Numerical analysis and modeling of large deformation and necking behavior of tensile specimens

The present paper is concerned with numerical simulations of large deformation and necking behavior of axisymmetric tensile specimens. In particular, an efficient framework for the numerical analysis of finite deformation behavior of elastic-rate-independent plastic problems is summarized which is based on a plastic predictor method. Furthermore, numerical modeling of conventional tensile tests as well as their finite deformation and localization phenomena are discussed in some detail, and the results will be compared to those obtained by simplified numerical simulations.     

Investigation of the working region of kapron fibers

Kapron fibers with various stretch ratios have been subjected to tensile stress relaxation tests at constant clamped length. The relaxation constants — activation energy U₀ and the coefficient — are calculated from the results of the experiments. It is shown that the fiber parameters U₀ and depend on the given molecular orientation.All-Union Scientific-Research Institute of Synthetic Fibers, Kiev Branch. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 736–739, July–August, 1968.     

Conoscopic investigation of the optical properties of kapron and polyethylene monofilaments

The conoscopic method of investigation is applied to anisotropic crystalline polymers (kapron and polyethylene monofilaments). The conoscopic figures obtained for various stretch ratios show that the optical properties of the monofilaments are similar to those of biaxial positive crystals and can be characterized by an optic indicatrix in the form of an ellipsoid with three nonequal principal axes. The angle of the optic axes 2E is the measured parameter of the optic indicatrix. This angle varied with the stretch ratio and over the cross section of the monofilaments. The variation of the angle 2E with stretch ratio may be associated both with orientation of the crystallites and with the nature of the packing in the crystalline regions of the monofilament. The variation of the angle 2E over the cross section of the monofilaments indicates nonuniformity of the optical properties in the radial direction.T. G. Shevchenko Kiev State University. Translated from Mekhanika Polimerov, Vol. 4, No. 4, pp. 598–602, July–August, 1968.     

Fatigue properties of kapron (nylon-6) and kaprolon

It is shown that kaprolon has high fatigue strength as compared with kapron (nylon-6) and other thermoplastics. This is attributable both to its high static fatigue strength and to its high fatigue coefficient. For both kapron and kaprolon a sharp increase in hysteretic heat production is observed after critical self-heating at 15° C; in this case the endurance of both materials is low.Mekhanika Polimerov, Vol. 1, No. 2, pp. 118–122, 1965     

Temperature dependence of the mechanical properties of oriented kapron fibers crosslinked with formaldehyde

Comparative regions of effective performance of oriented kapron fibers crosslinked with various amounts of formaldehyde are obtained on the basis of tensile test data in a broad temperature interval. As the degree of crosslinking increases, the region of softening of the crosslinked fibers is displaced in the direction of higher temperatures.Mekhanika Polimerov, Vol. 4, No. 2, pp. 304–308, 1968     

Effect of extension on the structure and thermophysical properties of kapron (nylon 6)

The effect of extension on the structure and thermal conductivity of kapron has been investigated experimentally in the temperature range +20–130° C. The thermophysical characteristics were determined via a method based on the principle of the regular regime. The structure of the kapron was investigated by infrared spectroscopy and x-ray and microstructural analysis. The mechanical loads produced important structural changes that affected the thermophysical parameters of the kapron.Mekhanika Polimerov, Vol. 4, No. 1, pp. 180–182, 1968     

Effect of gamma radiation on the mechanical properties and structure of oriented polycaprolactam (kapron)

Mechanical tests and x-ray diffraction measurements at large and small angles indicate that when oriented polycaprolactam is exposed to gamma radiation the "damage" is chiefly concentrated in the amorphous intercrystallite regions.Mekhanika Polimerov, Vol. 4, No. 1, pp. 173–177, 1968     

Spatial effects in problems on the deformation of cylindrical shells of anisotropic composites

Mechanics of Composite Materials -     

Investigation of the energy effects accompanying the elastic deformation of uniaxially oriented crystalline polymers

The energy (thermal and mechanical) effects accompanying the elastic deformation of uniaxially oriented crystalline polymers have been investigated; it has been established that, when these polymers are stretched, heat is released. It is shown that the heat release in uniaxial tension is a consequence of localization of the elastic deformation in the poorly ordered regions of the polymer. The relation between the thermoelasticity of uniaxially oriented crystalline polymers and their supermolecular structure is examined.Institute of Heteroorganic Compounds, Academy of Sciences of the USSR, Moscow. Translated from Mekhanika Polimerov, No. 5, pp. 785–798, September–October, 1970.     

