![]() The numerical method was found to consistently over-estimate focal peak intensity (+40% on average), however, for transducers with a central hole it was more accurate than using the solid bowl assumption (+70% over-estimation). The FPF measurement method was found to provide focal peak intensity estimates that agreed most closely (within 15%) with the hydrophone measurements, followed by the pressure ratio method (within 20%). The calculated intensities were compared with those derived from focal peak pressure measurements made using a calibrated hydrophone. Spatial- peak intensities were estimated for 8 transducers at three drive powers levels: low (approximately 1 W), moderate (~10 W) and high (20-70 W). 20 259-69), (ii) a numerical method derived from theory, (iii) a method using measured sidelobe to focal peak pressure ratio, and (iv) a method for measuring the focal power fraction (FPF) experimentally. Four methods are compared: (i) a solid spherical bowl approximation (after Hill et al 1994 Ultrasound Med. Improved strategies for determining focal peak intensity from a measurement of total acoustic power are proposed. A hole in the centre of the transducer results in over-estimation of the peak intensity. This paper demonstrates theoretically and experimentally that this expression is only strictly valid for spherical bowl transducers without a central (imaging) aperture. 20 259-69) provided a simple equation for estimating spatial- peak intensity for solid spherical bowl transducers using measured acoustic power and focal beamwidth. (author)įocused ultrasound transducer spatial peak intensity estimation: a comparison of methodsĬivale, John Rivens, Ian Shaw, Adam ter Haar, GailĬharacterisation of the spatial peak intensity at the focus of high intensity focused ultrasound transducers is difficult because of the risk of damage to hydrophone sensors at the high focal pressures generated. Furthermore, through the dislocation density it was possible to verify the influence of stacking fault energy (SFE) in the evolution of the copper samples deformation process and its alloy, and that the presence of texture in rolled samples did not impair the measurements obtained by XRD technique. The results indicate that the XRD is a powerful tool for the characterization of the microstructure in relation to the dislocation density, as they were consistent to the TEM measurements, and also showed good relationship with measurements of hardness. The materials used in this study were pure copper and brass α as alloy 268 (6 % Cu and 34 % Zn), deformed by rolling and ECA (equal channel angular extrusion) processes. The measurements obtained by XRD were compared with those obtained from images observed by transmission electronic microscopy (TEM). ![]() ![]() In this work, the dislocation density was analyzed through peak broadening of Xray diffraction ( XRD) using Convolutional Multiple Whole Profile (CMWP) program. This is due to the fact that the dislocations are the main responsible for plastic deformation, which, thereafter, markedly influences the mechanical properties. The determination of dislocation density in metallic materials has been available for many years in scientific environment. International Nuclear Information System (INIS) Evaluation of dislocation density in copper and brass α deformed by XRD peak width analysis
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