Mechanics of Solids最新文献

This research investigates the behavior of amplitude ratios (AR) of different waves at the interfaces between non-local micropolar elastic solid (NLMES) and linear viscoelastic solid (LVES) half-spaces. The study analyzes both longitudinal and coupled waves obliquely incident on these interfaces. Using various governing equations and boundary conditions for perfect and imperfect interfaces, and by applying specific values for various constants and parameters, numerical results has been obtained for both interfaces. These results indicate that the amplitude ratios of reflected and refracted waves are significantly affected by the material properties of the NLMES and LVES half-spaces and vary with the angle of incidence. The numerical results were plotted graphically using MATLAB, demonstrating variations in amplitude ratios for incidence angles from 0° to 90°. Additionally, three special cases i.e. normal force stiffness, transverse force stiffness, and welded contact were analyzed, each case has been showing specific amplitude ratio patterns and highlighting the importance of stiffness parameters at the interface. These results have concluded the significance of emergent waves in different scenarios.

The distributions of the principal stresses, the radial velocity, and the relative density are determined in an infinite dilatant medium in which a spherical cavity expands from a zero radius. The medium obeys the Drucker–Prager yield criterion. The plastic potential is also of Drucker–Prager type but differs from the yield criterion. Moreover, it involves the relative density and results in the incompressibility equation at a certain relative density value. A detailed analysis of the solution is provided for a specific dependence of the plastic potential on the relative density. It is shown that the qualitative behavior of the solution near the cavity’s surface depends on a constitutive parameter involved in this dependence. A numerical example illustrates the general solution.

The purpose of this research is to examine the effects of magnetic field and thermal diffusion on a photo-thermoelastic semiconducting medium under the theory of hyperbolic two-temperature. During the formulation of the problem using the hyperbolic two-temperature theory, the relation between plasma and thermoelastic waves was explored. The medium is assumed to be a semiconducting medium with isotropic and homogeneous characteristics. The Laplace transform technique is used to construct analytic formulations for physical quantities such as stresses, displacement components, temperature field, and mass concentration. To show the results, numerical computations are done using the MATHEMATICA program for the selected material (Si). To demonstrate the significance and effectiveness of the obtained results, the full solutions of the major physical variables in the space-time domain are found using a numerical method based on the inverse of the Laplace transform. A comparison is carried out with and without a magnetic field, at different theories (CTE, LS, GL) and with another research that agree with the previous paper when the new parameters neglected.

Some effects of the stress-strain state, such as vibration creep, creep acceleration and ratcheting, observed and studied in the experimental mechanics of a deformable solid, are proposed to be modeled on the basis of constitutive relations implemented in tensor nonlinear viscoelastic models of the Maxwell type. The apparatus of isotropic tensor functions is used, depending on two symmetric tensor arguments. Examples are given of a complex stress state in a tubular sample, when there is a significant disproportionate increase in time of the axial component of deformation under the combined action of constant axial and oscillatory shear loads compared to the case of action of only axial load. The concepts of generalized and combined ratcheting under complex stress conditions are introduced.

Preserving the integrity of wells and preventing sand production processes are among the key problems in the operation of underground gas storage facilities. Previously, the authors have stated that a key role in the processes of destruction and sand production is played by changes in formation pressure in the reservoir as a whole, since it has a decisive influence on the magnitude of the stresses acting in the vicinity of the wells. This thesis differs from the point of view of many researchers who associate these negative processes with a change in the stress state in the bottomhole zone of the formation caused by drawdown/overbalance in wells. The main goal of the article is to study the influence of unequal components of the initial stress state, as well as elastic and strength anisotropy of reservoir rocks on the stability of wells. It is shown that the presence of unequal components of the initial stress state and elastic anisotropy can lead to stress concentrations on the well contour that differ significantly from the isotropic case. It is also shown that in the presence of strength anisotropy, a change in the location of the points of the beginning of well destruction can be observed. The calculations performed have been confirmed by experimental studies carried out on rocks of the Uvyazovsky underground gas storage facility under conditions of true triaxial independent loading.

