scholarly journals Non-contact Crack Detection in Metals Using a Cutoff-Cavity Probe

2021 ◽  
Vol 21 (3) ◽  
pp. 167-176
Author(s):  
Ki-Chai Kim ◽  
Jong-Woo Kim ◽  
Jae-Yong Kwon ◽  
No-Weon Kang
Keyword(s):  
Crack Detection ◽  
Resonance State ◽  
External Control ◽  
Control Element ◽  
Contact Method ◽  
Series Resonance ◽  
Narrow Slot ◽  
Maximum Current ◽  
Lift Off ◽  
Parallel Resonance

This paper presents a non-contact method for the detection of surface cracks in metal materials through a forced-resonance microwave method (FRMM) using a cutoff cavity-backed narrow slot as a crack detection probe without using a vector network analyzer (VNA) at microwave frequencies. The FRMM uses the deviations in the ammeter or voltmeter readings of the forcefully obtained resonance of a cutoff-cavity probe for a metal material with or without cracks. The cutoff cavity-backed narrow slot on metal with no cracks produces a series resonance (maximum current) or a parallel resonance through an external control element located on a post inside the cutoff cavity. Cracks were detected by a change in this forced-resonance state (maximum current) when the cutoff-cavity probe was scanned over a crack. The characteristic crack signal was derived from the resonance current deviation on the ammeter located on a post inside the cavity probe. Galerkin’s method of moments was used to obtain a forced-resonance state from which the crack signal of the FRMM was calculated. The experimental measurements for non-contact (remote or lift-off) crack detection are also presented.

scholarly journals Characteristics of a Cutoff Cavity Probe Applicable to Crack Detection Using the Forced Resonance Microwave Method

2020 ◽  
Vol 20 (4) ◽  
pp. 285-292
Author(s):  
Ki-Chai Kim ◽  
Jong-Woo Kim ◽  
Jae-Yong Kwon ◽  
No-Weon Kang
Keyword(s):  
Crack Detection ◽  
Point Of View ◽  
Detection Sensitivity ◽  
Control Element ◽  
Microwave Method ◽  
Series Resonance ◽  
Current Characteristics ◽  
Parallel Resonance ◽  
Two Stages ◽  
Resonance Microwave

This paper presents the current characteristics inside a cutoff cavity slot probe applied to crack detection using the forced resonance microwave method (FRMM). Crack detection using FRMM has two stages: preparation and detection. In the preparation stage, the current characteristics inside the probe with a shorting plate are important for determining the crack signal and detection sensitivity. The cutoff cavity probe produces a forced resonance by adjusting a control element. There are two kinds of forced resonance: series resonance (SR) and parallel resonance (PR). Four types of current characteristics are applied to crack detection using FRMM: SR, the region around SR, the region around PR, and non-resonance. These current characteristics are discussed from the point of view of current change for crack detection. The experimental results are compared with the theoretical results to check the current state inside the cutoff cavity probe.

Improvement of Crack Detection Probability by Using Magnetic Camera and Image Processing

2007 ◽  
Vol 353-358 ◽  
pp. 2375-2378 ◽  
Author(s):  
Se Ho Choi ◽  
Ji Seong Hwang ◽  
Jong Woo Jun ◽  
Jin Yi Lee ◽  
Cheol Woong Kim
Keyword(s):  
Image Processing ◽  
Detection Probability ◽  
Crack Detection ◽  
Mechanical Vibration ◽  
Processing Method ◽  
Magnetic Sensors ◽  
Magnetic Lens ◽  
Analog To Digital ◽  
Lift Off ◽  
Magnetic Camera

Magnetic camera consists of magnetic source, arrayed small magnetic sensors, magnetic lens, analog-to-digital converter and interface, computer and monitor. The quantitative magnetic field around crack and its processed results could be obtained by using magnetic camera, and the crack could be inspected and evaluated quantitatively. In addition, the magnetic camera has to uphold with large lift-off to protect sensors from weak environment such as high temperature and mechanical vibration. However, the sensor sensitivity would be decreased when the lift-off was increased. Correspondingly, the improved techniques are necessary for increasing sensitivity of magnetic camera and probability of crack detection at the large lift-off. This paper proposes an image processing method, which separates a global full scale to the several regions and repeats shadings in each region, to increase a crack detection probability in the magnetic camera images such as ∂B/∂x and ∂2B/∂x∂y.

scholarly journals Reduction of Coil-Crack Angle Sensitivity Effect Using a Novel Flux Feature of ACFM Technique

2021 ◽  
Author(s):  
Ruochen Huang ◽  
Mingyang Lu ◽  
Ziqi Chen ◽  
Wuliang Yin
Keyword(s):  
Magnetic Field ◽  
Crack Detection ◽  
Sine Wave ◽  
Destructive Testing ◽  
Computation Efficiency ◽  
Detection Approach ◽  
Excitation Coil ◽  
Lift Off ◽  
The Magnetic Field ◽  
Sensor Probe

