Study of the effect of test piece geometry on the propagation velocity and logarithmic decrement of longitudinal vibrations in fluoroplastics

The effect of the geometry of teflon test pieces on the speed of sound and the logarithmic decrement of longitudinal vibrations has been investigated. Conditions for the determination of the speed of sound in an infinite medium and in a rod have been obtained. A method is given for determining the dynamic moduli of longitudinal elasticity, the shear modulus, and the dynamic Poisson's ratio on test pieces in the form of rods and prisms, starting with a length of 30 mm.Mekhanika Polimerov, Vol. 2, No. 4, pp. 557–564, 1966     

Increasing the wear resistance of graphitoplast parts

The effect of compression molding conditions on the physicomechanical properties of graphitoplast is studied. The question of the correlation between the microstructure of the material and its wear resistance is considered. It is shown that in order to obtain optimal properties it is necessary to establish the proper compression molding conditions for each part, in particular, the molding pressure and its conditions of application.Mekhanika Polimerov, Vol. 1, No. 3, pp. 115–119, 1965     

Equations for determining the deformation of filled polytetrafluoroethylene materials

Experimental data are given on the deformation of polytetrafluoroethylene (teflon) filled with S-1 colloidal graphite. Design equations are proposed for estimating the deformation of filled teflon materials in relation to the percentage of filler in the mixture, compressive stress, and test duration.Mekhanika Polimerov, Vol. 1, No. 3, pp. 57–62, 1965Communication II. For Communication I see [1].     

Effect of hydrostatic pressure combined with uniaxial tension on certain physical properties of polymers

The residual changes in the density and swelling properties of high-density polyethylene, teflon, PVC, and ebonite after extension under hydrostatic pressure have been investigated. It is shown that in this case the density of all the materials tested is higher and the swelling lower than in the case of uniaxial tension alone. This effect of hydrostatic pressure is attributable to the creation of favorable conditions for the healing of cracks formed in the deformation process.Mekhanika Polimerov, Vol. 3, No. 6, pp. 1018–1023, 1967     

Investigation of the supermolecular structure of polyformaldehyde in an injection-molded block

The process of variation of the spherulitic and "superspherulitic" structure in an injection-molded block of polyformaldehyde has been investigated as a function of the molding conditions with allowance for the structural inhomogeneity of the block. The molding conditions corresponding to the formation of "superspherulitic" structures have been determined. The thermal stability of these structures has been investigated.Mekhanika Polimerov, Vol. 4, No. 3, pp. 394–401, 1968     

Supermolecular structure of teflon and its role in the manufacture of metal-polymer antifriction materials

The question of the formation of supermolecular structures in teflon is considered. It is shown that during processing they become oriented, causing anisotropy of the material properties. The realtive rheological characteristics of the anisotropic materials are given as a function of the directionality of the force field. Specimens are obtained on the basis of the experimentally determined laws and certain properties of a polymer-metal antifriction material consisting of a high tin, porous bronze impregnated with teflon are investigated.Institute of the Chemistry of High Molecular Compounds, AS UkrSSR, Kiev. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1122–1124, November–December, 1968.     

Effect of process parameters on injection compression molding of pickup lens

The residual stresses and shrinkages of pickup lens in injection compression molding are investigated in this study. It was realized that the behavior of residual stresses in injection compression molding parts was affected by different process conditions such as melt temperature, mold temperature, compression pressure and time. Moldings under different conditions were numerically investigated to study the effects of the process conditions on the residual stresses and shrinkage of a pickup lens with large thickness variations. The mold temperature and compression were found to be the most important factors that affect the shrinkage of lens in the thickness direction, resulting in surface profile deviation. The effect of heat transfer coefficient of the mold wall used in the molding simulation was also discussed.     

Optimization of the injection molding process for short-fiber-reinforced composites

A fast and effective methodology integrating the finite-element and Taguchi methods is presented to determine the optimal design conditions of the injection molding process for short-fiber-reinforced polycarbonate composites. The finite-element-based flow simulation software, M-flow, was employed to simulate the molding process to obtain the fiber orientation distributions required. The Taguchi optimization technique was used to identify the optimal settings of injection molding parameters to maximize the shear layer thickness. The effects of four main parameters — the filling time, melt temperature, mold temperature, and injection speed — on the fiber orientation or the shear layer thickness were investigated and discussed. It is found that the dominant parameter is the filling time. The best levels of the four parameters to acquire the thickest shear layer are also identified.     

Pressure distribution in molding GRP parts of complex shape

This paper presents the results of an experimental study of the pressure distribution in the mold in molding parts consisting of cylindrical and conical components. The effect of the weight of molding compound introduced into the mold and the loading conditions on the pressure distribution is investigated. It is shown that the hypothesis of hydrostatic pressure transmission to the walls of the mold is incorrect in relation to the manufacture of glass-reinforced plastic (GRP) parts of complex shape.Mekhanika Polimerov, Vol. 1, No. 4, pp. 130–135, 1965     

Investigation of the Poisson's ratio of certain crystalline polymers under a constant compressive load

The results of an investigation of the Poisson's ratio in compression for two crystalline polymers, low-density polyethylene and teflon, are given. The effect of time under load and temperature on the value of the Poisson's ratio is examined.Mekhanika Polimerov, Vol. 1, No. 4, pp. 43–46, 1965     

Creep of certain polymers under hydrostatic pressure

The problems of an experimental investigation of polymer creep under omnidirectional hydrostatic pressure are considered. The method of investigation is discussed, and the loading devices are described. The results of tests on low-pressure polyethylene and teflon are reported.Mekhanika Polimerov, Vol. 4, No. 2, pp. 232–236, 1968     

