Experimental investigation by laser ultrasonics for high speed train axle diagnostics

Cavuto, A.; Martarelli, Milena; Pandarese, Giuseppe; Revel, Gian Marco; Tomasini, Enrico Primo

doi:10.1016/j.ultras.2014.08.010

Cited by 53 publications

(25 citation statements)

References 15 publications

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“…After these two signals acquisition, the cross-correlation operation (d) is applied between them [8,11,12], and the ultrasonic TOF and PtP can be evaluated from the cross-correlation output (e). Even if SNR can be calculated through a large variety of methods [4,5,8,10,11], it is always represented by the formula: = , where is a generic quantity which considers only the portion of acquired signal interested by the US after the cross-correlation application, while the same applies for the noise with . The noise is coherent with the generated US, which makes the cross-correlation technique more efficient than other time-frequency methods like Wavelet Transforms [20].…”

Section: Methodsmentioning

confidence: 99%

“…The more utilized instruments for this kind of inspection are narrow band, piezoelectric probes which need the contact with the inspected object to be guaranteed. Non-contact applications use high-power pulsed lasers as a source of elastic waves [3][4][5][6], mainly in order to allow an on-line inspection [7]. These waves are generated by the material expansion and contraction due to the laser quick heating and the subsequent sudden cooling.…”

Section: Introductionmentioning

confidence: 99%

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Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Vangi

Virga

Gulino

2017

J. Phys.: Conf. Ser.

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Abstract. Low-power laser generated ultrasounds are lately gaining importance in the research world, thanks to the possibility of investigating a mechanical component structural integrity through a non-contact and Non-Destructive Testing (NDT) procedure. The ultrasounds are, however, very low in amplitude, making it necessary to use pre-processing and post-processing operations on the signals to detect them. The cross-correlation technique is used in this work, meaning that a random signal must be used as laser input. For this purpose, a highly random and simple-to-create code called T sequence, capable of enhancing the ultrasound detectability, is introduced (not previously available at the state of the art). Several important parameters which characterize the T sequence can influence the process: the number of pulses , the pulse duration δ and the distance between pulses . A Finite Element FE model of a 3 mm steel disk has been initially developed to analytically study the longitudinal ultrasound generation mechanism and the obtainable outputs. Later, experimental tests have shown that the T sequence is highly flexible for ultrasound detection purposes, making it optimal to use high and δ but low . In the end, apart from describing all phenomena that arise in the low-power laser generation process, the results of this study are also important for setting up an effective NDT procedure using this technology.

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Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Vangi

Virga

Gulino

2017

J. Phys.: Conf. Ser.

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“…Application of a transient heating creates a sudden expansion and a consecutive contraction in the material, generating longitudinal, shear and surface ultrasounds [3]. The technique's fundamental advantage is the possibility of a non-contact inspection, therefore usable in operation too [7][8][9][10]. The thermo-elastic effect is generally obtained through pulsed lasers: a brief and single pulse (in ns) with a power of approximately 1 MW, creates a broad band oscillation with frequencies up to hundreds of MHz.…”

Section: Introductionmentioning

confidence: 99%

Study on the most influential parameters in low-power laser generated ultrasound

Vangi¹,

Virga²,

Gulino³

2017

FME Transaction

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“…During the hybrid inspections, ultrasonic waves are generated by a high‐power pulsed laser, and the ultrasonic field can be acquired by an air‐coupled transducer. Cavuto et al applied the laser‐ultrasonic to inspect a high‐speed train axle with typical fatigue defects created according to standard specifications. The results demonstrated that the applicability of a laser‐ultrasonic procedure to improve the performances of train axle ultrasonic inspection.…”

Section: Introductionmentioning

confidence: 99%

Damage detection for high-speed train axle based on the propagation characteristics of guided waves

Qiu

Wang

2016

Struct. Control Health Monit.

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The currently defect identification techniques based on guided wave is not feasible for high-speed train axle because the structure complicates wave propagation. A novel damage detection method especially for train axle is proposed in this paper. Piezoelectric patches are used as actuator to excite waves in the axle. Guided wave generated by single actuator and circumferential, limited number of actuator configurations is discussed to optimize the transducer network. The axle is simplified to a variable cross-sectional and thick-walled hollow cylindrical structure. Eight piezoelectric actuators that evenly distributed at the axle end surface are used to excite simplex longitudinal waves. Signals of circumferential and axial displacement of the monitoring points are researched before and after introducing the flaw on the surface, and their sensitivity to the depth and length of defect are also discussed. From the view of practical feasibility, the difference of signals from two axisymmetrical measure points of same axial position is proposed for the defect identification. Experimental verification is conducted, and the results demonstrate that the proposed approach is reliable in the axle inspection. laser-ultrasonic to inspect a high-speed train axle with typical fatigue defects created according to standard specifications. The results demonstrated that the applicability of a laser-ultrasonic procedure to improve the performances of train axle ultrasonic inspection. Mineo et al. [5] presented a nondestructive inspection method of in-service axles based on a hybrid laser-ultrasonic system. And a numerical method based on explicit integration was used to investigate a new approach that could be developed for a non-contact in-service inspection of railway axles at trackside. However, laserultrasonic technique could greatly affect the surface quality of axle because of the high energy of laser beam, and the cost of the detection system is relatively high.Ultrasonic guided waves (GWs) can propagate in structures for a long distance with low attenuation, and they are sensitive to mini flaws in waveguides. Hence, GW-based techniques are given to high expectations in SHM field. Axles in high-speed train in China are hollow cylindrical structures, which can help reduce weight. Thus, GW technique for pipes can provide some experience for its application in axles of high-speed train. Circular bonded piezoelectric (PZT) actuators are used to generate only longitudinal-mode GWs. However, axles are thick walled and variable cross-sectional hollow cylindrical structures. Multiple modes and intrinsic dispersive properties of the GWs complicate the SHM process. Moreover, interpretation of the received echo GW signals could be very complex because of the variable cross-sections. Therefore, current approaches for pipe-like structures should be modified to adjust the changes from the train axles.Fatigue cracks generally caused by fretting fatigue. Typical site of those cracks are initially at the wheel seat because of the interacti...

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Experimental investigation by laser ultrasonics for high speed train axle diagnostics

Cited by 53 publications

References 15 publications

Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Random Sequence for Optimal Low-Power Laser Generated Ultrasound

Study on the most influential parameters in low-power laser generated ultrasound

Damage detection for high-speed train axle based on the propagation characteristics of guided waves

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