A New Self-Coupled Ultrasonic Pipe Defect Detection System

In order to solve the problem that it is difficult to detect the local ice layer debonding when the thermal protection system is working, an on-line ultrasonic detection method for the melting degree of interface between skin and ice layer based on the theory of ultrasonic transmission in multi-layer media was studied. A multi-layer medium acoustic model including skin, water film, ice water transition layer, ice layer and air layer is constructed. Ultrasonic pulse waves with different center frequencies are used as excitation sources, and the echo signals of multi-layer medium interface are obtained by using the numerical calculation. The ultrasonic signal processing algorithm for ice melting and debonding measurement is developed. The original echo signal is processed and the characteristic parameters of the echo signal of interface between skin and ice layer are extracted. The ultrasonic reflection coefficient of interface between skin and ice layer is proposed to evaluate the degree of ice melting. The ultrasonic ice detection system was built, and the low-temperature ultrasonic sensor was designed and fabricated. The ability of the system to measure the degree of ice melting under the action of electric heating was verified in the low-temperature environment. The ultrasonic ice detection system was built, and the low-temperature ultrasonic sensor was designed and fabricated. The ability of the system to measure the degree of ice melting under the action of electric heating was verified in the low-temperature environment. The theoretical results show that when the ice on the skin melts and produces a thin water film, the degree of ice melting can be reflected by the change of ultrasonic reflection coefficient at the skin-attachment interface. In this paper, the ultrasonic reflection coefficient more than 0.8 is used as the criterion of ice melting. With the increasing of center frequency of the ultrasonic signal, the thinner water film can be identified. The identification thickness of the water film corresponding to 7.5 MHz center frequency signal is 10 μm. The experimental results show that under the conditions of clear ice, mixed ice and frost ice, the ultrasonic detection system can out-put the ice layer debonding signal at the initial stage of electric heating. The propagation characteristics of ultrasonic pulse wave of interface between skin and ice layer in the thermal protection are preliminarily explored. The present method for detecting the degree of ice melting is expected to further reduce the energy consumption of thermal protection.

During the manufacture and the installation process, defects are easy to introduce in prefabricated cable accessories. The existing standards of cable accessories product require that there should be no defects such as bubbles and metal impurities in insulation, but no corresponding detection means are put forward. At present, the main defect detection methods are high voltage test and partial discharge test after installation. It is easy to misjudge because of the installation process, environmental noise and other reasons, and cannot locate the specific location of the defect. It is useful to find these defects through ultrasonic detection and ensure the safety of the cable accessories. In this paper, a set of ultrasonic automatic defect detection system for SR (silicone rubber) was developed. The relationships between the detection ability and the system parameters were investigated. The axial resolution and sensitivity of the ultrasonic wave in the SR Cable joint sample were measured using excitation signal with different pulse width. The relationships between the resolution (or the sensitivity) and pulse width were investigated. The attenuation coefficient and axial resolution were measured by ultrasonic probes with different central frequencies. The relationships between the attenuation coefficient (or the axial resolution) and the central frequency were also investigated. Finally, the negative pulse with pulse width of 200ns was selected as the excitation signal and 2.5MHz was selected as the central frequency of the probe. With the proper system parameters, the attenuation coefficient was 0.059dB/mm and the axial resolution was about 3mm in SR. Two different defect imaging methods were developed by analyzing the amplitude, phase and frequency spectrum of the ultrasonic echoes. The first imaging method, which applied to defects such as air gaps and impurities, constructed images using the amplitude of the flaw echo. The second imaging method, which applied to defects such as uneven distribution of material, constructed images using the average sound velocity. SR samples with different thicknesses and types of defect (air gaps, and metal impurities) were scanned by the system. The results showed that the detection system could accurately identify defects larger than 1 mm. The depth of defects could reach 50mm. The ultrasonic detection method could be applied to instruct the insulation diagnosis for SR Cable accessories.

This paper describes how to design an industrial phased array ultrasonic flaw detection system based on Internet of Things technology. The system uses FPGA as the core chip. CPU module, digital precision delay module, PLL module, FIFO module, data compression module and echo synthesis module are packaged in one FPGA chip. It adopts wireless transmission technology, uses RS9110-N-11-22 wireless module to transmit the processed and compressed data to Post-processing and Man-machine interface station. This design simplifies the system structure, increases system flexibility, reliability and anti-jamming capability, and reduces costs as well.

