Papers by Keyword: Microscopic Analysis

Abstract: To meet the demands of higher speeds, higher power density and the ability to adapt to harsh operating environments over a long period of time, structural designers use various materials to fabricate rotor parts for turbine assemblies. This introduces high requirements for stable rotation and rotor life. It is therefore important to analyse and determine the mechanical properties for a turbine rotor taking into account the manufacturing process. This paper focuses on laboratory mechanical testing for determination and analysis of turbine components consisting of a rotor, from 42CrMo4 (DIN EN 10083-3) and a turbine, made from Inconel 713C in laser welded assembly. The tests carried out consists of tensile testing for the turbine – rotor assembly, microhardness measurements, macro and microscopic examinations of the welded joint. The obtained results stand as a validation for the welding process technology used for this type of application ensuring the superior mechanical characteristics required for operation in harsh enviornments.

Abstract: The paper presents the study of morphological characteristics of cement particles and reveals the influence of the structure of the cement grain composition on the physical and mechanical properties of cement. The following portland cements produced by “Hrazdan Cement Corporation” LLC, which have 52,5 MPa and 42,5 MPa compressive strength limit and hydraulic additives up to 20% and over 20% have been used for the experiment: CEM II/ A-P 42,5N, CEM II/ B-P 42,5N, CEM II/A-Q 42,5N, CEM II/B-Q, CEM II/A-L 42,5N, CEM II/B-L 42,5N, CEM II/A-M 42,5N, CEM II/B-M, CEM III/A-S 42,5N and CEM III/B-S 42,5N. Grain distribution in all the samples has been studied using a CILAS laser analyzer. Microscopic analysis of all the fractions has been carried out with the help of James Swift optical microscope. The given grain compositions have undergone chemical analysis in compliance with the requirements of interstate ISO 5382-2019 and ASTM C114-18 standards. Experimental studies and analyses show that the cements with microsilica have the highest value of water-cement ratio-W/C = 0.7, the highest by volume compression are the cements with volcanic slag-4 mm, the beginning of the bonding period is the longest in case of limestone cements - t = 140 minutes, followed by microsilica cements, and in third place there are artificial slag cements, the results of which are as follows: 130; 124 minutes. The summarized data show that microsilica cements have the highest compressive strength limit among the cements having the same percentage of additives-48.87 MPa.

Abstract: The ocean islands are far from inland and the concrete sandstone aggregates are scarce. In this paper, high-performance seawater all-coral concrete was developed by seawater mixing and room temperature maintenance design, and by optimizing the water-to-binder ratio, regulating internal curing, changing auxiliary cementing materials and blending ratio, incorporating expansion agent, adjusting fiber blending, etc. Combined with the consideration of work performance and mechanical properties, the concrete self-shrinkage is adjusted to further optimize the mix design. The mechanical properties of the optimized high-performance seawater all-coral concrete were studied, and the relevant durability tests were carried out according to the natural environment characteristics of the island. This is of great significance to the construction of island projects, repair and construction, and construction of protective projects [1].

Abstract: Nowadays due to the active step of urbanisation and rapid development of industry, the contamination of atmospheric air is one of the key aspects of environmental mechanics. Polluted air deteriorates the appearance of historical buildings and architectural monuments. With the help of modern methods, aimed at preservation of cultural heritage objects, it is possible to evaluate the impact of dusty air on the appearance of historical buildings in order to save them, because it is a demonstration of architectural and design features of various temporary periods.

Abstract: By the method of EVA emulsion coating, cron stalk-magnesium oxychloride cement composites (C-MOC) was modified to study the effect of EVA emulsion content on C-MOC density, the coefficient of thermal conductivity, water resistance and mechanical properties. Furthermore microstructure of C-MOC was analyzed by SEM. The results show that: with the increase of EVA emulsion content, the coefficient of thermal conductivity and softening of C-MOC increase, but water absorption reduces. When the content is 80%, the flexural strength after 28 days could reach 3.65 MPa and the compressive strength is 4.69 MPa, reaching the maximum. At the same time, C-MOC density is 816 kg/m³ and thermal conductivity is 0.111 W/(m·k). Water absorption is 36% and softening coefficient was 0.47. It is believed that EVA emulsion could form a thin film on the outer surface of the corn stalk by microscopic analysis, increasing the roughness of the straw surface and reducing the gap between the stalk. Since the EVA emulsion has good compatibility with the magnesium oxychloride cement, they could constitute a whole jointly with glue liquid, crystal and fiber, playing the role of enhancing the surface. Therefore, water resistance, thermal conductivity and mechanical properties of C-MOC have been improved effectively.

Abstract: The pore structure of concrete is a very important material property influencing the durability of concrete. Concrete pore structure is influenced, among others, by the composition of concrete, water/cement ratio, aeration or cracking [1]. The experiment described in this paper understands concrete cover to be 40 – 60 mm from the surface of the specimen.The paper focuses on the determination of air void content in different concrete mixtures by means of microscopic analysis. Mixtures differ in the amount of cement and plastifying agent added while maintaining the consistency of the fresh concrete. In order to determine the air void characteristics, the experiment used manual and automated microscopic analysis.

Abstract: Microscopic analysis represents a non-invasive method for both intermediate and final control. It can be performed without very expensive and complicated equipment and may be available for all kind of composite material parts meant to be used in various fields, starting with industry and finishing with medicine and sports. Using microscopic analysis allows obtaining information about the structure of the material, aspect of the ruptures after the specimen’s failure, thus being able to decide whether the material is suitable for the intended purpose or some changes in its structure, composition or manufacturing technique is required.

Abstract: The tensile failure of fiber reinforced composite is a progressive damage process. Combined with microscopic analysis measures to study matrix, fiber and interface, the failure mechanism of material would be further researched. Two different types of matrix of GFRP bars were selected in the tensile test. The results of tensile test and SEM observations revealed: the vinyl GFRP bar has better composite material structure and interface than unsaturated polyester, and the progressive damage level of unsaturated polyester bar is higher than vinyl in the same stress state; There are clear links between the tensile strength and meso-structure change with different uniaxial stress; When the load exceeds 80% of the failure load, the meso-structure exhibit obvious split between fiber and matrix, and body damage and stripping between fiber and matrix are correlative.

Abstract: Stainless steel products are used in some building for excellent performance. But actually using in complex environment and influencing by several factors, the products may be eroded. The objective of this study was to account for the cause of the corrosion of the submitted funnel sample. In general, the approach is to formulate and conduct a series of laboratory tests, and interpret the results. Based on the findings, corrosion of the submitted stainless steel funnel could be attributed to three factors, such as material factor, site condition and corrosion.

Abstract: The microscopic analysis of 93W-4.9Ni-2.1Fe (wt. %) tungsten heavy alloy by hot-hydrostatic extrusion with severe plastic deformation strengthening were experimentally investigated mainly by transmission electron microscopy. Due to the profound differences in hardness of the tungsten particles and the NiFeW matrix a special TEM specimen preparation method had to be employed.It was shown that the microstructure of the as-extruded alloy was characterized by elongated tungsten particles with refinement cellular sub-structures consisting of high-density dislocations embedded in a binding Ni-Fe-W matrix phase with fine dynamically re-crystallized grains.