Alternating current field measurement (ACFM) testing is one of promising techniques in the field of non-destructive testing with advantages of the non-contact capability and the reduction of lift-off effects. In this paper, a novel crack detection approach is proposed to reduce the effect of the angled crack (cack orientation) by using rotated ACFM techniques. The sensor probe is composed of an excitation coil and two receiving coils. Two receiving coils are orthogonally placed in the centre of the excitation coil where the magnetic field is measured. It is found that the change of the x component and the peak value of the z component of the magnetic field when the sensor probe rotates around a crack follows a sine wave shape. A customised accelerated finite element method solver programmed in MATLAB is adopted to simulate the performance of the designed sensor probe which can significantly improve the computation efficiency due to the small crack perturbation. The experiments have also been carried out to validate the simulations. It is found that the ratio between the z and x components of the magnetic field remains stable under various rotation angles. It shows the potential to estimate the depth of the crack from the ratio detected by combining the magnetic fields from both receiving coils (i.e., the x and z components of the magnetic field) using the rotated ACFM technique.

scholarly journals A Langasite Crystal Microbalance Coated with Graphene Oxide-Platinum Nanocomposite as a Volatile Organic Compound Sensor: Detection and Discrimination Characteristics

Sensors ◽  
2020 ◽  
Vol 20 (2) ◽  
pp. 334 ◽  
Author(s):  
Ainan Leong ◽  
Tridib Saha ◽  
Varghese Swamy ◽  
Narayanan Ramakrishnan
Keyword(s):  
Graphene Oxide ◽  
Resonance Frequency ◽  
Film Surface ◽  
Series Resonance ◽  
Wave Resonator ◽  
Resonance Frequencies ◽  
Volatile Organic ◽  
Sensitivity And Selectivity ◽  
In Series ◽  
Parallel Resonance

We propose a novel langasite crystal microbalance (LCM) sensor with a graphene-based sensing medium to detect and discriminate volatile organic compounds (VOCs) at room temperature. A thin film of graphene oxide embedded with Pt nanostructures (GO-Pt nanocomposite) was deposited on the electrode surface of the LCM, a thickness-shear acoustic wave resonator. Ethyl acetate, acetic acid, and ethanol were chosen as typical VOCs for this study. Sensitivity and selectivity of coated LCM were investigated for different concentrations of the VOCs by analysing the resonant properties of the sensor. When exposed to VOCs, a negative shift in series resonance frequency was observed due to the mass loading of VOC molecules. Simultaneously, changes in equivalent resistance and parallel resonance frequency of the sensor were also observed due to the interaction of VOCs with charge carriers on the GO-Pt nanocomposite film surface. This dual measurement of both series and parallel resonance frequencies allowed for detection and discrimination of VOCs. Moreover, the high thermal stability of langasite makes the proposed sensor suitable even for harsh environmental conditions.

Design of orthogonal eddy-current probe for weld crack detection of carbon-steel plate

2020 ◽  
Vol 64 (1-4) ◽  
pp. 1347-1355
Author(s):  
Tao Chen ◽  
Xiaoqi Xiao ◽  
Lihong Zhang ◽  
Cheng Lv ◽  
Zhiyang Deng ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Eddy Current ◽  
Crack Detection ◽  
Steel Plate ◽  
Signal To Noise Ratio ◽  
Detection Sensitivity ◽  
Scanning Angle ◽  
Length Width ◽  
Lift Off ◽  
Detection Effect

Due to uneven surface and lift-off effect, it is difficult to detect weld crack by eddy-current testing. A new orthogonal eddy-current probe for weld crack detection of carbon-steel plate was designed in this paper. Based on COMSOL Multiphysics, the influence of scanning angle on detection sensitivity of the probe was compared firstly. Then, the effects of coil width, coil side length, detection coil height, and lift-off distance on detection sensitivity of the probe were studied, respectively. Finally, the test piece of carbon-steel plate weld with crack, and the physical probe used to verify the crack detection effect were made. The experimental results show that the weld crack of carbon-steel plate with length × width × depth of 20.0 mm × 0.3 mm × 1 mm can be effectively identified, and the lift-off noise can be effectively suppressed by the method presented in this paper. At the same time, the signal-to-noise ratio of the probe keeps constant in the lift-off distance range of 0.3 mm–3.0 mm.

