| 1. |
- Carlson, Johan, et al.
(författare)
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A simple scattering model for measuring particle mass fractions in multiphase flows
- 2002
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Ingår i: Ultrasonics. - 0041-624X .- 1874-9968. ; 39:8, s. 585-590
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we present a simple theoretical model of how pulsed ultrasound is attenuated by the particles in a solid/liquid flow. The theoretical model is then used to predict the attenuation of sound, given the mass fraction, the density, and the size distribution of the solid particles. The model is verified experimentally for suspensions of 0–10% (by mass) Dolomite ((Ca,Mg)CO3) particles and water. The experimental results show that the attenuation of sound due to particles varies linearly with mass fraction, and that the proposed theoretical model can be used to predict this attenuation. In all experiments the transmitter and receiver array were clamped onto the pipe wall, thus providing a completely non-invasive and non-intrusive measurement technique.
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| 2. |
- Delsing, Jerker
(författare)
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Ultrasonic gas flow meter with corrections for large dynamic metering range
- 1989
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Ingår i: Ultrasonics. - 0041-624X .- 1874-9968. ; 27:6, s. 349-356
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Tidskriftsartikel (refereegranskat)abstract
- Extreme accuracy is required in sing-around type gas flow meters in the sing-around period measurement. Thus the detection of the ultrasound is critical. Accurate detection of an ultrasound pulse transmitted through gas is not straightforward. Normally a zero crossing technique is applied, where a level trigger determines when to enable the zero crossing triggering. In a flowing gas, the ultrasound amplitude is modulated due to turbulence, humidity and changes in dynamic gas pressure. This introduces uncertainty as to the cycle in which the ultrasound pulse is detected. This in turn results in large errors in sing-around type gas flow meters. This paper discusses a new correction algorithm which will eliminate such trigger errors. To accomplish the verification of the new correction algorithm, a microprocessor-based sing-around gas flow meter, using 500 kHz ultrasound has been designed. The correction algorithm significantly increases the repeatability of this meter. Repeatability better than 0.5% over a dynamic meter range of 1 to 35 has been measured. Limitations of the sing-around method imposed by the new correction algorithm have been derived theoretically.
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| 3. |
- van Deventer, Jan, et al.
(författare)
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Apparent transducer non-reciprocity in an ultrasonic flow meter
- 2002
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Ingår i: Ultrasonics. - 0041-624X .- 1874-9968. ; 40:1-8, s. 403-405
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Tidskriftsartikel (refereegranskat)abstract
- This paper investigates the effects of non-identical ultrasonic transducers on reciprocity and zero-flow calibration in transit time flow meters. According to the theorem of reciprocity, there should not be any difference between the up- and downstream acoustic times of flight in a zero-flow situation. This would thus eliminate zero-flow estimation drifts. The flow meter is modeled as a one dimensional system with equivalent electrical circuits and simulated with simulation program with integrated circuits emphasis. The work shows that variations between the two transducers cause false estimates of flow and indicate which parameters have the largest influence. It indicates that reciprocity holds only for identical transducers.
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| 4. |
- Wiklund, Martin, et al.
(författare)
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Ultrasonic-trap-enhanced selectivity in capillary electrophoresis
- 2003
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 41:4, s. 329-333
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Tidskriftsartikel (refereegranskat)abstract
- We combine ultrasonic trapping and capillary electrophoresis (CE) with the goal to detect ultra-low concentrations of proteins via size-selective separation and enrichment of antibody-coated latex spheres. An 8.5 MHz standing ultrasonic wave is longitudinally coupled into the sub-100-muM diam capillary of the CE system. Competition between acoustic and viscous forces result in inflow separation of mum-diam spheres according to their size. Experiments separating 2.8- and 2.1-mum-diam fluorescent latex particles, which model a protein-specific immunocomplex/free particle mixture, indicate a potential improvement of the concentration limit of detection of 10(4) compared to current CE systems. Theoretical calculations show room for further improvement.
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| 5. |
- Aitomäki, Yvonne, et al.
(författare)
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Material property estimates from ultrasound attenuation in fibre suspensions
- 2009
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 49:4-5, s. 432-437
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of a new method for measuring fibre material properties from ultrasonic attenuation in a dilute suspension of synthetic fibres of uniform geometry is presented. The method is based on inversely solving an ultrasound scattering and absorption model of suspended fibres in water for the material properties of the fibres. Experimental results were obtained from three suspensions of nylon 66 fibres each with different fibre diameters. A forward solution to the model with reference material values is compared to experimental data to verify the model's behaviour. Estimates of the shear and Young's modulus, the compressional wave velocity, Poisson's ratio and loss tangent from nylon 66 fibres are compared to data available from other sources. Experimental data confirms that the model successfully predicts that the resonance features in the frequency response of the attenuation are a function of diameter. Consistent estimated values for the compressional wave velocity and the Poisson's ratio were found to be difficult to obtain but in combination gave values of shear modulus within previously reported values and with low sensitivity to noise. Young's modulus was underestimated by 54% but was consistent and had low sensitivity to noise. The underestimation is believed to be caused by the assumption of isotropic material used in the model. Additional tests on isotropic fibre would confirm this. Further analysis of the model sensitivity and the reasons for the resonance features are required.
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| 6. |
- Bezek, Can Deniz, et al.
