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Nondestructive Evaluation (NDE) of Materials and Structures from Production to Retirement
Published in Yoseph Bar-Cohen, Advances in Manufacturing and Processing of Materials and Structures, 2018
As a high-resolution and high-magnification ultrasonic visualization technique, acoustic microscopy with an acoustic lens can focus an ultrasonic field to a micron-scale spot. Sokolov first presented the concept of an acoustic microscope in 1949 (Sokolov, 1949). He realized that the wavelength of sound in water at a frequency of 3 GHz was 0.5 μm and thus predicted that the acoustic microscope with a resolution comparable to that of the optical microscope could be produced one day. During the early 1970s, his proposition was taken seriously. Several techniques for acoustic microscopy were proposed, but the scanning acoustic microscope (SAM) was unique in its image quality and resolution. The use of mechanical scanning brings about several advantages that made it possible to record high-quality acoustic images with submicrometer resolution. The image, which records the mechanical properties (such as density, elasticity, and viscosity) of the sample being investigated, can be obtained either in reflection or transmission mode (Wickramasinghe, 1983). A SAM is simply a system that allows one to mechanically raster scan a very-high-frequency acoustic probe over a submerged object or specimen (typically in a water-immersion bath) to generate an acoustic image and to volumetrically examine the object.
Nondestructive Evaluation of Materials
Published in J. David, N. Cheeke, Fundamentals and Applications of Ultrasonic Waves, 2017
As the frequency is varied over the bandwidth, the RC reaches a minimum at the resonance frequency fR where d2 = λR/4. From Equation 19.29, measurement of the differential phase at resonance leads to a determination of d. In fact, Lee and Tsai [19] show that the best approach is fit the full RC as a function of frequency to Equations 19.26 through 19.29, which yields values of V2, d2, and ρ2. For the frequency range used in this work, films of thickness 3–30 μm could be measured. Submicron films could be studied using this technique with frequencies above 600 MHz. Another advantage of the SAM technique is the high spatial resolution that can be attained.
Assessment of the force-velocity relationship during vertical jumps: influence of the starting position, analysis procedures and number of loads
Published in European Journal of Sport Science, 2020
Danica Janicijevic, Olivera M. Knezevic, Dragan M. Mirkov, Alejandro Pérez-Castilla, Milos Petrovic, Pierre Samozino, Amador Garcia-Ramos
The main advantage of the SAM procedure is that it enables to determine the F-V relationship in field conditions with cost-effective devices such as smartphone applications (MyJump2) (Balsalobre-Fernandez et al., 2015). However, although the SAM procedure has been extensively used in scientific research, this is the first study that has evaluated the reliability of the F-V relationship parameters. The results of the present study suggest that the SAM procedure can provide the F-V relationship parameters with a comparable reliability than the FP procedure when the knee angle is fixed (SJ90), while it can provide even a higher reliability during the SJpref. The lower reliability of the FP procedure observed during the SJpref could be explained because the mean values of force and velocity could present a higher variability when the knee angle is not strictly controlled (higher values at higher knee angles) (Mandic et al., 2015; Petronijevic et al., 2018). The high validity of the SAM procedure to determine the F-V relationship parameters previously reported was confirmed in the present study by the large to very large correlations observed between the FP and SAM procedures (Jiménez-Reyes et al., 2014). Therefore, the SAM procedure could be recommended to determine the F-V relationship due to the very high validity and the comparable, if not higher, reliability of the F-V relationship parameters in comparison with the FP procedure. However, it should be noted that the SAM procedure, especially during the SJ90, could overestimate the values of V0 and Pmax compared to the FP procedure.
Development of Scanning Acoustic Microscopy System for Evaluating the Resistance Spot Welding Quality
Published in Research in Nondestructive Evaluation, 2022
Van Hiep Pham, Tan Hung Vo, Dinh Dat Vu, Jaeyeop Choi, Sumin Park, Doan Thong Nguyen, Byeong-Il Lee, Junghwan Oh
Following the industry standard, the RSW quality was evaluated by measuring some geometrical dimensions. Indentation and nugget diameter were the most common dimensions used in the evaluation. Till date, with the improvement in inspection technology, nondestructive testing (NDT) for the RSW quality evaluation has become increasingly common because of its convenience, reliability, and cost effectiveness [4,5]. Several NDT methods can be used to evaluate the RSW quality. Examples include Eddy current, ultrasonic, X-ray, and magnetic resonance imaging. Ultrasonic testing is the most frequently used method. Manually operated A-scan ultrasonic equipment is commonly used for RSW testing, but the results depend on the contact angle of the probe with the specimens. As a result, this technique requires an experienced operator, who can control the probe and interpret the result [6–9]. Moreover, the diameter of the required probe must be the same as that of the weld spot [10–13], so a series of probes must be prepared for different requirements of spot weld diameter. Recently, some studies have focused on using the ultrasonic methods to evaluate the RSW quality by measuring the nugget diameter [14–19]. The scanning acoustic microscopy (SAM) system is a potential ultrasonic testing instrument that uses an ultrasound (US) transducer integrated with a scanner module to inspect the RSW quality. Using the scanner module, the scanning ranges of SAM ranges from several millimeters to a meter, which is suitable for scanning different spot welds. In addition, the US transducer is fixed on the z-axis, and the contact angle is kept constant during the scanning process. Based on the US signal, the SAM system provides both surface and internal information by propagating US waves into the specimens. In this way, the same US transducer is used to send and receive the US signal to generate the A-, B-, and C-scan images. The geometrical parameters were determined using A-scan signals, and B-, and C-scan images, thereby evaluating the RSW quality. Several studies used the SAM systems to evaluate the RSW quality of specific materials [15–19]. Although the influence of the input welding parameters was analyzed, but the analyzed results had not determined the good welding parameters for specific materials. In addition, the transducers with low frequency (under 20 MHz) were used, which provide the low sensitivity of nugget shape and size.