Stress dependency on ultrasonic wave propagation velocity

The velocity of an ultrasonic wave propagating in the uniformly deformed isotropic solid was analysed by the Eulerian viewpoint. The pseudo elastic coefficient (PEC) was used to solve the equation of motion of the elastic wave under finite deformation. The infinitesimal displacement gradients are connected to the stress increments by thePEC. Using thePEC and the partial differential equation of motion, the velocity of ultrasonic wave was quantitatively related to applied stress, moreover, the stress dependence on longitudinal and transverse wave velocities propagating in the direction parallel or perpendicular to the uniaxial tensile direction could be cleared. Consequently, the Murnaghan's third order elastic constants can be calculated by precisely measuring the uniaxial tensile stress and ultrasonic wave velocity.     

Errors and uncertainties in the measurement of ultrasonic wave attenuation and phase velocity

This paper presents an analysis of the error generation mechanisms that affect the accuracy of measurements of ultrasonic wave attenuation coefficient and phase velocity as functions of frequency. In the first stage of the analysis we show that electronic system noise, expressed in the frequency domain, maps into errors in the attenuation and the phase velocity spectra in a highly nonlinear way; the condition for minimum error is when the total measured attenuation is around 1 Neper. The maximum measurable total attenuation has a practical limit of around 6 Nepers and the minimum measurable value is around 0.1 Neper. In the second part of the paper we consider electronic noise as the primary source of measurement error; errors in attenuation result from additive noise whereas errors in phase velocity result from both additive noise and system timing jitter. Quantization noise can be neglected if the amplitude of the additive noise is comparable with the quantization step, and coherent averaging is employed. Experimental results are presented which confirm the relationship between electronic noise and measurement errors. The analytical technique is applicable to the design of ultrasonic spectrometers, formal assessment of the accuracy of ultrasonic measurements, and the optimization of signal processing procedures to achieve a specified accuracy.     

Measurement of ultrasonic wave velocity in steel for various structures and degrees of cold-working

A pulse-echo technique based on the averaging of a large number of measurements (up to 10⁷ is described for the accurate estimation of longitudinal and transverse wave propagation velocity at megahertz frequencies. This technique was used for the investigation of slight velocity changes associated with different low-alloy steel microstructures derived by graded tempering of martensite. Further measurements show the marked influence of the rolling process on ultrasonic transverse wave velocity in austenitic 304L and 316L steels.     

Measuring the acoustic wave velocity and sample thickness using an ultrasonic transducer array

We suggest a new method for determining the longitudinal and transverse acoustic wave velocities and sample thicknesses, which is based on the measurement and analysis of pulsed echo signals by an array of ultrasonic transducers. Analytical expressions relating the delay of signals detected by the array and the values of parameters to be determined are obtained within the framework of a ray model of the measuring system. Measurements on a reference sample have been performed. The values of ultrasonic wave velocities and sample thickness obtained using the proposed technique agree with the results of measurements using independent methods.     

Distribution of hydroxyapatite crystallite orientation and ultrasonic wave velocity in ring-shaped cortical bone of bovine femur

At the nanoscopic level, bone consists of calcium phosphate, which forms incomplete hydroxyapatite (HAp) crystals. The preferred orientation of the c-axis of HAp crystallites induces anisotropy and inhomogeneity of elastic properties in bone. In this study, the effect of the preferred orientation of HAp crystallites on the spatial distribution of ultrasonic wave velocity was experimentally investigated, considering bone mineral density (BMD) and microstructure. Three ring-shaped cortical bone samples were made from a 36-month-old bovine femur. Longitudinal wave velocity was measured by a conventional ultrasonic pulse system, using self-made polyvinylidene fluoride transducers. The integrated intensity of the (0002) peak obtained using X-ray diffraction was estimated to evaluate the amount of preferred orientation. The velocity distribution pattern was similar to the distribution of integrated intensity of (0002). The effect of the preferred orientation of HAp crystallites on velocity was clearly observed in the plexiform structure, despite the fact that the BMD value was almost independent of the preferred orientation of HAp crystallites. Velocity measurement of cortical bone can reveal information about HAp crystallite orientation.     

