“…Eddy current testing is vulnerable to the lift-off effect, which is an effect when the distance between the eddy current sensor and the surface of the specimen changes [ 1 ]. There are different methods to suppress the effect such as signal processing [ 2 ], lookup table [ 3 ], sensor design [ 4 , 5 ] and so on. For the sensor design method, the sensors are designed with differential structures to be immune to the effect and there are two kinds of differential eddy current sensors: differential exciting type and differential pickup type [ 6 ].…”
The Koch curve exciting coil eddy current sensor is a kind of novel flexible planar eddy current probe. In this study, an intersection angle spectrum entropy index and a radial direction energy spectrum entropy were proposed to evaluate the eddy current distribution. Eddy current distributions induced by one turn of a circular coil and one turn of a second order Koch curve coil feed with different exciting frequency alternative currents and at different lift-off distances, were simulated and the eddy current distributions varying with lift-off distance in different exciting frequencies were compared by the two proposed indices. With the increase of the lift-off distance or the decrease of exciting frequency, the similarity between the shape of the Koch curve and the eddy current distribution became weakened and the degree of the concentration of the eddy current distribution in the specimen under the exciting coil was loosened.
“…Eddy current testing is vulnerable to the lift-off effect, which is an effect when the distance between the eddy current sensor and the surface of the specimen changes [ 1 ]. There are different methods to suppress the effect such as signal processing [ 2 ], lookup table [ 3 ], sensor design [ 4 , 5 ] and so on. For the sensor design method, the sensors are designed with differential structures to be immune to the effect and there are two kinds of differential eddy current sensors: differential exciting type and differential pickup type [ 6 ].…”
The Koch curve exciting coil eddy current sensor is a kind of novel flexible planar eddy current probe. In this study, an intersection angle spectrum entropy index and a radial direction energy spectrum entropy were proposed to evaluate the eddy current distribution. Eddy current distributions induced by one turn of a circular coil and one turn of a second order Koch curve coil feed with different exciting frequency alternative currents and at different lift-off distances, were simulated and the eddy current distributions varying with lift-off distance in different exciting frequencies were compared by the two proposed indices. With the increase of the lift-off distance or the decrease of exciting frequency, the similarity between the shape of the Koch curve and the eddy current distribution became weakened and the degree of the concentration of the eddy current distribution in the specimen under the exciting coil was loosened.
“…Hwang et al. 26 used an array of linearly integrated Hall sensors to make a magnetic camera for the detection of wheel tread defects. The layout of the system is shown in Figure 5.…”
Section: In-workhop Inspectionmentioning
confidence: 99%
“…Figure 6.Eight surface cracks on a specimen of wheel and the results of the differential-type magnetic camera. 26 …”
Condition monitoring systems are commonly exploited to assess the health status of equipment. A fundamental part of any condition monitoring system is data acquisition. Meaningfully estimating the current condition and predicting the future behaviour of the equipment strongly depends on the characteristic of the data measurement stage. Nowadays, condition monitoring has wide applications in the railway industry and various monitoring approaches have been proposed for the inspection of wheel and rail conditions. In-service condition monitoring of wheels provides the real-time data required for maintenance planning, while in-workshop inspection is normally done at fixed intervals carried out periodically. In-service data acquisition can be divided into on-board and wayside measurements. In this paper, on the basis of these classifications, the existing data acquisition techniques for the monitoring of railway wheel condition are reviewed, and the state-of-the-art methods and required research are discussed.
“…The inservice inspection is divided into onboard measurement and wayside measurement. The inworkshop inspection system can be divided into ultrasonic techniques [7][8][9][10][11], infrared and thermography inspection [12][13][14][15], and magnetic methods [16][17][18] according to the selected sensors. These methods are mostly used for detecting wheel crack.…”
We establish the Injury Model of Wheel Flats with 10 degrees of freedom and calculate the dynamic responses of the railway vehicle system, which include different vehicle speeds and different length flats. The Hilbert envelope spectrum method based on Empirical Mode Decomposition (EMD) is proposed according to the nonstationary characteristics of axle box acceleration (ABA) signal. The vibration characteristics of the ABA are studied thoroughly. And then the effects concerning speed and flat length on the diagnosis results are analyzed. The simulation results show the amplitude corresponding to the frequency component of wheel flats raise with the increasing of the wheel flat length when the single or double wheel flats impact the track at the same vehicle speed. In other words, the longer the wheel flat is, the greater the magnitude of the decomposition result is. In the same vehicle speed, the amplitude corresponding to the frequency component of wheel flat is minimum when the two flats’ phase difference is 180°. With the same flat length (single or double wheel flats), the amplitude corresponding to the frequency components of wheel flats decreases with the increasing of the speed. This method could accurately and effectively identify the frequency of wheel flats.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
