Improvement in transient piezoelectric responses of NDE transceivers using selective damping and tuning networks

NDE ultrasonic applications for quality control purposes, based on piezoelectric devices working as pulsed ultrasonic probes, usually include some tuning circuit either across the pulser output connectors or close to the piezoelectric probe electrodes. Classic criteria to determine tuning parameters in ultrasonic transducers do not perform very well in transient regime under the typical electrical conditions and peculiar output impedances of the required high-voltage pulsers. In most practical situations, the tuning values are manually adjusted in specific circuits for each NDE case, testing each channel of a multiprobe inspection system to find the best sensitivity. In this paper, the positive influences of certain selective damping and tuning networks on the time and frequency behaviors of NDE piezoelectric transceivers are analyzed in detail. Different waveforms and spectra of received ultrasonic signals are comparatively evaluated for different real tuning conditions, after passing through two ultrasonic processes linked in cascade: a transmitter of industrial type and a broad-band ultrasonic receiver. Piezoelectric transducer impedances, transduction transfer functions, and HV output spikes from a piezoelectrically loaded NDE pulser, are computed, to identify separately the influence of each stage. In order to improve amplitude and axial resolution in the received transient responses, relative contributions from emission and reception tuning networks are individually evaluated for a particular NDE two-stage piezoelectric channel. Also shown are the final experimental results relative to the ultrasonic test pulse and detected in a through-transmission NDE configuration, gradually improved by using distinct tuning levels.

[1]  A. Ramos,et al.  Different tuning contributions in piezoelectric transceivers improving transient signals for ultrasonic imaging , 1998, ISAF 1998. Proceedings of the Eleventh IEEE International Symposium on Applications of Ferroelectrics (Cat. No.98CH36245).

[2]  G. Hayward,et al.  Discrete-Time Modeling of the Thickness Mode Piezoelectric Transducer , 1984, IEEE Transactions on Sonics and Ultrasonics.

[3]  G. Kossoff.  The Effects of Backing and Matching on the Performance of Piezoelectric Ceramic Transducers , 1966, IEEE Transactions on Sonics and Ultrasonics.

[4]  L.G. Ullate,et al.  Analysis of the ultrasonic field radiated by time-delay cylindrically focused linear arrays , 1994, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[5]  T. Rhyne.  Computer optimization of transducer transfer functions using constraints on bandwidth, ripple, and loss , 1996, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[6]  G. Kino.  Acoustic waves : devices, imaging, and analog signal processing , 1987 .

[7]  F. M. Espinosa,et al.  Broad-band driving of echographic arrays using 10 ns-500 V efficient pulse generators , 1987 .

[8]  J. Andersen,et al.  Computer-Aided Design of Ultrasonic Transducer Broadband Matching Networks , 1974, IEEE Transactions on Sonics and Ultrasonics.

[9]  R. Coates,et al.  Design of matching networks for acoustic transducers , 1988 .

[10]  R.N. Thurston.  Effect of Electrical and Mechanical Terminating Resistances on Loss and Bandwidth According to the Conventional Equivalent Circuit of a Piezoelectric Transducer , 1960, IRE Transactions on Ultrasonic Engineering.

[11]  Gordon Hayward,et al.  The influence of pulser parameters on the transmission response of piezoelectric transducers , 1985 .

[12]  J.W. Hunt,et al.  The design of protection circuitry for high-frequency ultrasound imaging systems , 1991, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[13]  W. A. Verhoef,et al.  Optimization of ultrasonic transducers. , 1985, Ultrasonics.

[14]  L. J. Augustine,et al.  An algorithm for the design of transformerless broadband equalizers of ultrasonic transducers , 1979 .

[15]  W. E. Lawrie,et al.  Ultrasonic testing of materials: 2nd English Edition, translated from the 3rd German Edition, J. & H. Krautkrämer Springer-Verlag, Berlin, Heidelberg, New York (1977) 667 pp, $65.20, DM 148 , 1978 .

[16]  P. T. Sanz,et al.  A 5 MHz high-voltage demultiplexed ultrasonic array system for rapid-scan testing of advanced materials , 1993 .

[17]  M. G. Silk,et al.  Ultrasonic transducers for nondestructive testing: Adam Hilger, Bristol, UK, 1984 (176 pp, £24, $39) , 1985 .

[18]  H. Carlin,et al.  Theoretical Limitations on the Broad-Band Matching of Arbitrary Impedances , 1961 .

[19]  L. Capineri,et al.  Ultrasonic transducers as a black-box: equivalent circuit synthesis and matching network design , 1993, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[20]  F. Foster,et al.  Ultrasound Transducers for Pulse-Echo Medical Imaging , 1983, IEEE Transactions on Biomedical Engineering.

[21]  J. L. San Emeterio,et al.  Electrical matching effects on the piezoelectric transduction performance of a through-transmission pulsed process , 1997 .

[22]  P. J. Howard,et al.  Ultrasonic Maximum Aperture Saft Imaging , 1995 .

[23]  J. Krautkrämer,et al.  Ultrasonic Testing of Materials , 1969 .

[24]  J. L. San Emeterio,et al.  Distortions on the output waveforms of high-voltage spike generators induced from piezoelectric loads , 1999 .

[25]  Wai-Kai Chen,et al.  Explicit formulas for the synthesis of optimum broad-band impedance-matching networks II , 1977 .