Ultrasonic waveguide based level measurement using flexural mode F(1,1) in addition to the fundamental modes.
TL;DR: By monitoring all three wave modes simultaneously, a more versatile and redundancy in measurements of the fluid level inside critical enclosures of processing industries can be achieved by compensating for changes in the fluid temperature using one mode, while the level is measured using another.
Abstract: This paper reports on an ultrasonic waveguide sensor for liquid level measurements using three guided wave modes simultaneously. The fundamental wave modes longitudinal L(0,1), torsional T(0,1), and flexural F(1,1) were simultaneously transmitted/received in a thin stainless steel wire-like waveguide using a standard shear wave transducer when oriented at an angle of 45° to the axis of the waveguide. Experiments were conducted in non-viscous fluid (water) and viscous fluid (castor oil). It was observed that the flexural F(1,1) wave mode showed a change in both time of flight (due to the change in velocity and dispersion effects) and amplitude (due to leakage) for different levels (0-9 cm) of immersion of the waveguide in a fluid medium. For the same level of immersion in the fluid, the L(0,1) and the T(0,1) modes show only a relatively smaller change in amplitude and no change in time of flight. The experimental results were validated using finite element model studies. The measured change in time of flight and/or the shift in central frequency of F(1,1) was related to the liquid level measurements. Multiple trials show repeatability with a maximum error of 2.5% in level measurement. Also, by monitoring all three wave modes simultaneously, a more versatile and redundancy in measurements of the fluid level inside critical enclosures of processing industries can be achieved by compensating for changes in the fluid temperature using one mode, while the level is measured using another. This ultrasonic waveguide technique will be helpful for remote measurements in physically inaccessible areas in hostile environments.
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01 Jan 2021
TL;DR: In this paper, a single transducer is attached to multiple waveguides of different lengths (each waveguide is designed with a single bend) for temperature measurement at multiple locations using the multiple waveguide configurations.
Abstract: This paper describes a technique for measurement of temperatures at multiple locations using the multiple waveguide configurations. A single transducer has been used for transmitting and receiving the torsional wave T(0,1) mode in the waveguides. Here, a single transducer is attached to multiple waveguides of different lengths (each waveguide is designed with a single bend). This method improves upon the earlier reported studies using straight waveguides, where the non-consideration of the temperature gradient issues. The temperature measurement range is from room temperature to the maximum utility temperature of the waveguide material. The time of flight difference (δTOF) of reflected ultrasonic torsional guided wave modes (T(0,1)) from the bend, which is the reference signal, and another signal from the end of the waveguide is utilized to measure the corresponding temperature of the surrounding media. The T(0,1) wave mode is less dispersive as compared to L(0,1) mode in the same material from the early reported work. The wavelength of the T(0,1) mode is significantly smaller than that of L(0,1) mode due to torsional velocity is less than the longitudinal velocity of ultrasonic sensor. Hence, it can be improved the sensitivity of the temperature measurements. This temperature measurement technique is more interest in several industrial applications, where using the furnaces and melters.
2 citations
TL;DR: In this article , a new ultrasonic sensor system for measuring small filling levels using longitudinal and surface acoustic wave analysis is described, which consists of one transducer for the longitudinal wave analysis and two transducers for the acoustic wave analyses.
Abstract: Measurement of the small filling levels in closed steel container systems is still a challenge. Ultrasound, however, is a sensitive and non-invasive technique and is suitable for online monitoring. This study describes a new ultrasonic sensor system for sensing small filling levels using longitudinal and surface acoustic wave analysis. The sensor system consists of one transducer for the longitudinal wave analysis and two transducers for the longitudinal and surface acoustic wave analysis. All transducers were mounted to the outer wall of the steel container, ensuring non-invasiveness, and a filling level ranging from 0 to 5 cm was investigated. Combining both approaches, a consistent determination of small filling levels was achieved for the entire measuring range (R2 = 0.99).
01 Jan 2022
TL;DR: In this paper , an ultrasonic waveguide sensor for sensing the temperature changes in a long region of interest using a long (length >20 m) waveguide and fundamental longitudinal L (0, 1) wave mode is presented.
Abstract: This work reports an ultrasonic waveguide sensor for sensing the temperature changes in a long region of interest using a long (length >20 m) waveguide and fundamental longitudinal L (0, 1) wave mode. The long waveguide can cover large (area/volume) region of interest and may also allow for an increased number of sensors along the length of waveguide while measuring the properties of the surrounding medium. The accessible length of the waveguide is dependent on the velocities (longitudinal (VL) and torsional (VT)) of the ultrasonic waves. Thus, a larger region of interest can be covered by a longer waveguide using L (0, 1) mode as compared to torsional T (0, 1) wave mode in the same time scale. The waveguide approaches presented in this work are generic in nature and can be applied using both T (0, 1) as well as L (0, 1) modes. Hence, the longitudinal wave mode is more suitable for designing the long-range waveguide sensor as compared to torsional mode due to its faster velocity (4960 m/s). A pair of waveguides of similar lengths (Alumal 23 m and Chromel 24 m) is connected to a single transducer (shear/longitudinal) at different orientations to study the possibilities of increasing the coverage length (for example, 47 m) for the large monitoring region of interest.
TL;DR: In this article , an ultrasonic waveguide technique using U-shaped configurations to measure the fluid level was reported. But the level measurement experiments were performed based on the drop in amplitude and change in time of flight of the received sensor signals.
