The primary target of this project consists of combining the technique of rapid prototyping and casting to produce aluminum parts in a sand mold being made the corresponding models and core boxes by means of the technology of rapid tooling, FDM (fused deposition modeling) of ABS. The followed process to obtain the pieces is casting, that consists of the fused metal spill in a mold pattern previously conformed, followed of a cooling and later rinding of the solidified piece. The models and core box, generally, is made in wood or plaster, but in this case they were made by means of a Rapid prototyping machine of the company 3Ddimension. The phase of design and manufacture of the model and the mold are most expensive and critical of the process. In this work it is tried to study the valuation of the time of manufacture of the models, core box and molds. The application Catia V5 R17 has been used for the geometric definition of the model and care box. This model is exported in stereolithography format (stl) and after this, the file was sent to the printer Dimension BST 768 and begin the construction of the models. The proposal methodology using rapid prototyping to generate the models is a clean and fast solution, and in addition it allows to obtain geometries that are nonviable by another procedure. The surface finish quality of the model is appropriate for the casting process , and reproduces with a high reliability the model CAD.
Purpose: Recently, Polyamide 66 and Teflon as plastic materials have been widely used at the manufacturing of gear mechanism. The purpose of the paper is to examinee the load capacity of PC/ABS spur gears and investigation of gear damage. Design/methodology/approach: In this study, usability of PC/ABS composite plastic materials as spur gear was investigated. PC/ABS gears were tested by applying three different loading at two different numbers of revolutions on the FZG experiment set. Findings: As a result of the experiments, load capability of PC/ABS materials was seen rather high, if one of the spur gear pair was steel (AISI 8620). Practical implications: In fact that, PC/ABS materials are durable against flame, air, ultraviolet lights and holding lower moisture than PA66 GFR 30 materials, the usage of them brings an advantage in many industrial areas. Originality/value: Using PC/ ABC materials provides many advantages due to fire, air and ultraviolet light durability and low moisture holding properties.
Dense (>95% of theoretical density) TiAl and Ti3Al based composites reinforced with 10-50 vol. % of B4C, TiC or TiB2 particles were successfully prepared by pressureless reaction sintering of reaction mixtures consisting of commercial titanium aluminide powders (TiAl and Ti3Al) blended with the appropriate amount of ceramic reinforcement. The green compacts made from the blended powder mixture were reaction sintered at 1300 °C for 2 h in an Ar+4 vol. % H2-rich environment using a vacuum furnace. The morphology of the commercial powders and the microstructure of the as-sintered composites were studied by SEM-EDS and X-ray diffraction analysis. The mechanical properties were measured by tensile tests performed at room temperature. In the case of reactive systems (TiAl-B4C, TiAl-TiC and Ti3Al-B4C, Ti3AlTiC), densification proceeds via formation of various secondary bonding phases, whilst in non-reactive system (TiAl-TiB2 and Ti3Al-TiB2) the process seems to proceed by diffusion in liquid state. Regarding the room temperature tensile properties of the composites, superior improvement was observed in TiAl-B4C, TiAl-TiC and Ti3Al-B4C, Ti3Al-TiC samples with 50 vol. % of ceramic particles. However, in TiAl-TiB2 and Ti3Al-TiB2 samples the improvement was significantly lower, most probably due to the lack of chemical affinity between ceramic reinforcement and TiAl3 matrix.
The effect of different polymer binders and effect of binder percentage on morphology and hardness of synthesized Nd-Fe-B bonded composites is studied and presented. The ratio of epoxy binder content regarding to the Nd-Fe-B powder is varied as follows 22: 78; 50:50; 75:25; 10:90,; for two different combinations of polymer binder. The goal of this preliminary investigation was to obtain good morphology characteristics and satisfactory hardness values.
For the purpose of better understanding of the effect of different Nd content on the magnetic properties of three types of commercial Nd-Fe-B alloys with 10-12 wt% Nd (Nd-low), 21-25 wt% (Nd-stoich.), and 26-29 wt% Nd (Nd-rich) were simultaneously analyzed using X-Ray and Fe-57 Mossbauer spectroscopy analysis. The observation was based on correlation of starting chemical composition with phase composition and magnetic properties of the alloys in optimized magnetic state.
The Co-Ni-Mo alloy powders were electrochemically deposited from alkaline ammonical electrolyte containing two or three different elements, Co, Ni and/or Mo at a constant current density. The obtained Co-Ni-M powders were studied using EDS, X-Ray and SEM analysis. Based on the obtained experimental results it can be concluded that by appropriate selection of chemical composition of the electrolyte for deposition, varying of Co, Ni and Mo ions ratios and current density it can be influenced on the particle sizes of deposited powders. X-ray results suggest that the obtained powders have amorphous structure.
