Propagation Of Ultrasonic Signals Research Articles

Влияние геометрической формы демпфера на эффективность работы ультразвукового пьезоэлектрического преобразователя

Purpose of the work: To evaluate the influence of the geometric shape of the damper in the form of a truncated cone on the efficiency of the ultrasonic piezoelectric transducer. Materials and methods: Numerical and experimental modeling of the processes of propagation of ultrasonic signals in the damper of an ultrasonic transducer was used. Results: A damper in the form of a truncated cone is considered, the generatrix of which has an angle of inclination α with respect to the diameter of the piezoceramic plate. The shape of the damper in the form of a truncated cone is chosen based on the a priori assumption that this contributes to an increase in the path of the wave in the damper material due to numerous reflections inside it. A criterion for the efficiency of the damper is proposed. Theoretically and experimentally, the optimal (from the point of view of the efficiency of the damper) value of the angle α was determined. The technology of its manufacture is described. A satisfactory agreement between the results of theoretical and experimental studies was noted. Conclusion: The efficiency of a conical damper filled with a mixture of tungsten powder and KDA resin in a 1:1 ratio is higher than that of a cylindrical damper. A damper made from such a mixture can be effectively used in the manufacture of converters with a frequency of at least 2.5 MHz. For lower frequencies, it is required to select a different damping composition with a different filler or with a different ratio of its constituent components. The maximum efficiency of a cone damper is achieved when the cone generatrix is tilted α = 64…66.

Gas-insulated switchgear partial discharge acoustic–electric joint localisation method based on the Salp Swarm Algorithm and least squares estimation

Partial discharge (PD) is an early warning of gas-insulated switchgear (GIS) insulation faults. Consequently, accurate localisation of PD is crucial for the safe operation of GIS. The time difference of arrival method based on acoustic emission technology is more favorable for the engineering application of PD source localisation owing to its noninvasive characteristics and the small amount of required data. However, because PD ultrasonic signal propagation in GIS will introduce a variety of errors, current localisation algorithms suffer from problems of low accuracy and poor stability. Therefore, this study simulate and analyse the ultrasonic propagation characteristics as well as the sources of errors in GIS, based on which a joint acoustic–electric localisation method based on the Salp Swarm Algorithm is proposed, and an error-correction method based on least squares estimation is introduced. The localisation results show that the proposed method can effectively reduce the localisation error caused by multiple sources of error, and the mean localisation error can be reduced to within 20 mm in different structural gas chambers of GIS, which is more accurate and more stable compared with other methods, and it has good value for engineering application.

An ultrasonic signal propagation model of transformer partial discharge considering nonlinear attenuation in the temperature gradient field

An ultrasonic signal propagation model of transformer partial discharge considering nonlinear attenuation in the temperature gradient field

An Ultrasonic RF Acquisition System for Plant Stems Based on Labview Double Layer Multiple Triggering.

Ultrasound is widely used in medical and engineering inspections due to its non-destructive and easy-to-use characteristics. However, the complex internal structure of plant stems presents challenges for ultrasound testing. The density and thickness differences in various types of stems can cause different attenuation of ultrasonic signal propagation and the formation of different echo locations. To detect structural changes in plant stems, it is crucial to acquire complete ultrasonic echo RF signals. However, there is currently no dedicated ultrasonic RF detection equipment for plant stems, and some ultrasonic acquisition equipment has limited memory capacity that cannot store a complete echo signal. To address this problem, this paper proposes a double-layer multiple-timing trigger method, which can store multiple trigger sampling memories to meet the sampling needs of different plant stems with different ultrasonic echo locations. The method was tested in experiments and found to be effective in acquiring complete ultrasonic RF echo signals for plant stems. This approach has practical significance for the ultrasonic detection of plant stems.

Design of a complete simulator for underwater acoustic localization systems based on spread-spectrum signals

Deploying prototype positioning systems in underwater environments is expensive and an especially challenging task, so a first common approach is to carry out simulated studies to evaluate the requirements and restrictions imposed by the environment. In this regard, it is helpful to have simulation models that allow the generation of a wide range of tests as a previous step to any experimental prototype implementation. For that purpose, this work focuses on the design of a simulation tool that facilitates research on underwater positioning systems by considering several parameters and features, such as the design of the signals emitted by the acoustic transducers (encoding techniques, modulation schemes, etc.), the frequency response and location of emitters and hydrophones, the bathymetry of the seabed, and the channel effects on the ultrasonic signal propagation, implemented in a model based on ray tracing for the propagation of acoustic signals. The simulation tool has been validated through a complete set of tests for different configurations and situations, analyzing the signals involved at different processing stages: baseband, modulated signals, received signals, and final estimated positions. This simulation tool is a valuable asset to research different positioning system configurations or to illustrate several concepts in a pedagogical context.

