scholarly journals Subsurface Stress Measurement in GIS Epoxy Composite by Using LCR Waves

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3725
Author(s):  
Zhouyiao Zou ◽  
Yanpeng Hao ◽  
Yao Zheng ◽  
Weiming He ◽  
Fangyuan Tian ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Internal Stress ◽  
Stress Measurement ◽  
Epoxy Composite ◽  
Propagation Time ◽  
Subsurface Zone ◽  
Wave Technique ◽  
Similar Materials ◽  
Set Up ◽  
Relative Errors

Internal stress in basin insulators of gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which affects the safe operation of these apparatuses. In this research, we proposed a subsurface internal stress measurement method for GIS epoxy composites. This method is based on an ultrasonic longitudinal critically refracted (LCR) wave technique. In this study, some epoxy composite specimens were synthesized with similar materials and manufacturing processes to those of 252 kV GIS basin insulators. An ultrasonic stress measurement system that utilized the LCR wave technique was set-up to investigate the relationship between stress and LCR wave propagation time, as well as to measure the compressive stress of the epoxy specimen within 0–50 MPa. The results show that LCR wave propagation time linearly decreased when stress increased in the subsurface zone and the acoustoelastic coefficient was −4.95. We found the relative errors of stress measurements to be less than 13%.

scholarly journals An Ultrasonic Pulse-Echo Method to Detect Internal Defects in Epoxy Composite Insulation

Energies ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4804 ◽  
Author(s):  
Fangyuan Tian ◽  
Yanpeng Hao ◽  
Zhouyiao Zou ◽  
Yao Zheng ◽  
Weiming He ◽  
...  
Keyword(s):  
Epoxy Composite ◽  
Ultrasonic Pulse ◽  
Propagation Time ◽  
Reflected Waves ◽  
Surface Flashover ◽  
Similar Materials ◽  
Set Up ◽  
Different Diameters ◽  
Pulse Echo ◽  
Made In

Voids or cracks in basin insulators inside a GIS (gas-insulated metal-enclosed switchgear) could trigger partial discharges or surface flashover under electrical stresses, threatening safe GIS operation. For this paper, some epoxy composite specimens were made from similar materials and manufacturing processes to make 252 kV GIS basin insulators. Some voids with different diameters or cracks with different diameters and orientations were artificially made in the specimens with different thicknesses. An ultrasonic pulse-echo system was set up, and ultrasonic tests were carried out on the specimens with voids or cracks. A method to calculate the depth of a defect was proposed by the propagation time of defect reflected waves. The results showed that a depth of 50 mm, a diameter φ of 2 mm void, and a diameter φ of 1 mm crack in epoxy composite insulation were detected by the ultrasonic system using a 1 MHz transducer.

scholarly journals An Ultrasonic Longitudinal Through-Transmission Method to Measure the Compressive Internal Stress in Epoxy Composite Specimens of Gas-Insulated Metal-Enclosed Switchgear

Energies ◽  
2020 ◽  
Vol 13 (5) ◽  
pp. 1248 ◽  
Author(s):  
Zhouyiao Zou ◽  
Yanpeng Hao ◽  
Fangyuan Tian ◽  
Yao Zheng ◽  
Weiming He ◽  
...  
Keyword(s):  
Internal Stress ◽  
Stress Measurement ◽  
Epoxy Composite ◽  
Ultrasonic Method ◽  
Epoxy Composites ◽  
Propagation Time ◽  
Transmission Method ◽  
Acoustoelastic Effect ◽  
Stress Measurements ◽  
Internal Stress Measurement