Purpose: The purpose of paper is to analyse Spray drying as a method of producing silk sericin powders. Design/methodology/approach: Aqueous sericin solutions were used as raw material for the production of dry powders using a lab-scale spray dryer. A linear regression analysis of agglomeration was employed, in addition to experimental designs at two levels with three factors for the analysis of three responses: moisture content, particle type and agglomeration degree. The process factors were the drying air temperature (120oC and 160oC), the feed rate (1.25 × 10-7 and 2.5 × 10-7 m³/s), and the concentration of sericin solutions of 10% and 30% (w/w) fed to the spray dryer. Findings: The three responses were analyzed statistically to determine the effective parameters and it was concluded that moisture content depended on three factors--drying air temperature being the dominant parameter. Particle size and shape depended mainly on feed rate and agglomeration depended on the moisture content of the product. Practical implications: As a result of the growing interest in drug delivery through a pulmonary route for local and systemic effects, the crucial physical characteristics of the spray-dried sericin influencing the dispersion and deposition behaviour including particle size, morphology, moisture content and agglomeration degree were examined for formulation and spray drying variables. Originality/value: The most effective parameters on particle size and morphology were found to be the feed solution concentration and feed rate, while the temperature was an insignificant variable.
Purpose: The goal of the paper is to evaluate the effect of the microstructure of EB-PVD thermal barrier coatings on the thermal conductivity and the methods to reduce the thermal conductivity. Design/methodology/approach: In this study, the effect of microstructure of the coating to the thermal conductivity of EB-PVD TBCs and the methods to reduce the thermal conductivity of these coatings have been investigated. Findings: Microstructure of the EB-PVD coating - it is found that they are formed in two different structure and microstructural characteristics and they are different from each other. Practical implications: Nowadays, selection of materials for usage purpose is getting important because of new high technologic developments. Especially for the parts operating at high temperatures, materials which have low thermal conductivity and high mechanical resistance are preferred. Thermal Barrier Coatings (TBCs) are used in aerospace, diesel engine and power plant technologies due to porous structures and low thermal conductivity. Generally these coatings are applied by two methods, Electron Beam-Plasma Vapour Deposition (EB-PVD) and Atmospheric Plasma Spray (APS). Originality/value: This paper reviews the current status of EB-PVD thermal barrier coatings technology and investigation to reduce the thermal conductivity in future generations of EB-PVD thermal barrier coatings.
AbstrAct Purpose: The goal of this paper is to present the thermal characteristics of magnesium alloy using the novel Universal Metallurgical Simulator and Analyzer Platform. Design/methodology/approach: The objective of this work is determine the liquidus, solidus temperature and beginning nucleation temperature to understanding crystallization of magnesium alloys. Findings: The research show that the thermal analysis carried out on UMSA Technology Platform is an efficient tool for collect and calculate thermal parameters. It was determined that the higher solidification rate decreases the solidus temperature. In addition, it was observed that the beginning of nucleation of α(Mg)-β(Mg-Mg 17 Al 12 ) eutectic temperature constituent increases when the solidification rate increases. Research limitations/implications: This paper presents results for one alloy – MC MgAl6Zn1 only, cooled with three different solidifications rate i.e. 0.6, 1.2 and 2.4oC/s, for assessment for the liquidus, solidus temperatures and describe a beginning of nucleation of α(Mg)-β(Mg-Mg
Purpose: The purpose of paper is to evaluate effects of B4C addition on the microstructural and thermal properties of hot pressed SiC ceramic matrix composites. Design/methodology/approach: The effect of B4C addition on microstructural and thermal properties of the SiC-B4C powder composites were investigated after high energy milling and hot pressing. SiC powders containing 5wt%, 10wt%, 15wt% B4C were mechanically alloyed in a high energy ball mill for 8 h. Findings: Microstructural characterisation investigations (SEM, XRD) were carried out on mechanically alloyed SiC powder composites containing 5 wt %, 10 wt %, 15 wt % B4C powders and on these powder composites sintered in vacuum at 50 MPa at 2100oC. The thermal properties were characterised using DTA, TGA and dilatometer. The results were evaluated. Research limitations/implications: In this study, the effect of B4C addition on microstructural and mechanical properties of the SiC-B4C powder composites was investigated after high energy milling and hot pressing. Originality/value: Ceramic matrix composite (CMC) material systems are stimulating a lot of interest to be used and provide unique properties for aircraft and land-based turbine engines, defence applications, rocket motors, aerospace hot structures and industrial applications. Boron carbide (B4C)-silicon carbide (SiC) ceramic composites are very promising armour materials because they are intrinsically very hard. Advanced SiC-based armour is desired so that the projectile is completely defeated without penetrating the ceramic armour.
The brushes are used for transmission of electric current from or to rotating surfaces depending on the type of electrical machines. Besides the process of current transmission, what is significant for the brushes is the tribological process, which is the subject of the experiment. The brush was exposed to a planned experiment and a regression and correlation analyses of tribological process of brush wearing relative to the time were undertaken. The interdependency has been tested and determined by regression analysis and by correlation analysis, the connection between the length of wearing Y of the examined brush and observing time X, taken in mode of statistics agglomerates. The wearing of brushes in practice varies relative to the time. The variations may result in extreme wearing of brushes, changes in the current transmission arcing of brushes and the like.