(författare)
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Analytical Estimation of Beamforming Speed-of-Sound Using Transmission Geometry
- 2023
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Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 134
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Tidskriftsartikel (refereegranskat)abstract
- Most ultrasound imaging techniques necessitate the fundamental step of converting temporal signals received from transducer elements into a spatial echogenecity map. This beamforming (BF) step requires the knowledge of speed-of-sound (SoS) value in the imaged medium. An incorrect assumption of BF SoS leads to aberration artifacts, not only deteriorating the quality and resolution of conventional brightness mode (B-mode) images, hence limiting their clinical usability, but also impairing other ultrasound modalities such as elastography and spatial SoS reconstructions, which rely on faithfully beamformed images as their input. In this work, we propose an analytical method for estimating BF SoS. We show that pixel-wise relative shifts between frames beamformed with an assumed SoS is a function of geometric disparities of the transmission paths and the error in such SoS assumption. Using this relation, we devise an analytical model, the closed form solution of which yields the difference between the assumed and the true SoS in the medium. Based on this, we correct the BF SoS, which can also be applied iteratively. Both in simulations and experiments, lateral B-mode resolution is shown to be improved by ≈ 25% compared to that with an initial SoS assumption error of 3.3% (50 m/s), while localization artifacts from beamforming are also corrected. After 5 iterations, our method achieves BF SoS errors of under 0.6 m/s in simulations. Residual time-delay errors in beamforming 32 numerical phantoms are shown to reduce down to 0.07 µs, with average improvements of up to 21 folds compared to initial inaccurate assumptions. We additionally show the utility of the proposed method in imaging local SoS maps, where using our correction method reduces reconstruction root-mean-square errors substantially, down to their lower-bound with actual BF SoS.
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| 7. |
- Broberg, Patrik, 1983-, et al.
(författare)
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Improved Corner Detection by Ultrasonic Testing using Phase Analysis
- 2013
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 53:2, s. 630-634
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Tidskriftsartikel (refereegranskat)abstract
- In ultrasonic testing, corners are used for sensitivity calibration in the form of notches, for measuring the sound velocity in the material, and as known reference points during testing. A 90° corner will always reflect incoming waves in the opposite direction due to a double reflection and therefore give a strong echo. This article presents a method for separating the echo from a corner from other echoes and more accurately find the position of the corner. The method is based on analysing the phase of the reflected signal. The proposed method was tested on a steel calibration block and the width of the indication was reduced by up to 50% compared to the amplitude signal. This results in a more accurate positioning of the corner. Using the phase instead of the amplitude will also improve the reliability, since reflections other than from corners will disappear.
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| 8. |
- Chai, Guocai, et al.
(författare)
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Study of Crack Initiation or Damage in Very High Cycle Fatigue Using Ultrasonic Fatigue Test and Microstructure Analysis
- 2013
-
Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 53:8, s. 1406-1411
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Tidskriftsartikel (refereegranskat)abstract
- Fatigue damage behaviors of four metal materials in the very high cycle fatigue (VHCF) regime have been studied using ultrasonic fatigue test and microstructure analysis. The results show that the fatigue crack initiation in VHCF regime could occur at subsurface non-defect fatigue crack origin (SNDFCO), where the accumulated cyclic strains or damage in the specimens were highly localized, especially in the materials with some softer phase, where the local maximum strain can be eight times higher than the average strain value in the specimen. This high strain localization can cause a local plasticity exhaustion that leads to a stress concentration and consequently fatigue crack initiation, and finally the formation of SNDFCO. For pure single phase austenitic material, strain localization can also occur due to dislocation accumulation at or near grain boundaries, which can become fatigue crack initiation origin in the VHCF regime. The results in this study show that fatigue damage and crack initiation mechanisms in the VHCF regime can be different in different metals due to the mechanisms for local plasticity exhaustion.
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| 9. |
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| 10. |
- Erkki, Heikkola, et al.
(författare)
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Multiobjective Optimization of an Ultrasonic Transducer using NIMBUS
- 2006
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 44:4, s. 368-380
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Tidskriftsartikel (refereegranskat)abstract
- The optimal design of an ultrasonic transducer is a multiobjective optimization problem since the final outcome needs to satisfy several conflicting criteria. Simulation tools are often used to avoid expensive and time-consuming experiments, but even simulations may be inefficient and lead to inadequate results if they are based only on trial and error. In this work, the interactive multiobjective optimization method NIMBUS is applied in designing a high-power ultrasonic transducer. The performance of the transducer is simulated with a finite element model, and three design goals are formulated as objective functions to be minimized. To find an appropriate compromise solution, additional preference information is needed from a decision maker, who in our case is an expert in transducer design. A realistic design problem is formulated, and an interactive solution process is described. Our findings demonstrate that interactive multiobjective optimization methods, combined with numerical simulation models, can efficiently help in finding new solution approaches and possibilities as well as new understanding of real-life problems as entirenesses. In this case, the decision maker found a solution that was better with respect to all three objectives than the conventional unoptimized design.
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| 11. |
- Grishenkov, Dmitry, 1983-, et al.
(författare)
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In vitro contrast-enhanced ultrasound measurements of capillary microcirculation : Comparison between polymer- and phospholipid-shelled microbubbles
- 2011
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 51:1, s. 40-48
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Tidskriftsartikel (refereegranskat)abstract
- The focus of contrast-enhanced ultrasound research has developed beyond visualizing the blood pool and its flow to new areas such as perfusion imaging, drug and gene therapy, and targeted imaging. In this work comparison between the application of polymer- and phospholipid-shelled ultrasound contrast agents (UCAs) for characterization of the capillary microcirculation is reported. All experiments are carried out using a microtube as a vessel phantom. The first set of experiments evaluates the optimal concentration level where backscattered signal from microbubbles depends on concentration linearly. For the polymer-shelled UCAs the optimal concentration level is reached at a value of about 2 x 10(4) MB/ml, whereas for the phospholipid-shelled UCAs the optimal level is found at about 1 x 10(5) MB/ml.Despite the fact that the polymer shell occupies 30% of the radius of microbubble, compared to 0.2% of the phospholipid-shelled bubble, approximately 5-fold lower concentration of the polymer UCA is needed for investigation compared to phospholipid-shelled analogues. In the second set of experiments, destruction/replenishment method with varied time intervals ranging from 2 ms to 3 s between destructive and monitoring pulses is employed. The dependence of the peak-to-peak amplitude of backscattered wave versus pulse interval is fitted with an exponential function of the time gamma = A( 1 - exp(-beta t)) where A represents capillary volume and the time constant beta represents velocity of the flow. Taking into account that backscattered signal is linearly proportional to the microbubble concentration, for both types of the UCAs it is observed that capillary volume is linearly proportional to the concentration of the microbubbles, but the estimation of the flow velocity is not affected by the change of the concentration. Using the single capillary model, for the phospholipid-shelled UCA a delay of about 0.2-0.3 s in evaluation of the perfusion characteristics is found while polymer-shelled UCA provide response immediately. The latter at the concentration lower than 3.6 x 10(5) MB/ml have no statistically significant delay (p < 0.01), do not cause any attenuation of the backscattered signal or saturation of the receiving part of the system. In conclusion, these results suggest that the novel polymer-shelled microbubbles have a potential to be used for perfusion evaluation.
