This paper aims to provide an overview of the experimental and simulation works focused on the detection, localisation and assessment of various defects in pipes by applying fast-screening guided ultrasonic wave techniques that have been used in the oil and gas industries over the past 20 years. Major emphasis is placed on limitations, capabilities, defect detection in coated buried pipes under pressure and corrosion monitoring using different commercial guided wave (GW) systems, approaches to simulation techniques such as the finite element method (FEM), wave mode selection, excitation and collection, GW attenuation, signal processing and different types of GW transducers. The effects of defect parameters on reflection coefficients are also discussed in terms of different simulation studies and experimental verifications.

Detection, Localisation and Assessment of Defects in Pipes Using Guided Wave Techniques: A Review.

Development of ultrasonic guided wave inspection methodology for steam generator tubes of prototype fast breeder reactor.

The accumulation of fouling within a structure is a well-known and costly problem across many industries. The build-up is dependent on the environmental conditions surrounding the fouled structure. Many attempts have been made to detect fouling accumulation in critical engineering structures and to optimize the application of power ultrasonic fouling removal procedures, i.e., flow monitoring, ultrasonic guided waves and thermal imaging. In recent years, the use of ultrasonic guided waves has been identified as a promising technology to detect fouling deposition/growth. This technology also has the capability to assess structural health; an added value to the industry. The use of ultrasonic guided waves for structural health monitoring is established but fouling detection using ultrasonic guided waves is still in its infancy. The present study focuses on the characterization of fouling detection using ultrasonic guided waves. A 6.2-m long 6-inch schedule 40 carbon steel pipe has been used to study the effect of (Calcite) fouling on ultrasonic guided wave propagation within the structure. Parameters considered include frequency selection, number of cycles and dispersion at incremental fouling thickness. According to the studied conditions, a 0.5 dB/m drop in signal amplitude occurs for a fouling deposition of 1 mm. The findings demonstrate the potential to detect fouling build-up in lengthy pipes and to quantify its thickness by the reduction in amplitude found from further numerical investigation. This variable can be exploited to optimize the power ultrasonic fouling removal procedure.

/pdf/characterization-of-the-use-of-low-frequency-ultrasonic-2583810xvo.pdf

Characterization of the Use of Low Frequency Ultrasonic Guided Waves to Detect Fouling Deposition in Pipelines

Pipeline structures are important structural components that cannot be replaced in actual engineering applications. Damage to a pipeline structure will create substantial safety hazards and economic losses in a project. Therefore, it is extremely important to study damaged pipeline structures. In this paper, L(0,2) mode guided waves are used to identify, locate, and image single and double defects in straight pipe structures. For the case where there is a single defect in the straight pipe section, the influence of different excitation frequencies on the reflection coefficient of L(0,2) modal guided wave is studied, and the optimal excitation frequency of L(0,2) guided wave is 70 kHz when single damage is determined. For the case of double defects in the straight pipe section, the double-defect size, the distance between the defects, and the relative defect positions are studied, and the influence of the defect recognition effect is analyzed. The propagation path of the ultrasonic guided wave in the double-defect pipe section is analyzed. Finally, the effectiveness of the three-point axial positioning method and damage imaging method is verified by the single-defect tube segment ultrasonic guided wave flaw detection experiment.

/pdf/research-on-pipeline-damage-imaging-technology-based-on-4rdwu1x8z6.pdf

Research on Pipeline Damage Imaging Technology Based on Ultrasonic Guided Waves

Long-range ultrasonic guided waves are widely used for the detection of defect founded in the long distance pipeline. Numerical simulation of guided wave propagation is considered for an experimental pipe with various forms of defects. The pipe is subjected to the propagation of the torsional guided wave . Numerical models are constructed for a sample pipe without defect and two sample pipes with two different types of defects: a notch and a notch with a hole. The desired T(0, 1) guided wave is simulated by a special excitation pressure function applied to one end of the pipe, which spreads via shearing motion parallel to the circumferential direction. Finite element software ANSYS is used to build 3D solid and finite element models of the sample pipes and perform full transient analysis. The simulation results allow obtaining information on the amplitude and the transit time of the impulse reflected from the defect and from the end of the pipe. The results also include the investigation of influence of the length and depth of the notch on the stress-strain state of the pipe.

Numerical Simulation of Ultrasonic Torsional Guided Wave Propagation for Pipes with Defects

Modeling Three-dimensional Ultrasonic Guided Wave Propagation and Scattering in Circular Cylindrical Structures using Finite Element Approach

In high-temperature continuous forging process, according to the real-time monitoring of workpiece thickness and flaws, the processing parameters can be adjusted accordingly, so we can remove defective components in time, which has essential research value for avoiding the interruption of production line and improving their yield and quality grade. We established a finite element (FE) model of the carbon steel’s laser-electromagnetic acoustic transducer (laser-EMAT) testing process. Based on the simulation model, we analyzed the effects of laser parameters, EMAT parameters, and sample thickness on the detected ultrasonic signal amplitude, and we also achieved the optimized Laser-EMAT design parameters. Subsequently, we developed a high-temperature resistant spiral coil EMAT and measured the high-temperature forging with a thickness of 100 mm and temperatures from 300 °C to 730 °C. Based on the experiments, we researched the effect of specimen temperature on the received ultrasonic wave amplitude. The results show that the excitation efficiency of laser-induced ultrasonic waves improves by decreasing pulse duration, decreasing laser spot radius, and increasing pulse laser energy. The receiving efficiency of the shear wave (SW) detected by the EMAT enhances when reducing the diameter of the EMAT wire and increasing the permanent magnet height. When the radius of the permanent magnet is equal to the radius of the EMAT coil, the receiving efficiency of SW is the highest. As the sample thickness increases, the size of the EMAT should increase accordingly to the acoustic beam divergence for obtaining a higher ultrasonic wave intensity. The amplitude of the SW signal received by the EMAT increases by 679% after the optimization design. With rising carbon steel forging temperature, the SW signal amplitude increases first and then decreases sharply, reaching its maximum at 617 °C, which is 29% higher than at room temperature, and the signal-to-noise ratio (SNR) of the SW is 20.5 dB.

