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卷 55, 编号 5 (2019)
- 年: 2019
- 文章: 9
- URL: https://journals.rcsi.science/1061-8309/issue/view/11350
Acoustic Methods
A Mirror Method for Measuring Directional Patterns in the Auxiliary (Azimuthal) Plane of Angle Transducers
摘要
A new mirror method is proposed for measuring directional patterns of angle piezoelectric transducers in an auxiliary (azimuthal) plane. Measurements of directional patterns in the auxiliary plane were carried out for transducers with angles of probe ranging from 34° to \(70^\circ \) using the mirror method on a steel sample with plane-parallel surfaces. It has been established that for transducers with wedge angles close to the first critical one (probe angle \(34^\circ \)), the beam angle of the directional pattern in the auxiliary plane widens; this can be explained by a refracted longitudinal (head) wave participating in pattern formation. It is shown that directional patterns can be effectively measured in the auxiliary plane of piezoelectric transducers for azimuthal angles ranging within \( \pm 15^\circ \) from the acoustic axis.
345-352
Improving the Efficiency of Ultrasonic Testing Based on Additional Information on Defect Scattering Indicatrices
摘要
An ultrasonic testing (UST) method is proposed that allows one to classify internal defects in welded joints into planar and bulk ones by using defect scattering indicatrices. Dedicated angle twin-crystal transducers of the Duet type with probe angles of 29° and 61°, exciting a head wave in the test object, are employed as a transmitter and receiver for ultrasonic testing. Informative signs of defects based on using their scattering indicatrices are considered. These signs make it possible to improve the reliability of ultrasonic testing results. It is shown that due to the peculiarities of propagation of head waves, defect scattering indicatrices are most informative for the probe angle of 29° (a wedge angle close to the first critical value for the PMMA–aluminum-magnesium-alloy pair of materials) and the probe angle of 61° (the angle close to the value complementing the angle of 29° to 90°). The statistical significance of the results of calculating correlation and concordance coefficients were estimated for given significance levels \(\alpha = \) 0.05 and \(\beta = \) 0.05, where α and β are the probabilities of the errors of the first and second kind, respectively. Correlation matrices were compiled for the obtained defect scattering indicatrices. Additionally, the reliability of the results was verified by comparing the obtained data with a database of previously performed measurements and their results.
353-362
Discrete Wavelet Transform based Denoising of TOFD Signals of Austenitic Stainless Steel Weld at Elevated Temperature
摘要
Abstract—Time of flight Diffraction technique is an advanced ultrasonic NDE methods, adopted in weld integrity testing. During the Time of flight Diffraction (TOFD) inspection of the stainless steel welds at high temperature, grain scattering noise is developed. In Time of flight Diffraction testing, the quality of the signal plays a dominant role in characterizing the defects. Hence, signal denoising is an essential prerequisite for the successful application of Time of flight Diffraction testing. In this work, one austenitic stainless steel weldment was artificially induced with slag defect. At high temperatures, the Time of flight Diffraction testing has been conducted on the weld piece and the resultant signals are applied over the proposed algorithms. Various combinations of wavelets, decomposition levels with different thresholding levels are applied to select an optimum denoising method. The evaluation of wavelet based denoising is achieved by calculating the Signal to Noise Ratio (SNR). Results show that the noises can be suppressed well and Signal to Noise Ratio is improved.
363-368
Magnetic Methods
Comparison of Magnetic Parameters of Quenched Pipe Steels with X-Ray–Evaluated Residual Macro- and Microstresses
摘要
Residual micro- and macrostresses have been determined by X-ray diffraction analysis in 22KhG2A, 30KhMA, and 32G2 grade steels quenched and tempered from various temperatures. It is demonstrated that not only residual macrostresses need to be determined, as prescribed by existing regulatory documents, but also microstresses, which characterize the extreme values of residual stresses. The possibility of using magnetic parameters for evaluating residual micro- and macrostresses has been investigated. It has been established that coercive force, maximum magnetic permeability, and Barkhausen magnetic noise characteristics can be used as informative parameters in the evaluation of microstresses.
