Papers by Keyword: Micro-Hardness

Abstract: Commercial applications for Ti 6Al 4V, an alloy composed of titanium, aluminium, and vanadium, are possible. The features of titanium alloy include: Lightweight, non-magnetic, high melting point, outstanding fatigue strength, superior specific strength, great corrosion resistance, and biocompatibility. Reviewing the electro-discharge machining of titanium alloy (Ti 6Al 4V) as a workpiece, silicon carbide particle combined with EDM oil, and coated tungsten carbide electrode, this research examines this process. Dielectric fluid's impact on microhardness, surface finishing, TWR, and MRR. MRR is raised by silicon particles and coated tungsten carbide electrodes with EDM fluid. According to the study, the most important input parameters for determining TWR, MRR, surface finishing, and micro-hardness are voltage, current, pulse on time (Tonne), and pulse off time (Toff).

Abstract: Friction stir welding (FSW) is a solid–state joining process that is increasingly being used in various industrial applications due to its numerous advantages over conventional welding techniques. FSW uses a non-consumable rotating tool to generate frictional heat and plasticize the material in the joint, resulting in a defect-free, high-quality bond between two pieces of metal without the need for any filler material or shielding gas. The process is particularly well-suited for welding lightweight and high-strength materials, such as aluminium, magnesium and titanium and is known for its ability to produce joints with superior mechanical properties, including high fatigue strength and improved corrosion resistance. This paper addresses the need for future development in Friction Stir Welding.

Abstract: Bobbin friction stir welding (BT-FSW) is a variant of the conventional friction stir welding (C-FSW). This method has been applied of welding high density polyethylene (HDPE) plates; where a rotating symmetrical tool causes a fully penetrated bond, it can weld the upper and lower surface of the work-piece in the same pass. BT-FSW process involves complex heat generation and HDPE flow, which directly affects on the weld area and on mechanical properties of welded joint. Heat generation and material flow during BT-FSW are significantly affected by the tool design features, process parameters and mechanical behavior of work piece materials. Studying the temperature of polyethylene sheets welded by BT-FSW can help in analyzing the mechanism of weld formation and also can provide theoretical guidance for the tool design, process parameter selection and even new process development. In the unique work described in this paper, the 11.4 mm-thick HDPE plates were welded successfully by bobbin-tool friction stir welding. Measurements of the material temperatures were performed by thermocouples which are placed near and at the weld seam. The weld quality was determined in terms of no defects in the stir zone and the tensile strength of the joint. It was found that considerable melting occurred between the rotating shoulders and on the trailing side of the rotating pin. Movement of the molten material by the rotating tool created a very black band in the stir zone. Thermocouples measurements indicated that the temperatures were higher on the advancing side (AS) compared to those on the retreating side (RS). Tensile tests and hardness measurements were performed on welded and seamless sheet samples. The results were analyzed to compare the mechanical properties. To demonstrate the variation in micromechanical properties between welded and seamless sheet samples, micro hardness (HV) testing was used to explain the difference. The HV of the HDPE plates weld by BT-FSW, were relatively symmetrical with respect to the parting line. The maximum hardness levels were reached in the weld bead at around 66 HV in the welded nugget; there was a rise in the level of hardness, in particular at retreating side (RS) and at advancing side (AS) where the value reached 68.60 HV.

Abstract: The paper deals with complex material analysis of a shaft after failure. The shaft was operated as part of an "Abradable rig" device used to test the resistance of coatings at high speeds, which simulates a turboprop engine's operating conditions. The shaft is made of 16MnCr5 material with subsequent cementation. The subject of interest is a complex material analysis (i.e. control of the chemical composition of the material and complete fractographic and metallographic analysis) and verification of the shaft design. The aim of the study is a precise determination of the specific cause of component failure.

Abstract: Two sets of cylinder specimens with a height to diameter ratio of 1.5 made of annealed technical copper and AK12pch silumin were tested for uniaxial compression to different degrees of plastic deformation. At the first stage of the experiments, the ends of the specimen were ground on skins of different grain sizes and polished. Then the micro-hardness of the ends of each sample was measured. Micro-hardness measurements were carried out by the Vickers method at three loads on the indenter: 0.196, 0.490, and 0.980 N. At the second stage, the samples were cut along the meridional section, each sample was poured with a compound based on epoxy resin into an individual mold so that the meridional section of the cut sample came out onto the surface of the mold. After the process of grinding and polishing the meridional section, the micro-hardness of the center of the section was measured under the same loads that were used for measurements at the ends. At the third stage, the dependences of the micro-hardness on the intensity of plastic deformation were made. A comparative analysis of the indicated dependences, made from the results of measurements at the ends of the specimen and the surface of their meridional sections, showed that friction at the ends of the specimen during compression has a significant effect on the position of the dependence “micro-hardness - plastic deformation”. The evaluation of hardening based on the micro-hardness of the ends leads to significant errors.

