Effect of structural-chemical modification of a polycaprolactam block on the retention of strength during thermo-oxidation

The structure and strength of a block of polycaprolactam (PC) have been investigated in relation to diffusion stabilization and thermo-oxidation. It is shown that structural modification of the surface layers of the PC block with zinc iodide has an important effect on the retention of strength during prolonged thermo-oxidation.Kaunas Polytechnic Institute; Institute of Physicotechnical Problems of Energetics, Academy of Sciences of the Lithuanian SSR, Kaunas. Translated from Mekhanika Polimerov, No. 1, pp. 10–14, January–February, 1970.     

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.     

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.     

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.     

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.     

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.     

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.     

Strength and deformability of a glass — Plastic warped by cylindrical plungers such as bolt stems

Conclusion 1. The process of subcritical fracture of a laminate glass-plastic subjected to warping by cylindrical plungers such as bolt stems is characterized by features peculiar to fracture of such brittle materials as cast iron and stone under an identical load. The established dependence of warping strength on the ratio F/F_W in the case of a laminate glass-plastic can be seen as following a curve which is the arithmetic average of such analogous curves for stone and cast iron, respectively.2. Prior to supercritical fracture the ratio of stress to strain follows closely Hooke's law for all the glass-plastics studied, during compression with plungers of any diameter as well as under simple tension. The percent deformation at which supercritical fracture begins is approximately the same for all plunger diameters and all distances between the plungers. This seems to indicate that fracture occurs at the same stress level in each case.3. The size of wedges forming around one contact zone is proportional to the plunger diameter, while the degree of comminution around the contact zones becomes higher with a smaller plunger diameter.4. The trends of these relations and processes as well as the nature of fractures, comminution, and separation are all determined by the redistribution of stresses due to overlapping of stress concentration zones and also by the splitting of a specimen into laminations of rather low stability.A. Snechkus Kaunas Polytechnic Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1038–1042, November–December, 1978.     

Effect of temperature on the nature of the tear surface of styrene polymers

The tear surfaces of polystyrene and SKS-85 butadiene-styrene copolymer (85% styrene) have been investigated at temperatures from –45 to +100°C and from –60 to +40°C, respectively. The fracture surface of these polymers changes not only on transition from the glassy to the high-elastic state, but also within the glassy state itself, changes being observed both in the relative extent of the individual zones contributing to the fracture surface and in the nature of those zones. Changes in the nature of the fracture surface associated with a slowing of the fracture process occur at 0 and 40°C in the case of polystyrene and at –10°C in the case of copolymer SKS-85 and are attributable to secondary transitions in the polymers.Moscow Technological Institute of the Meat and Dairy Industry. State Institute of Polymer Adhesives, Kirovakan. Translated from Mekhanika Polimerov, Vol. 5, No. 2, pp. 257–264, March–April, 1969.     

Role of the supermolecular structure of PMM in the morphology of fracture and features introduced by the type of loading

The spherulitic supermolecular structure of PMM, expressed in the fracture surface, determines the fracture pattern and kinetics. The effect of the type of loading on the morphology of the fracture surface is described. Banding of the fracture surface is attributed to periodic energy pulses leading to quasi-brittle fracture at the moving crack front and selective local crack development at the band edges.Riga Lenin Komsomol Institute of Civil Aviation Engineers. Translated from Mekhanika Polimerov, Vol. 4, No. 5, pp. 776–782, September–October, 1968.     

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.     

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.     

Effect of fiber tension on the unwinding resistance of hardening layers of glass-reinforced plastic

The shear fracture toughness characteristics of glass-reinforced plastics used for strengthening metal pressure vessels have been determined by testing metal-GRP rings. The shear fracture toughness characteristics are statistically estimated for a unidirectional GRP as a function of the winding tension.K. É. Tsiolkovskii Moscow Aviation Engineering Institute. Translated from Mekhanika Polimerov, No. 5, pp. 935–938, September–October, 1975.     

Effect of fiber length on the strength and fracture properties of a fiber-filled silicone composite

The mechanism by which fillers strengthen polymers is discussed, and the effect of fiber length on static and impact bending strength and on the area of the fracture surface is studied with reference to the example of a silicone composite. A correlation is established between the strength properties and the area of the fracture surface. On the basis of the data obtained it is shown that, as the fiber length increases, the fracture mechanism changes from extraction of the ends of the fibers along the fracture path to breakage of the fibers.Moscow Lomonosov Institute of Fine Chemical Technology. Ter-Gazaryan State Scientific-Research Planning Institute of Polymer Adhesives, Kirovakan. Translated from Mekhanika Polimerov, No. 3, pp. 445–449, May–June, 1971.     

Investigation of the relief of the fracture surfaces of epoxy compositions subjected to cyclic loading

Epoxy compositions containing various amounts of plasticizer have been fractured by cyclic loading under conditions of circular cantilever bending. The relief of the fracture surfaces is discussed.Design-Technological Scientific Research Institute, Tallinn. Translated from Mekhanika Polimerov, No. 6, pp. 1014–1017, November–December, 1969.     

Electron diffraction investigation of the fracture surfaces of filled mixtures of SKS-85 butadiene-styrene copolymer

As the result of an electron microscope study of replicas from the fracture surface during the disintegration of samples of mixtures of SKS-85 butadiene-styrene copolymer with 20 vol.% DG-100 carbon black and chalk, in the temperature range from +60 to –60°C, it is shown that, in the region of vitrification of the copolymer and of the loss of the reinforcing effect of the carbon black, there is a sharp change in the character of the fracture micro-surface, and the particles of carbon black become the sites of additional fracture. In the region of the temperature transition of the copolymer, connected with the mobility of the phenyl groups in the same way as in the vitrification region, there is a sharp decrease in the number of particles of carbon black at the fracture surface, while the fracture surface of a mixture with chalk passes selectively along the contact boundary of a polymer with larger particles. The microstructure of the Wallner lines on the surface of a mixture with carbon black, at Tst, is made up of traces of secondary fracture, arising around the particles of carbon black.Moscow Institute of Technology for the Meat and Dairy Industry. M. V. Lomonosov Institute for the Technology of Fine Chemicals, Moscow. É. L. Ter-Gazaryan State Scientific-Research and Design Institute, Kirovakan. Translated from Mekhanika Polimerov, No. 3, pp. 437–444, May–June, 1970.