Determination of the strength of the bonds between the fibers in cellulose compositions

It has been shown that the magnitude of the tensile strength of the bonds between the fibers in cellulose compositions can be determined from data obtained by measuring the tensile strength of a specimen at standard and zero length. The influence of the thickness of the material on some of its strength and optical characteristics has been studied. It has been confirmed experimentally that there is a functional relationship between the tensile strength of the bonds between the fibers and the magnitude of the light-scattering coefficient in the cellulose compositions studied.     

A nondestructive method of testing the mechanical strength anisotropy of cellulose compositions

A nondestructive method of testing the mechanical tensile strength anisotropy of cellulose compositions from the coefficients of reflection of polarized shf waves is described. Equations for finding the reflection coefficient from the measured value of the SWR of the shf wave are presented. It is shown that there is a close linear correlation between the mechanical strength anisotropy and the anisotropy of the shfwave reflection coefficient.     

Changes in the strength characteristics of human intervertebral disks under compression

Conclusions 1. The strength of intervertebral disks undergoes significant changes during the human lifetime. The data obtained allow the distinction of three periods: 1) a period of strength gain (newly born babies-18 years); 2) a stable period (20–40 years); and 3) a period of strength loss (from 50 to the death). The safety factor of strength of the intervertebral disks is the highest during the first two decades and decreases during the following age periods.2. The sex has a significant influence on the strength characteristics of the intervertebral disks.3. Changes in the limiting load of the intervertebral disks of the spine are characterized by a caudocranial gradient and the changes in the strength and the safety factor of strength, by a cranio-caudal gradient. The existing relationships do not depend on age or sex and reflect the significance of the functions of support and motion in different sections of the spinal column.4. The strength of the intervertebral disks depends on the degree of the degenerative-distrophic process, the mineral content of the tissues, the water content, and the ability of the disk tissues to retain water.S. V. Kurashov Kazan' State Medical Institute. Translated from Mekhanika Polimerov, No. 5, pp. 897–902, September–October, 1976.     

Destruction of polyethylene-oxide films during storage

Conclusion In lengthy storage of PEO films the amorphous part of the material is subjected most to destruction under the effect of environmental factors; consequently, films with a higher degree of crystallinity are more suitable for storage. The resistance of individual sections of film to environmental factors is a random variable, and the nature of the encountered patterns of destruction can therefore be reproduced with the aid probabilistic models.Translated from Mekhanika Kompozitnykh Materialov, Vol. 30, No. 4, pp. 464–470, July–August, 1994.     

Deformability and strength of compact bone tissue during tensioning

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.     

The stressed state of glass disks during strength testing

By applying the improved theory of plates, which makes it possible to determine all components of the stress tensor, we study the stressed state of glass disks under axisymmetric bending. We obtain a closed-form solution of the corresponding boundary-value problem for systems of singularly perturbed equations. It is shown that the size of the zone of pure bending-the domain with uniformly stretched surface-differs from those known in the literature. The results obtained make it possible to determine the optimal geometric parameters of the punch-glass disk-support system in strength testing of the glass by the method of axisymmetric bending.Translated fromMatematicheskie Metody i Fiziko-Mekhanicheskie Polya, Issue 34, 1991, pp. 73–79.     

Degree of deformation and strength of compact bone tissue during torsion

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.Institute of Polymer Mechanics, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No.5, pp. 911–918, September–October, 1973.     

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.     

Effect of antioxidants on the changes in the effective viscosity and tensile strength of polypropylene during processing and aging

The effective viscosity of an isotactic polypropylene (IPP) melt during processing and aging has been investigated together with the changes in the mechanical properties of stabilized IPP during aging. In the presence of polymeric antixoidants there is an increase in the effective viscosity of the IPP melt attributable to interaction with the degraded IPP molecules. During the aging of IPP articles the characteristic properties of polymeric antioxidants associated with their high molecular weight are not especially in evidence.Moscow Lomonosov Institute of Fine Chemical Technology. Translated from Mekhanika Polimerov, No. 5, pp. 938–941, September–October, 1970.     

The extent of strength in the club filters

In this paper we consider whether the minimal normal filter onP _κλ, the club filter, can have strong properties like saturation, pre-saturation, or cardinal preserving. We prove in a number of cases that the answer is no. In the case of saturation, Foreman and Magidor prove the answer is always no (except in the caseκ =λ = ℵ₁—and in this case saturation is known to be consistent). The first author was partially supported by NSF grant DMS-9626212.     

Effect of bond strength on the breaking strength of two-layer cellophane film materials

The effect of bond strength on over-all tensile strength has been investigated in relation to two-layer materials consisting of cellophane film cut in the longitudinal and transverse directions and bonded with polyisobutylene. It is shown that there is a linear correlation between the bond strength and the combination hardening effect. The breaking stress of two-layer materials is higher than that of the individual films. A possible explanation of this effect is proposed.Mekhanika Polimerov, Vol. 3, No. 1, pp. 89–94, 1967     

Problems of the anisotropy of strength

The concept of a strength tensor, analogous to the tensor of elastic constants, has been introduced with a view to using its components for approximate determination of laws governing the variation of strength of anisotropic materials in uniaxial tension or pure shear as a function of the orientation of the stress state. It has been shown that the plasticity condition postulated by Mises can be used as a criterion of strength of many "weakly" anisotropic materials, if one rejects the hypothesis according to which the condition is invariant in respect to hydrostatic pressure. In the case of "strongly" anisotropic materials, wood in particular, the Mises condition is at variance with the results obtained for variously oriented specimens tested in uniaxial tension. A strength condition in the form of a fourth-degree polynomial, based on the assumed existence of a strength tensor analogous to the tensor of elastic constants, has been postulated for these materials. The validity of this criterion has been demonstrated by constructing surfaces of equicritical plane stress states from experimental data obtained for pine wood, plywood, and glass-reinforced plastic laminates.Mekhanika Polimerov, Vol 1, No. 2, pp. 79–92, 1965     

Measurement of the strength of plastics in high-speed compression

A previously developed [1] method of determining the strength of plastics in high-speed compression is extended to the temperature range –196° to +150°C. Dynamic strength data have been obtained for epoxy-polyester and polyvinyl butyral resins and glass-fabric reinforced plastics based on these resins in the indicated temperature range.Mekhanika Polimerov, Vol. 1, No. 5, pp. 34–38, 1965     

Estimating the impact strength of plastics

A method of estimating the impact strength of plastics in transverse two-support bending is proposed. It is shown that if specimens of different size are tested under certain conditions, the ratio of the work done in breaking the specimen to the volume of the specimen between the supports will be the same.Novosibirsk Kuibyshev Structural Engineering Institute. Translated from Mekhanika Polimerov, No. 6, pp. 1109–1112, November–December, 1971.     

On the irregularity strength of trees

For any graph G, let n_i be the number of vertices of degree i, and . This is a general lower bound on the irregularity strength of graph G. All known facts suggest that for connected graphs, this is the actual irregularity strength up to an additive constant. In fact, this was conjectured to be the truth for regular graphs and for trees. Here we find an infinite sequence of trees with λ(T) = n₁ but strength converging to . © 2004 Wiley Periodicals, Inc. J Graph Theory 45: 241–254, 2004     

Testing the strength of anisotropic rings

A study was made of the distribution of stresses in an anistropic ring under compression or tension with rigid cams, taking into account the final dimensions of the zone of contact.Moscow Power Engineering Institute. Translated from Mekhanika Polimerov, No. 1, pp. 175–177, January–February, 1974.