Abstract: The process of fabricating reliable materials according to efficient usage has become one of the most vital concerns. In this paper, the fabrication of functionally graded materials (FGMs) is the target using a specified application of an internal combustion engine piston model to achieve such a gradient. With a convenient rotational speed under the concept of centrifugal casting technique, the required gradient piston was successfully produced from two pure aluminum alloys A336 and A242 by such a new mechanical technique for having the required gradient. The percentages of internal ingredients, mainly, silicon were controlled axially through the piston. Chemical composition analysis, micro-hardness and wear resistance tests were performed to check the gradient and to know the difference between mechanical properties for each piston portion from its top combustion chamber to its skirt, achieving compatible results through performed tests. Obvious opposite direction gradient of silicon content to copper content appeared. Micro-hardness, wear resistance and coefficient of friction values showed a successfully gradient in the axial direction of the piston model.

Abstract: In this paper the methods of mechanical testing of metal and the possibility of their implementation, using mathematical modeling by the finite element method in Deform software package, are considered. As the studied parameters, both the strength indicators (yield strength, tensile strength, Brinel micro-hardness), and the plasticity indicator (the number of kinks before the crack is formed), were studied. The values obtained in the simulation have a very high convergence with the real data.

Abstract: One of ways to increase the strength of a structural material is to grind its microstructure to an ultra-fine-grained state. But with the simultaneous increase in strength properties in ultrafine materials, there is an inevitable decrease in its plastic properties. The use of metal materials with a gradient structure is an effective way to solve the problem of increasing the plasticity of metal products in general. This work is devoted to the study of the possibility of a gradient structure forming in austenitic stainless steel AISI-321 using radial-shear rolling. The results of the studies showed that the UFG-structure extends in the bar from its surface to a depth of at least a quarter of the radius of the bar. The transition zone is in the region between 0.5 R and 0.25 R of the bar section. Anything deeper is rolling texture. Due to the structural heterogeneity of the cross-section of the bar, there is a smooth drop in the micro-hardness of the central zone of the bar by 10.2 %. All this testifies to the gradient character of the structure formed in bars of AISI-321 steel deformed on the radial-shear rolling mill.

Abstract: Introduction: The purpose of this study was to evaluate the relationship of modulus of elasticity and micro-hardness of denture bases to pressure transmission under the thermoplastic nylon denture base.Material and Methods: Mandibular first molar acrylic denture teeth (Bioeco) embedded on 15x15x3 mm³ thermoplastic nylon (TCS and BioTone) and poly methyl methacrylate denture bases were evaluated (n=9). A 100N force applied on the specimen using universal testing machine and the pressure transmitted under the specimen observed using pressure transducer. The modulus of the elasticity (n=16) measured on 64x10x3,3 mm³ specimens and micro-hardness (n=16) measured on 10x10x3 mm³ specimens. Data were statistically analyzed using One-way Anova followed by Tukey HSD post hoc test. Pearson correlation test used to evaluate the relationship of modulus of elasticity and micro-hardness on denture bases to pressure transmission (α ≥ 0,05).Results: The results showed that poly methyl methacrylate has the highest pressure transmission compared to others. There was a significant relationship between modulus of elasticity and micro-hardness to pressure transmission under the denture base.Discussion: This study can help dentists to determine the design of dentures, especially in the selection of denture base materials.

Abstract: Additive Friction Stir (AFS) has the potential for extensive future application in metal based additive manufacturing. Powder based AFS is specifically useful for fabricating functionally graded structures. But, the consolidation of powder inside the hollow tool used in this operation hinders the powder based AFS process. This problem could be resolved by Additive Friction Stir Processing (AFSP) while maintaining the key advantages of AFS. A 3D deposit structure of height 5 mm and width 64 mm was made from Al6061 alloy powder by AFSP. Mechanical properties like ultimate tensile strength, yield strength and micro-hardness of the deposit were evaluated in both longitudinal and transverse directions. The ultimate tensile strength and micro-hardness of the deposit were comparable to Al6061-O and there was a significant increment in tensile yield strength. Also, the isotropic nature of the deposit could be inferred from similar mechanical properties in the longitudinal and transverse direction. Dimple ruptures seen in fractographic analysis gave evidence to the ductile nature of the deposit.