Ultrasonic Inspection and Analysis Using the Synthetic Aperture Focusing Technique (SAFT) on Dissimilar Metal Welds With Inter-Granular Stress Corrosion Cracks

Cases of inter-granular stress corrosion cracking (IGSCC) in dissimilar metal welds have led to an increased interest in the reliability of non-destructive testing of these welds and this crack type. The challenges related to ultrasonic testing of dissimilar metal welds (DMW) result from the elastic anisotropy of the material in combination with the grain structure of the weld. The inhomogeneous, anisotropic structure of the weld affects ultrasound propagation and leads to a decrease in the signal-to-noise ratio, thus complicating the interpretation of ultrasonic signals. As a result, cracks located exclusively in the weld material are usually harder to detect. Detection of cracks inside the weld material is particularly important in the case of a circumferential crack in a pipe weld, which could otherwise grow to a critical size before being detected. Studies have shown that the reflected ultrasonic amplitude is considerably smaller for IGSCC than it is for artificial reference flaws. In this paper, we will present the results of ultrasonic inspection and analysis using the Synthetic Aperture Focusing Technique (SAFT) on dissimilar metal welds with IGSCC.

Download Full-text

Synthetic Aperture Focusing Technique for Detecting Transverse Cracks in Austenitic and Dissimilar Welds

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.569-570.1036 ◽

2013 ◽

Vol 569-570 ◽

pp. 1036-1043

Author(s):

Jens Prager ◽

Christian Höhne ◽

Mehbub Ur Rahman

Keyword(s):

Wave Propagation ◽

Reconstruction Algorithm ◽

Synthetic Aperture ◽

Primary Circuit ◽

Transverse Cracks ◽

Dissimilar Welds ◽

Weld Material ◽

Testing Techniques ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique

The inspection of austenitic and dissimilar welds using ultrasound demands for sophisticated testing techniques. The application of reconstruction methods like the Synthetic Aperture Focusing Technique (SAFT) on the measurement results provides an appropriate approach for defect characterization and sizing. Nevertheless, the reconstruction algorithm has to consider the aniso-tropic wave propagation inside the inhomogeneous weld material. In recent years the detection of transverse cracks has become increasingly important for ensuring the structural integrity of pipes in the primary circuit of nuclear power plants or longitudinally welded, cladded pipes. However, relia-ble inspection techniques are hardly available. In this particular case, it is expected that the compar-atively long propagation path of the ultrasonic wave field inside the inhomogeneous weld material enhances the effect of anisotropy and influences the accuracy and the signal-to-noise-ratio of the reconstruction result. In this contribution we suggest an advanced ultrasonic testing technique for detecting and sizing of transversal cracks in austenitic and dissimilar welds. The method applies a SAFT reconstruction algorithm considering the anisotropy and the inhomogeneity. A V-arrangement of the transducers in pitch-catch technique is chosen to avoid a direct coupling on the weld face. The reconstruction algo-rithm is based on an extended 3-dimensional weld model and uses a ray-tracing approach for de-termining the wave propagation paths. Along with the reconstruction algorithm the transducer set-up and experimental results of different specimens with artificial transverse flaws are presented. The availability of the proposed method for crack sizing is assessed in comparison to conventional testing techniques.

Download Full-text

Application of Synthetic Aperture Focusing Technique for inspection of plate-like structures using EMAT generated Lamb waves

MATEC Web of Conferences ◽

10.1051/matecconf/201814505010 ◽

2018 ◽

Vol 145 ◽

pp. 05010

Author(s):

Yordan Mirchev ◽

Krasimir Staykov ◽

Damyan Ganchev

Keyword(s):

Lamb Waves ◽

Signal To Noise Ratio ◽

Guided Wave ◽

Synthetic Aperture ◽

Defect Characterization ◽

Signal To Noise ◽

Main Challenge ◽

Noise Ratio ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique

The main challenge for guided wave inspection is exact defect characterization and sizing. EMAT generated Lamb waves usually have low signal-to-noise ratio which reduces the defect detection, characterization and sizing capabilities. That's why in most cases the method is used only as a screening tool. The Synthetic Aperture Focusing Technique is a process that increases the signal-to-noise ratio by numerically focusing the acoustic fields. In this paper the application of SAFT is tested over EMAT generated Lamb waves. The improvement of lateral resolution and signal-to-noise ratio is evaluated. Results are presented as a comparison between standard B-scan and SAFT processed data.

Download Full-text

Laser-induced ultrasonic measurements for the detection and reconstruction of surface defects

Acta Acustica ◽

10.1051/aacus/2021031 ◽

2021 ◽

Vol 5 ◽

pp. 38

Author(s):

Feiming Qian ◽

Guangzhen Xing ◽

Ping Yang ◽

Pengcheng Hu ◽

Limin Zou ◽

...

