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[en] Highlights: • Cement-stabilized natural aggregate was replaced by crumb rubber of similar gradation. • Static and dynamic modulus of elasticity declined. • Quantitative assessment of fractured surfaces confirms more tortuous cracks. • Ultrasonic pulse velocity is well correlated with flexural strength. - Abstract: The purpose of this paper is to investigate the flexural characteristics and to quantitatively study the flexural-induced cracking of reference and rubberized cement stabilized aggregate mixtures. Four volumetric replacement percentages (0%, 15%, 30% and 45%) of 6 mm fraction size were used. This modification was found to affect the material strength detrimentally. However, material toughness was improved and stiffness was reduced. The latter findings were supported by quantitative assessment of the fractured surfaces which revealed more tortuous and rougher cracking as a result of rubber content increasing. This, in turn, may ensure a good load transfer across the cracks after their formation. Overall, using rubber in pavement construction is a sustainable solution that ensures consumption of large quantities of these waste materials. At the same time, it may be considered as a promising method to reduce cracking tendency and sensitivity which may improve shrinkage, thermal and fatigue performance.
[en] The aim of this study is to investigate the behavior of the ultrasonic parameters in a duplex stainless steel type 2205 (UNS31803/EN1.4462) through aging heat treatments at 750 °C during different times. The main objective is to promote the precipitation of secondary phases, especially chi (χ) and sigma (σ). The microstructural evolution was studied using optical microscopy and scanning electron microscopy and afterwards the specimens were evaluated using the ultrasonic pulse echo technique. Electrochemical experiments were carried out to evaluate the uniform and localized corrosion resistance of the specimens. The results revealed that the relative amounts of χ and σ phases increase with the time of heat treatment at ferrite/ferrite and ferrite/austenite grain boundaries, especially inside the ferritic grain. The longitudinal wave velocity and the attenuation coefficient presented a trend that coincides with the microstructural changes generated by the effect of the heat treatment. The electrochemical evaluation revealed a high resistance to uniform corrosion; however, the results showed a correlation between the increase in aging treatment time and the loss of localized corrosion resistance.
[es]El presente estudio evalúa el comportamiento de las variables ultrasónicas en probetas de acero inoxidable dúplex 2205 (UNS31803/ EN1.4462), tratadas térmicamente a 750 °C durante distintos tiempos, con el objetivo de promover la precipitación de fases secundarias, chi (χ) y sigma (σ). Se estudió la evolución microestructural mediante microscopía óptica y electrónica de barrido, y utilizando la técnica ultrasónica pulso eco de contacto. Finalmente, se realizaron ensayos electroquímicos con el objetivo de evaluar la resistencia a la corrosión. Los resultados revelaron que a medida que aumenta el tiempo de tratamiento térmico se produce un incremento de las cantidades relativas de fases χ y σ a lo largo de las interfases ferrita/ferrita y ferrita/austenita, especialmente hacia el interior del grano ferrítico. La velocidad de onda longitudinal y el coeficiente de atenuación presentaron una tendencia que coincide con los cambios microestructurales generados por efecto del tratamiento térmico. La evaluación electroquímica reveló una alta resistencia a la corrosión uniforme. No obstante, se observó una correlación entre el aumento del tiempo de tratamiento térmico con la pérdida de la resistencia a la corrosión localizada.
[en] This paper presents an efficient method for stress measurement propagation. Pulse-echo method are used as stress measurement method on railway wheels. Hard service conditions and brake failures can lead to dangerous stress on the railway wheels. Stress measurements so important for wheels. Especially wheel expose to severe drag braking conditions in freight service. Residual stresses can significantly reduce the engineering properties and fatigue life of materials such as railway components. The paper presents results of stress state investigation of ER7 steel. Finally, the article briefly discusses how to adopt the pulse-echo method to railway wheels. Reducing cost of residual stress measurement investigated.
