On a mixture of an MGT viscous material and an elastic solid

A lot of attention has been paid recently to the study of mixtures and also to the Moore–Gibson–Thompson (MGT) type equations or systems. In fact, the MGT proposition can be used to describe viscoelastic materials. In this paper, we analyze a problem involving a mixture composed by a MGT viscoelastic type material and an elastic solid. To this end, we first derive the system of equations governing the deformations of such material. We give the suitable assumptions to obtain an existence and uniqueness result. The semigroups theory of linear operators is used. The paper concludes by proving the exponential decay of solutions with the help of a characterization of the exponentially stable semigroups of contractions and introducing an extra assumption. The impossibility of location is also shown.

Novel Methods for the Computation of Small-Strain Damping Ratios of Soils from Cyclic Torsional Shear and Free-Vibration Decay Testing

This paper illustrates two novel methods for computing the small-strain hysteretic material damping ratio, λmin, of soils from the cyclic torsional shear (TS) and computing the small-strain viscous material damping ratio, Dmin, from the free-vibration decay (FVD) testing. Both λmin and Dmin are challenging to measure, due to the significant level of ambient noise at small strains (<10−4%). A two-step method is proposed combining the Fourier Transform and a phase-based data fitting method for torsional shear testing, and this method can effectively eliminate the ambient noise at small strains. A Hilbert Transform-based method is proposed for the free-vibration decay testing in order to achieve a more accurate measurement of the viscous material damping ratio, D, at different strain levels, especially at small strains. The improved λmin and Dmin at small strains are compared to data available in the literature. The two novel methods are shown to be accurate in computing the small-strain damping ratios.

Morphological descriptions and DNA barcodes of Oziella viscida n. sp. (Eriophyoidea, Phytoptidae) and two infrequently reported Trisetacus species (Nalepellidae) from Crimea

We report on a new phytoptid mite species, Oziella viscida n. sp., collected in Western Crimea from sea rush, Juncus maritimus (Juncaceae), and give supplementary descriptions of two rarely encountered nalepellid species of the genus Trisetacus from pines: T. confusus Livshits & Vasilieva, 1982 (in Vasilieva et al. 1982) from needle sheaths of Pinus nigra ssp. pallasiana (Pinaceae), an endemic subspecies restricted to Crimea, and T. brevisetus Livshits & Sekerskaya, 1982 (in Vasilieva et al. 1982) from needle sheaths of Pinus brutia ssp. pityusa (Steven) Silba, a relatively isolated subspecies of Turkish pine (P. brutia Tenore) growing in Georgia, Caucasus and Crimea. Oziella viscida n. sp. is remarkable in that most specimens were found inhabiting the basal part of leaves and stems of J. maritimus, an area covered by a transparent, sticky exudate apparently secreted by the plant epidermis. The mites were completely embedded in this substance and, rather than crawling with their legs, were observed moving through the viscous material while bending their opisthosoma in a serpentine or wormlike manner—an adaptation that appears to be currently unreported in eriophyoids and possibly reminiscent of locomotion of ancestral “protoeriophyoids” associated with soil. In comparison to females, males of O. viscida n. sp. and T. confusus have a more distinct prodorsal shield pattern consisting of a larger number of longer lines. Three new barcode gene sequences were obtained: MZ220550 (Cox1, O. viscida n. sp., 1159 bp), MZ224497 (18S, 2012 bp, T. brevisetus), and MZ224498 (18S, 2013 bp T. confusus). A BLAST search of the 18S sequences of T. brevisetus and T. confusus shows them as slightly closer to other 18S sequences of Trisetacus from Pinaceae (95.5%–96.3% identity) than to Trisetacus from Cupressaceae (93.6%–94.0% identity). Comparison of sequences of nalepellids currently present in GenBank suggest that a complete 18S sequence KJ841938.1 (2252 bp) from China belongs to an identified Trisetacus from Pinaceae rather than to Setoptus koraiensis as labelled, highlighting the necessity to review carefully the sequences of Eriophyoidea prior to using them in phylogenetic analyses, as well as the need to recollect and resequence S. koraiensis to clarify the nature of the problematic data from GenBank assigned to this species.