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| 12. |
- Hutchinson, Bevis, et al.
(författare)
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Anomalous ultrasonic attenuation in ferritic steels at elevated temperatures
- 2016
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Ingår i: Ultrasonics. - : Elsevier B.V.. - 0041-624X .- 1874-9968. ; 69, s. 268-272
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Tidskriftsartikel (refereegranskat)abstract
- An unexpected peak in attenuation has been observed at ∼800 °C when heating low carbon steels in a laser-ultrasonic instrument. An explanation is given in terms of enhanced crystalline anisotropy with increasing temperature in the bcc ferrite range combined with subsequent transformation to austenite at still higher temperatures. An analysis based on theoretical models of attenuation in the Rayleigh regime is in good agreement with the experimental observations.
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| 13. |
- Hutchinson, Bevis, et al.
(författare)
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Elasticity and wave velocity in fcc iron (austenite) at elevated temperatures – Experimental verification of ab-initio calculations
- 2018
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Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 87, s. 44-47
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Tidskriftsartikel (refereegranskat)abstract
- High temperature crystal elasticity constants for face centred cubic austenite are important for interpreting the ultrasonic properties of iron and steels but cannot be determined by normal single crystal methods. Values of these constants have recently been calculated using an ab-initio approach and the present work was carried out to test their applicability using laser-ultrasonic measurements. Steel samples having a known texture were examined at temperatures between 800 °C and 1100 °C to measure the velocity of longitudinal P-waves which were found to be in good agreement with modelled values.
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| 14. |
- Imani Jajarmi, Ramin, et al.
(författare)
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Acoustic Separation of Submicron Solid Particles in air
- 2015
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 63
-
Tidskriftsartikel (refereegranskat)abstract
- The use of ultrasound to continuously separate submicron particles suspended in air is investigated in a rectangular channel with adjustable height. An electrostatic transducer is used to generate a standing wave in the 50-80 kHz frequency range and the particles experience forces within the acoustic field causing them to concentrate at the pressure nodes. To assess the effect of several key design parameters on the separation efficiency, a simple method based on light scattering is implemented to provide information on the particle concentrations as a function of position in the channel. The images acquired are processed to yield a separation efficiency metric that is used to evaluate the effect of acoustic, flow and geometrical parameters. The results show that, in qualitative agreement with theoretical models, the maximum separation efficiency increases with the pressure amplitude of the sound wave. The separation efficiency is also linearly proportional to the standing wave frequency, when it is varied between 50-80 kHz. On the other hand, the effect of the average fluid velocity is less pronounced than expected, suggesting that in our channel separation is not limited by the interaction length between the acoustic field and the suspended particles. The effect of the parallelism of the reflector relative to the transducer is also investigated.
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| 15. |
- Jasiuniene, Elena, et al.
(författare)
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Ultrasonic non-destructive testing of complex titanium/carbon fibre composite joints
- 2019
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Ingår i: Ultrasonics. - : Elsevier B.V.. - 0041-624X .- 1874-9968. ; 95, s. 13-21
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasonic inspection is widely used for non-destructive evaluation of composite adhesive joints. However, there are serious challenges in applying ultrasonic testing on metal to composite hybrid joints, because they are multi-layered, made out of dissimilar materials and relatively thin. The ultrasonic signals reflected by different layers are overlapped, scattered and attenuated. The aim of this research was to develop an ultrasonic inspection technique suitable for defect detection in hybrid metal to composite joints where the metal part has pin arrays, which entangle with the composite part. The immersion pulse echo technique was used to collect data. In order to overcome the problems related to the rough surface and non-parallel layers a novel signal post-processing algorithm for reconstruction of the joint area was developed and validated experimentally. It is shown that using the proposed technique the positions of different defects can be determined.
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| 16. |
- Johansson, Jonny, et al.
(författare)
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Microelectronics mounted on a piezoelectric transducer : method, simulations, and measurements
- 2006
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 44:1, s. 1-11
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes the design of a highly integrated ultrasound sensor where the piezoelectric ceramic transducer is used as the carrier for the driver electronics. Intended as one part in a complete portable, battery operated ultrasound sensor system, focus has been to achieve small size and low power consumption. An optimized ASIC driver stage is mounted directly on the piezoelectric transducer and connected using wire bond technology. The absence of wiring between driver and transducer provides excellent pulse control possibilities and eliminates the need for broad band matching networks. Estimates of the sensor power consumption are made based on the capacitive behavior of the piezoelectric transducer. System behavior and power consumption are simulated using SPICE models of the ultrasound transducer together with transistor level modelling of the driver stage. Measurements and simulations are presented of system power consumption and echo energy in a pulse echo setup. It is shown that the power consumption varies with the excitation pulse width, which also affects the received ultrasound energy in a pulse echo setup. The measured power consumption for a 16 mm diameter 4.4 MHz piezoelectric transducer varies between 95 μW and 130 μW at a repetition frequency of 1 kHz. As a lower repetition frequency gives a linearly lower power consumption, very long battery operating times can be achieved. The measured results come very close to simulations as well as estimated ideal minimum power consumption.
