Grant project GACR 101/94/0971 (1994-1996)
New methods of acoustic emission signal processing
Principal investigator: Ing. P. Hora, CSc.
The project dealt with developing and verifying new acoustic emission (AE) signal processing methods. The fundamental problem of the acoustic emission analysis is to extract properties of AE sources from detected signals. In order to solve this inverse problem one has to apply some model of the AE phenomenon. Exact analytical modeling by elasto-dynamic equations lead to ill-posed problems and was, therefore, not convenient. As an alternative, the empirical modeling based on adaptive methods was introduced. It was performed by an information processing system composed of an array of sensors and an artificial neural network simulated on a computer.
The detail knowledge of behaving piezoelectric broadband AE transducers is very important for successful practical operation, too. This was the reason for detailed dynamic analysis of the AE transducer by means of FEM.
Grant project GACR 101/97/1074 (1997-1999)
Characterization of acoustic emission sources in steel structures
Principal investigator: Ing. P. Hora, CSc.
One of the basic problems in an AE signal analysis, which are not yet solved, is the reliable identification of real parameters of AE source (i.e. the determination of its location, type, and extent). The goal of the project was to develop the AE source characterization method allowing AE source recognition on the basis of inverse elasto-dynamic problem solution. The necessary Green functions of investigated bodies are obtained by analytical, numerical, and experimental ways. Both the precise analytical modeling and empirical modeling using adaptive methods solve the inverse problem. Adaptive methods based on the artificial neural networks and fuzzy approach are used. The experimentally detected and digitized AE signals are compressed and parameterized by means of the wavelet transform.
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.
