out using the standing waves method, hidden defects were detected inside the prosthetic feet details made of composite material. When comparing the obtained amplitude-frequency spectra of intact samples and samples with defects based on the first peaks corresponding to the first bending wave modes, it was revealed that the values of the resonant frequencies of defective samples were lower relative to the frequency values of the spectra of the intact ones. That observation indicated that the material of defective products might have reduced strength characteristics. Also, when studying some samples, the presence of additional peaks was noted, which indicated the appearance of new reflection boundaries corresponding to the appearance of defects in the test samples. The maps of amplitude distributions in the studied samples were obtained. A preliminary comparison was made with the results of examining samples using the OmniScan X3 device manufactured by OLYMPUS company. The results obtained indicated the presence of an increased number of reflection boundaries, as well as an increased bulges content, which probably arise during the process of products gluing. The analysis confirms the possibility of successfully using the standing waves method as a method for detecting hidden defects in composite material.
An ultrasonic nondestructive evaluation technique is proposed for ultrasonically welded joints of multi-strand copper cables in automobile wire harness terminals. The 32/128 ultrasonic phased array system is used to acquire the complete matrix data of the pulse-echo of the wire harness joints. The eigenvalues of the time, frequency, and time-frequency domains are extracted, and the wire harness joint quality is classified by machine learning. Firstly, 28 wire harness terminal joint samples were prepared 14 under different welding parameters; 14 were okay (OK), and were negative (NG). Then a linear array probe 5L32-0.6 × 10 is used to collect and preprocess the complete matrix data in these joints, and 11 200 echo signals are obtained. A principal component analysis algorithm was employed for data dimensionality reduction and denoising. Finally, machine learning algorithms were used to train and verify the model. The accuracy and performance of the traditional algorithms such as Logistic Regression (LR), K-Nearest Neighbor (KNN), Decision Tree (DT), Naive Bayes (NB), Support Vector Machine (SVM), and Neural Network (NN) were compared. The KNN and NN perform well in this study. In the test set, the accuracy of KNN and NN reached 90%. The study showed that echo features could effectively identify joint quality.
In this article the methods of determining the position and size of non-flaws in albedo flaw detection are considered. Analytical and numerical solutions of the problem of determining the location of non-flaws on the basis of known parameters of the collimation system are shown. The dependence of the location of the flaw on the parameters of the collimation system is shown. It is proposed to determine not the true size of the flaw, but its equivalent area, similar to ultrasonic flaw detection.
Timber buildings show the exquisite skills of craftsmen in China. Under the influence of nature and human activities, damage and destruction of ancient timber structures lead to the loss of China’s cultural heritage. Therefore, it is particularly important to study the existing defect detection methods of timber members and provide excellent restoration plan for the preservation of timber structures. Defects of timber structure members were found to consist mainly of cracking, decay, insect-attack, bending and pullout of tenons, etc. These defects are the main factors that affect the mechanical properties of timber members and endanger the stability of timber structures. Pilodyn, resistograph, stress wave, radar, ultrasound, X-ray, infrared spectroscopy and piezoelectric transducers are all were studies for detection methods mentioned, which belong to semi-destructive testing and non-destructive testing. In detail, the principle, development status and application cases of wood building detection technology are elaborated to demonstrate the advantages and disadvantages of these technologies in various scenarios. New and feasible detection technology should be developed, and the development direction of damage detection technology for timber structures in the future is put forward.
Classification of buckwheat grains is important because the absence of defective grains is a guarantee of yield and quality. Buckwheat grains were randomly selected from a batch with grains that varied in quality. The identification and classification of buckwheat grains according to the degree of fulfillment was carried out by a combination of microfocus X-ray and hyperspectral image analysis and multivariate analysis techniques. Using microfocus radiography, buckwheat grains were categorized into groups according to the degree of fulfillment. Hyperspectral image of buckwheat grains in the range of 935–1720 nm was acquired using a Specim FX17 camera. Using the polygon selection function, the averaged spectra were obtained and a data matrix of grain samples was generated. The bands of the spectrum contributing most to the grading of the grain samples by the degree of fulfillment were identified using the principal component analysis. The classification model of grading buckwheat grain into groups by the degree of fulfillment was constructed by partial least squares discriminant analysis method. The results showed that hyperspectral image is a potential tool for rapid and accurate identification of buckwheat grains, which can be used in large-scale grain classification and grain quality determination.
An improved frequency-domain synthetic aperture focusing technique (F-SAFT) for laser ultrasonic testing (LUT) is proposed for internal defect detection of small-diameter cylindrical components. Firstly, a LUT automated detection platform is built, a pulsed laser is used to excite ultrasonic waves and a two-wave mixing (TWM) interferometer is used to detect ultrasonic waves. Since ultrasonic signals are affected by the thermal expansion of the pulsed laser, time-frequency analysis is used to obtain the frequency range for imaging longitudinal waves, and the influence of low-frequency clutter is eliminated through multiple filtering. Secondly, in order to balance signal acquisition efficiency and imaging quality, the peak signal-to-noise ratio (PSNR) is used to determine the optimal angular step size. Finally, the equivalent velocity of the longitudinal wave is corrected to compensate for the imaging position error caused by the separation of the ultrasonic excitation point and the detection point. The results show that the method proposed in this paper has high imaging accuracy, which could provide a new approach for in-service non-destructive testing of small-diameter cylindrical components.
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