scholarly journals Integrated defect sensor for the inspection of fiber-reinforced plastics using air-coupled ultrasound

2020 ◽  
Vol 9 (1) ◽  
pp. 127-132
Author(s):  
Yannick Bernhardt ◽  
Marc Kreutzbruck
Keyword(s):  
Lamb Waves ◽  
Incidence Angle ◽  
Signal To Noise Ratio ◽  
Scanning System ◽  
Angle Of Incidence ◽  
Fiber Reinforced ◽  
Destructive Testing ◽  
Reinforced Plastics ◽  
Resonance Angle ◽  
Correct Angle

Abstract. Air-coupled ultrasound (ACU) is a non-destructive testing (NDT) method with a rising significance in industrial use. Common cases where ACU is used are the testing of fiber-reinforced plastic or testing of weld joints between metal sheets. The advantage compared to contact ultrasound is the absence of a liquid, solid or gel-like couplant. The usage of a couplant is an obstacle for developers of automatic scanning systems for ultrasonic testing because it takes a huge effort to integrate a system that delivers a continuous flow of the couplant. In addition a further step of cleaning is often necessary. ACU needs specially adapted probes to compensate for the tremendous impedance difference between a solid and air. A standard method uses two ACU probes in a normal transmission mode. With slanted probes, it is possible to generate Lamb waves in plate-like materials. Because of the contact to the surrounding air, Lamb waves transmit ultrasound to the air on both sides of the plate continually. These so-called leaky Lamb waves can be used with only one accessible side, and by using a specific resonance angle, a higher signal-to-noise ratio (SNR) is achievable. In the past, the correct angle was determined using an iterative method, where the angle of incidence was changed manually while observing the amplitude level. With the stepper-motor-driven angle scanning system, introduced here, the determination of the resonance angle is possible automatically. The system allows changes of the incidence angle during the ultrasound scan too. This makes it possible to adapt the system to wall thickness changes and changes of the radii of the parts contour.

INCREASING SENSITIVITY OF EDDY CURRENT NON-DESTRUCTIVE TESTING OF DELAMINATION IN CARBON-FIBER REINFORCED PLASTICS

2021 ◽  
pp. 28-37
Author(s):  
P. N. Shkatov ◽  
G. A. Didin ◽  
A. A. Ermolaev
Keyword(s):  
Carbon Fiber ◽  
Eddy Current ◽  
Calculation Model ◽  
Fiber Reinforced ◽  
Destructive Testing ◽  
Carbon Fiber Reinforced Plastics ◽  
Reinforced Plastics ◽  
Fiber Reinforced Plastics ◽  
Carbon Fiber Reinforced ◽  
The Difference

The paper is concerned with increasing sensitivity of eddy current nondestructive testing of most dangerous delamination in carbon-fiber reinforced plastics (CFRP). Increased sensitivity is achieved by separate registration and comparison of eddy current signals obtained from a set of stratifications of carbon fibers with the same orientation. The separation of eddy current signals is possible due to pronounced anisotropy of the electrical conductivity of the layers dominant in the direction of the fibers of the corresponding layer. Eddy-current signals are registered by eddy current probes with maximum sensitivity in a given angular direction. Prior to the scan eddy current signals of the probe are leveled on a defect-free area. The influence of the working gap on the difference between the eddy current signals of the probe is suppressed by normalizing it according to one of the signals. The analysis of the registered signals from delamination has been performed using an approximate calculation model. The reliability of the obtained results has been confirmed by comparison with experimental results and calculations using the finite element method.

