Transducer Distance Research Articles

Passive imaging in composite plates using Green’s function reconstruction from the diffuse field

Aiming at the problem that enables damage detection in real-time without any active excitation sources, we propose a new passive detection way based on diffuse field for structural health monitoring of CFRP structures. In this work, the wave propagation was first simulated with a k-space pseudo-spectra method in CFRPs. A diffuse field can be generated after multiple scattering from fibers and boundary reflections. After that, the reconstruction of Green’s function was investigated through different parameters including the number of noise sources, pulse bandwidth, transducer distance, etc. The delamination inspection process was explored by contrasting the reconstructed Green’s function with the referenced Green’s function on the composite plate. Finally, a probability distribution-based imaging algorithm was further applied for delamination imaging.

Sintesis Biodiesel Dari Minyak Jelantah Dalam Reaktor Ultrasonik

Waste cooking oil is considered promising alternative to biodiesel production as substitute for diesel fuel becauce it it is environmentally friendly, biodegradable, non-toxic, and renewable energy source. This study aims to obtain the optimum operating conditions of ultrasonic reactors in biodiesel production using Response Surface Methodology (RSM) method. RSM with CCD was used to determine effect of transducer distance (1-5 cm) and reaction time (5-20 minutes) on biodiesel yield, to determine optimal operating conditions and to optimize biodiesel yield. In this study, waste cooking oil was transesterified into biodiesel with ultrasonic waves to intensify reaction. Transesterification waste cooking oil was carried out in a sodium hydroxide catalyst using methanol. Solution inserted into the erlenmeyer with the transducer distance and reaction time to determined by RSM. Once the reaction time was reached, mixture of biodiesel and glycerol was separated in separate funnel. Biodiesel obtained was then washed and evaporated the remaining solvent. Biodiesel yield was obtained under 88.33% under optimal conditions of 1 cm transducer distance with reaction time 20 minutes. Reaction time was the most important parameter based on the ANOVA test. The properties biodiesel produced including kinematic viscosity, density, acid number, methyl ester contents and monoglicerida have met the requirements of standards SNI 7182: 2015.

Ultrasonic Pulse Velocity Test Using BS Method And T-Method to Estimate Crack Depth of Concrete

Ultrasonic Pulse Velocity (UPV) as a non-destructive test is commonly used on concrete crack estimation. There are several methods are applied based on the transducer configuration. Among the methods, BS (British Standard) method and T method was used in this study. On this method, transmitter was fixed at certain distance from crack and receiver was moved at several constant intervals, then crack depth was analyze from the relation between the transducer distance and the transit time curve. This research is conducted to study the accuracy of BS method and T-method in estimating the crack depth of concrete using NDT James Instrument V-Meter M-K IV. Concrete beams were made with artificial crack depth 2 cm, and 4 cm. Transducers 54kHz of UPV Mark IV were set at constant interval. Thus, the comparation of actual depth and experimentally result was analyzed. The study concluded that, the accuracy of the BS method has a better estimation result with a relative error of 27,75% and 35,95%, compare to the T-method that has 79,30% and 79,82% error.

Modular Electromagnetic Transducer for Optimized Energy Transfer via Electric and/or Magnetic Fields.

In this paper, a modular electromagnetic transducer that achieves the optimal transfer of energy from the electric and/or magnetic fields is proposed. Both the magnetic field resonance coupling and the influence of the electric field near the copper transducers of the printed circuit board and inside the FR4-type epoxy material are considered. In our printed arrays of flat transducers, we consider face-to-face capacitances for the study of resonance coupling. Because the space between coil turns is almost double the plate thickness, the coplanar capacitance can be ignored for frequencies under 2 MHz. A radio frequency (RF) transmitter and transducer were built to demonstrate the increased energy transfer efficiency when using both electric and magnetic fields in the near-field region. The transversal leakage flux coupling of a long RF coil was more efficient than a simple axial magnetic field coupling when using pancake transceiver coils. The optimal configuration having one long coil at the base and two or more flat coils as capacitor plates near coil ends generated the highest tandem of magnetic and electrical fields. A power regression tool was used to convert and simplify the transducer current and voltage variation with distance. In this regard, the current change corresponded to magnetic field variation and the voltage change to the electric field variation. New formulas for estimating the near-field region and the self-capacitance of the RF transformer coil are proposed; the optimal function in the frequency domain for a given transducer distance was defined by simulation.