Investigation of elastoplastic effects of cables under large spatial deformation

Cables are complex components consisting of a multi-layer structure and various materials. The structural setup includes for example conducting wires, isolating shields and protecting sheaths. This leads to several inelastic effects under large deformations like pull-out of wires, delamination of layers or friction between the constituents. The materials used in cables belong to different material classes and consequently show different behavior under load. Elastoplastic behavior has to be expected for metallic wires, whereas polymer layers behave viscoelastically. The combination of these inelastic effects caused by the structure and constituents of cables motivates the inclusion of inelasticity in the material model on a phenomenological level. Since cables are flexible, slender structures, they can be described physically correctly by the theory of Cosserat rods. In this context, the constitutive equations are formulated in terms of the sectional quantities. The related model parameters have to be determined in suitable experiments. As cables undergo large multiaxial deformations in applications, uniaxial experiments are not sufficient for their characterization. (© 2015 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Analysis of the coupling effects of the longitudinal and transverse displacements on the deformation and internal forces of functionally graded beams

Functionally graded beams (FGBs) with an arbitrary gradation of the material properties along the thickness of the beams are analyzed. Such FGBs are of special interest in civil and mechanical engineering to improve both the thermal and the mechanical behaviour of the beams. In [1] and [3] free vibrations of functionally graded Timoshenko and Euler-Bernoulli beams have been considered. The obtained analytical solutions are based on the work of Li [2], where closed-form solutions of stress distributions, eigenfrequencies and eigenfunctions have been derived by means of a single differential equation of motion for the deflection. However, these previous works did not take into account the coupling between the longitudinal and the transverse displacements and its effects on the deformation and internal forces of the FGBs. This approach is appropriate only for a symmetrical material gradation but it may not be valid for general cases with an arbitrary material gradation. In this paper, the coupling effects of the longitudinal and transverse displacements on the deformation and internal forces of FGBs are investigated for different beam support conditions. Analytical solutions of the corresponding boundary value problem are derived. A comparison is also made with the numerical results obtained by the finite element method (FEM). (© 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim)     

On the orientation of graphs

Let G(V, E) be a finite, undirected graph, and let l(X) be a set function on 2^V. When can the edges of G be oriented so that the indegree of every subset X is at least l(X)? A necessary and sufficient condition is given for the existence of such an orientation when l(X) is “convex”.     

广义Cox模型下的逐步扩大域流相关问题研究

在本文中, 我们主要讨论了广义Cox模型的信息流扩大问题. 假设在市场中有两类投资者, 第一类投资者拥有市场信息, 这里由一个维的布朗运动和一个可积随机 测度驱动; 而第二类投资者具有扩大的信息流, 这里假设是由信息流和广义Cox的模型刻画的违约信息流生成. 我们建立和刻画了广义Cox模型并且求给出它的主要性质包括生存过程和违约条件密度. 与Cox模型显著区别的是, 如果违约由广义Cox模型模型刻画, 与Cox模型平凡的结果不同的是, 鞅的分解更复杂和具有一般性.     

Reversibility of the orientation effect in linear polymers

It is established that the orientation effect in polymethylmethacrylate, assessed from the alteration in its properties, does not completely vanish after stabilization of the volume of the polymer during heating. A comparative evaluation of the physicomechanical properties in the unoriented, oriented, and oriented-and-restored states of the polymer indicates that some traces of orientation are retained.Lenin Kom somol Riga Institute of Civil-Aviation Engineers. Translated from Mekhanika Polimerov, No. 5, pp. 830–834, September–October, 1973.     

Molecular orientation and the tensile strength of polystyrene

The tensile strengths of uniaxially oriented polystyrene films with molecular orientation determined by IR spectroscopy are compared. Two different orientation methods involving different time and temperature regimes are employed. It is found that the tensile strength is a unique function of the degree of orientation of the molecular segments of the polystyrene carbon chain irrespective of the means used to orient the specimens and increases linearly with increase in the degree of molecular orientation of the polymer. The experimental dependence is in satisfactory agreement with the results of a theoretical analysis.A. F. Ioffe Physico Technical Institute, Academy of Sciences of the USSR, Leningrad. Translated from Mekhanika Polimerov, No. 4, pp. 612–615, July–August, 1969.