Papers by Keyword: Roughness

Abstract: In this work we accomplished a study concerning the surface state of acrylic prosthetic biomaterials both optimized and non-optimized and we studied their compatibility on test animals. Various methods are seeking to improve the quality of implants and minimally invasive devices for body analysis, the increase of biocompatibility and resistance to corrosion of materials intended to come into contact with biological tissues. Poly (methyl methacrylate) is used in a wide range of applications and offers increased resistance and color stability over time and it can be relatively easy to smooth and polish. The morphology and roughness of the surfaces in case of acrylic prosthetic biomaterials were analyzed by atomic force microscopy that provides qualitative information regarding the chemical uniformity from phase.

Abstract: A finite-temperature analysis of a multiscale model, which couples finite element and molecular dynamics, is presented in this paper. The model is evaluated by the patch test and demonstrates its capacity. Then, the multiscale scheme is used to study 3D nanoscale contacts. The linear relationship between the contact area ratio and load is observed at small loads, but the temperature effect is small. However, the change in the root mean square (RMS) of heights depends on the temperature at high loads.

Abstract: The use of laser systems in the industrial manufacture of complex geometry details is growing. This phenomenon takes place thanks to laser technologies, such as selective laser sintering (SLS), direct laser metal sintering (DLMS) and selective laser melting (SLM) that make possible, in addition to production of details with complex geometric shapes, also the fast, cheap and effective restoration of damaged elements of the details. However, despite the abundant advantages of the above-mentioned technologies, the details produced on the basis of these innovative methods have typical problems (large value of surface roughness, low wear resistance). In the paper, the influence of changes of the principal technological parameters of the laser polishing on the technological characteristics of the external surface of details built by SLS was studied. Changes of the laser’s technological parameters impact the amount of energy supplied onto the area under processing. Thus, the correct selection of the technological parameters of the laser beam positively affect the microstructure and topography of the top surface layer of the manufactured details, its chemical composition and physical properties as well as diffusive processes in the laser beam impact area.

Abstract: Mechanical characterization of individual microstructural phases of hardly deformable magnesium alloys is of crucial importance for the development of multi-scale material models. The magnesium alloys are used for preparation of fine tubes with diameter of a few millimeters and tens of millimeters wall thickness. It is hard to control an ordinary drawing process for the preparation of such tubes. However, the tubes can be prepared with a laser dieless drawing process that is, in contrary to conventional drawing, able to draw low formability materials and it is able to produce variable cross-sections of the tube or a wire with high precision. The magnesium alloy tubes are used in various fields as micro-electro-mechanical systems, medicine, electrical, biological and chemical fields. In this paper, preliminary microstructural studies and local mechanical characterization of pure Mg, MgCa0.8 and AZ31 magnesium alloys used for tube extrusion, is provided. The material microstructure is studied by means of scanning electron, atomic force microscopes and nanoindentation. Elastic properties and volume fractions of mechanically distinct phases that are not accessible by standard testing methods are provided in the paper.

Abstract: A series of titanium carbonitride (TiCN) films with differing C content were deposited by cathodic arc evaporation of pure Ti in a gas composite environment of N₂ and C₂H₂. The increase of the C₂H₂ fraction in the gas environment leads to a continuous increase in the deposition rate of the TiCN thin films, as well as an increase in the adhesion of the films to the substrate. To evaluate the interaction of the material with the bacteria Escherichia coli CCM 3954 a method was used based on the ČSN EN ISO 56 0100 standard. The bacteria were inoculated in a liquid culture medium. It was observed that the monitored surfaces support the development of bacterial populations of E. coli depending on the type of TiCN thin films.

