Showing papers in "Polymer mechanics in 1975"
TL;DR: In this paper, an extension of existing methods of calculating fibrous composites to the case of reinforcement in three mutually perpendicular directions is presented, the properties of which are determined in terms of the elastic moduli of the binder and the reinforcement coefficient in one of the three directions.
Abstract: An extension of existing methods of calculating fibrous composites to the case of reinforcement in three mutually perpendicular directions is presented. The basic approach involves the introduction of a "modified" matrix, the properties of which are determined in terms of the elastic moduli of the binder and the reinforcement coefficient in one of the three directions. Approximate expressions are obtained for the elastic characteristics of materials with a high-modulus reinforcing phase. There is a considerable increase in the transverse modulus by comparison with the shear modulus, even for a low reinforcement coefficient in the third direction.
31 citations
TL;DR: In this paper, a more reliable correlation is observed between their static and fatigue strengths as a result of referring σ−1 to σ*, where σ* is the smaller of the stresses in tension or compression, determined from the inflection points on the static deformation curves.
Abstract: The conventional estimation of the fatigue strength of glass-fiber-reinforced plastics from the static strength in tension is shown to be inefficient by analysis of experimental data. It was found that a more reliable correlation is observed between their static and fatigue strengths as a result of referring σ−1 to σ*, where σ* is the smaller of the stresses in tension or compression, determined from the inflection points on the static deformation curves. Views are expressed on the use of the correlation found for reducing the amount of fatigue tests.
14 citations
TL;DR: In this article, the authors describe an apparatus and method for investigating the coefficient of thermal conductivity of high-density and low-density polyethylene, polypropylene, polyorthochlorostyrene, and polyparachlorostyrerene in relation to temperature and pressure.
Abstract: The authors describe an apparatus and method for investigating the coefficient of thermal conductivity of high-density and low-density polyethylene, polypropylene, polyorthochlorostyrene, and polyparachlorostyrene in relation to temperature and pressure.
13 citations
TL;DR: In this paper, the effectiveness of reinforcement in direction 3 has been estimated by investigating the mechanical characteristics of two types of three-dimensional reinforced materials differing with respect to the arrangement of the reinforcement and the fiber content in each direction.
Abstract: The effectiveness of reinforcement in direction 3 has been estimated by investigating the mechanical characteristics of two types of three-dimensionally reinforced materials differing with respect to the arrangement of the reinforcement and the fiber content in each direction. The superior transverse stiffness, shear strength, and transverse tensile strength of three-dimensionally reinforced composites based on a system of three mutually orthogonal fibers, as compared with laminated materials, is demonstrated. The theoretical values of the elastic constants, calculated from the relations of [5], are compared with the experimental data.
13 citations
TL;DR: It was found that at loading levels of up to 0.01 kg/mm2, the deformation properties of the wall of a large subcutaneous vein and femoral artery differ inappreciably, but on further loading substantial differences were observed between theDeformation and strength properties ofThe walls of vessels.
Abstract: A method is suggested for the determination of the initial length of a sample of a blood vessel wall at a longitudinal loading It was found that at loading levels of up to 001 kg/mm2, the deformation properties of the wall of a large subcutaneous vein and femoral artery differ inappreciably, but on further loading substantial differences were observed between the deformation and strength properties of the walls of vessels
13 citations
TL;DR: The experiments show that the compact bone tissue is an orthotropic material and that the bone is nonhomogeneous with respect to biochemical composition.
Abstract: Nondestructive and destructive methods have been used to establish a series of elastic and strength characteristics of the compact bone tissue in six zones of the cross section of the diaphysis of the human tibia. The quantity of five characteristic biochemical substances present in each zone has been determined. The experiments show that, from the standpoint of continuum mechanics, the compact bone tissue is an orthotropic material and that the bone is nonhomogeneous with respect to biochemical composition. The rank correlation coefficients between the mechanical characteristics and the biochemical concentrations are subjected to a detailed analysis. The important effect of the common glycoproteins on the elastic and strength properties of bone tissue in tension is established.
12 citations
TL;DR: In this article, the variation in the deformation and strength properties of compact bone tissue during torsion in various zones of the cross section of human tibia was discussed and a correlation was found between the specific energy of deformation consumed during the loading process and the level of stress attained.