THE BONE MICROSTRUCTURE IDENTIFICATION MODEL BASED ON BACKSCATTER MODE OF ULTRASOUND

Osteoporosis is defined by a decrease in bone mass and a deterioration in bone microstructure. It is a major public health issue and a significant economic burden for both individuals and society. Thus, monitoring bone mass and structure is necessary to prevent bone fragility and osteoporosis. This study aimed to develop a prototype of quantitative ultrasound (QUS) and to evaluate the feasibility of backscatter mode for the bone assessment. Ultrasound (US) signals that propagate through the bone can be characterized by comparing the signal from both transmitter and receiver transducers. The US backscattered signal depends on the characteristic of both medium and transducer. In this study, we analyzed the attenuated signal based on the parameters: type of bone (compact and spongy), type of coupling medium (air, starch, and gel), the angle between transducers and bone (30o, 60o, and 90o), and transducer distance (0, 10, 5, 15, 20 and 25 cm). We use only 1 MHz transducer frequency. The prototype has been evaluated by Digital Oscilloscope and LabVIEW user interface to observe received signals. The results of this study showed that there was a difference in amplitude of the US signal from compact and spongy bones. The amplitude is directly proportional to acoustic impedance and inversely proportional to the distance between transducers. There is a negative correlation between bone microstructure to attenuation, and compact bones have a greater attenuation coefficient than spongy bones.

The effect of tranducer distance on the concrete crack depth measurement using PUNDIT

The depth of crack in concrete structural elements can be measured using ultrasonic waves. One tool that can be used is PUNDIT. The research was conducted by measuring the depth of cracks on the concrete beam test object with a variation of the PUNDIT transducer distance. The purpose of this research is to determine the effect of the distance of the transducer (b) on the relative error (% error) measured in the cracked concrete depth. The results showed that the results of concrete crack depth measurements with the smallest relative error (% error) is obtained by adjusting the transducer distance to about 2/3 or 0.67 the thickness of the test object (h). At the distance of the transducer less than 0.67 or more than 0.67 the thickness of the test object, the relative error (% error) will be greater.

Comparison of Ultrasonic Velocities between Direct and Indirect Methods on 30 mm × 30 mm Spruce Lumber

This study investigates the relationship between ultrasonic velocity and density in the direct method, the effect of distance between transducers in the indirect method, and the difference between the direct and indirect methods with transducers placed at a distance of 200 mm in nondestructive ultrasonic testing of spruce lumber. The direct method using 54 kHz ultrasonic transducers was applied to two planes, namely, radial section (LR) and tangential section (LT) of samples. The indirect method measurements were taken using the same transducers. Two velocities were measured at the top and bottom of the LT plane and at the two sides of the LR plane; the two values for each plane were averaged. The relationship between density and ultrasound velocity in the direct method demonstrated a positive correlation between the two variables. The difference between the two planes, LT and LR, was not statistically significant. Moreover, the distance between the transducers in the indirect method affected ultrasound velocity, with the ultrasonic velocity increasing as the distance between the transducers became larger. A transducer distance of 200 mm yielded a close approximation of the direct method results with a ratio of 0.87. Finally, no statistical evidence of a difference between the two planes in the indirect method was found. If the direct method, which requires access to two surfaces, is impractical, the indirect method can be applied.

