Causes of the fluctuation of the strength of a block of polycaproamide exposed to the action of heat

Fractography and mechanical testing are employed to investigate the fracture mechanism of polyamide blocks exposed to the action of heat. The mode of fracture depends essentially on the dangerousness of the surface defects.Kaunas Polytechnic Institute; Institute of Physicotechnical Problems of Power Engineering, Academy of Sciences of the Lithunian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 4, pp. 642–645, July–August, 1969.     

Effect of heat treatment on the static and fatigue strength of polycaproamide

The changes in strength and the polymorphous transformations which occur during the aging in air of polycaproamide heat-treated under various conditions were investigated. It was shown that the strength after prolonged aging in air with normal relative humidity depends on the structural changes occurring in the heat-treatment process. The structural changes lead to changes in fatigue strength and also in the mechanism of the breakdown of polycaproamide on aging.Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, No. 1, pp. 59–62, January–February, 1972.     

Concerning the strength and fracture of thermally aged polycarbonate

The change in the strength, fractography, and supermolecular structure of polycarbonate after thermal aging has been experimentally investigated. It is shown that the fall in the strength of the polycarbonate after aging (T 160°C) is chiefly related with the formation of dangerous defects as a result of the destruction of the supermolecular structure at the surface of the block. It is noted that under the same conditions there is some ordering of the supermolecular structure of the polycarbonate at depths of 150 µ or more, but this has practically no effect on the strength characteristics.Institute of Physicotechnical Problems of Energetics, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 5, pp. 951–952, September–October, 1971.     

Construction of solutions of a partial differential equation with constant coefficients in the form of formal series. I

Kaunas Polytechnical Institute. Translated from Litovskii Matematicheskii Sbornik (Lietuvos Matematikos Rinkinys), Vol. 31, No. 3, pp. 411–419, July–September, 1991.     

Some characteristics of the failure of heat-sealed polyethylene film

It is shown that weld failure most often occurs in the inner weld zone. The mode of failure and deformation of the weld in uniaxial tension depends on the welding conditions. For severe welding conditions the _t-T curve has a certain maximum.Institute of Physicotechnical Problems of Power Engineering, Academy of Sciences of the Lithuanian SSR, Kaunas, Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, No. 3, pp. 537–538, May–June, 1971.     

Effect of multiple extension on the thermal degradation of triacetate fiber

The effect of multiple extension on the vacuum thermal degradation of triacetate fiber, in the starting state and treated with hot air or saturated steam, has been experimentally investigated.Lithuanian Scientific-Research Institute of the Textile Industry, Kaunas. Translated from Mekhanika Polimerov, No. 6, pp. 1114–1116, November–December, 1971.     

Shear stress distribution in glued joints between soft high-molecular materials

Photoelastic stress analysis is used to investigate the shear stress distribution in glued joints between soft high-molecular materials (rubbers) at finite deformations on the elastic range. The theoretic and experimental results are compared.Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, No. 2, pp. 353–355, March–April, 1971.     

Polycaprolactam hardening during cyclic loading

It has been shown that two competitive processes occur during the fatigue of polycaprolactam under symmetrical tension—compression: the buildup of defects—weakening—and the hardening of the material as a consequence of the removal of the plasticizer and structural changes.Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, No. 5, pp. 815–819, September–October, 1973.     

On convergence of the maximum of dependent random variables

Kaunas University of Technology, Studentu 50, 3028 Kaunas, Lithuania. Published in Lietuvos Matematikos Rinkinys, Vol. 32, No. 1, pp. 3–6, January–March, 1992.     

Effect of the crosslink density of elastic polyurethane fibers on their mechanical properties

The effect of the nature of the bonds and the degree of crosslinking on the properties of elastic polyurethane fibers has been investigated in relation to various fiber treatments. The fiber properties are mainly determined by the chemical bonds, the proportion of which should be not less than 40%.Leningrad Branch, All-Union Scientific-Research Institute of Artificial Fibers. Kaunas Artificial Fiber Plant. Translated from Mekhanika Polimerov, No. 3, pp. 515–516, May–June, 1976.     

Fatigue and fracture of plasticized and stabilized polyamides

Polyamides have been tested in cyclic bending to determine the effect of certain plasticizers, plasticizing conditions, diffusion stabilization, and aging on the mechanism and energy of fatigue fracture. The fracture surfaces of the most typical plasticized specimens are analyzed. The optimal conditions of diffusion stabilization of polyamides with quinhydrone, giving a considerable improvement in antifatigue properties, are selected.Institute of the Physicotechnical Problems of Power Engineering, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 693–697, July–August, 1968.     

Convergence of distributions of extremal independent random variables

Kaunas Polytechnic Institute. Translated from Litovskii Matematicheskii Sbornik (Lietuvos Matematikos Rinkinys), Vol. 30, No. 2, pp. 219–232, April–June, 1990.     