Velocity‐Based Earthquake Detection Using Downhole Distributed Acoustic Sensing—Examples from the San Andreas Fault Observatory at Depth

2019 ◽  
Vol 109 (6) ◽  
pp. 2491-2500 ◽  
Author(s):  
Ariel Lellouch ◽  
Siyuan Yuan ◽  
William L. Ellsworth ◽  
Biondo Biondi
Keyword(s):  
San Andreas Fault ◽  
Seismic Velocity ◽  
Incidence Angle ◽  
Signal To Noise Ratio ◽  
Plane Waves ◽  
Detection Algorithm ◽  
Angle Of Incidence ◽  
Acoustic Sensing ◽  
San Andreas ◽  
Distributed Acoustic Sensing

Abstract Conventional seismographic networks sparsely sample the wavefields excited by earthquakes. Thus, standard event detection is conducted by analyzing separate stations and merging their results. Emerging distributed acoustic sensing recording technologies allow for unbiased spatial sampling of the wavefield and, as a result, array‐based processing of the recorded signals. Using a cemented fiber in the San Andreas Fault Observatory at Depth main hole, 800 virtual receivers are sampled at a 1 m interval from the surface to 800 m depth. Recorded earthquakes are approximated as plane waves reaching the bottom of the array first. Following this assumption, the relative travel times of the recorded event depend on the local velocity at the array location and the angle of incidence at which the planar wavefront reaches it. Given the seismic velocity, a newly proposed detection algorithm amounts to a single‐parameter scan of the incidence angle and measurement of data coherency along the different possible travel‐time curves. Using the entire recording array, a much higher effective signal‐to‐noise ratio can be obtained when compared to individual channel processing. About 20 days of recorded seismic activity from the San Andreas Fault is analyzed. Using a downhole single array, the majority of cataloged events in the area are detected. In addition, a previously unknown event is unveiled. We estimate its magnitude at roughly −0.5.

Electron Channeling Patterns

1977 ◽  
Vol 35 ◽  
pp. 12-13
Author(s):  
David C. Joy
Keyword(s):  
Electron Diffraction ◽  
Incidence Angle ◽  
Photographic Plate ◽  
Diffraction Effect ◽  
Angle Of Incidence ◽  
Bulk Single Crystal ◽  
Time Resolved ◽  
Electron Channeling ◽  
Spatially Resolved ◽  
Large Bulk

Electron channeling patterns (ECP) were first found by Coates (1967) while observing a large bulk, single crystal of silicon in a scanning electron microscope. The geometric pattern visible was shown to be produced as a result of the changes in the angle of incidence, between the beam and the specimen surface normal, which occur when the sample is examined at low magnification (Booker, Shaw, Whelan and Hirsch 1967).A conventional electron diffraction pattern consists of an angularly resolved intensity distribution in space which may be directly viewed on a fluorescent screen or recorded on a photographic plate. An ECP, on the other hand, is produced as the result of changes in the signal collected by a suitable electron detector as the incidence angle is varied. If an integrating detector is used, or if the beam traverses the surface at a fixed angle, then no channeling contrast will be observed. The ECP is thus a time resolved electron diffraction effect. It can therefore be related to spatially resolved diffraction phenomena by an application of the concepts of reciprocity (Cowley 1969).

Effect of long climatic ageing on the microstructure of the surface of сarbon-fiber-reinforced plastics on base epoxy matrix

2019 ◽  
pp. 157-169 ◽  
Author(s):  
I. S. Deev ◽  
E. V. Kurshev ◽  
S. L. Lonsky
Keyword(s):  
Climatic Factors ◽  
Temperate Climate ◽  
Fiber Reinforced ◽  
Humid Climate ◽  
Climatic Zones ◽  
Reinforced Plastics ◽  
Carbon Plastics ◽  
Fiber Reinforced Plastics ◽  
Determining Factor

Studies and experimental data on the microstructure of the surface of samples of epoxy сarbon-fiber-reinforced plastics that have undergone long-term (up to 5 years) climatic aging in different climatic zones of Russia have been conducted: under conditions of the industrial zone of temperate climate (Moscow, MTsKI); temperate warm climate (Gelendzhik, GTsKI); a warm humid climate (Sochi, GNIP RAS). It is established that the determining factor for aging of carbon plastics is the duration of the complex effect of climatic factors: the longer the period of climatic aging, the more significant changes occur in the microstructure of the surface of the materials. The intensity of the aging process and the degree of microstructural changes in the surface of carbon plastics are affected by the features of the climatic zone. general regularities and features of the destruction of the surface of carbon plastics after a long-term exposure to climatic factors have been established on the basis of the analysis and systematization of the results of microstructural studies.

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