Defect Detection of Fiberglass Composite Laminates (FGCL) with Ultrasonic A-Scan Signal Measurement

Fiberglass composite laminates are widely used in many industries, due to its advantages of high specific strength and high specific modulus. Invisible defect such as delamination and inclusion may cause composite structural failure. Therefore, several research on ultrasonic testing for composite material defect detection have been done for the past few years. However, improper parameter setup may lead to significant error to determine the behavior of defects. In this paper, the intensive study on defect detection with ultrasonic single crystal immersion transducer has been conducted. In general, the defects detection thru acquired signal is determine the behavior of defects through the certain ultrasonic parameter setup such as sound velocity, pulse width, gain, sampling rate and transducer distance with specimen surface. Furthermore, an A-scan signal interpretation for FGCL defect detection is demonstrated and illustrated. This research is focusing on for FGCL with maximum thickness up to 10 mm in ambient temperature. The result shows an appropriate ultrasonic parameter will result better signal interpretation analysis.

Ultrasound pressure distributions generated by high frequency transducers in large reactors

The performance of an ultrasound reactor chamber relies on the sound pressure level achieved throughout the system. The active volume of a high frequency ultrasound chamber can be determined by the sound pressure penetration and distribution provided by the transducers. This work evaluated the sound pressure levels and uniformity achieved in water by selected commercial scale high frequency plate transducers without and with reflector plates. Sound pressure produced by ultrasonic plate transducers vertically operating at frequencies of 400kHz (120W) and 2MHz (128W) was characterized with hydrophones in a 2m long chamber and their effective operating distance across the chamber’s vertical cross section was determined. The 2MHz transducer produced the highest pressure amplitude near the transducer surface, with a sharp decline of approximately 40% of the sound pressure occurring in the range between 55 and 155mm from the transducer. The placement of a reflector plate 500mm from the surface of the transducer was shown to improve the sound pressure uniformity of 2MHz ultrasound. Ultrasound at 400kHz was found to penetrate the fluid up to 2m without significant losses. Furthermore, 400kHz ultrasound generated a more uniform sound pressure distribution regardless of the presence or absence of a reflector plate. The choice of the transducer distance to the opposite reactor wall therefore depends on the transducer plate frequency selected. Based on pressure measurements in water, large scale 400kHz reactor designs can consider larger transducer distance to opposite wall and larger active cross-section, and therefore can reach higher volumes than when using 2MHz transducer plates.

Numerical simulation of ultrasonic enhancement on mass transfer in liquid–solid reaction by a new computational model

Mass transfer coefficient is an important parameter in the process of mass transfer. It can reflect the degree of enhancement of mass transfer process in liquid–solid reaction and in non-reactive systems like dissolution and leaching, and further verify the issues by experiments in the reaction process. In the present paper, a new computational model quantitatively solving ultrasonic enhancement on mass transfer coefficient in liquid–solid reaction is established, and the mass transfer coefficient on silicon surface with a transducer at frequencies of 40kHz, 60kHz, 80kHz and 100kHz has been numerically simulated. The simulation results indicate that mass transfer coefficient increases with the increasing of ultrasound power, and the maximum value of mass transfer coefficient is 1.467×10−4m/s at 60kHz and the minimum is 1.310×10−4m/s at 80kHz in the condition when ultrasound power is 50W (the mass transfer coefficient is 2.384×10−5m/s without ultrasound). The extrinsic factors such as temperature and transducer diameter and distance between reactor and ultrasound source also influence the mass transfer coefficient on silicon surface. Mass transfer coefficient increases with the increasing temperature, with the decreasing distance between silicon and central position, with the decreasing of transducer diameter, and with the decreasing of distance between reactor and ultrasound source at the same ultrasonic power and frequency. The simulation results indicate that the computational model can quantitatively solve the ultrasonic enhancement on mass transfer coefficient.