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| 17. |
- Johansson, Linda, et al.
(författare)
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Temperature and trapping characterization of an acoustic trap with miniaturized integrated transducers - towards in-trap temperature regulation
- 2013
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 53:5, s. 1020-1032
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Tidskriftsartikel (refereegranskat)abstract
- An acoustic trap with miniaturized integrated transducers (MITs) for applications in non-contact trapping of cells or particles in a microfluidic channel was characterized by measuring the temperature increase and trapping strength. The fluid temperature was measured by the fluorescent response of Rhodamine B in the microchannel. The trapping strength was measured by the area of a trapped particle cluster counter-balanced by the hydrodynamic force. One of the main objectives was to obtain quantitative values of the temperature in the fluidic channel to ensure safe handling of cells and proteins. Another objective was to evaluate the trapping-to-temperature efficiency for the trap as a function of drive frequency. Thirdly, trapping-to-temperature efficiency data enables identifying frequencies and voltage values to use for in-trap temperature regulation. It is envisioned that operation with only in-trap temperature regulation enables the realization of small, simple and fast temperature-controlled trap systems. The significance of potential gradients at the trap edges due to the finite size of the miniaturized transducers for the operation was emphasized and expressed analytically. The influence of the acoustic near field was evaluated in FEM-simulation and compared with a more ideal 1D standing wave. The working principle of the trap was examined by comparing measurements of impedance, temperature increase and trapping strength with impedance transfer calculations of fluid-reflector resonances and frequencies of high reflectance at the fluid-reflector boundary. The temperature increase was found to be moderate, 7 degrees C for a high trapping strength, at a fluid flow of 0.5 mm s(-1) for the optimal driving frequency. A fast temperature response with a fall time of 8 s and a rise time of 11 s was observed. The results emphasize the importance of selecting the proper drive frequency for long term handling of cells, as opposed to the more pragmatic way of selecting the frequency of the highest acoustic output. Trapping was demonstrated in a large interval between 9 and 11.5 MHz, while the main trapping peak displayed FWHM of 0.5 MHz. A large bandwidth enables a more robust manufacturing and operation while allowing the trapping platform to be used in applications where the fluid wavelength varies due to external variations in fluid temperature, density and pressure.
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| 18. |
- Kothapalli, Satya V. V. N., et al.
(författare)
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Investigation of polymer-shelled microbubble motions in acoustophoresis
- 2016
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Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 70, s. 275-283
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Tidskriftsartikel (refereegranskat)abstract
- The objective of this paper is to explore the trajectory motion of microsize (typically smaller than a red blood cell) encapsulated polymer-shelled gas bubbles propelled by radiation force in an acoustic standing-wave field and to compare the corresponding movements of solid polymer microbeads. The experimental setup consists of a microfluidic chip coupled to a piezoelectric crystal (PZT) with a resonance frequency of about 2.8 MHz. The microfluidic channel consists of a rectangular chamber with a width, w, corresponding to one wavelength of the ultrasound standing wave. It creates one full wave ultrasound of a standing-wave pattern with two pressure nodes at w/4 and 3w/4 and three antinodes at 0, w/2, and w. The peak-to-peak amplitude of the electrical potential over the PZT was varied between 1 and 10 V. The study is limited to no-flow condition. From Gor'kov's potential equation, the acoustic contrast factor, Phi, for the polymer-shelled microbubbles was calculated to about -60.7. Experimental results demonstrate that the polymer-shelled microbubbles are translated and accumulated at the pressure antinode planes. This trajectory motion of polymer-shelled microbubbles toward the pressure antinode plane is similar to what has been described for other acoustic contrast particles with a negative Phi. First, primary radiation forces dragged the polymer-shelled microbubbles into proximity with each other at the pressure antinode planes. Then, primary and secondary radiation forces caused them to quickly aggregate at different spots along the channel. The relocation time for polymer-shelled microbubbles was 40 times shorter than that for polymer microbeads, and in contrast to polymer microbeads, the polymer-shelled microbubbles were actuated even at driving voltages (proportional to radiation forces) as low as 1 V. In short, the polymer-shelled microbubbles demonstrate the behavior attributed to the negative acoustic contrast factor particles and thus can be trapped at the antinode plane and thereby separated from particles having a positive acoustic contrast factor, such as for example solid particles and cells. This phenomenon could be utilized in exploring future applications, such as bioassay, bioaffinity, and cell interaction studies in vitro in a well-controlled environment.
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| 19. |
- Kotze, Reinhardt, et al.
(författare)
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Optimisation of Pulsed Ultrasonic Velocimetry system and transducer technology for industrial applications
- 2013
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 53:2, s. 459-469
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Tidskriftsartikel (refereegranskat)abstract
- Pulsed Ultrasonic Velocimetry, commonly referred to as Ultrasonic Velocity Profiling (UVP) in research and engineering applications, is both a method and a device to measure an instantaneous one-dimensional velocity profile in opaque fluids along a measurement axis by using Doppler echography. Studies have suggested that the accuracy of the measured velocity gradient close to wall interfaces need to be improved. The reason for this is due to distortion caused by cavities situated in front of ultrasonic transducers, measurement volumes overlapping wall interfaces, refraction of the ultrasonic wave as well as sound velocity variations (Doppler angle changes). In order to increase the accuracy of velocity data close to wall interfaces and solve previous problems a specially designed delay line transducer was acoustically characterised and evaluated. Velocity profiles measured using the delay line transducer, were initially distorted due to the effect of finite sample volume characteristics and propagation through the delay line material boundary layers. These negative effects were overcome by measuring physical properties of the ultrasonic beam and implementing a newly developed deconvolution procedure. Furthermore, custom velocity estimation algorithms were developed, which improved the time resolution and penetration depth of the UVP system. The optimised UVP system was evaluated and compared to standard transducers in three different straight pipes (inner diameters of 16, 22.5 and 52.8 mm). Velocity data obtained using the optimised UVP system showed significant improvement close to wall interfaces where the velocity gradients are high. The new transducer technology and signal processing techniques reduced previously mentioned problems and are now more suitable for industrial process monitoring and control.
