Applied Mechanics and Materials Vol. 772

Abstract: This paper presents a study of 3D surface texture measurements and analysis of several surface texture parameters. A stylus measuring instrument was used to measure 3D surface topographies. In experimental part of this study, two coated gas turbine blades used in aerospace industry were chosen to examine surface of the coatings in nano-scale. Surface texture parameters of Ti-Al coating and Ti-Al-N coating were measured and compared to each other. The aim of the research is to analyze the surface of these coatings in an areal (3D) manner. The results indicate slight differences between these two surface textures despite the fact that both are Titanium-based coatings, and the surface of base material for both samples was prepared in the same way before deposition. Further study with repeated measurements of surface texture for deposed coatings has to be made after erosion tests.

Abstract: This paper is focused on flow simulation in the sub channel of fuel rod assembly using code ANSYS Fluent 14, which is commercial computational fluid dynamics (CFD) code. Computational simulations are reported on convective heat transfer to carbon dioxide at a pressure of 7.59MPa. Pressure which is used in this simulation are just above the thermodynamic critical pressure value of CO₂. These have been carried out using a variable property, elliptic computational formulation incorporating low Reynolds number turbulence models of k–ε. Firstly, the simulations were compared with the effect of increasing heat flux on heat transfer coefficient. It has been found that the effect of buoyancy on turbulence production and heat transfer in fluids at supercritical pressure can be very significant even under conditions of relatively low buoyancy parameter based on bulk properties. It is clear that new heat transfer correlations are needed to account for such effects on heat transfer to supercritical pressure fluids as they come to be used more and more in new energy systems applications such as, advanced water-cooled nuclear reactors, high pressure water oxidation plant for waste processing.

Abstract: The paper deals with some selected methods for essential reliability measures estimation. Results for polymer composites are presented. The polymer composites were placed in various climatic environments and stressed with thermal and humidity load. These climate simulated accelerated influence of operational environment which the composites percept in service operation. After these stresses mechanical strength tests were performed. Outcomes of these mechanical tests were used for reliability characteristic estimations. For assessment of reliability measures several statistical tests were used. In this paper we present fundamental reliability measures of composites which were obtained during environment accelerated tests as basic research results.

Abstract: In this paper, a solution for the automatic control of a chemical exchange process carbon dioxide (CO₂) – carbamate for the ¹³C isotope enrichment, is presented. The main original achievement from the paper is the inclusion of the previously mentioned non-linear technological process in a control structure. The design of the automatic control structure of the ¹³C isotope concentration is based on the Internal Model Control (IMC) strategy. The implementation details of all the elements from the structure of the proposed control system, in MATLAB/SIMULINK, are presented. Also, some relevant simulations of the automatic control structure are presented.

Abstract: This paper presents a solution for modeling a chemical exchange process carbon dioxide (CO₂) – carbamate for the ¹³C isotope enrichment. A big difficulty in the process modeling procedure is the fact that it is a non-linear one. In order to solve this problem, an original modeling solution that permits the process simulation for the entire domain of the values of the input signal is used. The process modeling is made in order to include it in an automatic control structure of the ¹³C isotope concentration. Some relevant simulations of the open loop process are presented, both in the case when the disturbances do not occur and the case when they occur in the system.

Abstract: This paper presents experimental analysis of the phenomenon of friction that occurs between two surfaces, one of polyethylene and other ceramics. Alumina ceramic is being recognized like a good biomaterial for its high strength and toughness. This ceramic, is used to manufacture the femoral head for arthroplasty of the hip joint in association with an ultra-high-molecular-weight polyethylene (uhmwpe) socket. Wear-resistant properties of uhmwpe were screened on two principally wear devices: first made by polyethylene – alumina-magnesia ceramic and the second by polyethylene – alumina-magnesia ceramic covered with polyvinyl alcohol (pva) layer. Sterile physiological saline is chosen as the lubricant fluid media. After hydration the pva layer provide lubricant properties. Depending on the lubricant medium, the friction coefficient (cof) of polyethylene and alumina-magnesia ceramic-pva counterfaces was about 0.38 (24 times low that polyethylene and alumina-magnesia ceramic counterfaces). Polyethylene friction coefficient in contact with alumina-magnesia ceramic was more susceptible in saline solution in which was about 0.46 compared with 0.016 on alumina-magnesia ceramic-pva. On the other hand, fluid environment shows a strong effect on polyethylene wear in contact with ceramic surfaces, increasing friction coefficient by ceramic hydration. The wear particles obtained in dried conditions are aglomerated and well individualized compared with lubricated conditions which are poorly individualized and with fine structure.

Abstract: The aim of present paper is to realize the FEM simulation of laminated lightweight material processed through single point incremental forming. Thus a laminated material, aluminum - polypropylene - aluminum (Al-PP-Al), as sheet 1.2 mm thickness was used. For these material the hardening curve was determinate. These values were used to describe elastic-plastic behavior of the material during single point incremental forming process simulation. Single point incremental forming process simulation aimed to assess the distribution of values and maximum and minimum strains, the material thickness of the specimen and the technological force for the two strategies for obtaining the truncated cone shaped pieces: circular and spiral.

Abstract: The knowledge of the mechanical properties of the material used is a necessary prerequisite for the quality design of any structural unit. It applies to components manufactured using Rapid Prototyping technology (hereinafter only RP) multiple times, because it is not enough to only know the mechanical properties of a material from which the components are printed. Other factors affect the component printing, such as the orientation of the printed component, the selection of the component's internal structure, possibility of connection with other materials, etc. The article follows from the previous research of the experimental determination of the bend strength of parts printed by RP technology from polycarbonate, which focuses on bend-testing of samples printed with various internal structures. This article expands on the original research by experimental determination of the bend strength of printed components, which form a unit with another material. The obtained information can be utilised in the design of components manufactured with RP technology using professional printers.

Abstract: In the present research, zinc oxide (ZnO) films have been prepared by simple solution method and spray pyrolysis on different substrates (glass and sapphire) for different molar concentrations (0.2M & 0.25M). The films were subjected to different substrate temperatures (400 °C and 450 °C respectively. These were characterized for SEM and XRD and the average size of the crystallites were in range of 300 and 200nm for the films on Saphire and glass at higher substrate temperature. FTIR analysis has been carried out and optimization conditions were used in order to confirm the significant peaks and phase transformation. The films were subjected to ethanol gas for these substrates and corresponding electrical properties were carried out by two probe method and was found that the films for sapphire substrate prepared by spray pyrolysis method showed more conductance at higher temperatures than glass. Optical properties were also studied for these films and was found that films prepared by spray on sapphire shows less transmittance at higher substrate temperatures in comparison to the films on glass.