Mechanics of Solids最新文献

During long-term service of trains, the fatigue and damage of material caused by wheel/rail contact are becoming increasingly severe. In this article, the numerical calculation and fatigue experiment are used to study the fatigue damage of rail material. Firstly, a three-dimensional calculation model for fatigue contact of rail material is established to obtain fatigue parameters during rolling contact. Secondly, the fatigue parameters in the process of rolling contact are obtained, and then the fatigue life of rail material is calculated based on Jiang’s fatigue damage theory. Finally, the twin-disc rolling fatigue experiments are conducted according to the limit pass number, and the fatigue damage characteristics of rail material are researched. The results show the maximum Mises stress in the contact area is 576 MPa, the shape of contact area is approximately elliptical, the contact area is 0.82 mm², and the limit pass number of rail material is 7.73 × 10⁶. The peeling and pitting are very significant on the specimen surface. In the longitudinal section, cracks appear along the direction of plastic flow line. A large number of fatigue cracks can be found on the subsurface of transverse section.

The current work first develops a thorough mathematical formulation for the isogeometric analysis of stiffened plates made of different advanced materials. The material configurations considered in present work include those of fiber reinforced laminated composites, carbon nanotube (CNT) reinforced composites (FG-CNTRC), besides simple isotropic homogeneous configurations as a special case. A higher-order shear deformation theory (HSDT), namely the semi-refined higher order shear deformation theory (SRHSDT7) due to Bhar (2011), is used for the mathematical formulations to focus the significance of transverse shear deformation for thick laminated composite stiffened plates. For the aforementioned kind of stiffened plates, a formulation for linear static and free vibration analysis has been developed. The developed mathematical formulation is implemented into a FORTRAN computer program developed inhouse. This computer program is then utilized to thoroughly validate the results generated by this for various analysis of bare (unstiffened) and stiffened plate problems available in existing literature. Further additional results for various geometric and material configurations, stiffener numbers and locations, boundary conditions are also presented as parametric studies.

This paper presents the isogeometric analysis (IGA) based on SR-HSDT7 for the static and free vibration analysis of laminated composite and CNTRC stiffened plate. The same basis function is used by the IGA for geometric representation and numerical solution. The stiffener in CNTRC stiffened plates is distributed uniformly, however only one type of plate-FG-V, FG-O, and FG-X is functionally graded. The other type of plate is uniformly distributed (UD). The material properties of CNTRC plate are vary continuously along the thickness direction. Numerical examples are presented by increasing the number of stiffeners for different material configurations.

This study employed the theory of elastic wave propagation in frozen saturated porous media and single-phase elastic media to analyze the complex dynamics of plane-S-wave incidence at the interface between elastic media and saturated frozen soil. By considering the boundary conditions on the interface, analytical expressions for the amplitude coefficients of refracted and reflected waves were derived. The results indicate that the amplitude coefficients of refracted P₂, P₃, and S₂ waves gradually increase with the increasing incident angle. An intriguing observation is the disappearance of the reflected P wave at the critical angle, accompanied by the apparent pulses of refracted P₁ and S₁ waves. The study reveals a positive correlation between the amplitude coefficient of refracted S₁ waves and porosity, while it exhibits a negative correlation with other parameters. The amplitude coefficient of refracted S₁ waves accounts for over 90% of the sum of the amplitude coefficients of refracted and reflected waves. Furthermore, the research highlights the significant impact of various parameters on the amplitude coefficients of shear waves. Changes in incident frequency, cementation parameters, saturation, and contact parameters were identified as crucial factors significantly affecting the coefficients of refracted and reflected amplitudes. This nuanced study deepens our understanding of the complex interactions involved in the propagation of elastic waves in frozen saturated porous media, providing valuable insights for applications in geotechnical and geological engineering, as well as related fields.

The paper considers shape optimization of Euler–Bernoulli beams with circular, square and rectangular cross-sections made of axially functionally graded materials at a prescribed fundamental frequency. Optimization is carried out by the beam mass minimization. Considerations involve the case of coupled bending and axial vibrations, where complex boundary conditions are the cause of coupling. Pontryagin’s maximum principle is used to solve shape optimization, where a limited diameter or a beam cross-sectional width is used for control. Diameter limit is considered so that the optimized shape of a beam is within the limits of the validity of Euler–Bernoulli theory, and its strength does not decrease for smaller cross-sectional dimensions. The resulting system of differential equations is a two-point boundary value problem, and the shooting method is applied to solve it. The property of self-coupled systems is utilized, where all adjoint variables, except for one variable, are expressed through state variables, which facilitates solving the appropriate differential equations. Theoretical considerations are illustrated by an example. Also, the savings of beam mass in percent are determined, using the cantilever beam with optimal variable cross-section against the cantilever beam of a constant cross-section, where both beams have the same prescribed fundamental frequency.