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| 20. |
- Kvikliene, Adriana, et al.
(författare)
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Modelling of nonlinear effects and the response of ultrasound contrast micro bubbles : simulation and experiment
- 2004
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 42:01-Sep, s. 301-307
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Tidskriftsartikel (refereegranskat)abstract
- The propagation of diagnostic ultrasonic imaging pulses in tissue and their interaction with contrast micro bubbles is a very complex physical process, which we assumed to be separable into three stages: pulse propagation in tissue, the interaction of the pulse with the contrast bubble, and the propagation of the scattered echo. The model driven approach is used to gain better knowledge of the complex processes involved. A simplified way of field simulation is chosen due to the complexity of the task and the necessity to estimate comparative contributions of each component of the process. Simulations are targeted at myocardial perfusion estimation. A modified method for spatial superposition of attenuated waves enables simulations of low intensity pulse pressure fields from weakly focused transducers in a nonlinear, attenuating, and liquid-like biological medium. These assumptions enable the use of quasi-linear calculations of the acoustic field. The simulations of acoustic bubble response are carried out with the Rayleigh-Plesset equation with the addition of radiation damping. Theoretical simulations with synthesised and experimentally sampled pulses show that the interaction of the excitation pulses with the contrast bubbles is the main cause of nonlinear scattering, and a 2-3 dB increase of second harmonic amplitude depends on nonlinear distortions of the incident pulse. (C) 2004 Elsevier B.V. All rights reserved.
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| 21. |
- Larsson, Matilda, et al.
(författare)
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Ultrasound speckle tracking for radial, longitudinal and circumferential strain estimation of the carotid artery : An in vitro validation via sonomicrometry using clinical and high-frequency ultrasound
- 2014
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 56, s. 399-408
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound speckle tracking for carotid strain assessment has in the past decade gained interest in studies of arterial stiffness and cardiovascular diseases. The aim of this study was to validate and directly contrast carotid strain assessment by speckle tracking applied on clinical and high-frequency ultrasound images in vitro. Four polyvinyl alcohol phantoms mimicking the carotid artery were constructed with different mechanical properties and connected to a pump generating carotid flow profiles. Gray-scale ultrasound long-and short-axis images of the phantoms were obtained using a standard clinical ultrasound system, Vivid 7 (GE Healthcare, Horten, Norway) and a high-frequency ultrasound system, Vevo 2100 (FUJIFILM, VisualSonics, Toronto, Canada) with linear-array transducers (12L / MS250). Radial, longitudinal and circumferential strains were estimated using an in-house speckle tracking algorithm and compared with reference strain acquired by sonomicrometry. Overall, the estimated strain corresponded well with the reference strain. The correlation between estimated peak strain in clinical ultrasound images and reference strain was 0.91 (p < 0.001) for radial strain, 0.73 (p < 0.001) for longitudinal strain and 0.90 (p < 0.001) for circumferential strain and for high-frequency ultrasound images 0.95 (p < 0.001) for radial strain, 0.93 (p < 0.001) for longitudinal strain and 0.90 (p < 0.001) for circumferential strain. A significant larger bias and root mean square error was found for circumferential strain estimation on clinical ultrasound images compared to high frequency ultrasound images, but no significant difference in bias and root mean square error was found for radial and longitudinal strain when comparing estimation on clinical and high-frequency ultrasound images. The agreement between sonomicrometry and speckle tracking demonstrates that carotid strain assessment by ultrasound speckle tracking is feasible.
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| 22. |
- Manneberg, Otto, 1981-, et al.
(författare)
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Spatial confinement of ultrasonic force fields in microfluidic chips
- 2009
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 49, s. 112-119
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate and investigate multiple localized ultrasonic manipulation functions in series in microfluidic chips. The manipulation functions are based on spatially separated and confined ultrasonic primary radiation force fields, obtained by local matching of the resonance condition of the microfluidic channel. The channel segments are remotely actuated by the use of frequency-specific external transducers with refracting wedges placed on top of the chips. The force field in each channel segment is characterized by the use of micrometer-resolution particle image velocimetry ( micro-PIV). The confinement of the ultrasonic fields during single-or dual-segment actuation, as well as the cross-talk between two adjacent. fields, is characterized and quantified. Our results show that the field confinement typically scales with the acoustic wavelength, and that the cross-talk is insignificant between adjacent. fields. The goal is to define design strategies for implementing several spatially separated ultrasonic manipulation functions in series for use in advanced particle or cell handling and processing applications. One such proof-of-concept application is demonstrated, where. flow-through-mode operation of a chip with. flow splitting elements is used for two-dimensional pre-alignment and addressable merging of particle tracks.
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| 23. |
- Martinsson, Jesper, et al.