Ship Hull Diagnostics with the Use of Remotely Operated Underwater Vehicle

NDT World ◽  
2015 ◽  
Vol 18 (3) ◽  
pp. 12-15 ◽  
Author(s):  
Третьяков ◽  
Evgeniy Tretyakov ◽  
Бритвин ◽  
Vladimir Britvin ◽  
Вельтищев ◽  
...  
Keyword(s):  
Crack Detection ◽  
Flaw Detection ◽  
Surface Preparation ◽  
Steel Structures ◽  
Ship Hull ◽  
Contact Method ◽  
Remotely Operated Vehicle ◽  
Sh Waves ◽  
Dry Dock ◽  
Diagnostics System

Introduction. Nowadays ship hull diagnostics is carried out in dry-dock or using divers in the road. The both technologies are time consuming, labour and material resource demanding. Specialists from Bauman Moscow State Technical University have developed a diagnostics system that allows the ship hull underwater part inspection to be performed without calling at dry-dock and without divers. The system includes the following main elements: remotely operated vehicle that contains diagnostics tools; hydro acoustic navigation system; software; and diagnostics technology. Method. The technology is based on an acoustic method of non-destructive testing (NDT). SH-waves with elastic vibrations excitation by non-contact method are used without necessity of thorough surface preparation before testing. SH-waves are also used for flaw detection within damaged areas (areas of different thicknesses). As the research has shown, the mirror-shadow technique with bottom signal attenuation as a criterion for corrosion crack detection is most effective. The minimum detectable deep of the corrosion cracks is 1.5–2 mm. The proposed diagnostics technology uses electromagnetic acoustic transducers (EMAT) with a 5 MHz frequency. Results. The diagnostics system was successfully tested in the pool. The test results confirmed the system’s ability to perform automatic metal diagnostics with wall thickness measurements and defect detection within areas of corrosion. Discussions. Nowadays the system is under the process of Russian Maritime Register of Shipping approval. It is planned to develop a system with arc welding tools for underwater objects repair. Prospects of diagnostics system usage for the various underwater steel structures including ones located on the Russian Federation Arctic shelf are under consideration.

scholarly journals Synchronization of Heterogeneous Multi-Robotic Cell with Emphasis on Low Computing Power

2020 ◽  
Vol 10 (15) ◽  
pp. 5165
Author(s):  
Martin Juhás ◽  
Bohuslava Juhásová
Keyword(s):  
Time Synchronization ◽  
Control Unit ◽  
External Control ◽  
Control Element ◽  
Production Cycle ◽  
Problem Solution ◽  
Robotic Cell ◽  
Operating Cycle ◽  
Computing Power ◽  
A Cell

This paper presents a time-synchronization solution for operations performed by a heterogeneous set of robotic manipulators grouped into a production cell. The cell control is realized using master–slave architecture without an external control element. Information transmission in a cell is provided by a TCP/IP channel in which communication is ensured via sockets. The proposed problem solution includes an algorithm, which is verified and validated by simulation and tested in real environment. This algorithm requires minimal computational power thanks to an empirically oriented approach, which enables its processing directly by the control unit of each participating element of the robotic cell. The algorithm works on the basis of monitoring and evaluating time differences among sub-operations of master and slave devices. This ensures defined production cycle milestones of each robotic manipulator in the cell at the same time are attained. Dynamic speed adaptation of slave manipulators utilizing standard instructions of their native language is used. The proposed algorithm also includes a feedforward form of operations synchronization which responds to changes in the operating cycle of the master manipulator. The application of the solution proposal is supplemented with a visualization part. This part represents a complementary form of designed solution implementation.

Resonant response of harbours: an equivalent-circuit analysis

1971 ◽  
Vol 46 (2) ◽  
pp. 241-265 ◽  
Author(s):  
John W. Miles
Keyword(s):  
Equivalent Circuit ◽  
Broad Band ◽  
Helmholtz Resonator ◽  
Input Voltage ◽  
Electrical Circuit ◽  
Equivalent Circuit Analysis ◽  
Radiation Impedance ◽  
Series Resonance ◽  
Variational Approximations ◽  
Parallel Resonance

The surface-wave response of a harbour to a prescribed, incident wave is calculated on the hypotheses of shallow-water theory, an ideal fluid, and a narrow mouth,M.An equivalent electrical circuit is constructed, in which the incidentwave displacement inMappears as the input voltage and the flow throughMappears as the input current. This circuit contains aradiation impedance, ZM, which comprises resistive and inductive terms, and aharbour impedance, ZH, which comprises an infinite sequence of parallel combinations of inductance and capacitance that bear a one-to-one correspondence with the natural modes of the closed harbour, together with a single capacitor, which corresponds to the degenerate mode of uniform displacement and dominates the response of the harbour as a Helmholtz resonator. Variational approximations toZHandZMare developed. The equivalent circuit exhibits parallel resonance at the resonant frequencies of the closed harbour, ωn, and series resonance at a second set of frequencies,$\tilde{\omega}_n $, where$\tilde{\omega}_n\downarrow \omega_n > 0 $and$\tilde{\omega}_0\downarrow 0 $asM→ 0;$\tilde{\omega}_0 $corresponds to the Helmholtz mode. A narrow canal between the coastline and the harbour is represented by a four-terminal network betweenZMandZH. It is shown that narrowing the harbour mouth and/or increasing the length of the canal does not affect the mean response of the harbour to a broad-band, random input except in the Helmholtz mode, but that it does increase significantly the response in that mode, which may dominate tsunami response. The general results are applied to circular and rectangular harbours. The numerical calculation ofZHfor an arbitrarily shaped harbour is discussed.

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