369-377
On the Possibility of Evaluating Magnetostriction Characteristics of Bulk Ferromagnets Based on Their Magnetic Properties
摘要
Based on experimental research, a relationship has been established between the critical fields, which are determined by the shape of the magnetization curve and major hysteresis loop of bulk samples of iron–carbon alloys, with the magnitude of a positive maximum of magnetostriction in these samples. By varying the annealing temperature of cold-deformed 20G steel, it has been shown that the studied critical fields are much more sensitive to changes in the stress-strain state than the known coercive force and residual induction.
378-383
Optical Methods
Applying Digital Image Correlation Technique for Studying the Growth of a Fatigue Crack in VT23 Titanium Alloy Welded Joints
摘要
We present results of applying a combined approach to studying fatigue fracture processes in VT23 titanium alloy with a laser-welded joint. The approach involves fractographic examination using scanning electron microscopy and analysis of strain fields at the sample surface (using digital image correlation technique). Samples with permanent connections are presented in two forms: in the initial state and subjected to post-welding treatment by ultrasonic forging and pulsed high-energy impact. It is shown that applying the proposed integrated approach to the analysis of fatigue fracture has allowed identifying features in the development of processes of nucleation and propagation of cracks and locating them in the bulk of the material, as well as determining running times after which transition from one stage to another takes place: crack initiation, stable growth, and rupture. The results have made it possible to explain the mechanisms of how post-welding treatment of permanent joints affects their fatigue properties.
384-392
Attempt to Detect Nano Oil Film on the Surface of Polished KDP Crystal
摘要
Abstract—The KDP (Potassium Dihydrogen Phosphate) crystal is important in high-energy optical system as a high quality non-linear optical material. The residual oil film which even is of nanometer thickness has great adverse effect on the KDP optical performance, such as laser absorption and damage threshold. In this paper, spectroscopic imaging ellipsometry (SIE) is applied to investigate the residual oil film on KDP crystal surface during the processing, and atomic force microscopy (AFM) is applied as a reference of the SIE results. Two modes of SIE are applied to detect oil film thickness. A rotating substrate measurement scheme is proposed because KDP crystal is a uniaxial anisotropic material. An optical model with thin oil film and KDP substrate is built including a top surface roughness layer, a flat oil film layer and KDP substrate, which is used to fit the detection data. Then, the single-point measurement results and thickness maps of residual oil film are established to describe the oil film distribution quantitatively. The AM-FM mode of AFM is applied to detect the oil film distribution on KDP crystal after surface cleaning, and the oil film thickness established in AFM measurement corresponds well with the SIE results. The nano oil film on KDP crystal can be measured by SIE technology accurately and the measurement scheme can also provide a reference for the similar detection.
393-406
Radiation Methods
A Mathematical Model of Digital Linear Tomography
摘要
A mathematical model of digital linear tomography has been developed that takes into account the geometrical parameters of the scheme of testing, the depth of the layer of interest, the maximum energy of X-rays, the design of the digital detector, and the digit capacity of the analog-to-digital converter. The mathematical model is implemented in the MathCad software for engineering calculations. The results of a computational experiment are presented that confirm the possibility of producing the image of a layer with significantly reduced interference from images of other layers.
407-417
Vibration Diagnostics
Nondestructive Testing of CubSat Satellite Body Using Laser Vibrometry
摘要
The high reliability of modern 3D printing technologies makes it possible to create structural elements for aerospace and rocket industry products. Currently, the team of authors are developing a system for designing and additive manufacturing of composite and polymer structures for high-tech applications. In this paper, we studied the body of a Tomsk-TPU-120 CubSat satellite, the first Russian spacecraft to contain additive manufactured elements. Device quality control was carried out using resonant ultrasonic stimulation in conjunction with the use of scanning Doppler laser vibrometry, as well as experimental modal analysis. The testing results made it possible to reveal a defect at the butt end surface of the satellite body by analyzing the amplitude-frequency characteristic of surface vibrations. Experimental vibration-scanning data were used to verify a mathematical model developed using the ANSYS software.
418-425