It is very important, by analyzing and processing ultrasonic echo signals of seabed oil pipeline, to acquire the effective information. Because of the complicated detection system structure and ultrasound coupler impurity, there are inevitably different noises in echo signals. In order to improve the accuracy of detection, it is very necessary to process ultrasonic echo signals by de-noising. According to characteristics of ultrasonic echo signals, we proposed a de-noising method, based on wavelet packet in this article. With this method, the principle of wavelet packet de-noising and the selection of threshold functions are applied into detecting and de-noising ultrasonic echo signals. The experiment and simulation results show that this de-noising method, by increasing the signal-to-noise ratio, can obviously improve the noise suppression effect and detection accuracy on ultrasonic echo signals of seabed oil pipeline.

In any quantum communication system, such as a quantum key distribution (QKD) system, data rates are mainly limited by the system clock rate and the various link losses. While the transmission clock rate is limited by the temporal resolution of the single-photon detectors, losses in a fiber-based quantum communication system can be minimized by operating in the near infrared range (NIR), at 1310 nm or 1550 nm. Commercially available InGaAs-based avalanche photo-diodes (APDs) can be operated as single-photon detectors in this wavelength range [Hadfield, 2009]. Due to the severe after-pulsing, InGaAs APDs are typically used in a gated mode and this can limit their application in high-speed quantum communications systems. Superconducting single-photon detectors (SSPDs) can work in the NIR wavelength range with good performance [Gol’tsman et al. 2001; Hadfield, 2009]. However, SSPDs require cryogenic temperatures, and are not widely available on the commercial market at present. In addition, InGaAs/InP based photomultiplier tubes (PMT) can operate in the NIR range, but its performance is limited by very low detection efficiency (1 % at 1600 nm) and large timing jitter (1.5 ns) [Hamamatsu, 2005]. Microchannel plates (MCP) are micro-capillary electron multipliers coated with an electron-emissive material and multiply photon-excited electrons from a photon cathode [Wiza, 1979]. MCPs usually have faster rise times and lower timing jitter than is achievable with PMTs. InGaAs MCPs can work in the NIR range. These MCPs, but are limited by low detection efficiency (~1 %) [Martin, J. & Hink P. 2003]. On the other hand, silicon based avalanche photo-diodes (Si APDs) are compact, relatively inexpensive, and can be operated at ambient temperatures with high detection efficiency and low noise in the visible or near-visible range. Unfortunately they do not work at wavelengths longer than 1000 nm. For those wavelengths, an up-conversion technique has been developed that uses sum-frequency generation (SFG) in a non-linear optical medium to convert the signal photons to a higher frequency (shorter wavelength) in the visible or near visible range. The up-converted photons can then be detected by a Si APD. Up-conversion detectors use commercially available components and devices, and are a practical solution for many applications in quantum communications. To date, several groups have successfully developed highly efficient up-conversion single-photon detectors in the nearinfrared range using periodically poled lithium niobate (PPLN) waveguides [Diamanti et al., 2005; Langrock et al., 2005; Thew et al., 2006; Tanzilli et al., 2005; Xu et al., 2007;] and bulk crystals [Vandevender & Kwiat, 2004].

Wax appearance temperature (WAT) of live oil is a key index for determining the reasonable injected water temperature of high waxy oilfield. In view of the difference of the oil composition and pressure between live oil and dead oil under reservoir conditions, aiming at the practical problems such as the limitation to dead oil of the normal test method at home and abroad, based on the response of the ultrasonic parameters such as transit time, amplitude and frequency during waxy participation, a novel ultrasonic detection system used for the wax participation characteristics was designed. Taken typical oil samples of kingfisher oilfield as an example, WAT, amount of wax participated and dynamic wax participation process of both dead and live oil under different pressures were studied, respectively. Results showed that there exist two main stages for the wax participation process: nucleation and growth. The existence of the dissolved gas decreases the WAT significantly. The higher the pressure, the higher the WAT for the oil above the saturation pressure. Transit time, amplitude and frequency could all be used as sensitive parameters to estimate the WAT, amount of wax participated and dynamic wax participation process.