Optimization design of laser-EMAT and its application in high-temperature forgings detection

A method to improve the conversion efficiency based on surface cooling technology was proposed to achieve a low signal-to-noise ratio (SNR) of laser-electromagnetic acoustic transducer (EMAT) detection with high-temperature forgings. A finite element model of the laser-EMAT ultrasonic testing process operated with high-temperature forgings was established to study the effects of the laser source parameters and temperatures on laser-excited ultrasonic waves and their radiated acoustic field. The ratio of the magnetostriction and Lorentz force to the ultrasonic reception efficiency of the EMAT at different temperatures was analyzed and verified experimentally. The results indicate that the surface cooling technology can improve the energy conversion efficiency when the carbon steel temperature exceeds the Curie temperature. With the help of surface cooling technology, the SNR of the longitudinal wave increases by 26.5 dB at 766°C, and the SNR of the shear wave improves by 12.1 dB at 655°C. 

Analysis of Influencing Factors on the Conversion Efficiency of Laser-EMAT Ultrasound Detection with High-Temperature Carbon Steel Forgings

In order to solve the difficulty in localization and poor signal-to-noise ratio (SNR) of the angled shear vertical wave (SV wave) electromagnetic acoustic transducer (EMAT) in cracks detection of high-temperature carbon steel forgings, a finite element (FE) model of the angled SV wave EMAT detection process was established, and the influence of specimen temperature on the EMAT excitation, propagation, and reception processes was analyzed. A high-temperature resistant angled SV wave EMAT was designed to detect carbon steel from 20 °C to 500 °C, and the influence law of the angled SV wave at different temperatures was analyzed. Then a circuit-field coupled FE model of angled SV wave EMAT in the carbon steel detection process based on the Barker code pulse compression technique was established, and the effects of the Barker code element length, impedance matching method, and matching component parameters on the pulse compression effect were analyzed. In addition, the noise suppression effect and the SNR of the crack-reflected wave in the tone-burst excitation method and the Barker code pulse compression technique were compared. The results show that the amplitude of the block-corner reflected wave decreases from 556 mV to 195 mV, and the SNR decreases from 34.9 dB to 23.5 dB when the specimen temperature increases from 20 °C to 500 °C. When the temperature is 500 °C, the SNR of the crack-reflected wave obtained by the Barker code pulse compression technique can be improved by 9.2 dB compared to the tone-burst excitation method with 16 synchronous averages. The study can provide technical and theoretical guidance for online crack detection for high-temperature carbon steel forgings.

/pdf/application-of-pulse-compression-technique-in-high-18921cvu.pdf

Application of Pulse Compression Technique in High-Temperature Carbon Steel Forgings Crack Detection with Angled SV-Wave EMATs

A laser-electromagnetic acoustic transducer (Laser-EMAT) Rayleigh wave (RW) detection based on surface constraint mechanism and its optimisation design are proposed to solve the low signal-to-noise ratio (SNR) of its application in aluminium alloy detection at high-temperature. We established a finite element (FE) model of aluminium alloy’s Laser-EMAT RW detection process based on the surface constraint mechanism and investigated the effect of the surface constraint mechanism on laser-excited RW . We also studied the effects of laser parameters and meander-line coil (MLC) EMAT parameters on the ultrasonic wave amplitude and spectral composition. Finally, the enhancement effect of the surface constraint mechanism on RW amplitude was analysed by Laser-EMAT RW detection experiments on aluminium alloy at room temperature and high temperatures. The results show that the optimised MLC-EMAT can increase the RW amplitude by 1.97 times. When the laser line source width equals the MLC-EMAT turn spacing, the echo SNR is the highest. The enhancement effect of the surface constraint mechanism on the RW amplitude gradually decreasesas the specimen temperature increases. The RW amplitude can increase by 1.43 times when the surface constraint mechanism is applied at room temperature, and for the aluminium alloy specimen at 430°C, the RW amplitude can increase by 32%. 

Guo-zhu Chen

Papers

Modeling Three-dimensional Ultrasonic Guided Wave Propagation and Scattering in Circular Cylindrical Structures using Finite Element Approach

Optimization design of laser-EMAT and its application in high-temperature forgings detection

Analysis of Influencing Factors on the Conversion Efficiency of Laser-EMAT Ultrasound Detection with High-Temperature Carbon Steel Forgings

Application of Pulse Compression Technique in High-Temperature Carbon Steel Forgings Crack Detection with Angled SV-Wave EMATs

Optimisation of Rayleigh wave Laser-EMAT with the application of surface constraint mechanism