Volume 44, Issue 1

Abstract: The present paper deal with a less known subject from the unconventional technologies namely the fluid flow through a working zone situated between the tool and workpiece electrodes. One take into account the possible types of flow, one establish the mathematical model of the flow and based on this model one determine the process parameters and their influence on the fluid behavior during the process. One present some experimental results for the EDMUS process which confirm the concordance between the theoretical model and the experimental values of the rheological parameters. Key words: electrical discharge, shear stress, shear speed, dielectric liquid

Abstract: Grease degradation has an important influence concerning vibration level of ball bearings in running time. Resulted sediments after chemical and thermic degradation process alter frequency spectrum, similar with waves on inner and outer races. Unlike with these, the alters bring about sediments that appear and disappear in running time. So, they adhere or detach from race ways. Acquired signals analysis give more details about estimation of ball bearings grease life reserve. Keywords: lubrication, grease, ball bearing, vibration

Abstract: This work presents the results regarding the formation of charge clouds due to the oil movement through non-conductive plastic and glass pipes . We have analzsed the equations that depict the charge distribution, the measurement of electrical charges and their effects on plastic and glass pipes in the transport of oil products . Keywords: plastic pipes, a non-destructive test, oil, diffusion, migration and load conversion.

Abstract: Some new iron (II)-polymer complex structures having siloxane units included either in ligand structure or as co-monomer partner with an already metal (Fe2+) complexed structure were prepared and characterized by the spectral and elemental analysis. Solubility tests and viscosity measurements have also been performed. Keywords: siloxane, iron complexes, azomethine, ferrocene

Abstract: Using the well known Wurtz coupling technique in heterogenous system, polyhydrosilanes copolymers with diphenyl sequences were synthesized. This work describes the possibility to maintain stable Si-H group and to obtain functional polysilanes. Also, the poysilane copolymer with reactive Si-H side groups was obtained through a homogenous coupling reaction of dichlorodiphenylsilane with dichloromethylsilane. The reaction was carried out in a tetrahydrofurane solution of sodium-potassium alloy complex with 18-crown-6 with a well defined composition of alkali metal ion pairs (Mt+/ crown ether, Mt - ) at –75 0C. The results were compared with those obtained by the heterogenous coupling reaction of the same monomers. Keywords: polyhydrosilane, Wurtz heterogenous coupling, homogenous, crown

Abstract: This paper presents the possibilities of creating weldings for various products made of inteligent composite materials. The acoustical parameters and their influence on the quality of the weldings are analysed from the large domain of technological, mechanical and acoustical parameters of the welding process. Furthermore, the authors present the welding process of an inteligent car stop. Keywords: inteligent composite materials, welding, acousticals parameters

Abstract: This paper presents experimental results on tribological behaviour of some composites with PTFE matrix under water lubrication. The experimental work pointed out particular processes taking place in the superficial layers of the tested composites. The results were plotted in order to underline the existence of an optimal regime for a system with given geometry, materials and lubrication conditions. The composites with PTFE matrix have an optimal composition as concerning the adding materials concentration that gives better tribologiocal behaviour, including low friction coefficient and wear. For instance the composites with PTFE matrix and glass fibber have this optimal concentration range of 10…30%. There are presented maps for these two tribological parameters in order to reveal the importance of the sliding regime parameters as normal force and the sliding speed. The tests also underline that water lubrication could be o solution for sliding bearing taking into account the interest of scientists for environment protection. Keywords: tribological behaviour, composites , glass fibber, water lubrication

Abstract: The efficiency of a company’s activity can be estimated as referring to permanently updated BAT references. As a general rule, according to this quantifying system, the waste reduction at the enterprise level is a must. In Romania this methodology is poorly known and even less operational. Due to the European environmental legislative system this kind of waste reduction algorithms becomes more and more necessary for an enterprise survival on the market. This paper presents such a methodology, illustrated by a case study. Using a flow simulation, an optimized design for this system is described. Keywords: monitoring system, modelling and simulation, optimization, environment

Abstract: In this paper are comparatively presented a few characteristics of some indigenous distillation and oxidation road bitumens. Some differences between these two bitumen types are put into evidence, some of them being of importance in the case of the modification using polymers. The distillation bitumens exhibit the greatest deviation of penetration values by comparison with the assessed standard values for road bitumens. For this reason, this bitumen was modified by addition of an indenic resin. Consequently, the modified bitumen shows an increased value of the “ring and ball” softening point, a decreasing of penetration index and an enhancement of the elastic properties. Based on the experimental data, a content of 5-10% indenic resin was found having a positive effect on the studied distillation bitumen. Keywords: road bitumen, oxidation bitumen, distillation bitumen, indenic resin

