Table of Contents

  • TECHNOLOGIES

  • MACHINES

    • IMPROVED METHODOLOGY FOR DESIGN AND ELABORATION OF TEST MACHINES AND EQUIPMENT

      pg(s) 3-6

      The main objective of the presented research is to improve and upgrade the existing methodologies for design and layout of test machines and equipment. The authors’ team has a significant experience in creating new test machines in the area of Machine Science, Machine elements, Automation and Measuring. The application of CAD systems within this research process of multivariate design is an additional advantage for the evaluation and analysis of different layout versions for the elaborated new test machines. The priority of combining electronic and mechanical measuring options is pointed out. The improved methodology is applied within the design process of a test machine for the experimental research of cardan drives.

  • TECHNOLOGIES

    • CONSTRAINED SIMILARITY OF 2-D TRAJECTORIES BY MINIMIZING THE H1 SEMI-NORM OF THE TRAJECTORY DIFFERENCE

      pg(s) 33-35

      This paper defines constrained functional similarity between 2-D trajectories via minimizing the H1 semi-norm of the difference between the trajectories. An exact general solution is obtained for the case wherein the components of the trajectories are mesh- functions defined on a uniform mesh and the imposed constraints are linear. Various examples are presented, one of which features application to mechanics and two-point boundary value problems. A MATLAB code is given for the solution of one of the examples. The code could easily be adjusted to other cases.

    • IMPACT OF THE MICROSTRUCTURE ON THE HARDNESS DISTRIBUTION WITHIN DOUBLE SIDED WELDED JOINT

      pg(s) 36-39

      Submerged-arc welding (SAW) may be considered as a miniature casting and the final microstructure of a weld and a casting are both dendritic, but the differences are much greater than the similarities. The microstructure produced in a weld deposits is very complex and may contain several phases and hence has pronounced effect on the mechanical properties, such as hardness, strength and toughness.

      The microstructure of the double sided welds joint is generally non-uniform, being composed of areas of as deposited weld metal (first weld) and areas that have reheated by subsequent pass (second weld). The hardness values (HV1/15) within double sided submerged-arc weld metals are different and depends to the exact positioning of the measurements. The obtained results using LM (Light Microscopy), SEM (Scanning Electron Microscopy) and Vickers hardness testing (HV1/15) are presented in this work and this is an attempt to clarify a correlation between microstructure and hardness gradient within double- sided submerged-arc weld metals from microalloyed steel API grade X60.

    • WELDABILITY ASSESMENT OF STEEL FOR LINE PIPES

      pg(s) 40-43

      The steel for the production of welded pipes must possess good weldability to achieve high efficiency and effectiveness of the production process in production lines (in line) and ground, during welding of pipes in long distance pipelines and in lower temperature conditions. The main focu of this research was on weldability assessment of API Grade X52 steel at low temperature (0°C), which is used for the production of welded pipes, respectively pipelines. Carbon equivalent (CE), mechanical testing and metallographic analysis of the welded joint were conducted in order to assess the weldability. The results of mechanical tests and metallographic analysis show that steel API Grade X52, at low temperature (0°C) has excellent weldability, so the pipes produced can be welded in long distance pipelines, easy and unhindered, thereby ensuring high production efficiency and effectiveness.

  • MATERIALS

    • CHARACTER OF ANISOTROPY AND ELASTIC PROPERTIES OF HOT-FORGED ALUMINUM-MATRIX COMPOSITES PRODUCED BY DIFFERENT PRODUCTION MODES

      pg(s) 44-48

      The results of investigations of the structure and the elastic characteristics of the aluminum-matrix composites of Al-TiC system, produced by hot forging in accordance with different technological schemes are presented. It is shown that the materials obtained by hot forging differ in appreciable anisotropy, which is characterized by the elongation of the particles of the matrix phase in the direction normal to forging force. Hereupon the resulting values of both normal elasticity modulus and shear modulus in the plane normal to the direction of the deforming force during hot forging, are of 12-15% higher than the corresponding characteristics in the direction of deformation. For all of the above manufacturing processes the elastic characteristics of the investigated aluminum-matrix composites exceed by 40-70% (depending on the direction of sounding) the Young modulus of aluminum, and the respective characteristics of the shear modulus are higher by 8-15%.

