Strength properties and aging of sheet glass-reinforced plastics under various climatic conditions

Data on the variation of the physicomechanical properties of sheet glass-reinforced plastics exposed over a four-year period to different climatic conditions are reported. Polyester and phenolic laminates were exposed to the climates of Moscow and Batum either in the open air or in unheated warehouses. The tensile and bending strengths were taken as the principal indicators of changes in the mechanical properties of the materials. The property fluctuations are more considerable under humid subtropical conditions (Batum).All-Union Scientific-Research Institute of Glass-Reinforced Plastics and Fiberglass, Moscow Region. Translated from Mekhanika Polimerov, No. 3, pp. 554–558, May–June, 1971.     

Effect of molding conditions on the structure and properties of polyformaldehyde

The effect of molding conditions-melt temperature, dwell time in molten state, and cooling rate-on the structure and mechanical properties of polyformaldehyde is investigated.Mekhanika Polimerov, Vol. 3, No. 5, pp. 782–786, 1967     

Using laser-cantilever anemometry under various flow conditions

We present velocity measurements executed with the new laser-cantilever anemometer (LCA) under various flow conditions. Previously, the basic principles and characteristics of the LCA were investigated. Measurements led to results comparable to common measurement techniques for turbulent flows, such as hot-wire anemometry for air and hot-film anemometry for water [1]. Here we present further experiments where the LCA was used in a snow wind tunnel to investigate the behavior of the cantilever under particle impact. In comparison to data collected with a hot-film anemometer under same conditions, the times series of the LCA showed less pronounced impact characteristics than that of the hot-film, i.e. a recovery time that is shorter and easier to identify. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Dynamics of a spherical cavity under various conditions

We study the influence of the initial radius of the cavity, the time of energy input, and the distance to a solid wall on the parameters of a spherical cavity during electrical discharge in a liquid. The motion of the liquid was studied in gas-dynamic formulation. The solution is given by various finite-difference methods. To compute prolonged processes in large volumes we developed special adaptable mobile grids whose step was determined by the current radius of the cavity and the distance from the cell to the center. The results of the computation are in good agreement with experimental data obtained by other authors. Four figures. Bibliography: 7 titles. Translated fromTeoreticheskaya i Prikladnaya Mekhanika, No. 28, 1998, pp. 146–151.     

Variation of the mechanical properties of rigid thermoplastics under creep conditions

It has been found that as a result of tensile steady-state creep there is a decline in the rigidity and strength of PVC and plexiglas. A method is proposed for estimating the deterioration of the mechanical properties.Mekhanika Polimerov, Vol. 3, No. 2, pp. 204–206, 1967     

Dynamic properties for nonlinear viscoelastic Kirchhoff-type equation with acoustic control boundary conditions II

In this paper, we consider the nonlinear viscoelastic Kirchhoff-type equation with initial conditions and acoustic boundary conditions. Under suitable conditions on the initial data, the relaxation function $h(\cdot)$ and $M(\cdot)$, we prove that the solution blows up in finite time and give the upper bound of the blow-up time $T^*$.     

The effect of various boundary conditions on the nonlinear dynamics of slightly curved pipes under thermal loading

Slightly curved pipes are prevalent in many industries including oil installations especially in the Delta regions of the world. The aim of this paper therefore is to investigate the nonlinear dynamics of these pipes conveying fluids under the influence of thermal loadings. These investigations are for three different boundary conditions, namely simply supported ends, clamped-clamped ends and clamped-simply supported ends respectively. To derive the governing equations, small strains of initial curvature, temperature, tension, pressure, longitudinal and transverse strains are considered. Furthermore, strains due to curvature change during bending which are hitherto neglected in most of the previous works on slightly curved pipes are added. The strain due to initial curvature accounts for the geometric imperfection. Two coupled nonlinear differential equations in both longitudinal and transverse directions are obtained and solved using eigenfunction expansion method, up to four modes. Linear natural frequencies were obtained, and is shown that for various boundary conditions, it increases as the initial curvature increases and decreases as thermal loading increases. The nonlinear results obtained show that the amplitude of the pipe motion becomes larger due to the obvious effect of thermal loading. Nonlinear results for both vanishing and non-vanishing longitudinal displacements are presented.     

Some properties of generating functions obtained by Amann-Conley-Zehnder reduction

Consider an initial Lagrangian submanifold Λ₀ ⊂ T* ℝ ⁿ that admits a global generating function and a Hamiltonian isotopy Φ _H ^t . Then, we provide a global generating function for the Lagrangian submanifold Λ _t = Φ _H ^t (Λ₀) realized by applying the so-called Amann-Conley-Zehnder reduction. When Λ₀ is the zero-section, we study in some detail the asymptotic behavior of such generating functions and give an approximation result. __________ Translated from Sovremennaya Matematika i Ee Prilozheniya (Contemporary Mathematics and Its Applications), Vol. 33, Suzdal Conference-2004, Part 1, 2005.     

