Ustav fyziky
Ustav fyziky
Ustav fyziky
Old prodects of the Department of Physics
The use of acoustic methods for non-destructive testing of high-temperature-degraded concrete
Zdeněk Chobola - head GAČR 16-02261S 2016-2018 all years € 114469
Concrete structures may be exposed to high temperatures because of fire, explosion, or chemical reaction. If the concrete is exposed to extreme temperature changes its mechanical and chemical behavior, particularly allowable design stress in tension and compression elastic modulus, Poisson s ratio and more.
Morphology analysis of fracture surfaces and its consequences for stability of large civil engineering constructions
Tomáš Ficker - head 13-03403S 2013-2017 all years € 106250
The project is aimed at developing a new method for classifying morphology fetaures of solid surfaces to facilitate estimation of their roughness indicators. This will be coceptually new method able to distiguish between dirfferent types of two-dimensional Fourier wave modes that are formed on fracture srufaces.
Research and Development of Selected Measuring Method and Analyses for Building Mixture Behaviour Study at Hardening
Luboš Pazdera - head GAP104/10/0535 2010-2012 all years € 93000
The objective of the present project consists in measuring and analyzing some important processes taking place in selected cement composites,namely, the shrinking-induced micro-crack generation and the fracture-induced micro-crack growth and propagation. As a methodological innovation, the acoustic emission method, non-liner spectroscopy etc. will be used throughout.
Statistical dilemma of electron avalanches
Tomáš Ficker - head GA202/07/1207 2007-2009 all years € 43531
The project is aimed at solving long-lasted problems with peculiar statistical behaviour of high populated electron avalanches. These avalanches are precursors of streamer discharges in gasses. The present streamer theory fails in explaining their severesystematic deviations from the Furry statistics that is believed to be their governing statistical law. Such a deviated behaviour of pre-streamer avalanches seems to be a consequence of a special breakdown mechanism that is rather different from those known so far in discharge physics. The project tends towards formulating a new theoretical concept amending and extending the streamer theory. Correctness of the concept is corroborated by the series of experiments and the practical utilisation may be envisaged in the field of the non-destructive testing of high voltage components as well as in technical designs of discharge-based industrial products.
Acoustic and electromagnetic emission in materials research
Bohumil Koktavý - head 103/06/0708 2006-2008 all years € 56156
The goal of the project is to refine the knowledge of the origin of the acoustic and electromagnetic emission accompanying the crack generation and the dislocation displacement. Inter-atomic bonds are disturbed and energy is released in the course of these processes. The released energy is manifested by mechanical wave motion. Moreover, in consequence of the chemical band disturbance, electric charges are released, thus giving rise to electric and magnetic fields. The existence of a quasi-stationary magnetic field and its generation in consequence of the crack formation has not yet been sufficiently verified by experiments. The fundamental problem consists in designing an apparatus, whose shielding is sufficient. It is essential to suppress any electromagnetic signals emitted from the measuring apparatus to such a degree, that the respective electromagnetic noise is lower in magnitude than the signals arising from the charge carrier motion of on the crack faces.
Defectoscopy of reinforced concrete elements and structures using non-linear acoustic spectroscopy
Marta Kořenská - head GA103/06/1711 2006-2008 all years € 77500
The project deals with a complex methodology for the reinforced concrete structure diagnostics. Repetitive loading of reinforced concrete and pre-stressed elements gives rise to material fatigue and degradation. Minute cracks are arising in theconcrete, whose accumulation may result in the integrity disturbance, cause corrosion of reinforcing steel and lead to worsening of structure mechanical properties (e.g. the strength). The corrosion causes an additional concrete deterioration round the corrosion centres because of the corrosion products increasing. The research is envisaged to be applicable for concrete crack detection methods, which will be based on the acoustic-emission (AE) principle and, mainly, the non-linear ultrasonic spectroscopy in conjunction with the classical ultrasonic spectroscopy methods.
Noise Spectroscopy for Fast Non-Destructive Testing of the Quality, Releability and Lifetime of the Solar Cells
Zdeněk Chobola - head GA102/04/0142 2004-2006 all years € 40031
The objective of this project is to demonstrate - based on experimental research - that noise spectroscopy is a suitable tool to be used in fast and non-destructive testing of quality, reliability and service life time of solar cells, this unique source of pure energy. In the framework of the project, correlation between the noise spectroscopy and traditional quality and reliability testing parameters, such as charge carrier transport characteristic analysis, DLTS spectroscopy, third harmonic content based testing and photovoltaic scanning based inhomogeneity testing will be demonstrated. By means of elevated temperature and electric field enhanced accelerated degradation, the usefulness of noise parameter based method to forecast the device life time will be shown . Furthermore, the research will focus on the theory of stochastic processes, too. The stochastic model of RTS noise in PN junction structures will be further developed. In cooperation with Solartec, s.r.o. Rožnov, solar cell manufacturer, noise diagnostics will be applied to screen the devices by quality, reliability, aimed at achieving long life and a high energy conversion efficiency.
