Thermoelastoplastic deformation of a thick-walled cylinder with a radial crack

The thermoelastoplastic fracture mechanics problem of a thick-walled cylinder subjected to internal pressure and a nonuniform temperature field is solved by the method of elastic solutions combined with the finite-element method. The correctness of the solution is provided by using the Barenblatt crack model, in which the stress and strain fields are regular. The elastoplastic problem of a cracked cylinder subjected to internal pressure and a nonuniform temperature field are solved. The calculation results are compared with available data. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 3, pp. 173–183, May–June, 2008.     

Axisymmetric frictionless contact of functionally graded materials

The main interest of this study is a new method to solve the axisymmetric frictionless contact problem of functionally graded materials (FGMs). Based on the fact that an arbitrary curve can be approached by a series of continuous but piecewise linear curves, the FGM is divided into a series of sub-layers with shear modulus varying linearly in each sub-layer and continuous at the sub-interfaces. With this model, the axisymmetric frictionless contact problem of a functionally graded coated half-space is investigated. By using the transfer matrix method and Hankel integral transform technique, the problem is reduced to a Cauchy singular integral equation. The contact pressure, contact region and indentation are calculated for various indenters by solving the equations numerically. An erratum to this article can be found at     

Water wave radiation by a sphere submerged in water with an ice-cover

Using the multipoles method, we formulate the problems of radiation (both heave and sway) of water waves by a submerged sphere in deep as well as in uniform finite depth water with an ice-cover, with the ice-cover being modelled as an elastic plate of very small thickness. In each case this leads to an infinite system of linear equations which are solved numerically by standard techniques. The added-mass and damping coefficients for a heaving and swaying sphere are obtained and depicted graphically against the wave number for various values of the radius of the submerged sphere and flexural rigidity of the ice-cover to show the effect of the presence of ice-cover on these quantities. When the flexural rigidity is taken to be zero, the numerical results for the added-mass and damping coefficient for water with a free surface are recovered.     

Numerical method and models for anti-plane strain of a system with a thin elastic wedge

The paper presents a general method to find asymptotics for a (multi-)wedge system containing a thin wedge. It employs separation of the symmetric and anti-symmetric parts of the boundary displacements and tractions of the wedge. The method is applicable when the angle of the thin wedge turns to zero. A physical interpretation of the derived equations is obtained by using power expansions of non-polynomial functions, which appear after the Mellin transform. We establish that the first term in the expansion of the symmetric part corresponds to shear, while the first term of the anti-symmetric part describes deflection of the wedge axis. Numerical experiments, performed by using a code developed on the basis of the theory, show that using only the first terms of the expansions insignificantly influence accuracy: the approximate results coincide with the exact values of roots to the third significant digit even for the wedge angle of 30°.     

Nonlinear rheological behavior of silica filled solution‐polymerized styrene butadiene rubber

The reinforcement and nonlinear viscoelastic behavior have been investigated for silica (SiO₂) filled solution‐polymerized styrene butadiene rubber (SSBR). Experimental results reveal that the nonlinear viscoelastic behavior of the filled rubber is similar to that of unfilled SSBR, which is inconsistent with the general concept that this characteristic comes from the breakdown and reformation of the filler network. It is interesting that the curves of either dynamic storage modulus (G′) or loss tangent (tan δ) versus strain amplitude (γ) for the filled rubber can be superposed, respectively, on those for the unfilled one, suggesting that the primary mechanism for the Payne effect is mainly involved in the nature of the entanglement network in rubbery matrix. It is believed there exists a cooperation between the breakdown and reformation of the filler network and the molecular disentanglement, resulting in enhancing the Payne effect and improving the mechanical hysteresis at high strain amplitudes. Moreover, the vertical and the horizontal shift factors for constructing the master curves could be well understood on the basis of the reinforcement factor f(φ) and the strain amplification factor A(φ), respectively. The surface modification of SiO₂ causes a decrease in f(φ), which is ascribed to weakeness of the filler–filler interaction and improvement of the filler dispersion. However, the surface nature of SiO₂ hardly affects A(φ). © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 2594‐2602, 2007     

Epoxy resin containing polyphenylsilsesquioxane: Preparation,morphology, and thermomechanical properties

Polyphenylsilsesquioxane (PPSQ) was incorporated into an epoxy resin to prepare organic–inorganic composites, and two strategies were adopted to afford composites with different morphologies. Phase separation induced by polymerization occurred in the physical blending system. However, nanostructured composites were obtained when a catalytic amount of aluminum triacetylacetonate was added to mediate the reaction between PPSQ and diglycidyl ether of bisphenol A (DGEBA). The intercomponent reaction significantly suppressed the phase separation on the micrometer scale. Organic–inorganic composites with different morphologies displayed quite different thermomechanical properties. Both differential scanning calorimetry and dynamic mechanical analysis showed that the nanostructured composites possessed higher glass‐transition temperatures than the phase‐separated composites with the same loading of PPSQ, although the intercomponent reaction between PPSQ and DGEBA reduced the crosslinking density of the epoxy matrix. This result was ascribed to the presence of nanosized PPSQ domains in the nanostructured composites, which acted as physical crosslinking sites and thus reinforced the epoxy networks. The nanoreinforcement of the PPSQ domains afforded the enhanced dynamic storage modulus for the nanostructured composites in comparison with the phase‐separated composites with a PPSQ concentration less than 15 wt %. In terms of thermogravimetric analysis, the organic–inorganic composites displayed improved thermal stability and flame retardancy. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 1093–1105, 2006     

Superposition-model investigations of the zero-field splittings and their stress and temperature dependence for Mn in guanidinium aluminum sulfate hexahydrate

The zero-field splittings of sites I and II for Mn²⁺ in guanidinium aluminum sulfate hexahydrate (GASH) are calculated from the superposition model by using the normal intrinsic parameter ₂(R₀) obtained from Mn²⁺ ions in many oxygen octahedra. The results are in good agreement with the experimental findings. Based on this, the local compressibilities and local thermal expansion coefficients in the vicinity of the impurity ion Mn²⁺ have been studied from the stress and temperature dependence of zero-field splitting and are found to be half of the host ones. The reasonableness of these local values is discussed.