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Rubber is widely used for rolling stock and railway infrastructure parts. Rubber plates are used for rail – sleeper fastening systems and rubber parts are used for primary suspension of the Romanian (and abroad) electrical locomotives, of metro (underground) trains, of tramways; at tramways wheels are made as metal – rubber assembly with the purpose to minimize the unsprung mass. From above examples, it easy to see that rubber parts are used in railway field as elements which are directly involved in safety of circulation. Keywords: tests, locomotive, primary suspensions, rubber-metal

The vulnerability of ordinary Portland cement (OPC) concrete to acidic attack is a worrying subject regarding the future durability of this binder. On the other side of binder’s technology, the new technology of cement called ‘geopolymer’ had been studied widely in all over the world. Indeed, the major advantage of geopolymer compared to Portland cement is chemical resistance. This paper presents a study about the microstructural properties of geopolymer and OPC mortar. Visual inspection of both mortars had been performed. Stereo microscope device and Secondary Electron Microscope (SEM) were used to investigate the microstructural changes of the specimens. It was found that geopolymer mortars were less susceptible to the attack by sulfuric acid solution than the OPC cement mortars. Keywords: geopolymer, sulfuric acid attack, microstructural, SEM

The wide band dielectric spectroscopy analysis of the 1.5% multi walled carbon nanotube (MWNT) contain and 20% polyamide 6 (PA6) nanowebs obtained by three different treatments applied to the MWNTs (chemical, mechanical and mixed) was investigated. A morphological analysis of the samples was carried out using the scanning electron microscopy (SEM) and atomic force microscopy (AFM) principles. The evolution of the dielectric constant (Eps’), imaginary permittivity (Eps”), dissipation factor (Tan d) and the conductivity modulus were analysed, both from an experimental and a theoretical point of view. Keywords: nanowebs, polyamide 6, multi walled carbon nanotubes, wide band dielectric spectroscopy

The effects of tensile and morphological properties of styrene butadiene rubber/virgin chloroprene rubber blends (SBR/CRv) and styrene butadiene rubber/recycled chloroprene rubber blends (SBR/CRr) were investigated. The range size of CRr used in this study was 0.3 – 0.7 mm. Both SBR/CRv blends and SBR/CRr blends were prepared using two roll mill at room temperature with blend ratios 95/5, 85/15, 75/25, 65/35 and 50/50. It can be observed that, cure characteristics of SBR/CRr blends have lower cure time, t90 than SBR/CRv blends.SBR/CRr blends showed higher scorch time, t2 and minimum torque (ML) compared to SBR/CRv blends at all blend ratios compared with the SBR/CRv blends. However, maximum torque (MH) of SBR/CRr blends exhibit the opposite trend compared with the SBR/CRv blends. It can be observed that, the tensile strength and elongation at break of SBR/CRr blends show higher value than SBR/CRv blends particularly up to 15 phr of CRr in the blends. However, SBR/CRr blends shows higher value of tensile modulus (M100) than SBR/CRv blends at all blend ratios. The scanning electron microscopy (SEM) of tensile fracture surface of SBR/CRr blends at 50 blend ratios illustrated a better adhesion and dispersion in comparison with SBR/CRv blends. Keywords: chloroprene rubber, recycled chloroprene rubber, styrene butadiene rubber, tensile properties, SEM

In this paper, data on Melana-type polyacrylonitrile fibers dyeing with Methylene Blue in the presence of maleic acid copolymers with vinyl acetate or styrene are presented. Mathematical models of the studied dyeing processes have been developed and the necessary information on their significant factors are produced by means of experiment planning methods, known as Design of Experiment (DoE) or Experimental design. Optimal correlations between the application conditions and the color differences obtained on Melana fiber type have also been studied. Keywords: polyacrylonitrile fibers, dyeing, maleic acid copolymers, Methylene Blue, methods of planning experiments (DoE), color differences

Starting from the dynamic response of a sandwich beam with damping, (which is in free vibration), it is established a method used to determine the damping factor. We experimentally calculated the stiffness and damping factor per unit mass for beams with middle layer made of polypropylene honeycomb respectively; the external layers were made of epoxy resin reinforced with steel fabric. Keywords: sandwich beam, stiffness, damping factor, steel fabric, polypropylene honeycomb, free vibrations

In the research paper we present a study regarding the road traffic safety and the ageing phenomenon of vehicle bumpers. For our study we used the accelerated ageing in conventional environment which is the most complex and comprehensive method to determine the bumper ageing. This method is used for plastic materials and comprehends ageing methods which simulates the natural exposes: taking into account the temperature, humidity and the presence of some chemicals, oils and fuels. Also, the method consists in the ageing of plastic materials which initially were conditioned in climatic chamber. The final evaluation happens when the object we study is tempering to the ambient temperature in the same climatic chamber (T = 23°C ± 2°C , UR = 50% ± 5%). Keywords: ageing, strength depreciation, stress, strain, rheology, fracture

Monitoring of bone fracture healing evolution is performed in practice by repeated radiographic examination. We describe the use, on a clinical case of tibial diaphyseal fracture, of a method that records in progress the change of basic frequency of the healing fractured bone segement compared with the uninjured one. We ascertain an increasing evolution of the basic frequency of the fractured tibia tending to the values of parameters recorded in the unfractured segment. Approximately 100 days after trauma the recorded values enter the plateau phase, tending to those recorded contralaterally, which overlaps the healing period seen in practice. We, therefore, show the possibility to monitor the evolution of a diaphyseal bone fracture healing by the means of vibrations. Keywords: basic/main frequency, tibial fracture, biocompatibil material, accelerometer, bone healing

The elastic contention is the most efficient and used method to solve chronic venous insufficiency, being used in some countries by 71% of patients. In functional design of knitted orthoses with increased elasticity which exert a controlled pressure on a cylindrical surface of human body, used in the treatment of venous insufficiency, the model proposed allows optimal assessment of pressure values in knitting - anthropometric sizes - applied pressure ratio. Therefore starting from mechanical behaviour described by stress-strain diagrams of knittings from polyurethane yarns and using the pressure formula based on the model proposed we can assess accurately the applied pressure values for different anthropometric circumferences. Based on the model it was determined the calculation ratio of pressure exerted by the knitting versions for the cylindrical model embracement of different parts of human body. The choosing of orthoses is a difficult problem, few patients can find serial orthoses which fit the patients’ limbs configuration. Hence, the model can be used easily for designing and manufacturing on demand of the orthoses with controlled pressure potential. Keywords: graduated compression stockings, pressure modelling, stress-strain diagrams, chronic venous insufficiency, knitted fabrics, polyurethane yarns

The paper presents the effect of poly (vinyl-phenyl-ketone) used as prodegradant for styrene-isoprene block-copolymers exposed at natural aging. Keywords: styrene-isoprene block-copolymers, poly (vinyl-phenyl-ketone), physico-mechanical properties, photo-oxidative degradation