Barrier microdischares and their degradation effects
Tomáš Ficker - head GA202/03/0011 2003-2005 all years € 35938
The microdischarge transport represents the transfer of electrical charges realised by a series of discrete pulse discharges initiated in microscopic air gaps that appear with real interfaces metal-insulator or metal-dielectric. The research project continues the study of statistical features of the microdischarge transport and seeks for a quite new application of fractal geometry to the transport topology.
Monitoring and analysis of corrosion of reinforcement steel in corrored reinforced concrete structure by acoustic emission
Zdeněk Chobola - head GA103/03/0295 2003-2005 all years € 101219
Steel armature corrosion degrades the reinforced concrete structure properties and reduces the structure operating reliability and service life time. The project is aimed at developing a fast-operating, cost-effective, non-destructive AE-based method to assess the condition of reinforced concrete steel armatures, allowing the operator to carry out timely maintenance, which - the faults and defects being detected early - is much simpler and by far less costly. The AE-based method will be employed to monitor the status and development of fissures in concrete; in addition, a spectral analysis method (frequency domain inspection) will be employed to assess the armature steel condition. The results concerning the reinforced concrete structure armature steel corrosion which will be obtained from the AE method application will be compared with those obtained via traditional methods, such as visual inspection, determination of concrete carbonation degree and depth, determination of concrete’s passivating capacity, determination of concrete physical and chemical characteristics strength, water absorption capacity, porosity), concrete electrical conductivity and electric potential distribution between the steel armature and the concrete free surface.
The Study of the Emission of the Low-Frequency Electro-Magnetic Fields Generated by HV Conduction
Eleonora Čermáková - head GA103/03/Z048 2003-2003 all years € 11250
The objective of this study is the the emission of the low-frequency electro-magnetic fields generated by high-voltage lines ...
The employing the acoustic emission to assess the frost resistance of roofing tiles, both concrete and fired
Zdeněk Chobola - head GA103/02/1092 2002-2004 all years € 51750
The objective of the present project consists in employing the acoustic emission (AE) to assess the frost resistance of roofing tiles, both concrete and fired. The main task consists in the design of a screening line, which will, based on the measurement of an AE parameter, reject individual tiles on the basis of presumably low frost resistance and, consequently, short service life. Ensembles of roofing tiles, both concrete and fired, coming from three different producers, will be created. The AE parameters will be measured on different tiles before the cyclic temperature stressing and subsequently, after different degradation stages. "Impact Echo" method will be used, i.e., an AE signal, having been induced by a short-time mechanical impulse applied to the specimen surface, for example, by means of Schmidt impact hammer, will be measured. Thus generated acoustical signal will be reflected by defects presumably present in the bulk to propagate back to a surface mounted pick-up. In this way, defects located beneath the tile surface may be detected and reliable information on cavity, cracks, segregation or other defect location may be obtained. The pick-up output voltage will be analyzed in frequency domain. The spectral response distribution (frequency inspection) will make it possible to assess the condition of the tiles under test. Thus obtained results will be compared with those obtained by standard methods.
Noise Spectroscopy and Diagnostics of the Electro-Insulating Systems
Bohumil Koktavý - head GA102/99/1088 1999-2001 all years € 28313
Ttis project solve the problems of the noise spectroscopy and diagnostics of the electroinsulating materials and systems ...
Noise and galvanomagnetic spectroscopy of single crystalline materials of type II-VI
Pavel Schauer - head GA102/99/0953 1999-2001 all years € 39531
The project is aimed at growth and characterization of CdZnTe single crystals. CdZnTe single crystals will be prepared under variously defined conditions of growth. The stoichiometry of crystals will be changed by annealing experiments. The project is based on the idea to combine a technological research of a workplace dealing with II-VI single crystalline materials, specifically CdZnTe, with the research of a diagnosis oriented laboratory. The material characterization will concentrate on determination of the substance and structure of states in the energy gap, in order to define the change of electric properties of the material, which is very important from the point of view of practical applications in various optoelectronic devices. Noise diagnostic method will serve as a basic tool. Illuminated material noise spectra make an important source of information on the energy states, which give rise to the noise and deteriorate the material characteristics. Among other basic experimental methods to be used there are measurements of the temperature and field dependence of galvanomagnetic properties (conductivity, Hall effect). One of the most important benefits consists in that the technology oriented workplace will include the results of the diagnostics into the material preparation technology immediately.
Fractal Geometry in Transport Processes
Tomáš Ficker - head GA103/96/1637 1997-1999
The microdischarge transport represents the transfer of electrical charges realised by a series of discrete pulse discharges initiated in microscopic air gaps that appear with real interfaces metal-insulator or metal-dielectric. The research project continues the study of statistical features of the microdischarge transport and seeks for a quite new application of fractal geometry to the transport topology.
Acoustic Emission in Civil Engineering
Zdeněk Weber - head GA103/93/2201 1993-1995