A multimode approach based on the simultaneous application of several photothermal and photoacoustic methods is proposed for the study of thermal and thermoelastic effects in solids with residual stress. It includes photoacoustic gas microphone, photodeflection, photoreflectance and photoacoustic piezoelectric microscopy methods. This approach provides complementary information about thermal, elastic and thermoelastic properties of samples with residual stress. Some experimental results obtained within the framework of this approach for Vickers indentation zones in silicon nitride ceramic are presented. The model of the photoacoustic thermoelastic effect in solids with residual stress is proposed. It is based on the modified Murnaghan model of nonlinear elastic bodies which takes into account a possible dependence of the thermoelastic constant on stress. It is demonstrated that the developed theoretical model for the photoacoustic piezoelectric effect agrees qualitatively with the available experimental data.

A generalized theoretical model of the formation of a thermoelastic photoacoustic signal from real materials is proposed taking into account the presence of defects and impurities. An effective coefficient of thermal expansion was introduced that describes the dilatation effect of thermally activated lattice irregularities. Expressions for the thermoelastic photoacoustic signal obtained in the linear approximation were applied to describe aluminum membrane vibrations at the periodic laser excitation measured in other studies using a gas-microphone open-cell photoacoustic technique. The proposed theoretical model allows us to explain the experimental results in the 20 Hz–7 kHz modulation frequency range without invoking the assumption of the bulk absorption of pump laser radiation in aluminum membranes.

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