On the effect of the anisotropic dry friction and the deformed state of tires on the shimmy initiation

The shimmy theories based on the Keldysh assumption can be easily implemented analytically and are still quite efficient for the preliminary analysis of the stability of steady state rolling regimes with no slip and spin of tires. On the other hand, such a shimmy theory uses the non-holonomic rolling model, therefore it is inconsistent with unsteady rolling regimes characterized by the non-vanishing sliding and spin. The qualitatively different model accounting the dry friction effect on the stability of motion is constructed on the groundwork of the coupled dry friction theory. This model has shown its’ applicability to some practical problems of engineering design even if a wheel is assumed to be rigid. Here the improved model accounting for the tire deforming, the complex contact pressure distribution, an the anisotropy of the dry friction coefficient in case of the combined kinematics is presented

Numeric-analytical methods of the coefficients definition of the rolling friction model of the pneumatic aviation tire

A new approximate models of the tire rolling accounting for coupled longitudinal and lateral sliding as well as the spinning and the deformed state resulting in elastic forces were proposed in previous works [1-7]. The main goal of this investigation consists in the development of the numeric-analytical methods of these models coefficients definition

On the equations of the analytical dynamics of the quasi-3D plate theory of I. N. Vekua type and some their solutions

The plate theory of Nth order is constructed on the background of the Lagrangian variational formalism of analytical dynamics of continuum systems and the dimensional reduction approach of I. N. Vekua – A. A. Amosov. The plate model is defined within the configuration space, the set of field variables, and the Lagrangian density. The field variables are determined by the coefficients of the biorthogonal expansion of the spatial displacement vector field with respect to the dimensionless normal coordinate. The dynamic equations are derived as Lagrange equations of the second kind of the two-dimensional continuum system. The dynamics of the plane elastic layer is considered as an example, the normal wave propagation is described on the basis of refined plate theories of various orders, and the convergence of approximate solutions to the exact solution of the three-dimensional elastodynamics problem is analyzed for different wavenumbers

Molecular epidemiological study of clinical cases of acute hepatitis E in Belarus

Relevance. The frequency of occurrence of anamnestic antibodies to the hepatitis E virus (HEV) in the general population of the Republic of Belarus is 7.3%, which is clearly not consistent with the low incidence of hepatitis E (HE). Most of primary HEV infections remain undiagnosed. The intensive epidemic process of HEV in the Belarusian population is hidden. Conducting epidemiological studies, including genotyping of HEV sequences isolated on the territory of the republic, makes it possible to more accurately characterize the sources of HEV infection and the mechanisms of its transmission. Aim molecular epidemiological study of two cases of acute hepatitis E detected in patients from Belarus. Materials and methods. During 20212022, samples of biological material were obtained from two patients undergoing treatment with an established diagnosis of acute hepatitis E. Serum samples were tested to detect antibodies to HEV using enzyme immunoassay, HEV RNA was detected in fecal samples using nested RT-PCR. The nucleotide sequence was determined by an automatic sequencer using the Sanger method. Analysis of nucleotide sequences, their genotyping, and calculation of evolutionary distances were performed using MEGA X software. Results. The HEV sequence isolated from a pregnant woman who had an epidemiological episode of alimentary contact with raw pork meat is clustered into a common phylogenetic clade with HEV sequence obtained from the patient from Belarus with a history of kidney transplantation and HEV sequences isolated from a domestic pigs. The HEV sequence isolated from a patient with a history of travel to Pakistan belongs to the HEV genotype 1 and joins a clade of HEV sequences isolated in Pakistan, India, Nepal and Mongolia

ON HAMILTONIAN FORMULATIONS AND CONSERVATION LAWS FOR PLATE THEORIES OF VEKUA-AMOSOV TYPE

Some variants of the generalized Hamiltonian formulation of the plate theory of I. N. Vekua – A. A. Amosov type are presented. The infinite dimensional formulation with one evolution variable, or an “instantaneous” formalism, as well as the de Donder – Weyl one are considered, and their application to the numerical simulation of shell and plate dynamics is briefly discussed. The main conservation laws are formulated for the general plate theory of Nth order, and the possible motion integrals are introduce

On the effect of the anisotropic dry friction and the deformed state of tires on the shimmy initiation

The shimmy theories based on the Keldysh assumption can be easily implemented analytically and are still quite efficient for the preliminary analysis of the stability of steady state rolling regimes with no slip and spin of tires. On the other hand, such a shimmy theory uses the non-holonomic rolling model, therefore it is inconsistent with unsteady rolling regimes characterized by the non-vanishing sliding and spin. The qualitatively different model accounting the dry friction effect on the stability of motion is constructed on the groundwork of the coupled dry friction theory. This model has shown its’ applicability to some practical problems of engineering design even if a wheel is assumed to be rigid. Here the improved model accounting for the tire deforming, the complex contact pressure distribution, an the anisotropy of the dry friction coefficient in case of the combined kinematics is presented

Numeric-analytical methods of the coefficients definition of the rolling friction model of the pneumatic aviation tire

A new approximate models of the tire rolling accounting for coupled longitudinal and lateral sliding as well as the spinning and the deformed state resulting in elastic forces were proposed in previous works [1-7]. The main goal of this investigation consists in the development of the numeric-analytical methods of these models coefficients definition

A new approximate model of tyre accounting for both deformed state and dry friction forces in the contact spot on the background of the coupled model

A new approximate model of the tire rolling accounting for coupled longitudinal and lateral sliding as well as the spinning and the deformed state resulting in elastic forces is proposed. The main goal of this investigation consists in the construction of simple models with a few of degrees of freedom allowing one to implement them analytically in the engineering practice, primarily for the estimation of the rolling stability and for the prognosis of the instable rolling so-called ”shimmy phenomenon” and to numerical simulation of the transient dynamics of rolling wheels with sliding effects. Such a model could become useful at the earlier stages of the engineering design instead of complex numerical models that are usually resource consuming. The known models of the shimmy phenomenon are usually based on the nonholonomic condition of the steady rolling and consider as the main cause of instability only the tire deformation while the sliding and spinning are assumed to vanish, i. e. the dry friction effects are neglected. Another type of models consists in the ”rigid wheel” assumption, in other words only the dry friction effects are accounted on the background of the coupled dry friction theory whereas the deformed state effects are neglected. Such a theory is based on the complete accounting of the combined kinematics due to simultaneous sliding and spin and shows its efficiency for slightly deformed wheels and the unsteady rolling regimes. Our goal consists in the formulation of the combined model that takes into account as well as the deformed state as the dry friction effects. This model is based on the solution of some model problems for the tire using solid finite element simulation or various shell theories, the computing of a set of specific generalized rigidity factors for the tire model, and on the accounting for the shape of the contact spot and the contact pressure distribution after the numerical simulation of the tire-road contact interaction in quasi-statics. As a result, we obtain a model with only a few degrees of freedom but more general that the Keldysh’s or Klimov’s ones