Three-dimensional (3D) printing technologies are the most promising method in the production of functional parts. Although 3D printing technology includes various methods, fused deposition modelling (FDM) is the most widely used one. In FDM, generally polylactic acid (PLA) filaments are used to fabricate 3D geometry by stacking individual layers. In fact, FDM is a complicated process with numerous parameters that affect printing quality. Printing parameters such as printing orientation, layer thickness, printing orientation angle, filling ratio, filament feed rate, etc. have significant impact on the quality and performance of FDM printed parts. Since the mechanical properties are very important for functional parts, the effect of these parameters on the mechanical properties of the PLA specimens has been extensively studied. However, there is no sufficient data in the surface characterization literature of these parameters. In this study, the effect of layer thickness and printing temperature on the surface properties of PLA specimens printed using FDM was investigated.
Machines. Technologies. Materials.
Vol. 12 (2018), Issue 7
Table of Contents
REFINING THE PROCESS OF DESIGNING AN ELECTRICAL RESISTANCE HEATER FOR VACUUM FURNACE IN NON-STATIONARY PROCESSpg(s) 270-272
Designing an electrical resistance heater for vacuum furnace is a result of multiple thermo-technical and electro-technical calculations in order to determine the optimal power. The process of heating must also comply with the technological requirements for temperature differences between the inside and the surface of the processed products. Considering the complicated heat transfer in the furnace, there is no complete methodology for determining the heat conditions of the participants in the heat transfer differentiating in time and space. In this paper it is systemized a sequence of applied mathematical and numerical models as well as geometric dependence for deriving the angular coefficients of radiant interchange in the process of determining the temperature of every participant in the heat transfer in order to refining the E. Angelovaprocess of designing an electrical resistance chamber.
DEVELOPMENT AND IMPROVEMENT OF TECHNOLOGIES FOR PRODUCING STRUCTURAL MATERIALS WITH ULTRAFINE-GRAINED STRUCTURE BY SEVERE PLASTIC DEFORMATIONpg(s) 276-276
Paper presents an overall analytical review of recent achievements in the field of development and improvement of technologies for producing structural materials with ultrafine-grained structure by severe plastic deformation. Main modern methods of obtaining ultrafine-grained structure by severe plastic deformation are described. Special attention to combined process “helical rolling – pressing” is devoted.
During injection molding of highly filled polymers it is necessary to avoid any inhomogeneities arising from high shear rates/stresses created in molded parts, because they lead to uneven shrinkage after molding, dimensional instabilities and even cracks and voids in the final parts. The testing mold design to intercept so called powder-binder separation has been upgraded to a 3D cube-like model and constructed. Investigation of a tendency to phase separation is however strongly affected by a material and a surface structure of a processing tool. Therefore, flowability of various filled materials in the flow channels designed from different construction materials were tested and compared within this contribution.
The present paper is dedicated to constructing a phase fluorometer on a phase screen model. The numerical correlation method are applied to evaluate fluorescent signals. The phase shift between the reference signal and the fluorescence signal are studied as the function of statistic moments of random phase screen.
In this study wind potential investigated for the region to the east of Turkey’s Hakkari centers. The wind speed and direction information used in the study were taken from the measurement station belonging to the General Directorate of Meteorology in Hakkari Center. Data sets containing 5 year wind speed and wind direction between 2013 and 2017 taken from this measurement station were analyzed by the WASP program. The NASA SRTM data library in the WASP interface was used to create digital maps for the region. Regional barriers required for areas where wind potentials are searched and roughness maps were created using Google Maps. As a result of these analyzes, annual average wind speed value of 1.96 m / s and average power density of this region in Hakkari Center is calculated as 12 W / m2. The prevailing wind direction belonging to this region has been identified as Southwest, but it has been found that this dominant wind direction changes with great proximity to the Southeast-Northwest sector interval on the South side.
The process of producing powder permeable materials made of spherical bronze powders by tin-phosphorous pressing method has been investigated. A technique for producing experimental samples based on the granulation of powders by a pore-former has been described. The technology is simple to carry out and it does not require complex equipment. Products have a satisfactory set of properties.
INVESTIGATION OF HARDENING PROCESSES OF CORROSION-RESISTANT COATINGS DEPOSITED BY A FLUX-CORED WIRE WITH NITRIDE-BORIDE ALLOYINGpg(s) 291-293
This study explores the metal of a coating deposited by a high-chromium flux-cored wire alloyed with a BN-TiB2-ZrB2 complex. We investigated the changes in the durometric properties and fine structure of the coating after tempering and subsequent quenching. It is shown that the hardening of the metal of such a coating after quenching consists in the formation of a complex composite structure with an iron-chromium martensitic matrix, a large amount of eutectic and particles of hardening complexes, which leads to an increase in hardness and wear resistance. It has been established that phase transformations in the metal of such a coating are caused by the formation of an eutectic component based on chromium and iron borides, a framework structure and a large number of dispersed titanium nitride particles up to 2.5 μm in size.
REGULARITIES OF ELECTRON-BEAM TECHNOLOGY INFLUENCE ON OPERATING CHARACTERISTICS OF OPTICAL ELEMENTS WITH NANODIMENSIONAL OXIDE COATINGSpg(s) 294-297
It is determined, that electron-beam processing of elements from optical glasses with nanosized coatings from metal oxides leads to improvement of their physical and mechanical properties, that influence operational characteristics of elements: negative microdefects on the surface are excluded, its microporosity decreases by 5… 10%, as well as microroughness from 30… 35 nm to 9… 15 nm; the microhardness of the surface increases from 2,3…3,5 GPa to 23,7…24,9 GPa, thus the influence of the coating thickness on its value decreases by 30…40%; wear resistance increases by 7… 12% and service life of optical elements increases by 20… 30%. Mathematical model has been developed, allowing to pre-define critical modes of electron-beam processing of elements, control of which allows to prevent their possible destructions and increase the probability of nonfailure work at operation.
INVESTIGATION OF THE EFFECT OF DIAMETERS OF POLYACRYLONITRILE NANO FIBER WITH CARBON NANOTUBE ON MECHANICAL PROPERTIESpg(s) 298-301
In this study, pure polyacrylonitrile (PAN) nano fiber (8 wt. %) and PAN nano fiber with multi-walled carbon nanotubes (MWCNT) were prepared. The content of MWCNT was (1, 3 and 5 wt.%). Electrospin device was used in nanofiber production. Nano diameters of the produced nanofibers were examined by Scanning electron microscopy (SEM). The nanofiber samples were cut 0.5 cm wide and 2 cm long. These samples were subjected to a tensile test on the Shimadzu device. The effect of nanofiber diameters on mechanical properties was investigated. All the MWCNT based composite nanofibers presented larger diameters than those of pure PAN nanofibers. The maximum stress value (76.60 kN) was found to be at PAN nanofiber with 1% MWCNT (average nano fiber diameter is 369.45 nm).
Compositions of the products of the electrolysis of melts based on a eutectic mixture of sodium chloride–lithium fluoride and sodium tungstate, which contains molybdenum (VI) and tungsten (VI) oxides, molybdates, tungstates, and carbonates of lithium or sodium, are investigated. It is shown that, depending on the content of melt components, the products of electrolysis are carbon, molybdenum, tungsten, and their bronzes and carbides. The conditions of the deposition of galvanic coatings of molybdenum and tungsten carbides on carbon, nickel, and copper matrices are determined.