Abstract: During the past decade, a lot of effort has been spent to develop strategies to mitigate the damaging effects of earthquakes. This work has been directed at both civil structures and nuclear facilities. Polyurethane elastomers (PEs) based on polyethylene adipate diols and aliphatic diisocyanates can be used as passive isolation bearings in buildings applications. In the present study, polyesterdiol and 1,6-hexamethylene diisocyanate (HDI) have been used in polyurethanes, using glycerine, ethylene or diethylene glycols as chain extenders. Effect of varying the concentrations of diisocyanates and structure of chain extenders on PEs has been discussed with reference to mechanical properties. IR and thermal analysis techniques (TGA) were used for characterization. The results reveal that aliphatic character of diisocyanates lowers the temperature required to achieve the flexibility in the polymer. Based on their mechanical properties, PEs have great potential for applications where wind and earthquake loads resistance, dynamic-to-static stiffness ratio and vertical and lateral load characteristics are required. Keywords: aliphatic diisocyanates, passive isolation, chain extenders

Abstract: The paper presents the optimisation using genetic algorithms of some characteristics of the composite reinforced with plain weave fabric regarding the type of the polimers used as matrix and the type of the fibres, approaching a new geometric model of the woven structure which takes in consideration the fabric counts, different crimps in the warp and fill directions, the size of the gap between yarns of the two systems, the compactness of the yarns in the chosen structure. Keywords: composites, genetic algorithms, woven composites

Abstract: Rubber is often used as a vibration insulator for technical systems. Its behavior is linear until a deformation of at least 15%, by over this limit the behavior becomes non-linear. This means that the dynamic rigidity and implicitly the elasticity module change its value during the element is stressed under dynamic regime. The authors have developed a method to find out this parameters by processing data obtained by measurements with the Wigner-Ville Distribution. Keywords: rubber, mechanical properties, time-frequency representations

Abstract: This paper studies the bidimensional pulses generation in organic materials and technical polymers starting from a practical test functions basis, having as purpose their viscoelastic behaviour analysis. A heuristic algorithm for generating the test function using MATLAB procedures is presented. Keywords: viscoelastic behaviour, test functios, polymer

Abstract: The authors present a way of manufacturing composite materials for building use by adding value to a waste resulted in an oil refinery. The said waste is the spent caustic proceeding from the Fluid Catalytic C racking units. The manufacturing process implies: 1.The recovery of the organic content from the spent caustic 2.Transforming the organic phase into resin 3.Impregnating natural fibres with resin in order to obtain fibre reinforced materials .The possible materials to obtain are: boards and hydro-insulating materials for plumbing. The work was oriented towards the building material (boards). The paper presents: the chemical characterization of the waste (the spent caustic), the organic compounds recovery process, and the resin synthesis, the manufacture of the composite material by moulding and the results of the mechanical tests. Keywords: recycling, waste management, composite material

Abstract: Two macromolecular products, of polyethyleneimine and of polyamineamide type, were synthesized by the polycondensation of triethylenetetramine with 1,2 dichloroethane with adipic acid and e-caprolactam, respectively. The secondary amine groups of the two polymers were substituted with specific agents, e.g. the reaction product between triethylamine and epichlorohydrin and/or 1,2 dichloroetane, in order to produce their cationization. The intermediates and the polymers were characterized by FTIR spectroscopy, elemental analysis, solution viscometry and polyelectrolyte titration. Some properties of the synthesized polymers such as molecular weight, charge density, inability to crosslink, recommended them as retention or drainage agents in the papermaking, or as purification agents in the waste water treatment. Keywords: polyetyleneimine, polymineamide, retention aid, flocculation, polyelectrolyte titration

Abstract: The aim of this study is to calculate the kinetic parameters for thermal cracking of waste PET in presence of radical donors. The thermal decomposition of PET is carried out at different temperatures (693-773 K), high pressure and by using heavy paraffinic hydrocarbons as radical donors. A simple first order kinetic model was proposed for thermal cracking and kinetic parameters (A and E) were calculated. Radical donors assure a high degree of waste PET decomposition in valuable products as gas fraction, gasoline and middle distillate. The coke is very spongious and a small quantity of undecomposed PET is blocked inside of the cavities. Keywords: Thermal, cracking, waste, PET, radical donors

Abstract: The expresion of the twin screw extruder flow rate was established in correlation with the filling degree and pressure variation along the screw. Starting from the twin screw extruder flow rate expression, the pressure evolution and the maximum pressure in the melting area have been calculated. Keywords: twin-screw extruder, flow rate, crew

Abstract: The paper is a study regarding the obtaining of TiO2 nanostructured by the sol-gel reaction of tetraisopropoxytitanate in the presence of two templants, CTAB and DA. We are also interested in the effect of PTC on the capacity of nanostructuring. In the presence of CTAB nanostructured hibrids with interlamellar distance of 25,6Å were obtained, only in the absence of PTC. Nanostructured hibrids have been obtained in the case of DA addition, only in the presence of PTC with interlamellar distance of 32,7Å. For the nanostructured samples, the temperature with maximum decomposition speed of CATB and DA is the higest due to strong interaction between templants - TiO2. The SEM images put in evidence that the hibrids obtained in the presence of the templants are formed of submicronic units obtained during the sol-gel process. TiO2 prepared in the presence of CTAB catalizes the photo degradation of rodamine B (RB) in water. The samples obtained without CTAB followed by nanostructured hibrids present the most intense activity. The IR spectres evidenced that during irradiation, CTAB diffuses in water and stabilizes by micelles formed and RB becomes more stable at photodegradation. Keywords: templants, CTAB, TiO2, PTC, RB