For simulation of processes of compaction or forging of products from powder materials, a method of permeable elements is proposed. The essence of the method is to use elements whose shape is regulated in advance, and, unlike the finite element method, where the elements coincide with the material volumes and their masses are unchanged, here the masses elements are variable, and material can flow between adjacent cells. Examples of using the method for modeling the processes of forging of porous preforms in closed and open dies, as well as in a closed die with a compensation cavity, are presented.
Machines. Technologies. Materials.
Vol. 13 (2019), Issue 9
Table of Contents
We present non-trivial spatio-temporal patterns observed in reactive-wetting of mercury droplets spreading on thin metal (silver or gold) films on glass at room temperature. This is the only known study of reactive-wetting at room temperature. We show that there exist two main regimes, the bulk propagation regime and the interface kinetic roughening regime. In both regimes, rich spatio-temporal patterns are observed. We study and characterize these patterns using statistical physics tools, such as the growth, roughness and persistence exponents, and show the manifestation of surface tension relaxation in these statistical measures.
Experimentally verified mathematical model of the polymer plasticization process in the injection moldingpg(s) 382-387
The mathematical model of the polymer plasticization in the reciprocating screw injection molding machine is presented. According to the mathematical model, a computer program was developed. Based on the computer program, simulation studies of the injection molding process were conducted. Next, the experimental studies, evaluating the theoretical model from the accuracy and usefulness point of view, were carried out. Important output quantities, such as the temperature and pressure profiles, the power demand by the screw, the torque on the screw and the screw rotation time were measured. The studies were performed on a specially made
research office. The simulation results were compared with the experimental data measured for the most popular polymers and different operating parameters of the injection machine. The experimental studies have indicated the need to introduce some corrections to the mathematical model. Several modifications have been made to the model, related to the methods of stress determining in the polymer layer. Finally, the output characteristics of the plasticization process in the injection molding are now correctly determined by the model with an average error less than 10%.
Novel hybrid polyethersulfone membranes modified with polyvinylpyrrolidone and Ag/titanate nanotubespg(s) 388-391
In this work, the influence of addition of polyvinylpyrrolidone (PVP, 10kDa, 1-4.8wt%) and Ag-modified titanate nanotubes (Ag/TNTs, 0.1wt%) on physicochemical and transport properties of polyethersulfone (PES) ultrafiltration membranes was studied. The membranes were prepared via wet phase inversion method using N,N-dimethylformamide (DMF) as a solvent and water as a non-solvent. The Ag/TNTs nanocomposite was obtained via photodeposition method using AgNO3 as a precursor. It was found that the addition of PVP into the casting dope affected the cross-section structure of the membranes and their surface topography. The presence of PVP improved the dispersion Ag/TNTs agglomerates in the membranes structure. A positive influence of the introduction of the nanocomposite into the membranes matrix on their permeability was also proved.
The structure formation features of the alloy Zr41,2Ti13,8Cu12,5Ni10Be22,5 during the casting in the metal mold and the following heating amorphous ingotspg(s) 392-394
The structure formation features of the bulk glass alloy Zr41,2Ti13,8Cu12,5Ni10Be22,5 under conditions of melt casting in a copper mold and subsequent heating of amorphous ingots, are studied. It is shown that for certain parameters of the model (the thickness of the ingot and its heating rate), the main contribution to the total crystallized volume fraction passes from frozen crystal growth processes to the processes of nucleation and growth of new crystals. Regardless of the dominant crystallization process during heating, amorphous ingots of the Zr41,2Ti13,8Cu12,5Ni10Be22,5 alloy are crystallized to form a coarse crystalline structure.
Synthesis of the magnetic adsorbent based of graphene oxide and ZnO nanoparticles for environmental applicationspg(s) 395-396
In this study Fe3O4-ZnO and GO-Fe3O4-ZnO are synthesized as photocatalysis for decomposition of of methyl orange (MO) as organic dye pollutant model. The XRD results show that the prepared nanocomposites contain the modified GO with cubic structure of Fe3O4 and hexagonal wurtzite structure of ZnO nanoparticles. The photocatalytic results show that the degradation of MO using both of the synthesized photocatalysts enhances with respect to the time and weight fraction. The removal efficiency of MO using GO-Fe3O4-ZnO at each concentration and irradiation time is more than that of Fe3O4-ZnO.
The types of entrepreneurial activity and form of enterprises are investigational. Described business system and her elements. Sequence of executions and in accordance with principles which provide the acceptance of effective administrative decisions aimed at realization of investment strategy of industrial enterprises is offered. Tasks which must be the strategies of industrial enterprise taken into account in the process of choice are certain. The stages of life cycle of industrial enterprises are set from the period of “birth” to the period of “expansion”. Expediency of different forms of strategy of diversification of investment activity of industrial enterprises is reasonable.
