Temperature effects on wave propagation in nanoplates

This paper investigates the nonlinear bending behavior of a single-layer rectangular graphene sheet subjected to a transverse uniform load in thermal environments. The single-layer graphene sheet (SLGS) is modeled as a nonlocal orthotropic plate which contains small scale effect. Geometric nonlinearity in the von Karman sense is adopted. The thermal effects are included and the material properties are assumed to be size dependent and temperature dependent, and are obtained from molecular dynamics (MD) simulations. The small scale parameter e 0 a is estimated by matching the deflections of graphene sheets observed from the MD simulation results with the numerical results obtained from the nonlocal plate model. The numerical results show that the temperature change as well as the aspect ratio has a significant effect on the nonlinear bending behavior of SLGSs. The results reveal that the small scale parameter reduces the static large deflections of SLGSs, and the small scale effect also plays an important role in the nonlinear bending of SLGSs.

Wave propagation characteristics in fluid-conveying double-walled nanotubes with scale effects

Non-local continuum mechanics allows one to account for the small length scale effect thatbecomes significant when dealing with microstructures or nanostructures. Thispaper presents some simplified non-local elastic beam models, for the bendinganalyses of small scale rods. Integral-type or gradient non-local models abandonthe classical assumption of locality, and admit that stress depends not only onthe strain value at that point but also on the strain values of all points on thebody. There is a paradox still unresolved at this stage: some bending solutions ofintegral-based non-local elastic beams have been found to be identical to the classical(local) solution, i.e. the small scale effect is not present at all. One example is theEuler–Bernoulli cantilever nanobeam model with a point load which has application inmicroelectromechanical systems and nanoelectromechanical systems as an actuator. In thispaper, it will be shown that this paradox may be overcome with a gradient elastic modelas well as an integral non-local elastic model that is based on combining thelocal and the non-local curvatures in the constitutive elastic relation. The lattermodel comprises the classical gradient model and Eringen’s integral model, and itsapplication produces small length scale terms in the non-local elastic cantilever beamsolution.

This study provides a more detailed model for wave transmission and reflection in a complex thermodynamic framework. The governing equations are developed from multiphase electromagnetic size-dependent thermoelasticity models. The main focus here is on the development of the Modified-Green Lindsay nonlocal generalized thermoelasticity model that improves previous nonlocal approaches by incorporating additional strain and temperature rate terms. This study also examines how materials react to very short pulses and the effect of external electric and magnetic fields. The highly developed nonlinear equations in this study are solved using advanced programming techniques, including an iterative approach that combines finite element methods with a Newmark time-marching scheme. The results of this work established the nonlocal heat conduction theory of generalized thermoelasticity along with nonlocal continuum theory as a new improvement and progress in the field of thermoelasticity. This model shows that without considering thermal nonlocality interactions, predictions may miss essential aspects of wave behavior. The results show that the materials experience changes in mechanical properties, particularly an increase in hardness, when exposed to stronger magnetic fields. In addition, the results show that as the duration of laser pulses decreases, the speed of wave propagation increases. Shortening the pulse duration increases the wave propagation speed, which can create steep thermal gradients. In the case of pure metals heated by ultra-short pulse lasers, the fast electron heat conduction prevents the formation of significant thermal waves, while these pulses induce more intense and localized thermal stresses. Analysis of wave propagation also shows that the return time can exceed the forward time as the waves react to applied electric and magnetic fields.

Computational dynamic homogenization for the analysis of dispersive waves in layered rock masses with periodic fractures

In this paper, the small-scale effects on the flexural wave in the nanoplate are studied. Based on the nonlocal continuum theory, the equation of wave motion is derived and the dispersion relation is presented. Numerical simulations are performed to investigate the influences of the scale coefficient, the surrounding elastic matrix and the initial stress on the wave propagation properties. The results show that the nonlocal model provides an appropriate method to investigate the characteristics of the flexural wave in the nanoplate. Furthermore, the direction and amplitude of the biaxial load, the stiffness of the shearing layer and the Winkler foundation can change the wave properties, significantly.