Temperature dependences of longitudinal ultrasonic wave propagation velocity in gallium arsenide and indium phosphide single crystals

Results are considered for experimental studies of the longitudinal ultrasonic wave propagation velocity in gallium arsenide <001> and indium phosphide <100> single crystals in the temperature range 200–355 K with measurements made through each 0.5–1 K. Measurements were made by the ultrasonic echo-pulse procedure using calibration marks of time. The frequency of the sounding signal is 10 MHz.Translated from Problemy Prochnosti, No. 11, pp. 48–49, November, 1991.     

Prediction of ultrasonic wave velocities in sintered materials based on the ultrasonic properties of green or partially sintered compacts

This paper reports a new method of estimating ultrasonic properties of sintered materials from the ultrasonic properties of its powder compacts. The methodology is based on the observation that the ratio of ultrasonic shear wave velocity to longitudinal wave velocity is a function of porosity only and varies linearly with longitudinal velocity. The efficacy of the proposed method has been established with experimental data obtained from previously published studies. The method can be used as a potential tool for quality control of sintered products.     

Measurement of ultrasonic wave velocity in a solid under gas pressures up to 0·4 GPa

A set-up is described for the measurement of longitudinal and transverse wave velocities in a solid under gas pressures up to 0·4 GPa. To check the performance of the set-up, the elastic constants of Se and As₂Se₃ glasses and their pressure derivatives were obtained from the wave velocity data and compared with the data available in the literature.     

Continuous wave ultrasonic tomography

As an object rotates with respect to a stationary ultrasonic beam, the scattering centers within the object return echoes that are Doppler-shifted in frequency by amounts depending on the velocities of the individual scatterers. The scattering centers that lie on a line of constant cross-range all have the same effective velocity in the direction pointing toward the transducer; therefore, the backscattered echo amplitude at any particular frequency is the line integral of the scattered radiation at the cross-range corresponding to that frequency. The amplitudes of the returned signals at other frequencies give the line integrals for the scatterers at the corresponding cross-ranges. The amplitude as a function of frequency can be interpreted as a tomographic projection. A continuum of the projections at different positions is generated while the object is rotating. A tomographic reconstruction algorithm can produce an image of the distribution of scattering centers in the insonified object from these projections. A microscanner was developed to investigate the approach of using continuous wave (CW) ultrasound for cross-sectional imaging. The resolution is limited by the target size and the ultrasonic wavelength.     

超声检测中的兰姆波层析成像

兰姆波作为超声导波，可以对薄板类结构实现大范围快速的检测。然而，从兰姆波数据中提取定量信息时对检测人员的技术素质提出了很高的要求。文章用兰姆波层析成像仿真实现了铝板中不同缺陷的重建图像。结果表明：采用滤波反投影算法得到的层析图像给出了关于缺陷位置和类型的信息，从而使技术人员可以方便地识别出材料中的缺陷。     

Optical measurement of ultrasonic Poynting and velocity vector fields

This report describes a method for estimating several wide bandwidth ultrasonic field parameters from optical measurements of the local, acoustically induced, refractive index perturbation in water. These parameters include Poynting and particle velocity vector fields as well as pressure and density fields at any temporal delay under mild (forward-propagating) assumptions on the angular plane-wave spectrum of the ultrasound field. A sampling theorem is derived stating that two complete measurements of the three-dimensional pressure field separated in time by Δt allow release of the forward-propagating assumption for every acoustic wave number k satisfying k ≠ nπ/(cΔt), where c is the acoustic wave speed in the medium and n an integer greater than zero. The approach provides detailed measurements of very general ultrasound fields. Two optical measurement methods that acquire the Radon transform of the three-dimensional refractive index perturbation are briefly reviewed. It is shown that the Radon transform of the field itself satisfies a two-dimensional wave equation and may be propagated independently forward or backward in time under a source-free model. Conversely, the Radon transform of the ultrasound field measurement at several known time delays provides a means of applying a filter to the data based on known ultrasound propagation models. Each two-dimensional distribution may be propagated to a common time point and the ensemble averaged, thus incorporating the propagation model into the measurement. We support the presented theory with several experiments     

Thermal diffusivity and ultrasonic velocity of saturated R125

We report-to the best of our knowledge—the first data for the thermal diffusivity and ultrasonic velocity of both phases of saturated R125 in the temperature range from 20 °C to the critical point. The data were obtained in thermodynamic equilibrium by applying dynamic light scattering.     