FEM Simulation and Test Verification of PD Ultrasonic Signal Propagation in a Power Transformer Model

Ultrasonic signals will be generated when partial discharge occurs in internal insulation faults in large oil immersed power transformers: because the ultrasonic signal has strong anti-interference ability and has no direct electromagnetic contact with the equipment, it is widely used in transformer fault detection and positioning. In this paper, the finite element method (FEM) is used to simulate the ultrasonic signal in a 35 kV power transformer. The influence of transformer case on ultrasonic signal propagation is considered, and the propagation law of the ultrasonic signal inside the transformer is obtained. Fabry–Perot (F–P) fibre acoustic sensors with a centre frequency of 28 kHz were fabricated. A partial discharge detection test was carried out in a 35 kV transformer winding model using the F–P sensors. The test results show that the ultrasonic waveform detected by the F–P sensors are in good agreement with the simulation results, and the propagation of the ultrasonic wave inside the transformer is verified. It lays a foundation for detecting and locating PDs in power transformer by F–P acoustic sensors.

Ultrasound propagation in two-layer gas flow

The ultrasonic signal propagation in two-layer gas flow was studied. The intensity degradation of the signal was observed while the signal was propagating through the air-hydrogen-air two-layer gas flowing system. The concentration of flowing hydrogen (H2) gas was measured using ultrasound from the exterior of the pipe, and it was calculated that the intensity degradation of signal did not simply depend on the H2 concentration, however, the intensity varied every second. Schlieren photography was taken to visualize the motion of H2 gas after injecting into the flowing air of 2 m/s. It was observed that high concentration H2 gas was flowing in the middle of the airflow without quick diffusion into the air. A two-dimensional air-H2-air gas flow model was considered where 100% H2 was flowing in the middle of the airflow, and the gas layers were separated by two fluctuated interfaces. According to the calculation using this model, only limited conditions of the signals can reach to the receiver due to the refraction at the fluctuating air-H2-air gas interfaces while propagating. It was found that the receiver could hardly detect the signals; hence, the intensity of the signal looked degraded.

Effect of Temperature on Ultrasonic Signal Propagation for Extra Virgin Olive Oil Adulteration

Fraud cases involving adulteration of extra virgin olive oil has become significant nowadays due to increasing in cost of supply and highlight given the benefit of extra virgin olive oil for human consumption. This paper presents the effects of temperature variation on spectral formed utilising pulse-echo technique of ultrasound signal. Several methods had been introduced to characterize the adulteration of extra virgin olive oil with other fluid sample such as mass chromatography, standard method by ASTM (density test, distillation test and evaporation test) and mass spectrometer. Pulse-echo method of ultrasound being a non-destructive method to be used to analyse the sound wave signal captured by oscilloscope. In this paper, a non-destructive technique utilizing ultrasound to characterize extra virgin olive oil adulteration level will be presented. It can be observed that frequency spectrum of sample with different ratio and variation temperature shows significant percentages different from 30% up to 70% according to temperature variation thus possible to be used for sample characterization.

Review of Ultrasonic Signal Acquisition and Processing Techniques for Mechatronics and Material Engineering

Review of ultrasound applications in mechanical and material engineering is presented. Application examples in material thickness, profile measurement are given. Applications for load, stress, stiffness, porosity, density, viscosity, bond strength, hardening depth evaluation are discussed. Composite or polymer curing states can be monitored. Ultrasonic signal propagation velocity, attenuation or nonlinearity can be used for aforementioned parameters extraction. Signal acquisition setup configurations along with signal processing techniques are discussed. Ultrasound can be used for structure integrity testing or monitoring. Imaging of the inner material structure or properties distribution requires special reconstruction techniques. Presence of the structural noise is masking the defects. Image reconstruction and structural noise reduction techniques are outlined.

Estimation of parameter variation of wideband signals and their fields in media with attenuation

Wideband signals and their fields in media with frequency-dependent attenuation have been considered using an example of the analysis of propagation of ultrasonic signals in biological media. An analytical expression for the spatial frequency response of the layer of biological tissue with frequency-dependent attenuation for diagnostically meaningful frequency range was obtained by using a linear approximation of the problem under consideration. Quantitative estimates of the impact of a layer of biological tissue with attenuation on a radio pulse with Gaussian envelope were obtained. The presence of frequency-dependent attenuation in medium was shown to result in variation of spatial selectivity of antenna during its operation with wideband signals. The estimates of variation of spatial selectivity parameters are presented in case of using the radio pulses with Gaussian envelope.