Abstract: This paper discusses the variation in the deformation and strength properties of compact bone tissue during torsion in various zones of the cross section of human tibia. A correlation has been found between the specific energy of deformation consumed during the loading process and the level of stress attained. The degree of correlation between the deformation and strength properties of the bone tissue has been studied as a function of the concentration of certain biochemical substances in its composition.
12 citations
TL;DR: In this article, the vertical shift factor of a polyester glass-reinforced plastic in shear in the plane of reinforcement is calculated using macro-tests within the experimental time window.
Abstract: The shift factoraT for thermorheologically complex bodies is a function not only of temperature T but also of the deformation time t. A method is given for determining the vertical shift factor on the basis of macro-tests within the experimental time window. A procedure for determining the shift functionaT(T, t) is described with reference to the isothermal creep of a polyester glass-reinforced plastic in shear in the plane of reinforcement, and a master curve, simulating the long-term creep of a thermorheologically complex composite, is constructed. The predictions are compared with a long-term control experiment.
11 citations
TL;DR: In this article, the authors examined the possibility of constructing unified curves by joint application of time-temperature and time-stress analogies and showed that by using this method the time scale can be expanded in constructing the unified curves that serve as models of long-time creep of material on the basis of short-time tests.
Abstract: The possibility of constructing unified curves by joint application of time—temperature and time—stress analogies has been examined. It has been shown that by using this method the time scale can be expanded in constructing the unified curves that serve as models of long-time creep of material on the basis of short-time tests. The dependence of the influencing factorsaT andaσ on stress and temperature has been studied.
10 citations
TL;DR: In this paper, an experimental investigation of the effect of temperature on creep of an epoxyphenolic glass-reinforced plastic is presented, and an attempt is made to predict long-time nonlinear creep based on data of quick tests at high temperatures.
Abstract: Results of an experimental investigation of the effect of temperature on creep of an epoxyphenolic glass-reinforced plastic are presented. The characteristics of the observance of temperature—time analogy in nonlinear creep of the material are discussed. An attempt is made to predict long-time nonlinear creep based on data of quick tests at high temperatures.
10 citations
TL;DR: In this article, the results of studies on the reasons why degradation products of polymers migrate into the metal and the metal is transferred into the plastic material during friction are discussed, and a hypothesis has been put forward on the triboelectric and mechanochemical phenomena for the friction and wear processes of the plastic-metal and metal-metal pairs.
Abstract: The results of studies on the reasons why degradation products of polymers migrate into the metal and the metal is transferred into the plastic material during friction are discussed. Saturation of the steel surfaces with the degradation products of the polymers has been shown in the case of electropositive plastic counterbody, and decarbonization of steel surfaces in the case of the electronegative polymeric counterbody; a hypothesis has been put forward on the triboelectric and mechanochemical phenomena for the friction and wear processes of the plastic-metal and metal-metal pairs.
TL;DR: In this paper, the resolvents for the dynamic stability of an elastic orthotropic cylindrical shell are obtained in accordance with the Ambartsumyan and Timoshenko-type refined theories.
Abstract: The resolvents for the dynamic stability of an elastic orthotropic cylindrical shell are obtained in accordance with the Ambartsumyan and Timoshenko-type refined theories. The regions of instability given by the classical and refined theories are compared. The dependence of the refinements on the shell parameters, the shear moduli of the material, and the buckling modes are investigated.
TL;DR: In this article, the conditions determining the design of two-way glass-reinforced plastics with high compressive strength are investigated, and the relations between the physicomechanical and geometric parameters of the composite are obtained in the form of a system of inequalities, satisfaction of which ensures the obtaining of a high-strength material with a given utilization factor.
Abstract: The conditions determining the design of two-way glass-reinforced plastics with high compressive strength are investigated. The relations between the physicomechanical and geometric parameters of the composite are obtained in the form of a system of inequalities, satisfaction of which ensures the obtaining of a high-strength material with a given utilization factor. It has been shown experimentally that these inequalities can be used as a first approximation for the optimal design of a two-way reinforced composite with high compressive strength.
TL;DR: In this paper, the deformability and strength characteristics of compact bone tissue of human tibia during tensioning along all three main anisotropy axes were determined experimentally and a correlation was established between the mechanical characteristics and the biochemical composition of the bone tissue.
Abstract: The deformability and strength characteristics of compact bone tissue of human tibia during tensioning along all three main anisotropy axes was determined experimentally The character of change in the secant moduli of elasticity and specific energies of deformation during the loading process were studied A correlation was established between the mechanical characteristics and the biochemical composition of the bone tissue
TL;DR: In this paper, a method based on the random field theory for the calculation of the elastic properties of reinforced media was developed, which is obtained in the form of an operator series, each term of which is based on a formal component of the second derivative of Green's tensor of incompatibility equations.
