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This paper is focused on the main static and dynamic characteristics in case of rubber elements designated to damp the vibrations transmitted to the surrounding buildings by means of the railway. Thus, the experimental methods performed on a stand having harmonic excitation in case of actual loading under dynamic regime both stationary and transient attaining the resonance point are presented. Based on this, the system dynamic parameters such as: dynamic rigidity, critical damping fraction, dissipation coefficient (hysteresis) can be determined. Aiming this the free damped vibration method and the controlled excitation method with monotone increasing variation for the excitation frequency have been used. In this way can comparatively be determined both the rigidity and the damping dynamic characteristics of the rubber for various manufacturing receipts taking into account the chemical composition as well as the manufacturing process. Finally, the paper presents experimental results obtained by our research institute ICECON Bucharest in cooperation with University “Dunãrea de Jos” of Galaþi during the works carried out for the tram rails in Bucharest, Romania. Keywords: elastomer, rigidity, damping, vibration, structural noise, antivibrating insulation

Using the linearity of the term we will deduce a new formula for the calculus of the fracture strength for composites with randomly dispersed fibres. This formula will depend on the reinforcement volume fraction. Using the mean values for longitudinal and/or transversal modulus, with respect to the rotated reference system, we will obtain an original relation for the calculation of the elasticity modulus for composite plates with a randomly dispersed reinforcement. We preferred to write this relation in a similar manner to the one used for the failure strength, using the linearity related to . Experimental determinations were made for three sets of samples obtained from composite plates with various mass fractions of reinforcement, confirming thus the theoretical results obtained by the authors. Keywords: composite materials, fracture strength, longitudinal/transverse modulus

One major disadvantage of polymeric composites is their low electrical conductivity. This is a trail-and-error study regarding PMC’s conductivity modification by filling the polymer matrix with various powders. Clay, CNT and Ferrites were used as fillers, Epoxy Epiphen RE 4020 with Epiphen DE 4020 as hardener was used as matrix and simple type fabric of alternate kevlar and carbon untwisted tows was used as reinforcement. The mechanical properties of a PMC are improved by using reinforcements so it is naturally to ask what is happening when a reinforced composite is formed with filled polymer matrix. Plate samples were formed and their electrical conductivity was evaluated. The filler’s concentration was considered and information was used in order to form the reinforced composite with the highest conductivity. Keywords: CNT, Ferrite, Clay, Epoxy, Fiber Fabric Reinforcement

Cellulose composites with maleic anhydride – dicyclopentadiene copolymer matrix were obtained by “in situ” free-radical polymerization. The syntheses were carried out in two different solvents: toluene and dioxane, aiming at determining their influence upon both the polymerization process and properties of the resulting materials. The composite materials obtained were characterized both structurally by FT-IR, XRD and SEM, and from the thermal behavior point of view by TGA-DSC-MS analyses. Keywords: cellulose composites, maleic anhydride – dicyclopentadiene copolymer, in situ polymerization

Among the methods used nowadays for studying the microscopic properties of polymers, proteins, membranes and other bio-materials is the molecular dynamics. One of the widely used software in molecular dynamics is Gromacs developed at the University of Groningen. From a computational perspective, molecular dynamics requires large computational power and an increased storage capacity. Different physical models were recently defined for trying to reduce the complexity and to make more efficient the computational it molecular models. In this paper we present the Gromacs implementation of a new multiscaling MD model with a space dependent multiscaling parameter and we discuss efficiency measurements. Keywords: polymers, molecular dynamics, Gromacs, multiscaling modeling

A rheological study was performed in order to appreciate the compatibility of the expanded polystyrene beads with the concrete matrix. In order to prepare homogeneous dispersions of the expanded polystyrene (EPS) in the cement paste, the EPS beads were first surface pre-treated with carboxymethylcellulose (CMC), intending to achieve the compatibility between the hydrophilic concrete matrix and the hydrophobic polystyrene beads. In this study, the mass fractions of aggregates, cement and water were maintained constantly for all the probes and it was checked the influence of two parameters: the EPS mass fraction and the CMC concentration. The study was performed with EPS mass fractions between 0.0028 – 0.0041 and with CMC – water solutions having concentrations between 0.5% - 2% (mass). The results showed that CMC can achieve the compatibility between concrete and EPS and that within a 2% CMC solution an important amount of EPS beads can be incorporated. Keywords: lightweight concrete, expanded polystyrene, concrete rheology

Functionalized organogelators derived from 1,3;2,4-bis-O-benzylidene-D-sorbitol with methoxy and carbonylaminoethyl methacrylate moieties were prepared, characterized and their gelation ability was evaluated in order to be utilized as additives for dental materials obtained by photopolymerization of several dimethacrylate (DMA) monomers. Keywords: 1,3:2,4-bis-O-(p-methoxybenzylidene)-D-sorbitol, 1,3:2,4-bis-O-benzylidene-5,6-bis-carbonylamino -ethyl methacrylate-D-sorbitol, isocyanatoethyl methacrylate

Development of CAx for numerical simulation of injection molding and mold design have opened new possibilities of product analysis during the design process of plastic production. This development contributes to higher quality performance as well as to lower cost of production. The paper deals with the design of plastic products with state-of-the-art integrated CAD/CAE software for mold design. The possibility of solving problems in mold construction appeared by integrated CAx universal system with unique applications (CAE/II module) for mold parameters verification, mold calculation and selection and final mold modeling (CAD/II module). Thus, the specializated CAD/CAE system for automated mold design is successfully created. Keywords: plastic injection molding, mold design, CAD, CAE

The internal friction phenomenon in metallic and polymeric shape memory materials is analyzed. The experimental results permit validation of a theoretical model which describes qualitatively the temperature dependence of the internal friction for the investigated materials. Moreover, theoretical model accepts not only evaluations of different states of material (solid state structural transformations as martensite – austenite) but also materials very different as nature (metallic or plastic). Keywords: shape memory polymers, damping capacity, internal friction, martensitic transformation

For the modeling and usual analysis of mechanical structures it is considered that the whole structure and its components accomplish one of the fundamental conditions of strength of materials – the condition of continuity and homogeneity. This paper presents some modeling techniques useful for the optimization of the numerical models in order to improve the structural response for impact applications. As some parts have to be damaged a material model capable of material failure must be used. The differences between the results obtained using a model without failure and a model with failure compared to the experiments were discussed. The second procedure is regarding the random distribution of the thickness properties of the elements for a selected area within the user specified tolerance. Procedures implemented in custom written code and the algorithms presented for the random distribution were presented. Keyword: material homogeneity, material model, random thickness, numerical simulation