The effect of stabilizers on the fatigue strength of polycaproamide under tension - compression

The authors give the results of an investigation of the influence of various stabilizers (quin-hydrone, iodine, potassium iodide, DNPDA, and MoS₂) on the fatigue strength and endurance of polycaproamide (PCA) under cyclic compression/tension, both with _a = const and with _a = const. The effectiveness of the stabilizers is mainly governed by the structural changes in the polymer during the stabilization process.Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, Vol. 9, No. 3, pp. 562–564, May–June, 1973.     

Influence of structure on the mechanical properties of block copolymers

The relationship between the breaking strength and the temperature has been studied for butadiene/styrene block copolymers of the three-block configuration styrene-butadiene-styrene. The studies were carried out over the temperature range –20 to 60° at crosshead speeds of 5, 50, 250, 500, and 1000 mm/min. An analysis was carried out on the values of the parameter U in the equation linking the breaking strength with the temperature.For Communication 2 see [3].Voronezh Technological Institute. Translated from Mekhanika Polimerov, No. 3, pp. 392–398, May–June, 1974.     

Relation between the microstructure of block amorphous polymers and certain mechanical properties of the specimens

The structures of PMMA, PS, and PC are considered in relation to the mechanical properties. The part played by the individual elements of the microstructure and their influence on the mechanical strength and deformability of the material are determined. The experimental data obtained by various authors are interpreted on the basis of the microstructural characteristics of polymers.Institute of Problems of Mechanics, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 3, pp. 416–421, May–June, 1972.     

Resin cure monitoring system based on nondestructive dielectric spectrometry

An on-line indirect cure monitoring prototype system is described based on dielectric spectrometric measurements (frequency dependences of the dielectric modulus and/or dielectric permittivity and/or dielectric loss factor and/or relaxation spectrum). A key block of the system is the Dielectric Spectrometer. Model DS 7056-C interfaced with a standard PC. A variation of the dielectric frequency spectra during the cure process for two epoxy systems based on araldite resins LY556 and LY561-1 are considered as an illustration of capabilities of the described hardware and software.Institute of Polymer Mechanics, Riga, Latvia LV-1006. Published in Mekhanika Kompozitnykh Materialov, Vol. 32. No. 3, pp. 401–409, May–June, 1996.     

Tensile testing of high-strength unidirectional composites

Conclusions 1. In order to obtain stable values of the tensile strength of high-strength unidirectional composites it is necessary to use bar specimens with pressboard end reinforcement 90–110 mm in length.2. In determining the strength on specimens without end reinforcement it is necessary to select their size and shape with allowance for the transverse compressive strength, the shear strength and the taper of the grip jaws.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. All-Union Scientific-Research Institute of Aviation Materials, Moscow. Translated from Mekhanika Polimerov, No. 4, pp. 717–723, July–August, 1978.     

Study of the impact shear strength of polymer materials

A method is proposed for studying the dynamic strength of block polymers in terms of their resistance to impact shear. An original instrument for conducting tests are room and elevated temperatures is described. The results obtained with this instrument for alkathene and styrene carylonitrile copolymer are discussed. It is found that there is a considerable increase in specific shear energy in the region of transition from the glassy to the high elastic state. In the case of alkathene the investigated characteristic falls linearly on the temperature interval studied.Leningrad Kirov Institute of the Textile and Light Industries. Translated from Mekhanika Polimerov, Vol. 4, No. 6, pp. 1135–1137, November–December, 1968.     

Dependence of the dynamic strength of a glass-reinforced plastic on the mechanical and geometric parameters of its components

The dependence of the dynamic strength of a glass-reinforced plastic on the mechanical and geometric parameters of its components is investigated.Moscow Institute of Electronic Machine-Building; All-Union Institute of Glass-Reinforced Plastics and Glass Fiber, Moscow Oblast'. Translated from Mekhanika Polimerov, No. 2, pp. 366–370, March–April, 1974.     

The mechanism of fatigue failure of plastics

Based on the study of the kinetics of deformation or rigidity, of the rise in temperature, and of the fracture surfaces, the article describes the mechanism of failure of plastics. It as found that in a cyclically loaded solid there occur two processes: strengthening and loss of strength. The main factors affecting strengthening in fatigue were discovered. Among them are the structure of the material, the degree of crystallinity, the load level, conditions of deformation, etc. The kinetics of rigidity can yield the most accurate information providing an idea of the process of fatigue failure of plastics.Paper read at the 9th International Conference on the Mechanics of Composite Materials, Riga, October, 1995.Kaunas Technological University, Lithuania. Translated from Mekhanika Kompozitnykh Materialov, Vol. 32, No. 2, pp. 279–285, March–April, 1996.