NDT [2–10] or structural health monitoring (SHM)
[11–13] becomes of increasing interest to aerospace and
power generation communities since aging aircrafts and
power plants growing maintenance costs may limit their
lifetime. Also emerging new airplanes and power plants are
progressively required to be equipped with intelligence for
diagnostics of the health conditions of the critical parts and
structures. The objective of this investigation is to explore
the merits of combining ultrasound laser generation with
contact type UT receivers to perform NDT or SHM and
achieve the advantages (a), (b), (c) and possibly (d) mentioned
above. Such a hybrid approach would also eliminate
the high cost concern of a laser detection technique. There
have been good reports of this hybrid method [11–13] in
which laser pulses were used for the laser generation of ultrasound
and optically scanned to produce ultrasonic images,
but the fixed UTs used were not suitable for high temperature and curved surfaces. However, in a recent publication
[14] a lead-zirconate-titanate (PZT) transducer has
been bonded on top of a sample or a steel fiber welded to
the sample and used as an ultrasonic waveguide receiver up
to 140◦C together with scanned laser ultrasound generation.
Recently, integrated ultrasonic transducers (IUTs) made
of piezoelectric thick films (>40 μm) fabricated from a solgel
technique have been demonstrated [15–17]. These films
can coated onto both planar and curved surfaces. In previous
works [16–18] such IUTs were successfully used in pulseecho
or transmission mode on samples at up to 500◦C. The
aim of this study is to use such IUTs as receivers to detect
the ultrasound generated by pulsed lasers. The expected advantages
over conventional UTs used in the previous works
[11, 12] are that the IUTs are integrated, small, light weight
and work at high temperatures on curved surfaces. In addition,
IUTs can receive L, S [19], SAW [20] and PAWs [18].
They can be also easily arranged in mode selective array
configuration [18, 19] and have high piezoelectric sensitivities.
Also, the required electric power may quite be small for
IUTs used as receivers. They may therefore be operated using
battery or power obtained via energy harvested devices
and, wireless communicationmay be feasible. It follows that
the high electrical power pulser required for the generation
of ultrasound can be replaced by a remotely located pulsed
laser.