The performance of tissue imaging is improved by tissue harmonic imaging (THI) to expand and enhance the range and level of clinical diagnosis for many diseases. The separation based on High-pass filtering (S_HPF) is a commonly used method for extracting harmonic components from ultrasonic echo signals. However, the cut-off frequency, order and algorithm to realize a high-pass filter have a great influence on the separation accuracy of harmonic signals. In present study, a novel separation method (S_CEEMDAN) based on the complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) algorithm is proposed for adaptively separating harmonic components from ultrasonic echo signals. First, we calculate the ensemble size of CEEMDAN adaptively based on the added noise level, and draw a sum of intrinsic mode functions (IMFs) from the ultrasonic echo signals by CEEMDAN. Then, the spectrum of each IMF is computed and evaluated, and the IMFs containing both fundamental and harmonic components are further decomposed by using the CEEMDAN algorithm. This separation process is end until all of IMFs have been divided into either fundamental or harmonic categories. Finally, the corresponding fundamental and harmonic echo signals are yielded by accumulating separately these two categories. In experiments, simulated ultrasonic echo signals with a center frequency of 3.5MHz are separated by the proposed S_CEEMDAN method, and the results are compared with those processed by S_HPF. The edge of the harmonic image by S_CEEMDAN marginally better defined than S_HPF. The indices for the harmonic signals separated by S_CEEMDAN and S_HPF, respectively, are as follows: the center frequencies of 6.66 MHz and 6.65 MHz, 3 dB bandwidths of 1.04 MHz and 1.05 MHz, 6 dB bandwidths of 1.59 MHz and 1.55 MHz, signal-to-noise ratios (SNRs) of 14.00 and 13.63, and image contrasts of 7.01 and 7.06. In conclusion, due to good adaptive characteristics, and lower reconstruction errors, the proposed S_CEEMD method is superior to S_HPF in the performance of spectral accuracy and harmonic imaging. This method could be potentially alternative to the current method for the ultrasonic harmonic separation.

A MEMS Transducer for Ultrasonic Flaw Detection A. Jain, D. Greve, J. Oppenheim Pages 375-381 (2002 Proceedings of the 19th ISARC, Washington, USA, ISSN 2413-5844) Abstract: Metal structures can fail because of fatigue crack propagation or because of section loss from corrosion. Regular inspection is required to intercept such failures, and in situ sensors would be a superior technology for that purpose. We have designed and fabricated arrays of MEMS capacitive diaphragm transducers and we report on their performance as pulse-echo detectors in direct contact with solids. Our chip is approximately 1-cm square and features nine detectors in a linear array, each detector containing 180 hexagonal diaphragms. Performance of the detector array was studied by bonding the chip to test specimens and applying an ultrasonic pulse using a commercial ultrasonic transducer. One experiment recreates an on-axis excitation in which the pulse arrives uniformly at all detectors, and another experiment recreates an off-axis excitation in which the pulse arrival is delayed from one detector to the next along the length of the array, permitting accurate localization of the source using phased array signal processing. The results establish that MEMS transducers can function successfully as phased array detectors of ultrasonic signals in solids. Keywords: Diaphragm; flaw detection; MEMS; phased array; ultrasonics DOI: https://doi.org/10.22260/ISARC2002/0059 Download fulltext Download BibTex Download Endnote (RIS) TeX Import to Mendeley

Goaf detecting is of great significance to the safe operation of the power grid. The traditional detection technology has many disadvantages like single frequency transmission signal, low detection efficiency, anti-interference ability and so on, so they are not suitable for the detection of goaf under the transmission power line. This paper designs a multi frequency resistivity detection transmission system, which has a wide frequency range, rich frequency content, high detection efficiency. It also has the ability of anti-electromagnetic interference, more suitable for the goaf detection under power grid, and it is significant to ensure the safe operation of the power grid.

The ultrasonic (US) wave detection and an acoustic emission (AE) linear location system are proposed, which employ fiber Bragg gratings (FBGs) as US wave sensors. In the theoretical analysis, the FBG sensor response to longitudinal US wave is investigated. The result indicates that the FBG wavelength can be modulated as static case when the grating length is much shorter than US wavelength. The experimental results of standard sinusoidal and spindle wave test agree well with the generated signal. Further research using two FBGs for realizing linear location is also achieved. The maximum linear location error is obtained as less than 5 mm. FBG-based US wave sensor and AE linear location provide useful tools for specific requirements.