Situations of internal stress in basin insulators inside gas-insulated metal-enclosed switchgear (GIS) can lead to cracks, which can influence the safety and stability of apparatus. However, there is currently no research on internal stress measurements for composites of GIS basin insulators, and only measurements for surface stress. In this paper, an internal stress measurement method for GIS epoxy composite is proposed using an ultrasonic longitudinal through-transmission technique based on the acoustoelastic effect. An internal stress measurement system is developed to investigate the relationship between the uniaxial compressive internal stress and the velocity of the ultrasonic wave vertical to the stress in epoxy composite within a range of 0–70 MPa, and to calculate the acoustoelastic coefficient of epoxy composite. The effects of system delay are eliminated in measuring the propagation time. Some epoxy composite cuboid specimens with similar materials and using a manufacturing process similar to those of 252 kV GIS basin insulators are synthesized, and the uniformity of the internal stress in cuboid specimens is verified by finite element simulation. The results reveal a linear increase of the ultrasonic longitudinal wave velocity with increasing stress. It has been shown that the average acoustoelastic coefficient of GIS epoxy composites, using the longitudinal waves vertical to the stress, is 4.556 × 10−5/MPa. Additionally, the absolute errors of the internal stress measurements are less than 12.397 MPa. This research shows that the ultrasonic method based on the acoustoelastic effect for measuring the internal stress in GIS epoxy composites is feasible.

PROPAGATION OF THE BURNING WAVE IN A PULSED DETONATION COMBUSTOR OPERATING ON MIXTURES OF HEPTANE AND JET A-1 WITH AIR AND OXYGEN AT [O2/AIR] < 1

2020 ◽  
Author(s):  
M. S. ASSAD ◽  
◽  
O. G. PENYAZKOV ◽  
I. I. CHERNUHO ◽  
K. ALHUSSAN ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Combustion Wave ◽  
Equivalence Ratio ◽  
Pressure Sensors ◽  
Jet Fuel ◽  
Propagation Time ◽  
Burning Wave ◽  
Pulsed Detonation ◽  
Combustion Wave Propagation ◽  
Fuel Jet

This work is devoted to the study of the dynamics of combustion wave propagation in oxygen-enriched mixtures of n-heptane with air and jet fuel "Jet A-1" in a small-size pulsed detonation combustor (PDC) with a diameter of 20 mm and a length less than 1 m. Experiments are carried out after the PDC reaches a stationary thermal regime when changing the equivalence ratio (ϕ = 0.73-1.89) and the oxygen-to-air ratio ([O2/air] = 0.15-0.60). The velocity of the combustion wave is determined by measuring the propagation time of the flame front between adjacent pressure sensors that form measurement segements along the PDC.

Wave propagation improvement in two-dimensional bond-based peridynamics model

2021 ◽  
pp. 095440622098555
Author(s):  
Reza Alebrahim ◽  
Pawel Packo ◽  
Mirco Zaccariotto ◽  
Ugo Galvanetto
Keyword(s):  
Wave Propagation ◽  
Dynamic Performance ◽  
Numerical Dispersion ◽  
Motion Modeling ◽  
Minimization Method ◽  
Irregular Wave ◽  
Point Collocation ◽  
Potential Applications ◽  
Non Local ◽  
Set Up

In this study, methods to mitigate anomalous wave propagation in 2-D Bond-Based Peridynamics (PD) are presented. Similarly to what happens in classical non-local models, an irregular wave transmission phenomenon occurs at high frequencies. This feature of the dynamic performance of PD, limits its potential applications. A minimization method based on the weighted residual point collocation is introduced to substantially extend the frequency range of wave motion modeling. The optimization problem, developed through inverse analysis, is set up by comparing exact and numerical dispersion curves and minimizing the error in the frequency-wavenumber domain. A significant improvement in the wave propagation simulation using Bond-Based PD is observed.

scholarly journals From Loschmidt daemons to time-reversed waves

2016 ◽  
Vol 374 (2069) ◽  
pp. 20150156 ◽  
Author(s):  
Mathias Fink
Keyword(s):  
Wave Propagation ◽  
Time Reversal ◽  
Degrees Of Freedom ◽  
Point Of View ◽  
Propagation Time ◽  
Reversal Invariance ◽  
Spatial Boundary ◽  
Dual Approaches ◽  
Spatio Temporal

Time-reversal invariance can be exploited in wave physics to control wave propagation in complex media. Because time and space play a similar role in wave propagation, time-reversed waves can be obtained by manipulating spatial boundaries or by manipulating time boundaries. The two dual approaches will be discussed in this paper. The first approach uses ‘time-reversal mirrors’ with a wave manipulation along a spatial boundary sampled by a finite number of antennas. Related to this method, the role of the spatio-temporal degrees of freedom of the wavefield will be emphasized. In a second approach, waves are manipulated from a time boundary and we show that ‘instantaneous time mirrors’, mimicking the Loschmidt point of view, simultaneously acting in the entire space at once can also radiate time-reversed waves.

