Investigation of acoustic fields and elastic energy distribution is one of the most effective methods for defect detection and visualisation. This task of field investigation is now routine in ultrasonic testing but has special features if the materials under study are anisotropic. The elastic anisotropy of single crystals leads to a number of effects complicating the interpretation of the results. For example, if the propagation direction deflects away from the crystallographic axis, the elastic waves spread as two or even three eigenmodes where the directions of the phase and ray velocities do not coincide with one another. The influence of elastic anisotropy manifests itself even if the beam's axis coincides with a high-symmetry direction in the crystal. The lateral rays of the beam in this case are inclined in the relation to the crystallographic axis. The polarisation of these rays differs from the polarisation of the central part of the beam. The elastic energy distribution has to reflect the medium's anisotropy. The specific phenomena occur if the waves propagate near the acoustic axis and if the normal plane to the wave vector is not the plane of mirror symmetry [1]. The inner defect visualisation under crystallographic elastic symmetry conditions has a number of peculiarities. The study of the displacement distribution of elastic waves propagating in aluminium single crystals is the purpose of this paper. Aluminium is chosen as the object of investigation because its elastic properties are well known, and in addition high-purity, high quality single crystals are available. The effect of small beam deflection from the crystallographic axis is studied by the laser interferornetric method [2,3] and the experiments have been carried out when the waves propagate along both the [001] and [111] axes as well along directions close to the [111] axis. Of particular interest is the shear wave energy distribution in connection with the internal conical refraction (ICR) effect [4] if the wave propagates along [111] axis in a cubic crystal. Beyond that point the distortion of the elastic energy distribution caused by the inner defect exposed at the crystal surface has been studied.
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