    • FORMATION OF NEAR-NANO SIZE TiB2-TiN-Al2O3 POWDER BY SHS

      pg(s) 49-51

      Formation of TiB2 , TiN and Al2O3 powder mixtures were obtained through self-propagating high-temperature synthesis (SHS), starting from TiO2 + BN + Al mixtures. As a diluent, NaCl was added in 0-40 wt% range to the starting mixture in order to refine the size of the formed particles. Thermochemical calculations were performed by Factsage software. The products were subjected to XRD, SEM and particle size analyses. Intended reaction products were obtained in the TiB2, TiN and Al2O3 system according to XRD analyses, with no cross reaction products. The crystallite size of the products decreased with the increasing amount of NaCl according to the broadening of the peaks on the XRD patterns of the products. Particle size measurements revealed that near-nano size particles were formed. A decrease in the adiabatic temperature was calculated, a decrease in the velocity of the SHS wave front was observed and a decrease in the particle size of the obtained products was measured as a result of the increase in the diluent amount.

    • EXPERIMENTAL DETERMINATION OF THE ELASTIC CONSTANTS OF POLYMER CONCRETE COMPOSITES

      pg(s) 52-55

      This article has experimental nature. The values of the dynamic elastic modulus (Young’s modulus) of gamma polymer concrete composites are determined quantitatively. The tested samples have the form of a rectangular parallelepiped (type bar).

      The dynamic Young’s modulus of the samples is determined by the method of the experimental modal analysis. Impact excitation was applied for expressing the resonance frequencies in the tests of bending and twisting the sample. The test results were processed with regression analysis.

    • EFFECT OF CRYSTALLINE FORM (γ) OF POLYAMIDE 6 / GRAPHENE NANOPLATELETS (PA6/GN) NANOCOMPOSITES ON ITS STRUCTURAL AND THERMAL PROPERTIES

      pg(s) 56-59

      In this article, graphene nanoplatelets (GN) were used as nanofiller and twin-screw extrusion process was applied to synthesis of Polyamide 6 / Graphene Nanoplatelets (PA6/GN) nanocomposites. Fourier-Transform Infrared spectroscopy (FTIR), X-Ray Diffractions (XRD), and Thermogravimetric analysis (TGA) were used to characterize the resultant structure. According to the results of FTIR and XRD measurement, α phase dominated in neat PA6, while the γ phase also could be observed at PA6/GN nanocomposites. Compared with the neat PA6, the PA6/GN nanocomposites exhibited better improvement in thermal analysis results due to the new and dominant crystal form.

    • TRANSFORMATION OF EUTECTIC NON-METALLIC INCLUSIONS IN STEELS UNDER LASER ACTION

      pg(s) 60-62

      Melting and crystallization of eutectic non-metallic inclusions was investigated. It was shown that under laser action the initial structure of eutectic inclusion-steel matrix boundaries transits into unstable equilibrium high-energy condition that cause development of the dissipation processes connecting with aspiration of system inclusion-matrix to the state with minimum of free energy. In the result of the system eutectic inclusion-matrix transits to the state of unstable equilibrium which determines structure and properties of laser-quenched interphase boundary. Processes of melting, fusion and dissolution of eutectic non-metallic inclusions and also of the melting of steel matrix play the great role in transformation of inclusion-matrix boundaries under laser action.

  • MACHINES

    • SPRING ACTUATORS FOR CYCLIC MOVEMENTS

      pg(s) 7-11

      This paper discusses a spring-loaded accumulator with the output rotary link used in drives with energy recuperation for step movements. The basic principles of drives with energy recuperation made using the properties of oscillatory systems, when the energy spent on acceleration of the inertial mass moves from kinetic to potential energy. This drive must be equipped with accumulators of mechanical energy and managed retainers. The creation of such actuators is caused, mainly, by the necessity of increasing speed, large, in comparison with traditional, technical capabilities, when the comparative simplicity of their designs and low cost.