Abstract: A method has been developed, based on the random field theory, for the calculation of the elastic properties of reinforced media. The solution is obtained in the form of an operator series, each term of which is based on the formal component of the second derivative of Green's tensor of incompatibility equations. The zero (singular) approximation of such a series takes into account the local part of interactions between the inhomogeneity grains. The singular approximation was used to calculate the elasticity moduli of unidirectionl reinforced materials.
TL;DR: In this paper, the fracture surfaces in polymethyl methacrylate (PMMA) obtained during fatigue testing of small specimens with round console bending in the presence of a heating hysteresis were examined.
Abstract: This examines the fracture surfaces in polymethyl methacrylate (PMMA) obtained during fatigue testing of small specimens with round console bending in the presence of a heating hysteresis. It is shown that the accumulation of damage at all stages of the process of fatigue breakdown, as in the case of stabilized temperatures, has a scatter failure characteristic.
TL;DR: The possibility of extension of a simplified variant of nonlinear succession theory with the nature of the nonlinearity unchanged with time has been studied by use of a single equation for the description of creep under uniaxial tension and compression of anisotropic composition materials.
Abstract: The possibility of extension of a simplified variant of nonlinear succession theory with the nature of the nonlinearity unchanged with time has been studied by use of a single equation for the description of creep under uniaxial tension and compression of anisotropic composition materials.
TL;DR: The hardness distribution over the compact bone tissue of the human tibia is examined along the length and in six different zones of the cross section of the bone and the three-dimensional structure of the equal-hardness formations is studied.
Abstract: The hardness distribution over the compact bone tissue of the human tibia is examined along the length and in six different zones of the cross section of the bone. A correlation is established between the hardness numbers, on the one hand, and the characteristics of the mechanical properties and the biochemical composition of the bone tissue, on the other. The three-dimensional structure of the equal-hardness formations is studied. The results confirm the assumptions of [1] concerning the specific functions of each zone in the rheological adaptation of the bone to physiological loads.
TL;DR: In this paper, the strength of adhesion of epoxy polymer to fibers of various chemical natures has been studied and it has been shown that the magnitude of the adhesion depends not only on the nature of the fiber but also on its surface geometry.
Abstract: A study has been made of the strength of adhesion of epoxy polymer to fibers of various chemical natures, and it has been shown that the magnitude of the adhesion depends not only on the nature of the fiber but also on its surface geometry. Questions are discussed on the effect of residual (internal) stresses arising during the process of heat-treating or cooling samples of bonded articles on the strength of the adhesive bond.
TL;DR: In this paper, the effect of distortion and pretensioning of the reinforcement on the axisymmetricity of the strain field, the moduli of elasticity, and the strength in the direction of the fibers under external and internal pressure are investigated with allowance for the high compliance of the material in the transverse direction.
Abstract: The characteristics of composites associated with the essential anisotropy of the reinforcing fibers are studied. The effect of distortion and pretensioning of the reinforcement on the axisymmetricity of the strain field, the moduli of elasticity, and the strength in the direction of the fibers under external and internal pressure are investigated with allowance for the high compliance of the material in the transverse direction. Numerical estimates are obtained for the moduli of elasticity Eθ and Er, expansion coefficient αθ and αr, and initial temperature stresses σ
r
0
and σ
θ
0
for a model material. The dependence of the bursting pressure on the thickness of the rings is described and strength criteria are formulated. In all the problems considered it is necessary to make allowance for the high compliance of the composites in the transverse direction.
TL;DR: An experimental procedure is suggested for studying biaxial tensioning of soft biopolymeric material and the experimental data found at a monaxial and bia X-ray tensioning are compared.
Abstract: An experimental procedure is suggested for studying biaxial tensioning of soft biopolymeric material. The experimental data found at a monaxial and biaxial tensioning are compared.
TL;DR: In this paper, a variant of time-temperature superposition in the deformation regime with different values of δ is examined, and the master curve is obtained for partially crystalline high-density polyethylene.