The factors of disturbance such as clearance and elastic deformation of components are the primary contributors leading to the decline of performance and accuracy of the mechanism. In order to more accurately predict dynamics behavior, this paper takes six-bar mechanism as research object, and puts forward an accurate modeling method of the nonlinear dynamics of multi-link mechanism (MLM) under the coupling action of clearance and elastic deformation of the component. Based on the “contact–separation–collision” model, a revolute clearance model is established. Based on the reference point coordinate method (RPCM) and the absolute node coordinate formulation (ANCF), the rigid-flexible coupling dynamics model of the mechanism is established. Then, a dynamics model of rigid-flexible coupling mechanism with revolute clearance is derived by coupling revolute clearance and the rigid-flexible coupling dynamic model. Influence of the coupling action between revolute clearance and elastic deformation of the member on dynamics response of the MLM is investigated. Furthermore, the chaotic phenomenon is identified qualitatively and quantitatively by phase diagram, Poincare map and largest lyapunov exponent (LLE). The reliability of the mechanism is studied. The validity of the theoretical model is verified through a comparison of virtual simulation results and numerical results. This paper aims to provide a systematic theoretical foundation for the research of nonlinear dynamics of high-precision and high-performance MLM.

In this paper, the rapid axial unloading induced spontaneously rock core disking (or the interval fracture of rock pillar) is regarded as a self-sustained fracture. Mechanical model of rock pillar with initial stress subjected to rapid axial unloading under constant radial stress is established, the process of rock core disking is theoretically reproduced, and mechanism underlying the fracture process is analyzed. The expression that could not only reflect the relationship between the dimensionless core thickness d/D and the dimensionless initial axial stress ({{{{sigma }_{1}}} mathord{left/ {vphantom {{{{sigma }_{1}}} {{{sigma }_{t}}}}} right. kern-0em} {{{sigma }_{t}}}}), but also could reflect the influence factors on critical stress of rock core disking is deduced. Among the influence factors, the residual energy ratio is the most important one, the critical stress reaches its minimum value if ({{K}_{{rm I}}} = {{K}_{{{rm I}C}}}). By referring the field test data from URL of Canada in the existing study, the expressions for granite and granodiorite with parameters determined are presented, the residual energy ratio and critical stress of rock core disking are also calculated.

The prime objective of this research paper is to study the impact of gravity, hydrostatic initial stress and magnetic field on the wave propagation in the context of three phase lag (TPL) model with two temperature for magneto-thermoelastic medium. The governing equations of three phase lag (TPL) model have been solved by normal mode analysis to deduce the exact expression of displacement and stress variables. The physical quantities for Cobalt material have been used for the graphical representation in the presence and absence of gravity field. The results have been compared in the context of three phase lag (TPL) model and Lord–Shulman (L–S) theory with distinct values of both magnetic field and hydrostatic initial stress. It has been observed that there is significant effect of field quantities under the three phase lag (TPL) model and Lord–Shulman (L–S) theory.

The study focuses on the application of Haar wavelet discretization method (HWDM) and the differential quadrature method (DQM) to analyse the free vibration of a piezoelectric functionally graded porous (FGP) curved nanobeam embedded in a Kelvin-Voigt viscoelastic foundation and subjected to a hygrothermal magnetic environment. The nanobeam is composed of aluminium (Al) as the metal constituent and alumina (Al₂O₃) as the ceramic constituent, with material properties changing continuously along the thickness via a power-law distribution and described by an uneven porosity distribution. Base on Hamilton’s principle, grounded in quasi-3D higher-order shear deformation beam theory and nonlocal elasticity theory is employed to derive the governing equation for the FGP curved nanobeam. Pointwise convergence studies for HWDM and DQM have been conducted to exhibit the effectiveness of the methods. The study incorporates a Winkler-Pasternak-Visco elastic foundation model, assuming a Kelvin-Voigt-type viscoelastic foundation. Precision of the current model is effectively demonstrated through a comparative analysis of results obtained using both HWDM and DQM, showcasing outstanding accuracy. A comprehensive exploration of the power-law exponent, porosity volume fraction index, and thickness to material length scale parameter is undertaken to assess their impact on the natural frequencies. The investigation encompasses various boundary conditions, namely simply supported (S-S), clamped-clamped (C-C), clamped-free (C-F), and simply supported-free (S-F), elucidated with in-depth physical explanations. Additionally, mode shapes are graphically presented to qualitatively evaluate the dynamics of the structural component.

Negative creep of single crystals of two nickel-based superalloys has been studied. This phenomenon was observed for both alloys at temperatures of 980–1000°C and low or zero loading stresses. It is assumed that the main reason for negative creep is the formation of short-range order of atoms in the highly alloyed lattice of the matrix γ-phase. Additional factors influencing the magnitude and anisotropy of negative creep deformation can be the relaxation of residual stresses: at the microscopic level - misfit stresses between the γ-matrix and the strengthening γ′-precipitates, and at the mesoscopic level - dendritic stresses between the dendritic axes and interdendritic regions.