A great attention is now paid to the development of methods for residual stress detection. The ultrasonic, Raman spectroscopy, magnetic, X-ray, neutron diffraction methods are usually used for this purpose. Recently holographic interferometry based on the hole drilling method has also attracted serious attention for solution of this problem. The application of the photoacoustic (PA) effect for the diagnostics of mechanical stresses is considered at present with growing interest [1]. The main advantage of the PA method lies in its universal character. and in the possibility of application at microscopic and mesoscopic scales.
The problem of residual stress detection by PA and photothermal (PT) methods has been actively discussed for about twelve years but many important details of this problem are not solved up to now. The main task of this talk is to clear up the situation both by experimental and theoretical investigations. Experimental investigations of the work are based on new multimode approach proposed by us recently which is able to provide an important opportunity to control elastic, thermal and thermoelastic parameters of materials independently and locally. Different types of PA and PT experiments have been performed. They include PA and PT measurements and imaging of regions near Vickers indentations, PA and PT measurements under annealing, PA and PT imaging of solids under the given external loading. These experiments directly demonstrate the influence of stress on the PA signal and can be used for an estimation of sensitivity of the PA method to mechanical stresses in different materials.
The model of the PA thermoelastic effect in solids with residual stresses is proposed and used for the explanation of the obtained results. It is based on the modified Murnaghan model of nonlinear elastic bodies which takes into account a possible dependence of the elastic and thermoelastic properties of a material on stress. It is demonstrated that the developed theoretical model for the PA piezoelectric effect agrees qualitatively with the available experimental data.
This research was supported by RFBR (Russia) under grant number 06-02-17148 and by CRDF (USA).
1. K.L.Muratikov and A.L.Glazov. Mat. Sci. Forum. 524-525, 471(2006).
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