Keyword(s):

Surface Defects ◽

Signal To Noise Ratio ◽

Ultrasonic Measurement ◽

Laser Beams ◽

Synthetic Aperture ◽

Correct Identification ◽

Synthetic Aperture Focusing ◽

Sequential Generation ◽

Synthetic Aperture Focusing Technique ◽

Non Destructive

Laser-induced ultrasonic measurement is a non-contact non-destructive technology that can be employed for the testing and assessment of surface defects. In order to improve the correct identification of defects, the full matrix capture (FMC) and total focusing method (TFM) are applied on the imaging process. FMC data includes A-scans resulting from the combination of all measurement axes defined by the sequential generation and detection of utilized laser beams in the system. In this paper, an aluminium block with four holes whose diameters range from 1 mm to 2.5 mm is assessed through B-scans, the synthetic aperture focusing technique (SAFT) and FMC/TFM. The results demonstrate that the FMC/TFM technology can significantly improve the imaging quality and signal-to-noise ratio (SNR). In addition, this method has higher lateral resolution and larger imaging range compared with traditional B-scans.

Download Full-text

Investigation of the Synthetic Aperture Focusing Technique resolution for heavy rotor forging ultrasonic inspection

2013 IEEE International Ultrasonics Symposium (IUS) ◽

10.1109/ultsym.2013.0476 ◽

2013 ◽

Cited By ~ 1

Author(s):

Karl T. Fendt ◽

Hubert Mooshofer ◽

Stefan J. Rupitsch ◽

Reinhard Lerch ◽

Helmut Ermert

Keyword(s):

Ultrasonic Inspection ◽

Synthetic Aperture ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique

Download Full-text

Time Domain/Frequency Domain SAFT Imaging in Thin-Diameter Rod

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.380-384.3648 ◽

2013 ◽

Vol 380-384 ◽

pp. 3648-3652 ◽

Cited By ~ 1

Author(s):

Gao Yuan Zhao ◽

Chao Lu

Keyword(s):

Frequency Domain ◽

Time Domain ◽

Signal To Noise Ratio ◽

Synthetic Aperture ◽

Testing Device ◽

Signal To Noise ◽

Ultrasonic Flaw ◽

Reflected Signal ◽

Synthetic Aperture Focusing ◽

Synthetic Aperture Focusing Technique

The ultrasonic flaw reflected signal of the thin-diameter rod was acquired by the general ultrasonic C-scan testing device. And synthetic aperture focusing technique be used in ultrasonic imaging of thin-diameter rod. Respectively, Comparing B-scan imaging and Conventional synthetic aperture focusing technique imaging as well as Frequency domain synthetic aperture focusing technique imaging . The final results show that both time domain and frequency domain synthetic aperture method could obtain a higher signal-to-noise ratio and testing resolution.

Download Full-text

ULTRASONIC IMAGING SYSTEM USING A 2D ENVELOPE BEAMFORMING TECHNIQUE: IN-HOMOGENEITIES LOCATION

Journal of Computational Acoustics ◽

10.1142/s0218396x04002419 ◽

2004 ◽

Vol 12 (04) ◽

pp. 571-585

Author(s):

L. MEDINA ◽

E. MORENO

Keyword(s):

Imaging System ◽

Side Lobe ◽

Ultrasonic Pulse ◽

Image Resolution ◽

Synthetic Aperture ◽

Water Tank ◽

Synthetic Aperture Focusing ◽

Longitudinal Resolution ◽

Synthetic Aperture Focusing Technique ◽

Beamforming Technique

An algorithm has been developed to implement synthetic aperture focusing technique for B-scan. This is made at a several transmitter/receiver locations to form a map of ultrasonic reflectivity on the insonified region, considering the path travelled by the ultrasonic pulse from the transducer to the target and back again. To reconstruct the image, a time domain beam-former is applied to the envelope of the detected signals. This method minimizes the side-lobe amplitude and the restriction of λ/2 distance between two adjacent transducer positions can be neglected without loosing image resolution. The present work is focused on the location of the in-homogeneities, caused by the presence of a phantom immersed in a water tank. The results are presented when the distance between two adjacent transducer positions are varied from 0.5λ to 2.5λ showing that the longitudinal resolution is not affected but the lateral resolution becomes poorer when the distance is about 2λ. The error in the longitudinal location of in-homogeneities is within the minimum detectable distance of the system, while the lateral location error is increased when the distance between any two adjacent transducer positions is larger than 1.5λ.

Download Full-text