Photoelectric, Compton, and photopeak efficiencies have been calculated at several gamma-ray energies for large flat sodium iodide crystals in which the thickness ranges from ⅛−2 in. Also, the loss of position resolution by gamma-ray scattering within the scintillator is calculated, since this is of interest in the design of gamma-ray imaging devices like the scintillation camera. An examination of the data shows the advantage of using low energy gamma rays for imaging whenever possible. They are efficiently detected by solid sodium iodide scintillators ½ in. thick, and there is little loss of resolution due to scattering of gamma rays in the scintillator. In the higher energy range, a choice must be made between a thin scintillator with its relatively good position resolution and low detection efficiency, or a thick crystal with higher detection efficiency and less satisfactory resolution.

The knowledge of the fissile material mass is a key challenge to enhance radioactive waste management and to ensure a high level of safety in nuclear industry. Data is analyzed according to the principles of the neutron measurement techniques. As proportional counters filled with 3He gas display high neutron detection efficiency and a good gamma-ray discrimination, they are the reference detector for passive neutron coincidence counting. A charge preamplifier or a current amplifier, depending on applications, collects the electric pulse produced by neutron interaction in the 3He gas and a threshold discriminator produces a logic pulse used for neutron counting. This paper describes the performance assessment of different commercially available electronics from Mirion Technologies, Precision Data Technology (PDT), Mesytec, as well as MONACO electronics originally developed by CEA LIST for fission chamber measurements in experimental reactors. Comparative passive neutron measurements are carried out with these electronics at CEA/DEN Nuclear Measurement Laboratory in Cadarache. Overall, PDT and Mesytec electronics show similar detection efficiency as the ACH-NA98 charge amplifier, which is commonly used in our laboratory for such applications. However, MONACO electronics have a lower detection efficiency, similar to Mirion 7820 current amplifier used in specific high-count rate applications. An optimisation of MONACO settings would probably be necessary to adapt to 3He counters instead of fission chambers.

Stem water content is an important index of plant water balance. A new method based on changes in ultrasonic properties of stem was used to monitor stem water content in this paper, because the propagation of ultrasonic pulse echo signal and its attenuation characteristics in the material are closely related to the structure of the material. Ultrasound propagation echo signal was measured with an ultrasonic emission analysis system in the plant stem. The study showed that the increase of stem water content in the Populus simonii stem could cause the average amplitude, the root mean square (RMS) and the peak of value of the ultrasonic echo signal decreased obviously. The analysis of ultrasonic properties provides a new method for the detection of stem water content of trees and may be used to monitor plant water balance.

The performance of an ultrasonic flaw detection system is valued by its success in differentiating flaw echoes from those scattered by microstructures (e.g. grain scattering or clutter). In order to successfully detect and classify the target echoes from background noise, an effective feature extracting method and a robust decision process are required. In this study, we present a comparative evaluation of three orthogonal signal decomposition methods: constant B (bandwidth); constant E (energy); and constant Q (i.e., ratio of bandwidth to center frequency), spanning the entire frequency band of the signal. An efficient method of implementing orthogonal decomposition using the Haar filter is presented. Orthogonal decomposition of the signal offers feature vectors suitable for classification and signal evaluation. The differences observed in the probability density function of clutter and the flaw echoes resulting from orthogonal decomposition are utilized to design the Bayes and fuzzy discriminant classifiers for flaw detection. These classifiers show good sensitivities in detecting flaw echoes in the presence of strong clutter where the signal-to-noise ratio is about zero dB. In this paper we present a mathematical derivation for these techniques and experimental results to demonstrate their application in ultrasonic nondestructive testing.

The existing mechanical wear detection methods cannot accurately obtain the state characteristic data of mechanical equipment, resulting in high detection accuracy but low detection efficiency. In order to obtain more ideal results of mechanical wear detection, the mechanical wear detection technology of a high-power diesel engine based on thermodynamic coupling is designed. Through the coupling of thermodynamics, the thermal stress in the body is solved under the temperature field and corresponding boundary conditions. The state data of mechanical equipment are collected, the wavelet entropy in the state data of mechanical equipment is extracted as the feature of mechanical wear detection, and the least squares support vector machine is used to establish the mechanical wear detection model. The multi-domain unified language modelica is used to model the thermodynamic module and dynamic module of the diesel engine, respectively, to realize the joint simulation of thermodynamics and dynamics, and improve the simulation technology of mechanical wear detection of the high-power diesel engine. Through the simulation and verification test, it is found that the mechanical wear detection time is shorter, the mechanical wear detection efficiency is higher, and it has better practical application value.