Abstract: This paper reports an ultrasonic waveguide technique using U-shaped configurations to measure the fluid level. The longitudinal L(0,1) wave mode was propagated in the waveguide using through-transmission (TT) and pulse-echo (PE) techniques simultaneously using a single shear transducer. Initially, we used the Finite Element Method (FEM) to study the waveguide's wave propagation behavior while immersed in various fluids. Develop the level sensor using the waveguide’s first and second pass signals, corresponding to TT and PE. We have performed the level measurement experiments based on the drop in amplitude and change in time of flight of the received sensor signals. Studied the sensor’s sensitivity using TT1, PE1, TT2, and PE2 signals (1 and 2 represent first and second pass signals, respectively) with different fluid levels (petrol, water, castor oil, and glycerin). A comparison study was performed between straight waveguides using PE and U-shaped waveguides using TT techniques to find the limitations of waveguide sensors. During level-sensing experiments, the average error for U-shaped and straight waveguides was identified as 3.5% and 5.6%, respectively. We studied signal attenuation from straight and U-shaped waveguide sensors based on the sensor surface and dead-end region. In the designed U-shape waveguide, only the wave leakage effect was considered, avoiding the dead-end reflection during the immersion of the sensor in liquid and allowing for more fluid depth measurements. In addition, the U-shaped waveguide was further used for fluid-level sensing using three wave modes [L(0,1), T(0,1), and F(1,1)] simultaneously. This sensor can monitor fluid levels in hostile environments and inaccessible regions of power plants, oil, and petrochemical industries.
TL;DR: In this paper , an ultrasonic waveguide technique using U-shaped configurations to measure the fluid level was reported. But the level measurement experiments were performed based on the drop in amplitude and change in time of flight of the received sensor signals.
Abstract: This paper reports an ultrasonic waveguide technique using U-shaped configurations to measure the fluid level. The longitudinal L(0,1) wave mode was propagated in the waveguide using through-transmission (TT) and pulse-echo (PE) techniques simultaneously using a single shear transducer. Initially, we used the Finite Element Method (FEM) to study the waveguide's wave propagation behavior while immersed in various fluids. Develop the level sensor using the waveguide’s first and second pass signals, corresponding to TT and PE. We have performed the level measurement experiments based on the drop in amplitude and change in time of flight of the received sensor signals. Studied the sensor’s sensitivity using TT1, PE1, TT2, and PE2 signals (1 and 2 represent first and second pass signals, respectively) with different fluid levels (petrol, water, castor oil, and glycerin). A comparison study was performed between straight waveguides using PE and U-shaped waveguides using TT techniques to find the limitations of waveguide sensors. During level-sensing experiments, the average error for U-shaped and straight waveguides was identified as 3.5% and 5.6%, respectively. We studied signal attenuation from straight and U-shaped waveguide sensors based on the sensor surface and dead-end region. In the designed U-shape waveguide, only the wave leakage effect was considered, avoiding the dead-end reflection during the immersion of the sensor in liquid and allowing for more fluid depth measurements. In addition, the U-shaped waveguide was further used for fluid-level sensing using three wave modes [L(0,1), T(0,1), and F(1,1)] simultaneously. This sensor can monitor fluid levels in hostile environments and inaccessible regions of power plants, oil, and petrochemical industries.
References
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TL;DR: In this article, a two-dimensional Fourier transform (2D FFT) was used to measure the amplitudes and velocities of the Lamb waves propagating in a plate, the output of the transform being presented using an isometric projection which gives a three-dimensional view of the wave-number dispersion curves.
Abstract: A technique for the analysis of propagating multimode signals is presented. The method involves a two-dimensional Fourier transformation of the time history of the waves received at a series of equally spaced positions along the propagation path. The technique has been used to measure the amplitudes and velocities of the Lamb waves propagating in a plate, the output of the transform being presented using an isometric projection which gives a three-dimensional view of the wave-number dispersion curves. The results of numerical and experimental studies to measure the dispersion curves of Lamb waves propagating in 0.5-, 2.0-, and 3.0-mm-thick steel plates are presented. The results are in good agreement with analytical predictions and show the effectiveness of using the two-dimensional Fourier transform (2-D FFT) method to identify and measure the amplitudes of individual Lamb modes.
889 citations
01 Jan 1997
TL;DR: In this article, a general-purpose program that can create dispersion curves for a very wide range of systems and then effectively communicate the information contained within those curves is presented, using the global matrix method to handle multi-layered Cartesian and cylindrical systems.
Abstract: The application of guided waves in NDT can be hampered by the lack of readily available dispersion curves for complex structures. To overcome this hindrance, we have developed a general purpose program that can create dispersion curves for a very wide range of systems and then effectively communicate the information contained within those curves. The program uses the global matrix method to handle multi-layered Cartesian and cylindrical systems. The solution routines cover both leaky and non-leaky cases and remain robust for systems which are known to be difficult, such as large frequency-thicknesses and thin layers embedded in much thicker layers. Elastic and visco-elastic isotropic materials are fully supported; anisotropic materials are also covered, but are currently limited to the elastic, non-leaky, Cartesian case.
485 citations
TL;DR: In this article, it is shown that the L(0, 1) mode, which is comparable to the A0 Lamb wave mode in flat plate, can be generated with acceptable efficiency.
309 citations
TL;DR: In this paper, the authors used Lamb wave detection for detection of thin-walled structures due to their long propagation capability and sensitivity to a variety of different types of damage types.
Abstract: Lamb waves have shown great potentials in damage detection of thin-walled structures due to their long propagation capability and sensitivity to a variety of damage types. However, their practical ...
102 citations
TL;DR: From both theoretical and experimental studies, it also could be said that the amount of flexural modes reflected from a defect contains information on the reflector's circumferential angle, as well as potentially other classification and sizing feature information.
82 citations