卷 54, 编号 5 (2018)
- 年: 2018
- 文章: 9
- URL: https://journals.rcsi.science/1061-8309/issue/view/11332
Acoustic Methods
Determining the Speed of Longitudinal Waves in an Isotropic Homogeneous Welded Joint Using Echo Signals Measured by Two Antenna Arrays
摘要
A technique is proposed for measuring the speed of longitudinal ultrasonic waves in a homogeneous welded joint, based on comparing measured and computed echo signals reflected from the bottom of a test object when using two antenna arrays mounted on prisms and operating in the double scanning mode. The effect of errors in setting the values of such parameters as the distance between the antenna arrays, test-object thickness, and others on the accuracy of calculating the wave velocity in the weld has been analyzed. Results of numerical and model experiments on calculating the wave velocity in the welded joint are presented. In a model experiment, the technique has made it possible to measure the speed of longitudinal waves in the weld model with an error of less than 0.7%. The method can be used to find the initial approximation in a nonlinear inverse problem of tomographic inspection of welded joints in the wave approximation.
Applying Special Spatiotemporal Signal Processing Algorithms to Ultrasonic Testing of Large Antique Cast Bells
摘要
Original spatiotemporal signal processing algorithms have been developed to improve the reliability of ultrasonic testing of unique antique cast bronze articles. In particular, to inspect large bells on the grounds of the Moscow Kremlin, with numerous relief images that limit the surface available for mounting piezoelectric transducers, various spatiotemporal signal processing algorithms have been designed, including the ones based on rotating a double-crystal transducer with the summation of partial defectograms.
Modernization of Vibration Analyzers Based on Identification Measurements
摘要
A technology is described for revamping vibration analyzers by introducing an additional intelligent unit for analyzing temporal characteristics of measurement signals. The unit flowchart includes a database, storing expert appraisals, and a knowledgebase, constructed based on the method of identification measurements of the regularity/chaoticity properties in the characteristics of vibration signals using the technique of scales. A computer-aided device has been developed for studying the applicability of the proposed techniques. Results of the vibrodiagnostics of a pumpjack with this device are presented.
Attempt Towards the Replacement of Radiography with Phased Array Ultrasonic Testing of Steel Plate Welded Joints Performed on Bridges and Other Applications
摘要
This study was carried out to demonstrate if the phased array ultrasonic testing (PAUT) can be adopted as a suitable substitute of the radiography testing (RT) of steel plate’s welded joints required by codes and standards related to some projects such as bridges construction and inspection according to AWS D1.5 Bridge welding code. Such adoption, if approved, can realize considerable cost saving without taking any additional risk. The two cited inspection techniques had been applied to test four butt welded joints performed on steel plates having thicknesses up to 35 mm. These welded joints had been performed by shielded metal arc welding (SMAW) and containing selected artificial flaws. The comparison between the detection capabilities and characterization of flaws in the welded joints by the two inspection techniques reveals that; PAUT improves the detection capability and sizing of flaws in the welded joints and it can replace RT reliably in case of applying a suitable PAUT procedure that includes simultaneous application of sectorial scan from both sides of the welded joints axes by using encoder with wide active aperture phased array probes and applying supplemental manual scanning for edge testing.
Ultrasonic Velocity as a Tool for Physical and Mechanical Parameters Prediction within Geo-Materials: Application on Cement Mortar
摘要
This paper discusses the ability of ultrasonic wave velocity to evaluate some physical parameters within mortar. The behavior of ultrasonic pulse velocity within mortar subjected to incremetal stress was also studied. For experimentation, we carried out ultrasonic measurements on mortar samples before and during uniaxial compressive strength, perpendicularly to the stress direction. The water/cement ratios were varied in order to contribute certain specific characteristics. A set of expressions was obtained linking the initial velocities of longitudinal ultrasonic waves with compressive strength, density, porosity and load at elastic limit.The evolution of ultrasonic velocity through mortar samples under continuous incremental uniaxial stress were also investigated. The results illustrated the behavior of ultrasonic pulse velocity as a function of the applied stress. It was observed that velocity did not decrease under initial loading and until about 70% of the ultimate stress, where sudden decrease occurred, followed by the failure of the material.
Thermal Methods
Comparing the Efficiency of Ultrasonic Infrared Thermography under High-Power and Resonant Stimulation of Impact Damage in a CFRP Composite
摘要
The quality control of composite materials remains an important topic of research in nondestructive testing (NDT) of modern materials, in particular, the ones intended for aerospace industry. Over the last decade, there has been a noticeable increase in interest to the ultrasonic stimulation of tested materials and analysis of dynamic temperature distributions. This method is commonly implemented with two techniques, viz. high-power stimulation at a fixed acoustic-signal frequency and low-power resonant ultrasonic stimulation. Results are provided on comparing the above ultrasonic NDT methods using the example of an impact damage in a graphite epoxy-filled composite. The comparison is made based on the criteria of temperature signals, revealed flawed zone, and productivity of testing.
Quality Control of Armor Fabric by Modeling Thermomechanical Processes under Projectile Impact
摘要
Mechanical and thermomechanical processes of interaction between a projectile and the multilayer woven barrier made of a polymer fabric are considered. A simplified mathematical model is proposed to describe the deceleration of the projectile due to the dissipation of energy spent on irreversible stretching deformation of fabric fibers, fiber slip friction, and barrier material heating. The parameters of governing equations are estimated by means of identification based on experimental data. Results of a computational experiment using the mathematical model can be employed for the diagnostics of armor protection based on the measurements of dynamic temperature fields.
Electromagnetic Methods
Studying a Signal due to the Tangential Component of Stray Fluxes from a Surface Flaw Detected with a Vibrating Induction Transducer
摘要
Analytical dependences of the amplitude spectrum of the output signal of a vibrating induction transducer on its position with respect to a flaw and on vibration-displacement parameters have been derived. The locality of inspection and its selective sensitivity toward flaws have been evaluated. The results of theoretical research have been confirmed experimentally.
Eddy Current Testing of Metallic Materials Using Projection Methods
摘要
Using the example of nonmagnetic metallic materials, the projection methods of multidimensional analysis of multifrequency eddy-current testing measurement data presented for processing are considered. Based on the principal components method, the effects of electrical conductivity and sensor–material-surface gap on the results of testing have been separated. Using regression on principal components, the numerical values of the electrical conductivity and gap for manganese, copper, bronze, aluminum, and an aluminum alloy have been obtained. The results make it possible to extend the possibilities of nondestructive eddy-current evaluation of materials.