Abstract: A variant of time-temperature superposition in the deformation regime with different values of\(\dot \varepsilon\) is examined. A feature of the method is the use of statistical methods for estimating the parameters and taking decisions concerning the hypotheses suitable for the cases\(\dot \varepsilon\) = const, ɛ=const and σ=const. Master curves for the cases\(\dot \varepsilon\) = const and ɛ=const are obtained for partially crystalline high-density polyethylene. It is shown that the master curves are in satisfactory agreement with a long-term control experiment. Nonlinear theoretical relations that enable the master curves to be described on a broad time interval are presented.
TL;DR: In this article, from tension and torsion experiments under constant load, the authors determine the parameters of a material with physically nonlinear creep and examine the applicability of these parameters to represent the deformation properties of materials under other loading systems.
Abstract: From tension and torsion experiments under constant load, the authors determine the parameters of a material with physically nonlinear creep. They examine the applicability of these parameters to represent the deformation properties of materials under other loading systems. They give a method of drawing the reverse creep curve (in integral form) with parameters different from those of active creep.
TL;DR: In this article, it was shown that the Fourier series for a scalar function on the unit sphere Sn−1 can be expressed as a polynomial in the components of two completely symmetric tensors of rank l and l−1, respectively, provided that l ≥ 1.
Abstract: It is shown that eachl-th partial sum of the Fourier series for a scalar function on the unit sphere Sn−1 can be expressed as a polynomial in the components of two completely symmetric tensors of rankl andl−1, respectively, provided thatl≥1. It is proposed that this expansion should be used to describe the so-called limiting surfaces in second rank tensor spaces.
TL;DR: In this article, a method for constructing the coupled creep functions gβ(t) from the experimental longitudinal creep curves and the known Poisson's ratio is given, and it is shown that for this purpose it is sufficient to substitute for one of the parameters of the singular kernel a quantity containing the Poisson ratio and the parameter β determined from the solution of the elastic problem.
Abstract: A method is given for constructing the coupled creep functions gβ(t) from the experimental longitudinal creep curves and the known Poisson's ratio. It is shown that for this purpose it is sufficient to substitute for one of the parameters of the singular kernel a quantity containing the Poisson's ratio and the parameter β determined from the solution of the elastic problem.
TL;DR: In this paper, the authors used tensors to approximate strength surfaces in plane stress with the use of the method of expansion of the function on a sphere by means of tensors.
Abstract: Approximation of strength surfaces in plane stress is considered with the use of the method of expansion of the function on a sphere by means of tensors. Examples of the approximation are given for certain composite materials.
TL;DR: In this paper, the validity of the isotropy postulate is demonstrated and the vector and scalar properties of the material are studied qualitatively for strain paths having the form of a two-section broken line.
Abstract: Experiments have been carried out on thin-walled tubular samples of high pressure polyethylene for strain paths having the form of a two-section broken line. The validity of the isotropy postulate is demonstrated and the vector and scalar properties of the material are studied qualitatively.
TL;DR: In this article, six-sided and 14-sided cell models are used as a basis for calculating the Poisson ratio of foamed plastics as a function of the properties of the polymer base and the parameters of the cellular structure.
Abstract: Six-sided and 14-sided cell models are used as a basis for calculating the Poisson ratio of foamed plastics as a function of the properties of the polymer base and the parameters of the cellular structure. The extremal nature of the dependence of the Poisson ratio on the apparent density of foamed plastics is established and explained.
TL;DR: In this paper, a function of specific energy of deformation, selected in the form of a number of exponents, is proposed to describe the stress-strain state of anisotropic human blood vessel at large deformations.
Abstract: A function of the specific energy of deformation, selected in the form of a number of exponents, is proposed It describes well the stress-strain state of anisotropic human blood vessel at large deformations The constants of the material included in the deformation energy function are determined by experiments for a monoaxial tensioning, along the main anisotropy axes As an example, they were found for the human abdominal aorta, taken during an autopsy (male, age 29 years), by approximation of the experimental data on a computer by the method of least squares
TL;DR: In this article, it is shown that the discrete relaxation spectrum is a physically sounder characteristic and makes it possible to distinguish the most probable elementary relaxation processes, and that problems of predicting the relaxation processes in real polymers can be simplified by using the discrete spectrum.
Abstract: Methods of determining the continuous and discrete relaxation spectra are analyzed with the object of choosing a characteristic describing the actual relaxation processes. It is shown that the discrete spectrum is a physically sounder characteristic and makes it possible to distinguish the most probable elementary relaxation processes. Problems of predicting the relaxation processes in real polymers can be simplified by using the discrete relaxation spectrum.