Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing

Pollakowski, M.; Ermert, H.

doi:10.1109/58.308500

Cited by 160 publications

(84 citation statements)

References 7 publications

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“…In force of these considerations, the actual research on ECT is considering excitation signals containing wideband spectrums instead of the sinusoidal ones. To this aim some emerging techniques based on the use of multi-frequency, pulsed, chirp, and pseudo-noise signals, to cite a few, are proposed in literature as alternatives to traditional ECT signals in order to, primarily, improve the sensitivity of defect detection in some particular application field, and especially for small cracks, embedded deep in layered components [2][3][4][5][6][7][8][9][10][11][12][13]. Each one of these considered excitation signals present advantages and disadvantages that prevent the election of an absolute best excitation signal.…”

Section: Abstract Eddy Current Testing (Ect) Is a Nonmentioning

confidence: 99%

An experimental comparison of complex excitation sequences for eddy current testing

et al. 2015

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Eddy Current Testing (ECT) is a Non Destructive technique widely used in many industrial application fields in which it is very important to detect the presence of thin defects (generally called cracks) in conductive materials. Features of this technique are the cost-effective implementation and the kind of retrieved measured data that make possible to estimate the geometrical characteristics of a crack as position, length, width and depth. The analysis of these characteristics allows the user to accept or discard realized components then improving the production chain. To accomplish for this task some aspects have to be taken into account during the measurement process. They mainly concern the realization of suitable measurement setup and post processing stages. As far as the measurement setup is concerned, crucial aspects are the choice of measurement and excitation devices. The choice of optimized excitation devices and strategies is of interest for research on Non Destructive ECT (ND-ECT): together with common aspects as the amplitude and the frequency of the exciting signal, the attention has been paid to issues as the type of signal to be adopted. In particular it has been found as the use of complex excitation signals, meant as signals different from the sinusoidal ones and with wide frequency content, might raise eddy current responses trying to support the measurement, detection and characterization stages when "difficult cases" are explored (i.e. very small and/or annealed cracks). In this paper the authors propose an experimental comparison of different excitation signals designed to improve the quality of experimental data when difficult cases are experienced and, consequently, to obtain a more reliable extraction of defects geometrical features.

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Section: Abstract Eddy Current Testing (Ect) Is a Nonmentioning

confidence: 99%

An experimental comparison of complex excitation sequences for eddy current testing

et al. 2015

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“…The chirp signal is often used in cross-correlation analysis because it facilitates the detection of a peak even if the direct and reflected waves interfere with each other. 12,13) The TOF is defined as the elapsed time + Graduate Student, University of Tsukuba between the sending out of the ultrasonic wave and the first peak of the cross-correlation of input and received signals.…”

Section: Measurement Of Tofmentioning

confidence: 99%

“…13) These shear and compressive stresses may cause cracks as well as shape distortions. Despite numerous improvements in the casting process, it can still be difficult to overcome some of these problems and produce billets entirely free from defects.…”

Section: Introductionmentioning

confidence: 99%

Simulation of Internal Crack Detection in Shape-Distorted Cast Billets Using Time-of-Flight Measurements of Longitudinal Ultrasonic Waves

et al. 2012

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To detect cracks in shape distorted cast billets, we newly propose a method that is the use of ultrasonic computerized tomography (CT) in combination with measurements of time-of-flight (TOF) of longitudinal ultrasonic waves at multiple planes as a more robust reconstruction method. The TOF is measured by applying the transmission method, and the measured TOF is used to reconstruct the apparent sound velocity profile. Cracks are identified as a decrease in the apparent sound velocity, which is caused by an increase in the TOF after the diffraction of ultrasonic waves at the cracks. The combination makes it possible to remove the effects of shape distortion to be compensated by the TOF measurements at multiple planes. Therefore, cracks are clearly detected using this method. The detection ability of this method is evaluated by numerical simulations of a shape-distorted billet. The results of this study are validated with help of wave propagation simulations using the transmission line matrix (TLM) method. More specifically, the newly proposed method allowed us to detect cracks that could hardly be distinguished with the use of our previously proposed method owing to fluctuations of the apparent sound velocity caused by shape distortions. In addition, using the new method enables the detection of cracks located near the billet's surface whose dimensional change is as small as 5%. From the results of this study, we believe that the newly proposed method could be useful for the crack detection in shape-distorted billets.

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“…Since both amplitude and phase are accounted for, phenomena as frequency modulation can be in-cooperated in the design. In contrast to [7] attention is not only given to the phase-spectrum of the waveform but also to the amplitude spectrum. Thereby it is possible to lower the sidelobe level from ∼ -40 dB to ∼ -80 dB.…”

Section: Introductionmentioning

confidence: 99%

“…In [6], [7] this issue was addressed using non-linear frequency modulation (NLFM). This approach offers a flexible solution for designing waveforms with attractive amplitude spectral properties while maintaining a constant amplitude of the excitation signal.…”

Section: Introductionmentioning

confidence: 99%

P2F-6 Designing Non-Linear Frequency Modulated Signals for Medical Ultrasound Imaging

Gran

Jensen

2006

2006 IEEE Ultrasonics Symposium

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Abstract-In this paper a new method for designing non-linear frequency modulated (NLFM) waveforms for ultrasound imaging is proposed. The objective is to control the amplitude spectrum of the designed waveform and still keep a constant transmit amplitude, so that the transmitted energy is maximized. The signal-to-noise-ratio can in this way be optimized. The waveform design is based on least squares optimization. A desired amplitude spectrum is chosen, hereafter the phase spectrum is chosen, so that the instantaneous frequency takes on the form of a third order polynomial. The finite energy waveform is derived by minimizing the summed squared error between the desired spectrum and the obtained spectrum of the waveform. Having total control of the waveform spectrum has two advantages: First, it facilitates efficient use of the transducer passband, so that the amount of energy converted to heat in the transducer can be decreased. Secondly, by choosing an appropriate amplitude spectrum, no additional temporal tapering has to be applied to the matched filter to achieve sufficient range sidelobe suppression. Proper design results in waveforms with a range sidelobe level beyond -80 dB. The design method is tested experimentally using the RASMUS ultrasound system with a 7 MHz linear array transducer. Synthetic transmit aperture ultrasound imaging is applied to acquire data. The proposed design method was compared to a linear FM signal. Due to more efficient spectral usage, a gain in SNR of 4.3±1.2 dB was measured resulting in an increase of 1 cm in penetration depth. Finally, in-vivo measurements are shown for both methods, where the common carotid artery on a 27 year old healthy male was scanned.

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Chirp signal matching and signal power optimization in pulse-echo mode ultrasonic nondestructive testing

Cited by 160 publications

References 7 publications

An experimental comparison of complex excitation sequences for eddy current testing

An experimental comparison of complex excitation sequences for eddy current testing

Simulation of Internal Crack Detection in Shape-Distorted Cast Billets Using Time-of-Flight Measurements of Longitudinal Ultrasonic Waves

P2F-6 Designing Non-Linear Frequency Modulated Signals for Medical Ultrasound Imaging

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