Acta Mechanica最新文献

The present study offers a groundbreaking analysis of photo-thermal transport phenomena in semiconductor materials subjected to a mobile heat source. Addressing key limitations of traditional heat transfer theories, this research adopts the Atangana–Baleanu fractional derivative model, which is characterized by a non-singular kernel function. This modern mathematical framework enables a more realistic and accurate depiction of thermal behaviors by capturing the memory-dependent and non-local effects often neglected in classical models.

Using the Laplace transform technique combined with the eigenvalue approach, the study derives closed-form analytical solutions in the frequency domain. These solutions provide deep insights into the dynamic behavior of several field variables—namely temperature distribution, mechanical displacement, carrier density, and induced thermal stresses. Graphical simulations explore how these quantities evolve under varying parameters such as semiconductor depth, fractional-order values, photo-generated carrier lifetime, and the velocity and intensity of the heat source. One of the most significant outcomes of this investigation is the clear demonstration of the finite speed propagation of thermal waves, a feature that conventional hyperbolic thermoelastic models fail to accurately capture. By incorporating fractional calculus, the study reveals the nuanced and time-dependent nature of thermal interactions in semiconductor media. This distinction underlines the effectiveness of the Atangana–Baleanu model in portraying complex thermophysical phenomena.

Guided wave tomography (GWT) methods for precise multi-defect reconstruction are crucial for structural health monitoring. In this work, an improved physics-informed wave tomography framework (PIWT) is proposed for the quantitative reconstruction of multiple defects in plates. A trunk-branch network is employed to reconstruct the wave travel time and velocity field by synergizing the waveguide governing equations and the real travel time data from sensors. This approach speeds up the network convergence of loss function which includes the travel time data, its first-order derivatives, and the physical principle of wave equations to constrain the space of parameters for accurate defect reconstruction. Based on simulation data, the results demonstrate that PIWT achieves the highly accurate defect with the errors of 4.25% in position and 5.5% in depth. Also, experimental validations are conducted to demonstrate the feasibility of PIWT with a defect position error of less than 1.7% and depth location error under 15%. Furthermore, uniform manifold approximation and projection is applied to enable a clear visualization of trajectories representing the defect reconstruction convergence, thereby revealing how incremental sensor data enhance the model’s capability to approximate the true solution. This interpretation provides useful insights into the latent dynamics to bridge the gap between the black-box nature of deep neural networks and the need for transparent and explainable AI, ultimately reinforcing confidence in the model's applicability for broader engineering applications.

This paper investigates the well-posedness and asymptotic behavior of a suspension bridge system, modeling the deck using Timoshenko–Ehrenfest beam theory with fractional damping. Using semigroup theory, we establish existence and uniqueness via the Lumer–Phillips Theorem, showing that the system’s operator generates a contraction (C_0)-semigroup. Spectral analysis proves strong stability, while the Gearhart Theorem rules out uniform stability. Finally, polynomial decay is obtained via the Borichev–Tomilov and Batty–Chill–Tomilov Theorems.

This work advances the modeling of bioheat transfer in biological tissue by integrating the Atangana–Baleanu fractional derivatives into the bioheat equation, offering a more realistic representation of thermal damage by incorporating memory effects and non-local heat conduction. The fractional derivative (FD) is an effective approach for modeling transient thermal responses in biological tissues. This study introduces FD into the classical Pennes bioheat conduction formulation with one thermal relaxation time, formulating a corresponding bioheat transfer model based on the thermal energy conservation law. The fractional-order formulation employs non-singular and local kernels to account for the Atangana–Baleanu (AB) derivative. The Laplace transforms and numerical inverse transforms approach are employed to analyze thermal responses under pulsed heat flux conditions. The derived models are reduced to the classical Pennes and non-Fourier models, allowing for a comparative analysis of FD in transient bioheat transfer. A numerical investigation explores the impacts of the fractional derivatives, thermal relaxation and heat flux pulse times on temperature variation and distributions.

This analytical paper investigates multi-field stress, strain and deformation analyses of a graphene origami nanocomposite-reinforced plate subjected to mechanical and thermal loads using an improved higher-order and stretchable kinematic modeling. The plate structure is assumed composed of a copper matrix that is reinforced with graphene origami as a three-dimensional reinforcement. The graphene origami is prepared using hydrogenation of the graphene sheets that leads to foldability. The overall plate’s characteristics are experimentally obtained using the micromechanical models. The virtual work principle is employed to derive governing equations. The analytical solution is developed to trace impact of thermal loads, origami content and foldability on the bending results. The main novelties of this paper are investigating the folding parameter and reinforcement content on the various deflection parameters and stress distribution.

