The arrays of our interest are linear, phased and concave arrays. With this purpose, we started the theoretical study of wave propagation in solids, and up to now, we have developed a software package for modeling the wave propagation. They treat the array elements as point-like radiators. However in NDT applications, the problems of interest are often in the near-field range, and the physical size of the array elements must be taken into account on calculating sound fields because it is not small compared to the wave length. As presented in previous sections, the linear array is used to the immersion test of metals.
Elastic fields radiated by the array into copper block, therefore, are of our interest.
Here we present the basic theory of array and the model for elastic fields in the case of phased arrays. Specifying the phases in different ways, the array can generate different kinds of beams, such as steered and focused beams. While our interest is mostly in the immersion test of block in near-field. The refraction brings about the deflection of the incident beam in the solid. This means that the evaluation of such an elastic field is not an easy job.