(författare)
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Complete post-separation of overlapping ultrasonic signals by combining hard and soft modeling
- 2008
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 48:5, s. 427-443
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Tidskriftsartikel (refereegranskat)abstract
- In some ultrasonic measurement situations, an adequate signal separation is difficult to achieve. A typical situation is material characterization of thin media using pulse-echo or through-transmission techniques, when the time-of-flight in the media is shorter than the emitted signal's time support. Separated signals are necessary to obtain accurate estimates of material properties and transit times. In this paper a new method is proposed that enables complete post separation of measured coinciding signals. The method is based on a combination of hard physical and soft empirical models, which allows for a description of both known and unknown properties making a complete separation possible. The validity and limitations of the model and the separation results are thoroughly addressed. The proposed technique is verified using real measurements on thin dispersive samples and validated using residual analysis. The experimental results show a complete separation with uncorrelated and normally distributed residuals. The method enables characterization and/or flow analysis in difficult overlapping situations.
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| 24. |
- Martinsson, Jesper, et al.
(författare)
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Parametric estimation of ultrasonic phase velocity and attenuation in dispersive media
- 2006
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 44:Supplement 1, s. e991-e994
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Tidskriftsartikel (refereegranskat)abstract
- In ultrasonic characterization of liquids, gases, and solids, accurate estimation of frequency dependent attenuation and phase velocity is of great importance. Non-parametric methods, such as Fourier analysis, suffers from noise sensitivity, and the variance of the estimated quantities is limited by the signal-to-noise ratio. In this paper we present a parametric method for estimation of these properties. Pulse echo experiments in ethane, oxygen and mixtures of the two show that the proposed method can estimate phase velocity and attenuation with up to 50 times lower variance than standard non-parametric methods.
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| 25. |
- Pecorari, Claudio
(författare)
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A note on the sensitivity of SV wave scattering to surface-breaking cracks
- 2005
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 43:7, s. 508-511
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Tidskriftsartikel (refereegranskat)abstract
- The results presented in this communication show that the conventional configuration adopting a shear vertical wave at 45 degrees of incidence to detect cracks breaking the surface opposite the one on which the inspecting transducer is placed is not optimal when the crack depth is of the order of one wavelength of the inspecting wave or smaller. Angles of incidence proximal to the critical angle of longitudinal wave should be used instead.
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| 26. |
- Schäfer, Robert, et al.
(författare)
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Ultrasonic concentration measurement of aqueous solutions using PLS regression
- 2006
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 44:Supplement 1, s. e947-e950
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Tidskriftsartikel (refereegranskat)abstract
- This work demonstrates the use of a multivariate statistical technique called partial least squares (PLS) to extract material related data by analyzing spectra of ultrasonic pulses. We show how PLS can be used to estimate the concentration of sodium chloride in an aqueous solution. The paper describes the use of PLS and discusses pre-processing of ultrasonic data, the PLS algorithm as well as model validation. The measured concentrations are compared to reference values. The influence of disturbances and parameter changes is highlighted. The proposed method is easily adaptable to similar applications and permits a cost-saving implementation using existing and approved hardware
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| 27. |
- Svanström, Erika, et al.
(författare)
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Analytical one-dimensional model for laser-induced ultrasound in planar optically absorbing layer
- 2014
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 54:3, s. 888-893
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Tidskriftsartikel (refereegranskat)abstract
- Ultrasound generated by means of laser-based photoacoustic principles are in common use today and applications can be found both in biomedical diagnostics, non-destructive testing and materials characterisation. For certain measurement applications it could be beneficial to shape the generated ultrasound regarding spectral properties and temporal profile. To address this, we studied the generation and propagation of laser-induced ultrasound in a planar, layered structure. We derived an analytical expression for the induced pressure wave, including different physical and optical properties of each layer. A Laplace transform approach was employed in analytically solving the resulting set of photoacoustic wave equations. The results correspond to simulations and were compared to experimental results. To enable the comparison between recorded voltage from the experiments and the calculated pressure we employed a system identification procedure based on physical properties of the ultrasonic transducer to convert the calculated acoustic pressure to voltages. We found reasonable agreement between experimentally obtained voltages and the voltages determined from the calculated acoustic pressure, for the samples studied. The system identification procedure was found to be unstable, however, possibly from violations of material isotropy assumptions by film adhesives and coatings in the experiment. The presented analytical model can serve as a basis when addressing the inverse problem of shaping an acoustic pulse from absorption of a laser pulse in a planar layered structure of elastic materials.
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| 28. |
- van Deventer, Jan
(författare)
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One dimensional modeling of a step-down ultrasonic densitometer for liquids
- 2004
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 42:1-9, s. 309-314
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Tidskriftsartikel (refereegranskat)abstract
- This article studies the possibilities and limitations of modeling a step-down ultrasonic densitometer using its electrical analogous representation. The purpose of the model is to simulate the system in order to optimize its performance. The advantage of an analogous electrical is the complete simulation of both the electrical and mechanical parts of the system. The ultrasonic densitometer and the need for the step down are presented. The analogy to the electrical representation is briefly introduced along with the step down notion. Experimental results of probes equipped with piezoceramic disk of 10 and 16 mm in diameter are shown to consider diffraction. Simulated signals from modeled probes are judged against the real signals. The limitations of the simulations are discussed. They are beam spreading, reference echo to different media and superfluous multiple reflections.
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| 29. |
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| 30. |
- Yantchev, Ventsislav, et al.
(författare)
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Design of high frequency piezoelectric resonators utilizing laterally propagating fast modes in thin aluminum nitride (AlN) films
- 2006
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X .- 1874-9968. ; 45:1-4, s. 208-212
-
Tidskriftsartikel (refereegranskat)abstract
- Highly c-oriented aluminum nitride (AlN) thin piezoelectric films have been grown by pulsed direct-current (DC) magnetron reactive sputter deposition. The films were deposited at room temperature and had a typical full width half maximum (FWHM) value of the (0 0 2) rocking curve of around 2°. Resonant devices in thin film plates having surface acoustic wave (SAW) based designs were fabricated by means of low resolution photolithography. The devices were designed to operate with the fast Rayleigh and Lamb modes respectively. Both types of devices exhibited propagation velocities in excess of 10 000 m/s and sufficient electromechanical couplings. The device measurements illustrate the big potential of these modes for the development of low cost IC compatible electroacoustic devices in the lower GHz range. The basic properties of the modes studied are discussed in a comparative manner. Potential commercial applications are also outlined.