Wave propagation and transient response of a functionally graded material plate under a point impact load in thermal environments

Nonlinear internal resonance of double-walled nanobeams under parametric excitation by nonlocal continuum theory

Wellbore stability in extreme drilling environments remains a critical challenge. This study advances the understanding of these complexities through a comprehensive numerical modeling approach. By incorporating thermal, chemical, and hydraulic effects, four refined models were developed to simulate wellbore behavior under high pressures and temperatures. A comparative analysis of four failure criteria and a detailed investigation into the impact of fluid properties on pore pressure and stress distribution provide novel insights. The results indicate that pressure distribution and stress variations around the wellbore are significantly influenced by poroelastic, thermal, and chemical effects. The poroelastic effect increases pressure due to overbalanced drilling conditions, while thermal effects vary with fluid temperature, leading to notable pressure changes. Chemical effects are significant, with lower salinity mud increasing pore pressure and higher salinity decreasing it. Thermal effects primarily dominate stress distribution, altering radial, tangential, and axial stresses, with tangential stresses peaking in the direction of minimum horizontal stress. Collapse area predictions suggest that Mohr-Coulomb and Drucker-Prager criteria predict larger collapse areas compared to Mogi-Coulomb and Modified-Lade criteria, indicating a more conservative approach. Poroelastic effects slightly enlarge collapse areas due to increased pore pressure, while thermal effects reduce collapse areas with cooling and increase them with heating. Higher salinity mud improves formation stability by enhancing effective stress and reducing pore pressure. The results demonstrate that using higher salinity mud enhances formation stability and that careful management of temperature can mitigate stress variations and collapse risks. Regular monitoring and adjustments based on wellbore stability models are essential for optimizing performance and safety in drilling operations. The findings reveal that optimizing mud salinity and carefully managing temperature can effectively enhance formation stability, which offers practical guidelines for mitigating wellbore risks and optimizing drilling operations in challenging formations.

Thermal effect on wave propagation in double-walled carbon nanotubes embedded in a polymer matrix using nonlocal elasticity

In this work, the thermal buckling properties of carbon nanotube with small scale effect are studied. Based on the nonlocal continuum theory and the Timoshenko beam model, the governing equation is derived and the critical buckling temperature is presented. The influences of the scale coefficients, the ratio of the length to the diameter, the transverse shear deformation and rotary inertia are discussed. It can be observed that the small scale effects are significant and should be (...)

A size-dependent functionally graded Reddy plate model based on a modified couple stress theory

Wave propagation analysis can be employed in various fields, such as nondestructive testing and structural health monitoring, which makes it so interesting and attractive. In the present investigation, an analytical method based on an exponential function was used to solve the wave propagation problem in functionally graded (FG) beams with consideration for imperfection via refined higher-order shear deformation theory. The recently developed porosity-dependent homogenization model was used to analyze the influence of imperfection on the wave dispersion behavior of porous beams. Material properties of FG beams were assumed to change across the thickness. The conventional porosity model illustrates a linear relationship between the porosity coefficient and material properties. However, the influence of porosity is actually characterized by a nonlinear relationship. This statement rose from some experimental investigations. To examine the interchange between the porous beam and foundation, Winkler-Pasternak two-parameter models were used as the elastic foundation. Uniform temperature change is taken into account to study the thermal environment effect. The principle of Hamilton is implemented to derive equations of motion for imperfect FG beams. The obtained governing equations were analytically solved. The influence of the wave number, porosity coefficient, temperature change, gradient index, length-to-thickness ratio, Winkler and Pasternak coefficients on the wave propagation in porous FG beams was studied.

Wave propagation in bubbly two-phase, two-component flow was analyzed to assess the validity of some interfacial transfer laws for two-fluid models of two-phase flow. A dispersion relation was derived from the linearized conservation equations and the Rayleigh equation. The phase velocity and wave attenuation calculated from the dispersion relation, compared well with existing high- and low-frequency data. The virtual mass term was found to have a significant effect on wave dispersion in the bubbly flow regime. Thermal effects were found to be important in determining the resonance phenomenon and wave scattering was a major source of damping at frequencies higher than the resonance frequency.

This work presents a comprehensive analysis of electromagnetic wave propagation inside a two-dimensional photonic crystal in a spectral region in which the crystal behaves as an effective medium to which a negative effective index of refraction can be associated. It is obtained that the main plane wave component of the Bloch mode that propagates inside the photonic crystal has its wave vector k' out of the first Brillouin zone and it is parallel to the Poynting vector ( S' ? k'> 0 ), so light propagation in these composites is different from that reported for left-handed materials despite the fact that negative refraction can take place at the interface between air and both kinds of composites. However, wave coupling at the interfaces is well explained using the reduced wave vector ( k' ) in the first Brillouin zone, which is opposed to the energy flow, and agrees well with previous works dealing with negative refraction in photonic crystals.