Abstract: Due to the global warming and diminishing petroleum oil reserves the conversion of biomass in useful biodegradable materials represent a tremendous need in terms of economic and environmental problem. During the last years, enormous effort have been sustained by the researchers who tried to develop and improve green (recyclable, biocompatible, and biodegradable) materials from renewable resources strengthening this way the global sustainability. Following this need a new material Arboform – „liquid wood“, that meets all the above conditions was developed by a team of german researchers appearing shortly on the market. This material can be processed like any other plastic material, so no need changing in terms of technological equipment. Since the injection molding is the most widely used process in manufacturing polymer products, unavoidable surface quality problems appear. In order to obtain a clear image of surface sample are analyzed the inherent properties of the used material, injection parameters and conditions using a Talysurf CLI 2000 profilometer. The equipment is able to perform high-accuracy measurements of the surface topography for Arboform L, V3 Nature (A-LW) and Arboform L, V3 Nature Reinforced with Aramid Fibers (A-LWAF) samples. The experimental research was achieved by means of the Taguchi experiment plan, with 6 input parameters (injection pressure, melt temperature, cooling time, screw displacement injection time and injection angle) each of them having two levels of variation. In case of 90 degrees angle injection (samples from 1 and 2 experiments) the dispersion roughness (Ra) measured on east-west direction is lower (26.6% for A-LW and 23.7% respectively for A-LWAF) compared with the roughness measurement on north-south direction. At 0 degrees angle injection the dispersion had the same trend (lower for east-west direction) of the A-LWAF 4 and 6 samples and higher in the east-west direction for 3 and 5 samples of A-LW material studied.

Abstract: Compared to conventional metallic materials, biodegradable material magnesium and calcium (Mg-Ca) alloys are attractive to be new participants as implants. It can avoid stress shielding and provide sufficient mechanical strength as the similar mechanical properties to human bone. In this study, Mg-0.8wt%Ca and Mg-1.6wt%Ca are prepared and Mg-0.8wt%Ca is dry milled. Overall carbide tool is used in the process and the roughness generated by different combination of cutting parameters, i.e. cutting speed, feed, and depth of cut are studied.

Abstract: In electrical discharge machining (EDM) process, electrode polarity plays an important role during machining operation. This paper addresses the issues of EDM utilizing the positive and negative tool-electrode polarity to explore the effects on the performance criteria such as material removal rate (MRR), tool wear rate (TWR), surface roughness (SR) and micro-hardness during machining of Ti–5Al-2.5Sn (GradeVI) Ti alloy. The Ti-5Al-2.5Sn alloy was machined using copper-chromium electrode with positive and negative polarity by varying the peak current and pulse-on-time, while the pulse-off-time was kept constant. The result of study suggests that reverse polarity improves the MRR, TWR, SR while normal polarity improves the surface micro-hardness. The peak current has the maximum affect on machining performance for both types of polarities. Further the migration of different elements and formation of compounds on the machined surface was investigated using EDX and XRD analysis.

Abstract: Computer Numerical Control (CNC) vertical milling is a cutting tool of a work piece by giving CNC G-code program to the milling machine to give the chisel end mill perpendicular to the surface of the work piece. The distance between overhang tool and holder is usually not standard causing the end mill chisel experience minimum and maximum deflection during the cutting process. This research observed the cutting and measuring the surface roughness of the specimen made of BJ37 mild steel. It is of a square shape with a rectangular cross-section cutting parameters of overhang groove, vibration and feeding from the left, the middle, and the right surface. Measurement was done by testing the surface roughness under the conditions of changing the overhang groove, vibration, and small feeding. The observations result in smaller deflection and angle to obtain Ra = 1.64 μm average minimum level of roughness using 25mm overhang with the same feeding of 0.18mm/rev. Ra = 1.64 μm is classified into Group N7 smooth, compared to the use standard 35mm overhang which obtains Ra = 1.88 μm, Group N7 normal. The minimum level of roughness can be obtained due to the smaller feeding.

Abstract: Tempering is a heating treatment process to improve the elasticity with a little hardness. It is reheating the steel that has been hardened under the critical temperature of 723 ^oC and applying a holding time at that temperature, then cooling the steel in the air outside. The hardening was followed by gradual tempering process at different temperatures of 650°C, 550 ^oC and 450°C at 60, 120, and 180-minute holding times. The tempering process resulted in hard and tough not easily broken or worn tool steel. Besides, it improves the tensile strength and increases the durability of tool against collision. Tukey, Fisher Pairwise Comparison and Dunnet Method were applied to obtain Grouping Information data of 93%. Observations on eight tempering treatment processes show not only treatments 4, 5 and 6 (tempering with time delay) but also gradual tempering (in which the process was done some times by gradually dropping the temperature) resulted in better performance. Further observation was conducted in terms of the variation of dropping temperature and the most optimum holding time of the tempering process. Processes 7 and 8 (tempering without time delay) are not recommended, as the hardness value drops sharply, high vibration occurs when machining, and the cutting results in high roughness value.