Quality Controlling Surf Zone Acoustic Doppler Velocimeter Observations to Estimate the Turbulent Dissipation Rate

Abstract High-quality measurements of the turbulent dissipation rate ε are required to diagnose field surf-zone turbulence budgets. Quality control (QC) methods are presented for estimating surf zone ε with acoustic Doppler velocimeter (ADV) data. Bad ADV velocity data points are diagnosed with both the ADV signal strength (SS) and correlation (CORR). The fraction of bad SS data points (δSS) depends inversely upon the wave-amplitude-normalized transducer distance below the mean sea surface. The fraction of bad CORR data points δCORR can be elevated when δSS is low. The δCORR depends inversely upon the wave-amplitude-normalized sensing volume distance below the mean sea surface, and also increases with increased wave breaking, consistent with turbulence- and bubble-induced Doppler noise. Velocity spectra derived from both “patched” and “interpolated” time series are used to estimate ε. Two QC tests, based upon the properties of a turbulent inertial subrange, are used to reject bad ε data runs. The first test checks that the vertical velocity spectrum’s power-law exponent is near . The second test checks that a ratio R of horizontal and vertical velocity spectra is near 1. Over all δCORR, 70% of the patched and interpolated data runs pass these tests. However, for larger δCORR > 0.1 (locations higher in the water column), 50% more patched than interpolated data runs pass the QC tests. Previous QC methods designed for wave studies are not appropriate for ε QC. The results suggest that ε can be consistently estimated over the lower 60% of the water column and >0.1 m above the bed within a saturated surf zone.

Evaluation of ultrasonic sensing of methanol concentration for direct methanol fuel cell

This investigation evaluates the effectiveness of the ultrasonic sensing of methanol concentration and establishes two regression models based on measurements of sound propagation speed against methanol concentration. Uncertainty analysis reveals that propagation distance and equipment sampling rate affect the accuracy of sound speed measurement. An ultrasonic blind region is present because sensitivity declines at a temperature of approximately 63 °C. The accuracy of measurement of the speed of sound is increased by the calibration of transducer distance because of variations in temperature. Increasing the transducer distance to 20 mm reduces the error between the theoretical and experimental speed of sound to 0.59 m/s. If the transducer distance is well calibrated, then the range of temperatures associated with ultrasonic blindness is reduced to 2–6 °C. Frequency shift and attenuation in the blind temperature range are also investigated, indicating that these two parameters are insensitive to methanol concentration.

Modification of the ultrasound induced activity by the presence of an electrode in a sonoreactor working at two low frequencies (20 and 40 kHz). Part I: Active zone visualization by laser tomography

Sonoelectrochemical experiments differ from sonochemical ones by the introduction of electrodes in the sonicated reaction vessel. The aim of the study is to characterize the changes of the ultrasonic activity induced by the presence of an electrode located in front of the transducer. The scope of our investigations concerns two low frequencies vibration modes: 20 and 40 kHz. For this purpose, two laser visualization techniques have been used. The first part of the study, described in the present paper (part I), deals with the laser tomography technique which provides an accurate picture of the reactor actives zones, related to numerous cavitation events. For each frequency, two parameters were studied: the electrical power supplied to the transducer and the electrode transducer distance. At both frequencies, without electrode, we can observe distinct zones corresponding to cavitation production and stationary waves establishment. When increasing the input power, bubble clouds tend to form a unique cloud near the transducer. In presence of the electrode, bubble cavitation clouds are largely influenced by the obstacle. The second part of the paper (part II) will describe the Particle Image Velocimetry (P.I.V.) technique which allows to measure the velocity vector field in the fluid portion between the horn and the electrode.

Adjusting the phase of the signals transmitted from dual frequency probe for reducing second harmonic during propagation