Influence of technological processing parameters on the properties of carbon filled thermoplastics

The effect of processing parameters of injection molding on the mechanical and tribotechnical properties of carbon plastics based on polyacetals is investigated. The copolymer of 1,3,5-trioxane with 1,3-dioxolane is used as the polymer matrix. Hydrated cellulose Ural LO-24 carbon fibers are used as the reinforcing filler. The effect of molding temperature, pressing time, and temperature of the casting mould on the properties of carbon plastics is investigated. It has been found that for improving the mechanical properties of carbon plastics it is necessary to raise the molding temperature up to 200–210°C. Prolongation of the technological cycle leads to thermal degradation of the polymer in the cylinder of a casting machine. The mould temperature only slightly affects the composite strength properties, but lower temperatures create better conditions for polymer crystallization. As a result of our investigations, the optimal processing parameters of the above carbon plastics are determined.Ukrainian State University of Chemical Technology, Dnepropetrovsk, Ukraine. Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 3, pp. 385–392, 1999.     

Ⅰ型拉伸试样金属注射成形多相流动的三维数值模拟

将粉末注射成形充模过程视为粘结剂、粉末和空气的三相流动过程,基于多相流理论给出金属注射成形的多相流动控制方程。根据金属注射成形的工艺特点确定多相流动控制方程的初边界条件,用多相流数值分析软件CFX对Ⅰ型拉伸试样的铁粉注射成形充模流动过程实现了三维数值模拟,分析了模腔中不同位置处粘结剂一粉末流动的速度曲线。数值模拟结果表明在Ⅰ型拉伸试样金属注射成形充模流动过程中发生过两相分离的现象,数值模拟的瞬态信息可用于金属注射成形产品缺陷的分析与控制。     

Optimization of TQFP molding process using neuro-fuzzy-GA approach

This paper focuses on an integrated optimization problem that involves multiple qualitative and quantitative responses in the thin quad flat pack (TQFP) molding process. A fuzzy quality loss function (FQLF) is first applied to the qualitative responses, since the molding defects cannot be simply represented by the relationship between molding conditions and mathematical models. Neural network is then used to provide a nonlinear relationship between process parameters and responses. A genetic algorithm together with exponential desirability function is employed to determine the optimal parameter setting for TQFP encapsulation. The proposed method was implemented in a semiconductor assembly factory in Taiwan. The results from this study have proved the feasibility of the proposed approach.     

Mechanical properties of polyethylene and teflon over a broad range of strain rates

Tensile load-extension diagrams have been obtained for low- and high-density polyethylene and teflon. Conventional notions concerning the effect of strain rate on the properties of solids are found not to apply. The unconventional distribution of the family of - curves plotted for different strain rates is caused by the combination of high-elastic and plastic deformation associated with the extension of crystalline polymers. An attempt is made to correlate the data on a narrow range of strain rates with the aid of a model of a viscoelastic solid with variable relaxation time, and on a broader range by means of an equation incorporating the limiting dynamic diagram.Mekhanika Polimerov, Vol. 4, No. 1, pp. 45–52, 1968     

Verification of the hypothesis of the existence of a potential with reference to teflon

In establishing the rheological relations describing the behavior of materials during deformation it is often very useful to employ a potential function. The hypothesis of the existence of a potential is verified in relation to the deformation of teflon in a complex state of stress.Scientific-Research Institute of Mathematics and Mechanics, Leningrad Zhdanov State University. Translated from Mekhanika Polimerov, No. 3, pp. 565–567, May–June, 1969.     

Eine Kennzeichnung der Regel- und Gesimsflächen

We study two classes of surfaces in euclidean 3-space, namelyruled andmolding surfaces, specialsurfaces of revolution (molding surfaces are covered by a plane curve if the plane is rolling over a torse, in particularsurfaces moulures by G.MONGE for a cylindrical torse). The main result: A connected surface hyperosculating molding surfaces in every point is contained in a ruled or in a molding surface; a connected surface hyperosculating in every point surfaces of revolution is a surface of revolution. We characterize hyperosculating molding surfaces by means of the generating torse and study finally molding surfaces having contact of higher order.     

Effect of production technology upon the supramolecular structure of crystalline polymers

The supramolecular structure and some other properties (density, microhardness) of high-density polyethylene and polycaprolactam specimens, molded under various conditions and aged for periods up to five months, have been studied.The change in the nature of the supramolecular structure and properties of the tested materials was determined in relation to molding conditions and aging time. It was found that the properties of these materials are determined by their supramolecular structure.Mekhanika Polimerov, Vol. 1, No. 2, pp. 9–14, 1965     

Positron annihilation in annealed and quenched teflon and in sulphur

The value (τ₂) and the intensity (I₂) of the delayed component in the lifetime spectra of positrons annihilating in annealed and quenched teflon and in sulphur and crystex (polymer sulphur), at room temperature and at 77° K are reported. These data and the X-ray diffraction patterns for these materials are discussed in terms of the free volume model for the formation and quenching of positronium atoms in molecular materials.     

Hardness of polymers

Hardness was measured on a Rockwell type instrument modified to measure the depth of the unrecovered indentation. The indentors were balls of various diameters and cones with various vertex angles. The hardness of the following materials was investigated: aminoplast (amino resin), K-17-2, FKP-1, polymethylmethacrylate (plexiglas), polyvinyl chloride (PVC), polyethylene, and teflon. The hardness is related to the strength and elastic characteristics.Mekhanika Polimerov, Vol. 2, No. 3, pp. 337–349, 1966