[en] Some of the array elements in a phased array ultrasonic probe can become inactive temporarily or permanently during use. Array probes are expensive, thus, it would not be cost-effective to terminate use because of a few damaged elements or consider a series of examinations as invalid if a single element was discovered to have become inactive during examination. Therefore, it is necessary to be able to use a phased array probe even if some of its elements are inoperative. In order to support this technically, it is required to assess the influence of inactive elements on phased array ultrasonic inspection results and to determine how many inactive elements are acceptable for the inspection. In this study, we developed a method to evaluate the effect of inactive elements in a phased array ultrasonic probe using a reconstructed ultrasonic signal and image through post-processing data acquired via full matrix capturefor various numbers and patterns of inactive elements. The results were compared to those inspected by conventional phased array ultrasonic testing, and the proposed method was validated
[en] The North American standards for welded steel construction, CSA W59 and AWS D1.1, use an approximation for ultrasonic attenuation of 2dB/in. This approximation is based on the use of large, low frequency transducers which are not always well-suited to the wide range of weld thicknesses and geometries used in the codes. This paper documents computer simulations and experimental results performed to gauge the suitability of this linear factor to approximate a non-linear phenomenon. Additionally, models of smaller transducers and higher frequencies are included to study their effect. This is performed to determine how alternate criteria and procedures may be developed to retain the same levels of sensitivity but expand the range of transducers beyond that currently permitted. (author)
[en] Freehand ultrasound (US) is a technique used to acquire three-dimensional (3D) US images using a tracked 2D US probe. Calibrating the probe with a proper calibration phantom improves the precision of the technique and allows several applications in computer-assisted surgery. N-fiducial phantom is widely used due to the robustness of precise fabrication and convenience of use. In principle, the design supports single-frame calibration by providing at least three noncollinear points in 3D space at once. Due to this requirement, most designs contain multiple N-fiducials in unpatterned and noncollinear arrangements. The unpatterned multiple N-fiducials appearing as scattered dots in the US image are difficult to extract, and the extracted data are usually contaminated with noise. In practice, the extraction mostly relied on manual interventions, and calibration with N-fiducial phantom has not yet achieved high accuracy with single or few frame calibrations due to noise contamination. In this article, we propose a novel design of the N-fiducial US calibration phantom to enable automatic feature extraction with comparable accuracy to multiple frame calibration. Along with the design, the Random Sample Consensus (RANSAC) algorithm was used for feature extraction with both 2D and 3D models estimation. The RANSAC feature extraction algorithm was equipped with a closed-form calibration method to achieve automatic calibration. The accuracy, precision, and shape reconstruction errors of the calibration acquired from the experiment were significantly matched with the previous literature reports. The results showed that our proposed method has a high efficiency to perform automatic feature extraction compared to conventional extraction performed by humans. (author)
[en] At Darlington Nuclear Generating Station (DNGS), very large pipes (60' diameter for service water and 72' diameter for condenser cooling water (CCW)) deliver water to maintain reactor cooling and power plant optimal operation. Conditions that restrict flow in these pipes exist, and work programs are implemented to minimize flow impediment. Due to lack of flow indicators, effectiveness of these work programs are difficult to measure. In order to determine the most effective method for flow impediment reduction, flow measurement in these pipes are required. Ultrasonic flow meter is the ideal instrument for obtaining flow readings in these pipes. However, very large pipes pose various challenges for ultrasonic flow meters. These challenges must be overcome to ensure successful measurement. This document chronicles the innovative solutions that IRI personnel derived to overcome these challenges to successfully use Ultrasonic Cross Correlation Flow Meter (USCCFM) to measure flow in the 72' pipes. (author)
[en] Thermal fatigue cracking is one of the flaws that can occur in nuclear power plant components and cause problems in maintaining the integrity of nuclear power plants. Therefore, to prevent such problems, nondestructive testing of nuclear power plant components is being performed. Radiographic testing and ultrasonic testing are the primary applied as the inspection methods for components. However, radiographic testing is decreasing in proportion because of radiation exposure and nuclear safety regulations. Alternatively, the proportion of ultrasonic testing is increasing. In particular, phased array ultrasonic testing is applied, replacing a wide range of tests, such as radiographic testing. In this study, the accuracy and usefulness of phased array ultrasonic depth sizing of weldment cracks and artificial flaws are investigated through the evaluation of the average error and RMS error values
[en] Phased Array Ultrasonic Testing (PAUT) is an advanced technique that is fast replacing conventional ultrasonic testing (UT). PAUT has advantages over conventional ultrasonic such as the ability to steer and shape the beam. Besides that, PAUT inspection provides multiple scan views that increases the Probability of Detection as compared to conventional UT. In inspection of welds, raster scanning is done to obtain full coverage of the region of interest. However, for PAUT the ability to shape and steer the beam eliminates the necessity of raster movement of the probe. In parts where accessibility is limited, PAUT is possible to be performed where previously inspection is not possible using conventional UT. This paper discusses the optimum parameters and conditions to be considered prior to performing a reliable inspection of welds on spool fittings. The results and interpretations are also discussed. (author)