Study on Application of Stress Wave for Nondestructive Test of Wood Defects

2013 ◽  
Vol 401-403 ◽  
pp. 1119-1123 ◽  
Author(s):  
Wen Shu Lin ◽  
Jin Zhuo Wu
Keyword(s):  
Nondestructive Test ◽  
Stress Wave ◽  
Significant Influence ◽  
Modulus Of Elasticity ◽  
Dynamic Modulus ◽  
Wood Products ◽  
Propagation Time ◽  
Propagation Parameters ◽  
Wave Technique ◽  
Wooden Structures

The elm wood samples were tested by the technique of stress wave, and the testing results were analyzed by using the statistic software of SPSS. The results showed that the moister content of wood, wood crack, the sizes of holes and numbers of holes have significant influence on propagation parameters and dynamic modulus of elasticity. Under the same specifications, the propagation time of the stress wave was longer in the wood with holes or cracks than the perfect wood samples, and the time become longer with the increasing the sizes and numbers of holes or cracks. The studying results of the thesis will provide a sound background for the application of stress-wave technique in detecting the inner defects of wood products and other wooden structures.

Research on Outdoor Positioning Based on Ray Tracing Method

2014 ◽  
Vol 556-562 ◽  
pp. 3039-3042
Author(s):  
Xian Qiang Peng
Keyword(s):  
Wave Propagation ◽  
Ray Tracing ◽  
Radio Waves ◽  
Complex Environment ◽  
Simulation Experiments ◽  
Outdoor Environments ◽  
Positioning Method ◽  
Tracking Point ◽  
Set Up ◽  
Tracing Method

GPS can’t detect the signal because of the cell complex environment in the outdoor and poor radio wave propagation conditions, so that the positioning result is not ideal. However, the positioning method using the ray tracing prediction of radio waves, the tracking point of the scene from all the source radiation, record the relevant parameters, and then positioned within the microcell environment can satisfy the demand. The principle of ray tracing was firstly introduced in this paper, then an outdoor positioning model was set up, finally, the corresponding simulation experiments was implemented to demonstrate the effectiveness of ray tracing positioning in the outdoor environments.

scholarly journals Inferring the chromospheric magnetic topology through waves

2007 ◽  
Vol 3 (S247) ◽  
pp. 78-81
Author(s):  
S. S. Hasan ◽  
O. Steiner ◽  
A. van Ballegooijen
Keyword(s):  
Magnetic Field ◽  
Wave Propagation ◽  
Energy Density ◽  
Acoustic Wave ◽  
Acoustic Waves ◽  
Phase Speed ◽  
Time Correlation ◽  
Propagation Time ◽  
Fast Mode ◽  
The Magnetic Field

AbstractThe aim of this work is to examine the hypothesis that the wave propagation time in the solar atmosphere can be used to infer the magnetic topography in the chromosphere as suggested by Finsterle et al. (2004). We do this by using an extension of our earlier 2-D MHD work on the interaction of acoustic waves with a flux sheet. It is well known that these waves undergo mode transformation due to the presence of a magnetic field which is particularly effective at the surface of equipartition between the magnetic and thermal energy density, the β = 1 surface. This transformation depends sensitively on the angle between the wave vector and the local field direction. At the β = 1 interface, the wave that enters the flux sheet, (essentially the fast mode) has a higher phase speed than the incident acoustic wave. A time correlation between wave motions in the non-magnetic and magnetic regions could therefore provide a powerful diagnostic for mapping the magnetic field in the chromospheric network.

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