Simulation as a Support for Ultrasonic Testing

Ultrasonic testing is a very important non-destructive method for testing components for safety of nuclear power plants and other security and delicate parts in other industries. Nowadays, thanks to the development of computer technology, it is possible to simulate processes which occur during ultrasonic testing. That is why numerical simulations are becoming an integral part of non-destructive testing. Simulations are used to determine parameters of ultrasonic examination, especially parameters of probes and scan plan and also in the analysis of results. They are used in such cases, when it is necessary to verify applicability of probes and methods. This verification could be provided on the weld and test block which are not manufactured. It could be also provided on defects, which are not manufactured in test block, but their presence is possible in given weld joint. Simulations are very useful for verifying the propagation of ultrasonic signal in given area (e.g. weld area). If movement of probe is limited, possibility of whole volume scan should be verified.

Preliminary Study of the Measurement of Foreign Material in Galvanic Corrosion Using Laser Ultrasonic

A laser ultrasonic inspection system has the advantage of nondestructive testing. It is a non-contact mode using a laser interferometer to measure the vertical displacement of the surface of a material caused by the propagation of ultrasonic signals with the remote ultrasonic generated by laser. After raising the ultrasonic signal with a broadband frequency range using a pulsed laser beam, the laser beam is focused to a small point to measure the ultrasonic signal because it provides an excellent measurement resolution. In this paper, foreign materials are measured by a non-destructive and non-contact method using the laser ultrasonic inspection system. Mixed foreign material on the corroded part is assumed and the laser ultrasonic experiment is conducted. An ultrasonic wave is generated by pulse laser from the back of the specimen and an ultrasonic signal is acquired from the same location of the front side using continuous wave laser and Confocal Fabry-Perot Interferometer (CFPI). The characteristic of the ultrasonic signal of existing foreign material is analyzed and the location and size of foreign material is measured.

Acoustic Sensor Networks for Decommissioning

Progress is reported with an acoustic sensor network that offers the possibility to provide monitoring of nuclear storage ponds. The aim is to create a network that comprises a number of autonomous sensor nodes that communicate and localise using ultrasonic signals. The nodes are less than 20cm dimension and are able to manoeuvre themselves, horizontally and vertically, to selected positions where they can then record measurements of selected parameters. Ultrasonic signal propagation has been explored in a 6m benign test pond with representative clutter. The paper describes progress with communications, localisation and a small autonomous underwater vehicle. Results suggest that localisation might be achieved to an accuracy of about 10cm and data might be communicated up to 1 kbit/s assuming a bit error rate of 10–4.

E-Textiles for Autonomous Location Awareness

This paper describes an autonomous, wearable location awareness system that determines a user's location within a building given a map of that building. The system uses a moderate number of ultrasonic range transceivers as the sensing elements. Given a set of range readings from these sensors, the system attempts to match those actual readings to expected readings associated with a set of candidate locations for the wearer. These expected readings are calculated using a simulation model of the propagation of ultrasonic signals within a building. A complementary algorithm is given for determining the wearer's movement between rooms, allowing for the uncertainty associated with sensor readings in complex, multiroom environments. A wearable prototype system is described and results from this system in a range of scenarios are presented and analyzed

Laser ultrasonic study of porous silicon layers

Propagation of ultrasonic signals induced by nanosecond laser pulses in porous silicon (por-Si) is considered from both the theoretical and the experimental viewpoints. The experimental samples are por-Si layers with 5-to 40-µm thickness and porosity of 50–75%; these layers were formed on a single-crystal silicon substrate by electrochemical etching. It is shown that the suggested ultrasonic laser method allows both the thickness and the porosity of a layer to be determined with the respective accuracies of no worse than 1 µm and 5%.

Experimental investigation of the lunar seismic signals

This study presents the experimental investigation of the propagation of ultrasonic signals with distance along the surfaces of steel spheres. The results give a good indication of the frequencies and the phase velocities contained in the observed signals. An improved laboratory signal as compared to an earlier experiment gives a better comparison with the lunar seismic signal. Also the effect of a dent on the surface of a steel sphere has been studied. The results obtained due to the presence of the dent may give an indication to the effect the craters on the surface of the moon will have on a propagating seismic signal. The presence of the dent definitely reduces the amplitude of the signal propagating across it. The craters may reduce rather than enhance the recorded signal. The recorded signals are constituted of frequencies of 100–500 kHz and the phase velocity varies from 1.0 km/sec to 3.0 kms/sec.