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The subject of the research is study of an elastic-plastic behavior of the materials, S355N steel and Domex700MC steel, which are used in welded construction parts of car bodies, the Domex700MC steel is used with the intention of decreasing the weight of the parts. The solved problem is to determine the local static parameters of the steels without the possibility to use the standard mechanical testing. In order to assess the strength decrease, the critical area was experimentally simulated. The main aim of the paper is to ascertain strength differences in the heat affected areas originating as a result of welding. As the main tool for the assessment of the elastic-plastic response, the methodology based on an instrumented penetration test with the use of a cylindrical indenter was chosen. For validation of the used method, the standard tensile test was performed. The aim of the work is to state optimal methods for determining of yield strength and to find a changes tendency in these areas. The comparison these steels revealed different changes due to welding process. The substantial decrease of the yield strength of Domex700MC was observed on contrary to stable, or partially increased, yield strength of the S355N steel. Structural analyses revealed a different material response of the evaluated steels, according to a different hardness in the heat affected zone.

Keywords: mechanical properties, indentation method, microstructures, hardness, tensile test

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