During propagation of the ultrasound wave, nonlinearities of the medium, causes rise of higher harmonics that are seen in amplitude spectrum. In ultrasound contrast harmonic imaging this is unwanted effect, since it is expected to image only higher harmonics produced by contrast agents. In previous studies Christopher, Krishnan and Shen proposed transmitting either an inverted signal (collected by hydrophone), transmitting 2nd harmonic with broadband transducer or transmitting third harmonic to reduce the second harmonic at measurement point. Our study uses a dual frequency probe which transmits one wave at frequency f0 and one wave at double frequency 2f0 named second harmonic reduction signal (SHRS) for reducing the second harmonic in the propagating signal. The hardest task is the appropriate adjustment of the phase of the SHRS to reduce second harmonic during propagation in the focal area. We outline how to set phase and established that the phase of the SHRS in not affected by the nonlinear parameter B/A and excitation pressure P0 but rather by the excitation frequency and the ultrasound system geometry (transducer size and distance to focal area). A reduction of 25dB has been obtained in simulation (Po=100kPa, fo=2.25 MHz). Experiments in water tank, have shown the reduction of 2nd harmonic by 30dB.

Identifying source of acoustic emissions in structures using Lamb waves and vibration modes

A process for global monitoring of a structure for location of a source of acoustic emissions using the vibration modes of a structure together with the repetition rate of acoustic emission events in said structure thereby allowing determination of source location of acoustic emission events in said structure is provided. Further a process for identifying the arrival of different modes of lamb waves at the same transducer distance, based on the different propagation velocities of these modes is also provided so as to determine the distance from a single transducer to the source of said lamb waves.

An experimental comparison of different methods of measuring wave propagation in viscoelastic tubes

In this work the values of wave attenuation and phase velocity in a 6 × 9 latex rubber tube closed at the distal end were measured by means of different equations, and varying the distance between transducers. Three equations are based on two simultaneous pressure measurements and on the knowledge of the terminal reflection coefficient ( two-point methods). The fourth equation is based on three simultaneous pressure measurements ( three-point method). In all cases small amplitude pressure signals (20 mmHg peak-to-peak) were employed. The results of our experiments were then compared with those computed using a classic linear model of wave propagation, and with the high-frequency asymptotic values obtained experimentally using an original method recently developed by the authors. The results obtained with 40 cm between transducers demonstrate that phase velocity (about 15 m/s) and wave attenuation (about 0.003 Neper/cm at 10 Hz) are in agreement with the predictions of classic linear theories in the frequency range 1–15 Hz, provided wall tethering and viscoelasticity are taken into account. Only at certain critical frequencies, which depend on the particular equation employed, does the estimation of wave attenuation become inaccurate owing to an insufficient signal-to-noise ratio. Moreover, wave propagation measurements become inaccurate also at very low frequencies (<1 Hz). The results obtained using a small distance between transducers (10 cm) demonstrate that the two-point methods maintain greater accuracy than the three-point one. In particular, when reducing the separation between transducers, the three-point attenuation values become 3–4 times greater than the attenuation obtained using the two-point equations. This finding might explain the large differences between propagation values observed in recent in vivo experiments. Finally, asymptotic estimations of the high-frequency phase velocity and attenuation per wave-length turn out rather robust and insensitive to a reduction in the transducer distance. These estimations might, therefore, be usefully adopted during in vivo experiments performed in difficult conditions.

Influence of spectral broadening on continuous wave Doppler ultrasound spectra: a geometric approach.

A model is presented that enables the detailed effects of spectral broadening to be calculated for a continuous wave (CW) Doppler system by using geometric boundary arguments. The model assumes a uniform distribution of isotropic scatterers and treats the transmitter and receiver crystals as incremental sources and receivers. Detailed results for rectangular and circular geometries are presented in order to provide a physical understanding of the manner in which spectral broadening arises. Results are given for the circular geometry, to illustrate the manner in which the received spectrum is affected by the transducer size and distance from the vessel.

Effect of Turbulence Nearfield on a Shielded Transducer

When a transducer of finite size is used to measure the spectral density of a turbulent sound field, the results are dependent on the size of the transducer. If the transducer is separated from the turbulence by a non-turbulent medium, or by an elastic layer, then the recorded pressure is a function of both transducer size and layer thickness. Analysis of the effect of transducer size and separating layer is the purpose of this paper. The theory is developed for computation of attenuation of spectral density as a function of transducer size and distance from the turbulent layer.