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Projects / Programmes source: ARIS

The influence of the mesoscopic inhomogenities in materials on the life-time of safety significant components of nuclear power plants

Research activity

Code Science Field Subfield
2.03.04  Engineering sciences and technologies  Energy engineering  Energy systems 

Code Science Field
T000  Technological sciences   
T160  Technological sciences  Nuclear engineering and technology 
Keywords
life-time, safety, reology, material properties, stochastic fields, crack initialization, ultimate strength
Evaluation (rules)
source: COBISS
Researchers (4)
no. Code Name and surname Research area Role Period No. of publicationsNo. of publications
1.  07025  PhD Leon Cizelj  Energy engineering  Researcher  2003 - 2005  963 
2.  18292  PhD Marko Kovač  Materials science and technology  Researcher  2003 - 2004  176 
3.  21181  Zoran Petrič  Energy engineering  Researcher  2005  15 
4.  19910  PhD Igor Simonovski  Mechanical design  Head  2003 - 2005  149 
Organisations (1)
no. Code Research organisation City Registration number No. of publicationsNo. of publications
1.  0106  Jožef Stefan Institute  Ljubljana  5051606000  90,987 
Abstract
As a rule the continuum mechanics assumes homogenity and isotropicity of the involved material. These assumptions are satisfactory for engineering load capability analysis and the engineering life-time analysis of the parts that are significantly larger than the order of the material inhomogenities and are only moderately deformed. However, the inhomogenity of the material becomes more and more important when analyzing the initiation and propagation of cracks or load capability of the material in the vicinity of the limit strenght (e.g. large deformations, development of the macroscopic cracks). The structure of most of the metal materials (in the nuclear power plants e.g. steels and Ni alloys) is nonhomogenous mainly due to the random orientation of the anisotropic crystal grains. The random errors in the structure (e.g. inclusions, voids, large systems of dislocations, etc.) also increase the nonhomogenity of the material as a whole. The nonhomogenities are initiation sites for the microscopic damage that can develop into the macroscopic cracks and consequently cause the failure of the material. The research group is developing the methods and tools for direct simulation of the aggregates of randomly oriented and shaped crystal grains. The development of the methods and tools for the simulation of the crack initiation and propagation along the crystal boundaries and between the randomly placed inclusions is under way. The preliminary results are encouraging. Unfortunately the procedure is numerically quite demanding, restricting the analyses to the parts of about 1 mm3 in size and limiting the wider use of the procedure. The solution to this problem is envisioned by the development of the methods that transfer the significant data on the nonhomogenity into the classical macroscopic models. The interesting metod is the usage of the correlation length. The correlation length can be used to estimate the domain of influence of the individual nonhomogenities in the simulated aggregate of randomly oriented and shaped crystal grains. This information may be transferred to the macroscopic model as an additional material parameter. The main objectives of the proposed research are: -the development of the optimal method for the transmission of the nonhomogenity information to the macro level -the implementation of the optimal method on the selected commercially available computer program for the stress analysis, based on the finite element method -enable the application of the material models with the nonhomogenity informations for the estimation of the life-time of safety important components of the nuclear power plants The research group bilateraly cooperates with the Forschungszentrum Karlsruhe, Germany and Aristotel University in Thessaloniki, Greece. The research group is also a partner in the european project LISSAC (Limit Strains for Severe Accident Conditions), contract no. FIKS-CT1999-00012, 5th Euratom Framework programme 1998-2002, key action: nuclear fission.
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