This paper examines the axisymmetric consolidation of a poroelastic soil layer subjected to normal disc loading at the ground surface. The layer rests on a smooth-rigid impermeable base and the surface of the layer are assumed to be impermeable. The solid and fluid phases are assumed to be compressible. The solution for the displacements, pore-pressure and stresses is obtained by utilizing Laplace–Hankel transform methods. These solutions with the combination of boundary conditions provide the expressions of pore-pressure, displacements and stresses in transform domain. After the inversion of Laplace–Hankel transform the solutions can be obtained in the physical domain. The distribution of pore pressure in the layer and the vertical displacement of the soil layer is calculated numerically. The numerical results examined in the paper describe the effect of Biot Willis coefficient, drained/undrained Poisson’s ratio on the distribution of pore pressure and surface settlement with time. It is observed that compressibility of the solid components decreases the magnitude of pore pressure. Also, the magnitude of pore pressure increases as depth increases.

This study is aimed at designing, analyzing, and demonstrating the energy-absorbing capacity of ultra-thin honeycomb structures subjected to the quasi-static axial loading, and also to analyze their crashworthiness. The primary objectives of the study encompass the examination of the crushing response of aluminum honeycomb structures in the out-of-plane direction, utilizing a universal testing machine. Two different cell sizes (i.e., 12 and 19 mm) with constant cell wall thickness and nodal height were investigated for a honeycomb specimen. To carry out numerical simulations, commercially available ANSYS/LS-DYNA^® code was used. The honeycomb core was meshed with the Belytschko-Tsay (ELFORM2) shell element, and the material model MAT024 (Piecewise_Linear_Plasticity) was used for assigning the material to the honeycomb core. Crashworthiness characteristics like peak crushing load, mean crushing load, total energy absorption, specific energy absorption, and modes of deformation were studied for the honeycomb core under out-of-plane loading condition. Furthermore, to quantify the impact of changing the cell size on the honeycomb specimen’s ability to absorb energy across various deformation regions, a parametric study was performed using numerical method. The results revealed that the smaller cell size (3.2 mm as investigated in this study) honeycomb structure showed higher resistance to crushing in terms of higher crushing load and total energy absorbing capacity.

A new model of a rotating nonlocal thermoelastic medium is formulated based on the dual-phase-lag model with fractional derivative heat transfer. Using suitable non-dimensional variables, the problem is solved using Fourier series and Laplace transforms to obtain the exact expressions of physical fields. The distributions of the nondimensional temperature, displacements, and stresses are obtained and illustrated graphically. The effects of the rotation, the nonlocal parameter, the internal heat source, and the fractional- order parameter, on the considered variables are concerned and discussed in detail, and the results show that they significantly influence the variations of the considered variables.

In this study, we investigate the dynamic response of a two-dimensional half-space solid subjected to a thermal shock, considering magneto-thermoelastic coupling and time-fractional heat conduction effects. The material under consideration is homogeneous, isotropic, thermally and electrically conducting, with a free surface exposed to the thermal shock. We employ the L–S model of generalized thermoelasticity, incorporating fractional derivative heat transfer to account for second sound effects. Additionally, an initial magnetic field is applied parallel to the plane boundary of the medium. Through normal mode analysis and the eigenvalue approach, we solve the resulting non-dimensional coupled field equations to derive exact expressions for temperature, displacement, and thermal stresses. Numerical results for these dimensionless quantities are presented graphically and analyzed, with comparisons drawn between cases with and without the magnetic field.

In the present study, we consider a problem of skin tissue of the human head subjected to laser pulse and thermal diffusion with relaxation time. The chemical potential is also assumed to be a known function of time on the bounding plane. Due to the Laplace transform and its limit theorem, an analytical procedure is then imposed on this bioheat transfer model with diffusion. The thermal response of skin tissue subjected to laser heating on its boundary is solved by this analytical approach. The exact solutions of each physical field can be obtained and their distributions are illustrated. The effects of thermal lag parameter, the time parameter and laser intensity on skin tissue of the human being studied. The numerical results of the temperature, chemical potential and concentration are obtained and represented graphically. According to the results, the values of the time, the relaxation time and the laser intensity have significant effects on the physical quantities.

This study aims to explore the dynamic behavior of a planar multilink mechanism manifesting multiple clearances under varying operational conditions. It employs the planar six-bar mechanism as the subject of investigation, and deploys the L-N normal collision force model in combination with the modified Coulomb friction force model to construct a nonlinear dynamic model of a planar multilink mechanism with multiple revolute pair clearances. The Lagrange multiplier method is utilized to establish the rigid-body dynamics equations of a mechanism containing multiple revolving clearances. To scrutinize the mechanism’s stability, the paper introduces a novel approach to compose a kinematic accuracy reliability model which is based on strength-stress interference theory. The model is solved by numerical calculation. The effects of clearances at different joints and different numbers of clearance-containing kinematic pairs on the dynamic response, nonlinear characteristics, and reliability of kinematic accuracy of planar multi-linkage mechanisms are comparatively analyzed. The findings show that the peak dynamic response of the plane multilink mechanism with multiple clearances increases and the oscillation frequency of the dynamic response curve increases with the increase of the driving speed and the increase of the clearance value. Compared to the mechanism considering a single clearance, when multiple clearances coexist in the mechanism, the nonlinear dynamic behavior on the mechanism is greater and the dynamic reliability accuracy is significantly reduced. This study can provide a theoretical basis for the modeling and analysis of the dynamic output of plane multilink mechanism with multiple clearances under different working conditions, and provide a reference for the quantitative analysis of the reliability of multilink mechanism with multiple clearances.