Models of ultrasonic wave propagation in epoxy materials

This paper is concerned with modeling ultrasonic wave propagation in epoxy materials to better understand NDE procedures and to provide reliable input to more complex models of guided wave propagation in layered structures. Different physical models are considered in the context of how well they simulate the (known) linear relationship between bulk wave attenuation coefficients and frequency. The identified models are then extended to simulate wave propagation in materials with mechanical properties, which vary gradually in the spatial dimension. This is achieved using electric circuit transmission line analogs to the viscoelastic mechanical system. Verifying experimental results are included.     

High-temperature creep and resultant anisotropy in ultrasonic velocity in isotropic graphite

Plastic deformation of isotropic graphite in the vicinity of 2500 °C was studied using an Instron-type testing machine. The load-deflection curve was found to show a proportional limit at high temperature. Creep curves of graphite were also measured and were simulated by an empirical equation based on parabolic creep. Following the creep tests, ultrasonic velocity in the elongated graphite was measured. The velocity showed 5%–20% decrease after the creep. Below 2500 °C, the rate of velocity decrease along the elongation axis was always larger than that across the elongation axis. Above 2500 °C, this behaviour was reversed with the rate of velocity decrease across the elongation axis being the larger. The rate of decrease appeared to depend firstly on temperature and secondly on stress.     

Texture of metal-matrix composites by ultrasonic velocity measurements

An ultrasonic method is developed for the nondestructive characterization of texture in metal-matrix composites. In this approach, it is assumed that the presence of reinforcement particles changes the elastic properties of the composite but only the texture of the matrix. The method utilizes the measurements of the six independent ultrasonic velocitiesV _ij and the formulation given by Bunge. The examined composites are the silicon carbide (SiC)-particle-reinforced aluminum 8091, 7064, and 6061 metal-matrix composites. The fourth-order expansion coefficients of the orientation distribution function are determined as a function of the SiC content in these composites. The results show that the expansion coefficients change with the presence of SiC where the coefficients C ₄ ¹¹ and C ₄ ¹³ increase as the volume fraction of SiC is increased and the coefficient C ₄ ¹² is zero in all composites examined. The analysis of these results indicates that ultrasonics can provide a promising technique for the texture characterization of metal-matrix composites.     

利用CFD获取超声流量计截面速度分布

 通过CFD技术在超声波流量计设计过程中的引入,为流量系数的获取提供了新的途径.通过对特定管道的理论计算表明,采用CFD技术获取的管道内部流型完全可以与试验数据吻合,有助于超声波流量计应用场合流量系数曲线的获取及其精度的保证.     

Flexible piezopolymer ultrasonic guided wave arrays

Ultrasonic guided wave technology is being applied to a variety of gas and liquid transmission pipeline inspection applications. There are a variety of promising transduction techniques used to excite longitudinal, torsional, and flexural modes in pipe. Some of the more common methods include electromagnetic-acoustic, magnetostrictive, and piezoceramic array transducers. The objective of the work presented in this paper was to develop an array design that is simpler to manufacture and attach to pipelines compared to the current piezoceramic design. The design considerations for a flexible piezopolymer-based array are discussed in this paper along with the basic principles behind the selection of the array element width and spacing. The performance of a piezoceramic and piezopolymer array, with identical element spacing and width, are compared at four different frequencies. Tests were undertaken on a carbon steel pipe with a simulated defect. Evaluation of the different arrays was performed in terms of the defect response, in terms of amplitude, of the lower-order axisymmetric modes. It is shown that while the piezopolymer array provides comparable sensitivity to the piezoceramic array, the amplitude of the signals reflected from the simulated defect are 30 dB lower compared to those generated using the piezoceramic array.     

A high-power traveling wave ultrasonic motor

In the present work, a traveling wave ultrasonic motor (TWUSM) is proposed. It is composed of an annular-shaped stator and two cone-shaped rotors that are pressed in contact to the borders of the inner surface of the stator. A rotating traveling wave has been generated in the stator by using as vibration generators two bolted Langevin transducers (BLT) opportunely shifted in space and in time. The vibrational behavior of the stator as well as the traveling wave generation has been simulated with the finite-element method (FEM) software. A prototype of the motor has been manufactured and experimentally characterized. It exhibits a static torque of about 0.8 N x m and a maximum angular speed of about 300 rpm. Possible variations of the present design aimed to increase output torque or minimize encumbrance are described and discussed.