Some properties of rigid polyurethane foam obtained from oligoglycerooxalate

The dependence of the modulus of elasticity and compressive strength on the apparent density has been found for polyurethane foam based on oligoglycerooxalate.Institute of Wood Chemistry, Academy of Sciences of the Latvian SSR, Riga. Translated from Mekhanika Polimerov, No. 4, p. 739, July–August, 1973.     

Effect of molding conditions on fracture mechanisms and stiffness of a composite of grid structure

Methods of determining a complex of stiffness and deformability characteristics of a composite with rhomb-type grid structure were elaborated. Rhomb-type specimens were used for testing the ribs of the structure in tension, compression, and bending and the nodal points in shear in the plane of the ribs. The effect of additional tensioning of the ribs preceding the curing of the binder was investigated (ten tensioning levels ranging from 8 to 70 N/bundle with a linear density of 390 tex were applied). In testing epoxy-carbon specimens (UKN-5000+EHD-MK) in compression and tension, the failure mode changed depending on the tensioning level, i.e., the presence or absence of delamination and the appearance of dry fibers were detected. Dependences of the mechanical properties on tensioning were of a markedly pronounced extreme nature. The methods elaborated allow us to investigate the effect of other molding parameters, as well as the conditions and nature of loading, on the mechanical characteristics of composites.Translated from Mekhanika Kompozitnykh Materialov, Vol. 35, No. 1, pp. 71–78, January–February, 1999.     

Lateral vibrations of pretwisted rods with various boundary conditions

Zusammenfassung Unter Vernachlässigung der Scherung und der rotatorischen Trägheit werden die ersten vier Eigenfrequenzen der Biegeschwingungen von Stäben mit konstantem Querschnitt und konstantem Verdrehungswinkel je Längeneinheit mit Hilfe einer linearen Theorie berechnet. Der Einfluss der Randbedingungen und des Verhältnisses der effektiven Biegesteifigkeiten auf die Eigenfrequenzen wird untersucht. Es werden acht verschiedene Randbedingungen und drei verschiedene Verhältnisse der Biegesteifigkeiten behandelt. Die Resultate werden in der Form von Frequenzkurven gegeben, die sich über einen Bereich des totalen Verdrehungswinkels erstrecken, der von praktischem Interesse sein dürfte. Die Ergebnisse zeigen, dass die Eigenfrequenzen im allgemeinen stark vom Verhältnis der Biegesteifigkeiten abhängen und in gewissen Fällen merklich vom totalen Verdrehungswinkel beeinflusst werden.

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The work presented here was supported in part by the U.S. Army Research Office (Durham) under grant DA-ARO-D-31-124-G238.

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formerly with Space Technology Laboratoires where B. A.Troesch carried out most of his contribution.     

Optimal shape analysis of a column structure under various loading conditions by using differential transform method (DTM)

The effects of loading on the optimal shape of an Euler-Bernoulli column is investigated by considering four loading conditions which are mainly classified as eccentric compressive and follower type. The governing equations obtained from the structural stability condition of the column are used as a constraint to determine the minimum value of the volume by applying Hamilton principle. In the preceding task, the analysis is presented in step-by-step manner. The calculations are carried out by using differential transform method (DTM) which is a seminumerical-analytical solution technique that can be applied to various types of differential equations. By using DTM, the non-linear constrained governing equations are reduced to recurrence relations and related boundary conditions are transformed into a set of algebraic equations. The optimal distribution of cross-sectional area along column-length is obtained. Then, the volume of such column is calculated and compared to that of the uniform column which is also stable under given loading. The results obtained revealed out that DTM is a quite powerful solution technique for optimal shape analysis of a column structure.     

Dynamic journeying under uncertainty

We introduce a journey planning problem in multi-modal transportation networks under uncertainty. The goal is to find a journey, possibly involving transfers between different transport services, from a given origin to a given destination within a specified time horizon. Due to uncertainty in travel times, the arrival times of transport services at public transport stops are modeled as random variables. If a transfer between two services is rendered unsuccessful, the commuter has to reconsider the remaining path to the destination. The problem is modeled as a Markov decision process in which states are defined as paths in the transport network. The main contribution is a backward induction method that generates an optimal policy for traversing the public transport network in terms of maximizing the probability of reaching the destination in time. By assuming history independence and independence of successful transfers between services we obtain approximate methods for the same problem. Analysis and numerical experiments suggest that while solving the path dependent model requires the enumeration of all paths from the origin to the destination, the proposed approximations may be useful for practical purposes due to their computational simplicity. In addition to on-time arrival probability, we show how travel and overdue costs can be taken into account, making the model applicable to freight transportation problems.     

Viscous properties of amorphous polymers at longitudinal flow under constant rates of tensioning and deformation conditions

The lowest Troutonian viscosities and Troutonian branches of the longitudinal flow curves of polystyrene were determined at various kinematic and temperature conditions of the tensioning process. The temperature dependence of the longitudinal viscosity was examined, and a generalized temperature-time characteristic of the tensioning was obtained.