Вплив внутрішніх напружень на хвильові процеси та поглинання ультразвуку при зварюванні

Abstract

Using the bilinear approximation of the total strain tensor for an elastic wave process in the pre-sence of internal static stresses and deformations in welded optical polymeric materials, their influence on the process characteristics and ultrasound absorption has been theoretically investigated. For the case of a plane elastic wave and axially symmetric static stresses, a two-dimensional system of wave equations for the longitudinal and transverse wave components is obtained. It has been established that only inhomogeneous internal stresses and deformations lead to the appearance of a weak coupling between the components of the wave and a change in their amplitudes, as well as to the weakening of the longitudinal (acoustic) component of the elastic wave. For a simple example of a point force action on the surface, calculations are made of the decrements of ultrasound attenuation by amplitude in the meridian planes. It is shown that for sufficiently large gradients of static deformations near the pressing region of the welded parts, a region of maximum (resonance) absorption of ultrasound may be formed, whose dimensions are comparable to the effective length, which depends on the square root of the ratio of the applied pressing force to the modulus of elasticity of the material. This contributes to the localization of the ultrasound absorption region.