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| 31. |
- Zia, Shafaq, et al.
(författare)
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Prediction of manufacturing parameters of additively manufactured 316L steel samples using ultrasound fingerprinting
- 2024
-
Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 137
-
Tidskriftsartikel (refereegranskat)abstract
- Metal based additive manufacturing techniques such as laser powder bed fusion can produce parts with complex designs as compared to traditional manufacturing. The quality is affected by defects such as porosity or lack of fusion that can be reduced by online control of manufacturing parameters. The conventional way of testing is time consuming and does not allow the process parameters to be linked to the mechanical properties. In this paper, ultrasound data along with supervised learning is used to estimate the manufacturing parameters of 316L steel samples. The steel samples are manufactured with varying process parameters (speed, hatch distance and power) in two batches that are placed at different locations on the build plate. These samples are examined with ultrasound using a focused transducer. The ultrasound scans are performed in a dense grid in the build and transverse direction, respectively. Part of the ultrasound data are used to train a partial least squares regression algorithm by labelling the data with the corresponding manufacturing parameters (speed, hatch distance and power, and build plate location). The remaining data are used for testing of the resulting model. To assess the uncertainty of the method, a Monte-Carlo simulation approach is adopted, providing a confidence interval for the predicted manufacturing parameters. The analysis is performed in both the build and transverse direction. Since the material is anisotropic, results show that there are differences, but that the manufacturing parameters has an effect of the material microstructure in both directions.
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| 32. |
- Zohrevand, Milad, et al.
(författare)
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Softening mechanisms in ultrasonic treatment of deformed austenitic stainless steel
- 2021
-
Ingår i: Ultrasonics. - : Elsevier. - 0041-624X .- 1874-9968. ; 116
-
Tidskriftsartikel (refereegranskat)abstract
- The effect of ultrasonic treatment on the microstructural evolution and the related softening process in tensile pre-deformed 316 stainless steel was studied by means of electron backscatter diffraction method, optical microscopy, and microhardness measurement. It was observed that different levels of ultrasonic energy induced complex microstructural changes in the treated samples. A large decrease in twin boundaries was observed, which is an indication of the de-twinning process under ultrasonic treatment. A new mechanism for the de-twinning process under oscillatory stress of ultrasonic vibration was proposed. It was shown that de-twinning under ultrasonic treatment led to dislocation production from twin boundaries. Inverse pole figures investigation revealed strong grain rotation following ultrasonic treatment in tensile pre-deformed samples. Subgrain formation in the ultrasonic treated austenitic stainless steel samples indicated that considerable ultrasonic energy was induced by the ultrasonic vibration, which provided the activation energy needed for dislocation climb and cross-slip. The ultrasonic induced subgrain formation, dislocation annihilation, and de-twinning, which resulted in a decrease of the microhardness in the samples, can be considered as possible mechanisms for the acoustic softening in the austenitic stainless steels.
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| 33. |
- Wiklund, M, et al.
(författare)
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Ultrasonic-trap-enhanced selectivity in capillary electrophoresis.
- 2003
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Ingår i: Ultrasonics. - 0041-624X. ; 41:4, s. 329-333
-
Tidskriftsartikel (refereegranskat)abstract
- We combine ultrasonic trapping and capillary electrophoresis (CE) with the goal to detect ultra-low concentrations of proteins via size-selective separation and enrichment of antibody-coated latex spheres. An 8.5 MHz standing ultrasonic wave is longitudinally coupled into the sub-100-small mu, Greekm diam capillary of the CE system. Competition between acoustic and viscous forces result in in-flow separation of small mu, Greekm-diam spheres according to their size. Experiments separating 2.8- and 2.1-small mu, Greekm-diam fluorescent latex particles, which model a protein-specific immunocomplex/free particle mixture, indicate a potential improvement of the concentration limit of detection of 104 compared to current CE systems. Theoretical calculations show room for further improvement.
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| 34. |
- Fröjd, Patrik, et al.
(författare)
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Frequency selection for coda wave interferometry in concrete structures
- 2017
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 80, s. 1-8
-
Tidskriftsartikel (refereegranskat)abstract
- This study contributes to the establishment of frequency recommendations for use in coda wave interferometry structural health monitoring (SHM) systems for concrete structures. To this end, codas with widely different central frequencies were used to detect boreholes with different diameters in a large concrete floor slab, and to track increasing damage in a small concrete beam subjected to bending loads. SHM results were obtained for damage that can be simulated by drilled holes on the scale of a few mm or microcracks due to bending. These results suggest that signals in the range of 50–150 kHz are suitable in large concrete structures where it is necessary to account for the high attenuation of high-frequency signals.
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| 35. |
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| 36. |
- Jafarzadeh, Ata, 1992, et al.
(författare)
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Scattering of elastic waves by a sphere with orthorhombic anisotropy and application to polycrystalline material characterization
- 2024
-
Ingår i: Ultrasonics. - 0041-624X. ; 138
-
Tidskriftsartikel (refereegranskat)abstract
- Scattering of elastic waves by an anisotropic sphere with orthorhombic symmetry inside an isotropic medium is studied and applied to characterization of polycrystalline materials with anisotropic grains. For a single sphere the waves in the isotropic surrounding are expanded in the spherical vector wave functions. Inside the sphere, the elastodynamic equations are first transformed to spherical coordinates and the displacement field is expanded in terms of the vector spherical harmonics in the angular directions and power series in the radial direction. The governing equations inside the sphere give recursion relations among the expansion coefficients in the power series. The boundary conditions on the sphere then determine the relation among the scattered wave expansion coefficients and those of the incident wave, expressed as the transition (T) matrix. For low frequencies the elements of the T matrix are obtained in explicit form. According to the theory of Foldy the T matrix elements of a single sphere are used to study attenuation and phase velocity of polycrystalline materials, explicitly for low frequencies. Comparisons of the present method with previously published results and recent FEM results show a good correspondence for low frequencies. The present approach shows a better agreement with FEM for strongly anisotropic materials in comparison with other published methods.
