Phased Array Ultrasonic Measurement of Fatigue Crack Growth Profiles in Stainless Steel Pipes
01 Nov 2007-Journal of Pressure Vessel Technology-transactions of The Asme (American Society of Mechanical Engineers)-Vol. 129, Iss: 4, pp 737-743
TL;DR: In this paper, the authors reported experimental sizing of fatigue crack profiles initiated from artificially made circumferential starter notches in stainless steel pipes of 169 mm outer diameter and 14.33 mm thickness, which were subjected to cyclic bending loads in a four point bending load arrangement using two nondestractive evaluation (NDE) methods: (a) phased array ultrasonic technique and (b) alternating current potential drop technique.
Abstract: This paper reports experimental sizing of fatigue crack profiles that are initiated from artificially made circumferential starter notches in stainless steel pipes of 169 mm outer diameter and 14.33 mm thickness, which were subjected to cyclic bending loads in a four point bending load arrangement using two nondestractive evaluation (NDE) methods: (a) phased array ultrasonic technique and (b) alternating current potential drop technique. The crack growth estimated using the two NDE techniques were compared with the beach marks that were present in the fracture surface. A simulation study using the ray tracing method was carried out to model the ultrasonic wave propagation in the test specimen, and the results were compared with the experimental results.
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TL;DR: In this article, the authors used the finite-difference time domain (FDTD) method to simulate the effect of various angles of incidence on the defect definition, i.e., with respect to imaging and sizing, using the relative arrival time technique.
61 citations
Cites methods from "Phased Array Ultrasonic Measurement..."
...Advanced ultrasonic methods like the time of flight diffraction (TOFD) technique [7], synthetic aperture focusing technique (SAFT) [8] and phased array techniques [9,10] have been...
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TL;DR: In this paper, real surface breaking cracks are fabricated in 3-point bending specimens following ASTM standard E1820 and used to examine the performance of two array defect characterisation methods: image-based and scattering matrix sizing.
Abstract: Using ultrasonic arrays to detect and characterise surface breaking cracks is important in the non-destructive evaluation (NDE) field. It can provide early warning of failure and useful information for component integrity assessment. Typically, cracks are approximated by machined slots and used to examine and assess defect detection and characterisation methods. In this paper, real surface breaking cracks are fabricated in 3-point bending specimens following ASTM standard E1820 and used to examine the performance of two array defect characterisation methods: image-based and scattering matrix sizing. In both cases, an array is used to record the full matrix capture (FMC). In image-based sizing, the total focusing method (TFM) is used to form an image from which the defect size is measured directly. This approach is shown to work well for cracks greater than two wavelengths in size. The FMC is also used to extract the defect scattering matrix which is then compared to a pre-computed smooth-crack scattering matrix database. The best match between experiment and this database is found by cross-correlation and used to characterise the defect. This approach is shown to work well for defects in the range of 0.78–1.84 wavelengths. Within these ranges of applicability, both methods show excellent agreement between the known crack length and that measured ultrasonically, with errors less than 19% in all cases.
29 citations
TL;DR: In this paper, the authors used the array transducer to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components.
Abstract: New techniques developed using the array transducer, to image and size the bottom-surface and near-through-wall crack-like defects in thick carbon steel components are discussed. Three studies are reported here including (a) Optimal beam steering angle for focused and unfocused inspection using phased array method for bottom-surface crack sizing. (b) A front wall correction algorithm for sizing of near-through-wall crack-like defects. (c) A small aperture technique for sizing of near-through-wall crack-like defects. A Finite Difference Time Domain (FDTD) based simulation was used to study and verify the experimental observations. The application of time domain scheme relative arrival time technique (RATT), to measure the size of the near-through wall crack-like defects for the leak before break (LBB) criterion, was also investigated and found to be insufficient. A conventional SAFT algorithm was used for improving the sizing using the small aperture technique.
17 citations
Cites background from "Phased Array Ultrasonic Measurement..."
...Relative Arrival Time Technique (RATT) involves the measurement of the corner trap and the tip diffracted echoes (by the same angle) from a single A-scan signal for the estimation of the size of the crack [ 11 ]....
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TL;DR: In this article, a method is proposed to extract the scattered signals from a near-surface defect which overlap with signals from structural features in both the time and frequency domains, from which it is possible to characterise the defect.
Abstract: Ultrasonic arrays have been widely used and developed for defect detection and characterisation over the last 10 years. In this paper, the question of how to inspect and characterise near-surface defects that are small with respect to wavelength is addressed. The challenge is to overcome the effect of the proximity of these scattered signals to high-amplitude signals reflected from structural features, such as planar surfaces. Here, a method is proposed to extract the scattered signals from a near-surface defect which overlap with signals from a structural feature in both the time and frequency domains. The extracted signals are then used to generate a scattering coefficient matrix, from which it is possible to characterise the defect. In the proposed method, the location of the defect is first approximately identified from an image. The arrival time difference between the signals from the defect and the nearby planar surfaces for each combination of transmitter and receiver array elements is then...
15 citations
TL;DR: In this paper, the authors used the sector scan feature of a phased array transducer to image and size crack-like defects in large pipes, elbows, and tee sections.
Abstract: This article reports simulation studies of ultrasonic wave generation and reception using the sector scan feature of a phased array transducer to image and size crack-like defects in large pipes, elbows, and tee sections. The simulations were based on a two-dimensional implementation of the Finite Difference Time Domain (FDTD) method. Experiments were conducted to validate modeling results for pulse-echo simulations of the phased array transducer on pipe samples with notches of three different sizes. The defects were imaged using the sector scan mode of the phased array and sized using the Absolute Arrival Time Technique (AATT). A 64 element, 5 MHz linear phased array transducer with the ultrasonic beam swept over an angular range of 10°–75° (refracted angles), directly in contact with the specimen, was used. Simulation and experimental studies were also conducted to image and size cracks in elbow and tee section pipes.
9 citations
References
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TL;DR: In this article, the basic mechanisms of these phenomena are discussed and the basic concepts can be found in a number of good text books and it seems worthwile to recall them in a short comprehensive paper.
278 citations
TL;DR: Experiments calibrating the response of EMATs when a defect is present between the generator and receiver are reported, using a calibration sample with slots machined perpendicular to the surface to simulate surface breaking cracks.
78 citations
TL;DR: In this paper, a 256-channel array system has been developed for the inspection of weldment of BWR internal components such as core shrouds and the TOFD crack sizing technique also can be applied using this system.
77 citations
TL;DR: A surface acoustic wave method for in situ monitoring of fatigue crack initiation and evolution from a pit-type surface flaw is described in this paper, which is demonstrated for fatigue tests on Al 2024-T3 and Inconel 718 samples with different surface pit sizes.
65 citations
TL;DR: In this paper, the authors used the shear wave-diffracted signal instead of the longitudinal wave for near-surface inspection of a crack tip and demonstrated an increase in the defect sizing accuracy.
Abstract: Ultrasonic time of flight diffraction (TOFD) for sizing defects is based on the time of flight of the diffracted echo that is generated when a longitudinal wave is incident on a crack tip. This technique has the limitation during near-surface inspection due to signal superposition. Here, this limitation is overcome by using the shear wave-diffracted signal (instead of longitudinal wave) and hence called S-TOFD. Experiments were conducted on samples with defect tip closer to the surface of a flat plate sample to illustrate the utility of the S-TOFD technique. An increase in the flaw sizing accuracy, by using the shear wave-diffracted echoes from the tip and through the application of a signal processing technique (ESIT), was demonstrated.
55 citations