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The correct choice of a material in the process of structural design is the most important task. This study deals with determining and analyzing the mechanical properties of the material, and the material resistance to short-time creep and fatigue. The material under consideration in this investigation is austenitic stainless steel X6CrNiTi18-10. The results presenting ultimate tensile strength and 0.2 offset yield strength at room and elevated temperatures are displayed in the form of engineering stress-strain diagrams. Besides, the creep behavior of the steel is presented in the form of creep curves. The material is consequently considered to be creep resistant at temperatures of 400 °C and 500 °C when subjected to a stress which is less than 0.9 of the yield strength at the mentioned temperatures. Even when the applied stress at a temperature of 600 °C is less than 0.5 of the yield strength, the steel may be considered as resistant to creep. Cyclic tensile fatigue tests were carried out at stress ratio R = 0.25 using a servo-pulser machine and the results were recorded. The analysis shows that the stress level of 434.33 MPa can be adopted as a fatigue limit. The impact energy was also determined and the fracture toughness assessed.

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In this paper a theory of multi-walled carbon nanotubes and a suitable way for modelling them using the finite element method is presented. A brief reference to FE modelling of a singlewalled carbon nanotube (SWNT) is given as an introduction to modelling of multi-walled carbon nanotubes, consisting of several layers of SWNT. Also, a theory of the connection interface between nanotube layers and its influence on the loading is given. A SWNT finite element model is used to model a multi-walled carbon nanotube (MWNT). A brief theory concerning MWNT is given, as well as a theory of modelling a connecting interface between layers, as a result of van der Waals interactions. Different loading conditions are used as examples of multi-walled carbon nanotubes under specific loads. Results are compared with those given by other authors.

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