Grantový projekt GAČR 101/93/1195 (1993 - 1995)

Stanovení zákonitostí šíření signálu ve skořepinách pro potřeby akustických diagnostických metod

Řešitel: Ing. F. Valeš, CSc.

Main aim of the present project consists in determining relations between sources of generating signals and responses in shells. The determination of relations can indicate principles for increasing the accuracy and reliability of used measuring system. The solution assumes suitable combinations of analytical, numerical and experimental methods, in order to maintain an optimum relation between the accuracy of results and expended means. Basic solution is carried out for a force in a general position, acting on a shell surface, as a step function. The results are applied to calibrating measuring devices via a "pen test". By using the convolution, it is possible to obtain responses for an arbitrary time functions of excitation. The possibility of using the ray method, finite element method and boundary element method for determination of shell responses to internal excitation sources are analysed.

Grantový projekt GAČR 101/97/0409 (1997-1999)

Vliv geometrických nespojitostí pevných těles na šíření napěťových vln

Řešitel: Ing. F. Valeš, CSc.

The main goal of the project was to determine the influence of geometrical discontinuities on stress wave propagation in solid bodies. As geometrical discontinuities may be considered those of boundaries of the body (surface crack, sudden change of a shape) or internal ones (internal cracks, cavities, etc.). Non-stationary stress state at vicinity of discontinuities is determined by various methods: numerical (FEM), experimental (dynamic holography, AE transducers), analytical (integral transform matrix methods) with the aim to obtain conditions influencing propagation processes. The interest is also devoted to wave processes behind mentioned formations, which may cause problems during ultrasonic diagnostic measurements leading to measurement collapse.