Grant project ASCR 27007 (1991-1993)
The Utilisation of Stress Waves for Diagnostics of Material Defects
Principal investigator: Ing. F. Valeš, CSc.
Grant project GACR 101/93/1195 (1993 - 1995)
Determination of Laws of Signal Propagation in Shells for Needs of Acoustic Diagnostic Methods
Principal investigator: 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.
Grant project GACR 101/96/0128 (1996-1998)
Interaction of Stress Waves with Geometrical Discontinuities and Material Inhomogenities in Solid Bodies
Principal investigator: Ing. F. Valeš, CSc.
Grant project GACR 101/97/0409 (1997-1999)
Stress waves scattering from geometrical discontinuities in solid bodies
Principal investigator: 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.
Grant project GACR 101/00/0674 (2000-2002)
Influence of Materials Non-Linearities and Geometrical Discontinuities to Stress Waves Propagation in Solid Bodies
Principal investigator: Ing. F. Valeš, CSc.