Substantiation of Improvements for the Bearing Structure of an Open Car to Provide a Higher Security during Rail/Sea Transportation

This article presents the most frequent damage in the bearing structure of a rail car during rail/sea transportation. The study includes load modes for the bearing structure of an open car such as unloading with a grab and transportation by a train ferry. It was found that the most vulnerable element of the bearing structure of an open car during unloading with a grab is the top cord. The authors suggest applying a viscous material (an elastomer) to reinforce the top cord. This solution was confirmed by means of a strength calculation, whose results showed the efficiency of the solution. The bearing structure of an open car during the train ferry transportation can be protected by mounting special fixation units on the bolster beams. The geometry of such units was chosen according to that of a chain binder. The results of the strength calculation demonstrated that the strength of the bearing structure of an open car was provided with the application of the fixation units suggested. The article also presents the results of the experimental determination of the strength of the improved bearing structure of an open car based on the finite element method and full-scale bench testing. The research conducted might be used by those who are interested in higher operational efficiency of rail cars during rail/sea transportation.

Numerical modelling of strain localization by anisotropy generation during viscous deformation

&lt;p&gt;Localization and softening mechanisms in a deforming lithosphere are important for subduction initiation or the generation of tectonic nappes during orogeny. Many localization mechanisms have been proposed as being important during the viscous, creeping, deformation of the lithosphere, such as thermal softening, grain size reduction, reaction-induced softening or anisotropy development. However, which localization mechanism is the controlling one and under which deformation conditions is still contentious. In this contribution, we focus on strain localization in viscous material due to the generation of anisotropy, for example due to the development of a foliation. We numerically model the generation and evolution of anisotropy during two-dimensional viscous deformation in order to quantify the impact of anisotropy development on strain localization and on the effective softening. We use a pseudo-transient finite difference (PTFD) method for the numerical solution. We calculate the finite strain ellipse during viscous deformation. The aspect ratio of the finite strain ellipse serves as proxy for the magnitude of anisotropy, which determines the ratio of normal to tangential viscosity. To track the orientation of the anisotropy during deformation, we apply the so-called director method. We will present first results of our numerical simulations and discuss their application to natural shear zones.&lt;/p&gt;

A mathematical framework for peristaltic mechanism of non-Newtonian fluid in an elastic heated channel with Hall effect

Purposeobjective of the present investigation is to examine the influence of Hall on the peristaltic mechanism of Johnson-Segalman fluid in a heated channel with elastic walls. The transmission of heat is carried out. Relevant equations are computed for heat transfer coefficient, temperature and velocity. Low Reynolds number assumptions and long wavelength are employed. The interpretation of various parameters is analyzed. The results indicate that the heat transfer coefficient, temperature and velocity are larger for viscous material in comparison with Johnson-Segalman material.Design/methodology/approachThe transmission of heat is carried out. Relevant equations are computed for heat transfer coefficient, temperature and velocity. Low Reynolds number assumptions and long wavelength are employed. The interpretation of various parameters is analyzed. The results indicate that the heat transfer coefficient, temperature and velocity are larger for viscous material in comparison with Johnson-Segalman material.FindingsThe formulation of paper is executed as follows. Section 2 comprises problem summary and mathematical design. Solution methodology is discussed, and expressions for temperature, velocity and coefficient of heat transfer are derived in Section 3. Graphical outcomes for the parameters are reported in Section 4. Conclusions are outlined in Section 5.Practical implicationsPeristaltic phenomenon of fluids has a definite role in many physiological, industrial and engineering processes. The mechanical devices for instance finger and roller pumps operate via this process, and it is quite significant for vasomotion of blood vessels, consumption of food via esophagus, chyme flow in gastrointestinal zone, toxic liquid flow in nuclear industry and transport of corrosive fluids.Originality/valueLiterature review witnesses that information about peristalsis of conducting fluid in a heated channel with flexible walls and Hall effect is scarce. So, our goal is to discuss the peristaltic activity of non-Newtonian fluids in flexible channel. Johnson-Segalman fluid is taken into account. This model is used to allow non-affine deformations. Experimentalists relate “spurt” with wall slip. That is why the work presented is original.