Proceedings of Topical Meeting on Optoinformatics (pdf-format, 1.21 ...

SAINT-PETERSBURG, October 17 – 20, 2005 25
LASER PHOTOACOUSTIC MICROSCOPY OF MECHANICAL
STRESSES IN MODERN MATERIALS
K.L.Muratikov, A.L.Glazov
Physical-Technical Institute <strong>of</strong> RAS,
Polytekhnicheskaya 26, 194021, St.Petersburg, Russia
E-mail: klm@holo.i<strong>of</strong>fe.rssi.ru
The main concepts <strong>of</strong> modern photoacoustic and photothermal microscopy are
described. The problem <strong>of</strong> mechanical stress detection and imaging by
photoacoustic microscopy is analyzed both theoretically and experimentally.
Examples <strong>of</strong> the photoacoustic microscopy application for stress detection in
brittle and ductile materials are presented.
Recently photoacoustic and photothermal microscopy methods have been
successfully used for the diagnostics <strong>of</strong> defects in the bulk and near subsurface layers <strong>of</strong>
various materials. Photoacoustic and photothermal microscopies are able to provide
important information about local elastic, thermal and thermoelastic properties <strong>of</strong>
materials. These methods proved to be effective in detecting cracks, voids, delaminated
layers, and foreign inclusions. The main advantages <strong>of</strong> these methods are nondestructive
character, ability to detect subsurface defects and high spatial resolution. Essentially less
attention has been paid to the problem <strong>of</strong> mechanical stress detection by photoacoustic and
photothermal methods.The main purpose <strong>of</strong> this work is to present our results in the field
<strong>of</strong> mechanical stresses detection by photoacoustic method. The problem <strong>of</strong> residual and
mechanical stresses detection is an important problem <strong>of</strong> modern material physics,
mechanics and engineering. Various methods such as optical, ultrasonic, Raman
spectroscopy, magnetic, X-ray and neutron diffraction methods, stress pattern analysis by
measurement <strong>of</strong> thermal emission (SPATE), are usually used for this purpose. Hole drilling
and compliance methods are also actively investigated at present for residual stress
detection. Recently holographic interferometry based on the hole drilling method in
conjunction with holographic or speckle interferometry has attracted serious attention for
solution <strong>of</strong> this problem. These methods have been already implemented effectively for the
residual stress detection while the application <strong>of</strong> most <strong>of</strong> them is limited substantially by
the physical nature <strong>of</strong> the used effect.
The application <strong>of</strong> the photoacoustic thermoelastic effect for the diagnostics <strong>of</strong>
mechanical stresses is considered at present with growing interest [1-3] . The main advantage
<strong>of</strong> the photoacoustic thermoelastic method lies in its universal character and in the
possibility <strong>of</strong> application to objects <strong>of</strong> different nature at microscopic and mesoscopic
scales. Many important details <strong>of</strong> the problem <strong>of</strong> residual stress detection by photoacoustic
and photothermal methods are not solved up to now. In this work both experimental and
theoretical investigations are presented which are able to clear up the situation in this field.
Experimental investigations <strong>of</strong> the work are based on new multimode approach
proposed by us recently [3-5] which is able to provide an important opportunity to control
elastic, thermal and thermoelastic parameters <strong>of</strong> materials independently and locally.
Different types <strong>of</strong> photoacoustic and photothermal experiments have been performed. They
can be classified into three types:
(a) Photoacoustic and photothermal measurements and imaging performed in regions near
Vickers indentations.