The conducting polymers and polymeric composites have attracted considerable attention in recent years because of their potential applications in advanced technologies, for example, in antistatic coatings, electromagnetic shielding. The introduction of electrically conductive fillers such as graphite, carbon black, metal and metal oxide powders into the polymeric matrix is a promising approach to fabricate electrically conductive polymeric materials. The recent advancement of nano-scale compounding technique enables the preparation of highly electrically conductive polymeric nanocomposites with very low loading of conductive fillers. Compared with traditional composites, nanocomposites may offer enhanced physical features such as increased stiffness, strength, barrier properties and heat resistance, without loss of impact strength in a very broad range of common synthetic or natural polymers. In this study the conductive fillers were expanded graphite (EG) and untreated graphite (UG), the base material was ethylene- vinyl acetate copolymer (EVA). Nanocomposites containing up to 30 volume % of filler material were prepared by mixing them in a Brabender Plasticorder. The increase in thermal conductivity was more pronounced for EVA-UG nanocomposites than EVA-EG nanocomposites.
Purpose: This paper discusses improvements associated with the life of cutting tools used to machine M42 tool steel. To achieve this in an efficient way, experiments on a variety of tool coatings are conducted on AISI M42 tool steel (58-63 HRC). Design/methodology/approach: In order to assess the impact of different tool coatings on the machining process, initial experiments simulate existing machining operations; this provides a standard for tool life and surface finish. Findings: The findings in the paper show that TiAlCrYN coated WC-Co cutting tools perform better than uncoated cutting tools. Research limitations/implications: The implications of the paper tend to indicate that machining M42 tool steels without lubricant can be optimized using coated cutting tools. The limitations of the paper include machining at one specific cutting speed and the employment of a short-time tool wear method. Practical implications: The practical implications of the paper show that dry machining of hardened tool steels can be achieved under certain circumstances. Further research is needed to explain how the wear mechanism changes with varying machining conditions. Originality/value: The paper presents original information on the characteristics of dry machining of M42 tool steel under specific machining operations. The paper is of interest to manufacturing engineers and materials scientists.
Post-consumer PET (polyethylene terephthalate) containers in the Republic of Croatia are being baled and delivered to recycling plant, where they go through various phases of cleaning and separation of PET from other materials. Waste from the recycling process consists of different materials – PET, labels and sleeves (poly(vinyl chloride), paper and polystyrene) as well as caps (polypropylene and polyethylene). The intention was to make use of this waste, so mouldings were made by compression moulding and their mechanical properties were tested.
A numerical model was developed in order to predict the surface roughness before machining the part. This model is based on the geometric tool-part intersection and allows defining the surface topography of the part as a function of the feed and of the radii of the tool edges. In this first study the problem of runout, i.e. differences between the radii of the different tool edges, is analyzed. The computational model allows determining the value of the average roughness (Ra) and the maximum roughness height (peak-to-valley) (Rt) along a line, in the direction of the feed, for a family of tools defined by an average radius of the edge and its standard deviation, assuming a normal behaviour. It was observed that the obtained values of average roughness Ra do not follow a normal distribution even though the values of the radii were randomly taken according to a normal law. A graphic was also obtained with the maximum and minimum value of average roughness Ra for each value of feed per tooth and per turn fz.
Changes in the phase composition and crystallite size, as well as changes in the magnetic behavior of overstoichiometric Nd14Fe79B7 alloy (32 mass% Nd), caused by the thermomagnetic measurements (TM), were observed in regard to the optimal magnetic state of this alloy. In the optimized magnetic state, the hard magnetic phase Nd2Fe14B is identified as the primary phase (up to 95 mass %), with a mean crystallite size about 60 nm, as determined by XRD analysis and Transmission electron microscopy (TEM). The derogation of magnetic properties after TM is due to decreased amount of Nd2Fe14B phase, the formation of Nd2O3 and different Fe(O)B phases, as well as an increase in the mean crystallite size (e.g. Nd2Fe14B ≈ 95 nm).
In order to determine the formability of sheets and obtain the optimum process parameters for the processes, various experiments have to be performed. Some of these experiments are Limiting Dome Height (LDH) and Marciniak tests which are traditional biaxial tests and sheet hydroforming tests. For the purpose of determining process limitations and estimation of stamping characteristics in sheet metal forming, the forming limit diagram (FLD) is used. In this study, a test unit has designed for simulating the processes. In this test unit, traditional biaxial tests and hydroforming tests can be conducted. Detailed system shame for the unit is given. The punch has 35 ton punch force, 300 mm punch stroke and 5-250 mm/min punch velocity. The blank holder has 40 ton force. The hydraulic system's properties are; the fluid medium capable to have 10-700 bar, the pressurized fluid has 10 lt/min volume of flow. The electronic system is composed of a computer and an electronic circuit which are used for adjusting the blank holder force, pressure of fluid medium and punch velocity as using convenient hydraulic elements.