Research and justification of the possibilities, relevance and correctness of the monitoring and correction of the strategy, diagnosis of the prospects of its further use on industrial enterprisespg(s) 400-403
It is established that the main activities include: exercising control over the rational use of resources; reducing the cost of using and maintaining outdated equipment; increasing of production capacity; upgrading of equipment; improvement of production technology; production of unique products and improvement of their quality; diversification; automation of the production process by eliminating manual labor; reduction of pollutant emissions, search for new sources of raw materials; rational use of working capital and fixed assets. It is noted that marketing directions in the process of monitoring and adjusting the strategy, diagnostics and finding prospects for its further use include a set of actions concerning: exploring new markets for products; use of discount system for goods and services; application of modern pricing methods; product updates; production of new products according to existing orders; new methods of product promotion; improving customer service. The financial directions in the process of monitoring and adjusting the strategy, diagnostics and finding prospects for its further use are determined, they are aimed at providing the process of development and implementation of the IA strategy with sufficient financial resources, correlation of the planned effect with the achieved, estimation of the amount of expenses for carrying out research works, development technologies, their introduction into production, production of new products, its supply, search for consumers. The justified use of financial directions in the process of monitoring and adjusting the strategy, diagnostics and finding prospects for its further use allows to create some methods of protection from risks impact, to improve financial activity of the enterprise, to rise the effectiveness of IA organization, to increase sales volumes.. The factors of influence on the development of innovation strategy and the development of innovation activity of industrial enterprises are suggested.
Biomedical alloys 19Ti-59Zr-22Nb and 40 Ti-35Zr-25Nb were produced by blended elemental powder metallurgy approach using TiH2, ZrH2 and Nb powders. Usage of hydrogen as temporary alloying element for titanium and zirconium leads to activated sintering and decreased residual porosity of the alloys produced. Contrary, large amount of Nb powder negatively affects sintering and 6-9% residual porosity is observed in sintered alloys. Two-stage sintering (TSS) approach which includes preliminary sintering of powder blends, hydrogenation of sintered products, crushed in powder and sintering again, was used to obtain uniform alloys with reduced porosity. Volume changes of sintering of noted powder blends and prealloyed powders were investigated together with microstructure of sintered materials. Using prealloyed hydrogenated powders in TSS process resulted in activated densification, improved homogeneity of alloy microstructures and low (~2%) residual porosity.
Magnetic matrices for SMC powders by nanocomposite magnetic materials electroplating on copper foil rings with 50 μm thick were obtained. For each type of magnetic SMC matrices were measured magnetic properties in a transformer mode on a sinusoidal signal. As a result of the conducted research, it was shown that the application of the technique of applying composite nanomodified materials to a special substrate will allow the formation of heterogeneous composite magnetic components with the use of SMC material for microelectronics.
A statistical model is proposed to analyze the relationship between the clustering coefficient (CC) and the temperature and atomatom interaction potential. CC is defined as the ratio of the number of atoms in clusters to the total number of atoms in a system. The proposed technique is based on the statistical concept of entropy. The clustering coefficient is considered for the equilibrium state.
Formation of ZrB2-AlN mixed powder by self-propagating high-temperature synthesis (SHS) was investigated. Powders of Zr, B, BN and Al (purity >99 %) was used as the starting materials. Two initial mixtures were prepared and mixed at specific ratios. The first mixture was made of Zr and B, which were weighed at stoichiometric amounts to form ZrB2. The second mixture contained Zr, BN and Al; amounts of which were calculated so as to form ZrB2 and AlN.
The starting powders were mixed in a mortar and pestle, and then the reactant mixture was slightly pressed in a steel die. The SHS reactions were conducted in high purity argon atmosphere, in an SHS chamber. The reactant pellet was ignited from one end with a tungsten wire. The reaction products were examined with scanning electron microscopy and they were subjected to X-ray diffraction analyses.
It was found that when the reactants contained 40 % mixture-1 and 60 % mixture-2, according to the XRD results of the products, the peaks related to ZrB2 were dominant. The product contained some AlN and ZrN. When the amount of mixture-2 was increased to 90 %, the amounts of AlN and ZrN both were observed to increase. When Al amount in mixture-2 was increased by 30 % and mixture-2 was added as 90% into mixture-1, amount of AlN in the reaction products increased and amount of ZrN decreased. According to SEM examinations, ZrB2 particles were seen to be mixed with AlN particles in the reaction products. Size of ZrB2 particles were about 1 micron and AlN particles were larger.