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| 37. |
- Lei, Xiangyu, 1992, et al.
(författare)
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Experimental Validation of a Phased Array Probe Model in Ultrasonic Inspection
- 2020
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 108
-
Tidskriftsartikel (refereegranskat)abstract
- New manufacturing technologies such as additive manufacturing facilitate flexible and complex designs and production of components. However, these new techniques should not compromise the safety aspect, which imposes higher demands on the integrity insurance and inspection methods. Phased array ultrasonic testing (PAUT) provides advanced inspection and evaluation processes, whereas qualification is still needed when applied together with new manufacturing techniques. Numerical modeling, as one of the potential qualification methods, has been developed for decades and should be validated before practical applications. This paper presents an experimental validation work of the phased array probe model implemented in a software, simSUNDT, by comparing the maximum echo amplitudes between the physical experiments and simulations. Two test specimens with side-drilled holes (SDHs) and different materials are considered for validation and practical purposes. An experimental platform with a mechanized gantry system, which enables stabilized inspection procedure, is built and applied during the validation work. Good correlations can be seen from the comparisons and this model is concluded as an acceptable alternative to the corresponding experimental work. The relation between depth and beam angle is also noticed and investigated, which is essential to guarantee an accurate inspection.
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| 38. |
- Lilliehorn, Tobias, et al.
(författare)
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Trapping of microparticles in the near field of an ultrasonic transducer
- 2005
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Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 43:5, s. 293-303
-
Tidskriftsartikel (refereegranskat)abstract
- We are investigating means of handling microparticles in microfluidic systems, in particular localized acoustic trapping of microparticles in a flow-through device. Standing ultrasonic waves were generated across a microfluidic channel by ultrasonic microtransducers integrated in one of the channel walls. Particles in a fluid passing a transducer were drawn to pressure minima in the acoustic field, thereby being trapped and confined at the lateral position of the transducer. The spatial distribution of trapped particles was evaluated and compared with calculated acoustic intensity distributions. The particle trapping was found to be strongly affected by near field pressure variations due to diffraction effects associated with the finite sized transducer element. Since laterally confining radiation forces are proportional to gradients in the acoustic energy density, these near field pressure variations may be used to get strong trapping forces, thus increasing the lateral trapping efficiency of the device. In the experiments, particles were successfully trapped in linear fluid flow rates up to 1 mm/s. It is anticipated that acoustic trapping using integrated transducers can be exploited in miniaturised total chemical analysis systems (μTAS), where e.g. microbeads with immobilised antibodies can be trapped in arrays and subjected to minute amounts of sample followed by a reaction, detected using fluorescence.
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| 39. |
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| 40. |
- Olofsson, T, et al.
(författare)
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Maximum a posteriori deconvolution of sparse ultrasonic signals using genetic optimization
- 1999
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Ingår i: ULTRASONICS. - : ELSEVIER SCIENCE BV. - 0041-624X. ; 37:6, s. 423-432
-
Tidskriftsartikel (refereegranskat)abstract
- Deconvolution of sparse spike sequences has received much attention in the field of seismic exploration. In certain situations in ultrasonic non-destructive testing (NDT) of materials, similar conditions as those found in seismic exploration occur. One ex
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| 41. |
- Shoja, Siavash, 1982, et al.
(författare)
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Design optimization of transducer arrays for uniform distribution of guided wave energy in arbitrarily shaped domains
- 2020
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 103
-
Tidskriftsartikel (refereegranskat)abstract
- The use of an array of transducers to excite guided Lamb waves, within a plate or any complex structure, usually leads to a variation in the energy on the propagation direction. In this study, an optimization model is proposed to design an array of transducers to provide uniform energy distribution in a domain of an arbitrary shape. The model is based on finding the optimal placements of the transducers and the optimal time delay for excitation by using a genetic algorithm. The efficiency of the model was tested on an elliptically shaped domain, then on an arbitrarily shaped domain. Both cases showed promising results using various configurations/patterns of transducers. The method was experimentally validated on an aluminium alloy plate for two patterns of transducers including six and eight piezoelectric elements.
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| 42. |
- Trzaskowska, A., et al.
(författare)
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Dispersion of the surface phonons in semiconductor/topological insulator Si/Bi 2 Te 3 heterostructure studied by high resolution Brillouin spectroscopy
- 2021
-
Ingår i: Ultrasonics. - : Elsevier BV. - 0041-624X. ; 117
-
Tidskriftsartikel (refereegranskat)abstract
- The dynamics and dispersion of surface phonons in heterostructure semiconductor/ topological insulator Si/Bi2Te3 was investigated using high resolution Brillouin light scattering method in the GHz frequency range. Both Rayleigh and Sezawa surface acoustic waves have been observed for wave vectors ranging from 0.006 to 0.023 nm−1. Anomaly in dispersion relations ω(q) for both surface waves were detected for the wave vector q = 0.016 nm−1. The finite element method (FEM) was used to simulate the observed shapes of ω(q) and to find the deformation profiles of surface acoustic waves. We attribute the observed changes to the coupling between low energy electrons and surface phonons. The coupling between helical Dirac states and surface phonons is discussed in the frame of accessible theoretical models.
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| 43. |
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