In this study, the vibro-acoustic response and sound transmission of functionally graded (FG) graphene origami (GOri)-enabled auxetic metamaterial (GOEAM) plates are investigated in the thermal environment. Three kinds of distribution patterns of GOri are considered. The governing equations of the FG-GOEAM plates are derived using Hamilton’s principle and the high-order shear deformation theory. Subsequently, the sound power level (SPL) under concentrated harmonic surface force exciation and the sound transmission loss (STL) under harmonic sound wave incidence are determined. Finally, the effect of weight fraction of GOri, H atom coverage, temperature, and layer number of the FG-GOEAM plates on SPL and STL are analyzed and discussed. This study contributes to the design and manufacturing of FG-GOEAM structures.

For the first time, the issue of the consequences of an earthquake on the state of the fractured environment of mountainous regions is investigated using a rigorous mechanical and mathematical approach. It is known that Earthquakes in mountainous areas are characterized by the repetition of high-magnitude aftershocks compared to the cases of lowland earthquakes. For this purpose, in order to approach reality, for the first time, a dynamic mixed problem on the unsteady impact on the shores of the semi-infinite Griffiths crack, as one of the objects of the mountain environment, is considered. It is assumed that the crack is located in a half-space parallel to its boundary. It is assumed that the fractured rock environment is an anisotropic composite and is described by the corresponding equations. The mechanical effects on the crack banks are described by a function that continuously depends on the time parameter and the geometric parameters of the coordinate system, which makes it possible to take into account the real non-stationary effect on the crack caused by an earthquake. It is assumed that the impact is carried out over a semi-infinite time interval, starting from zero initial conditions. The problem under consideration is related not only to the problem of seismic processes occurring in the Earth's crust of complex structure, including mountainous territories, but also to the engineering practice of composite materials of anisotropic structure. The case of a three-dimensional problem in which geometric and temporal parameters are equally included is studied. The mixed problem is reduced to the two-dimensional Wiener–Hopf integral equation, for which the authors have recently developed a rigorous mathematical method. The obtained solution, depending on the geometric and temporal parameters, made it possible to identify a previously undescribed surge effect at the initial moment of the stress intensity coefficient at the crack tip. It is established that the time-dependent stress intensity coefficient at the crack tip as a result of unsteady action can grow indefinitely at the initial moment, destroying the crack. The result explains the appearance of aftershocks after the main earthquake, as a result of its impact on existing cracks in the environment. Such a phenomenon in seismology as a swarm of earthquakes, consisting in the occurrence of more than ten small earthquakes within one hour, is also explained by the result obtained in the article.

Instability analysis is very important for the service safety of functionally graded materials (FGM) sandwich structures. However, there is a great difficulty in identifying the critical points by the existing numerical or analytical methods due to the multiple solutions of nonlinear responses of structures in complex loading conditions. This paper aims to present an analytical method for instability response of FGM sandwich beams in thermo-mechanical loads without a priori assumption of response mode and instability type. Firstly, an analytical method of Emam and Nayfeh is extended to obtain approximate analytic solutions for bending, buckling and snap-through responses of FGM sandwich beams under the framework of strictly satisfying the governing equations and boundary conditions. Secondly, the influence of carbon nanotube (CNT) material component and distribution on the instability condition, type of sandwich beams with functionally graded-CNT reinforced (FG-CNTRC) panels are thoroughly discussed by the bifurcation diagram. In addition, the post-buckling paths of FGM sandwich beams are analytically searched out by the free energy evaluation. The results indicate that the symmetry is broken by the introduction of transverse mechanical load, and this variation makes thermal buckling behavior shift easily from rare bifurcation instability to widespread snap-through instability. By carefully controlling the loading and material parameters, the energy consumption of the deformation jumps can be adjusted, thereby enhancing the resistance to snap-through instability.

Flow structures have been experimentally obtained for the circular cylinders with porous media coatings (PMC) at Reynolds number values from Re = 5000 to Re = 10,000. Furthermore, flow characteristics have been exhibited for different contour graphics and the velocity profiles have been indicated at four downstream stations. The regions having minimum streamwise velocity component values approached the circular cylinders by increasing Reynolds numbers. Nevertheless, it is not valid for the cases of PMC1 and PMC2 from Re = 7500 to Re = 10,000. Because of the separated flows from the upper and lower cylinder surfaces, the maximum streamwise velocity components have been attained. The same effect has been observed for the cross-stream velocity component values, and these clusters approached the circular cylinders. As expected, the flow separations caused wake fluctuations. Nonetheless, the cluster sizes have also been decreased by the decrement of Reynolds numbers. It is significant for the occurrence of turbulence intensity in the wake regions of the circular cylinders. However, there is no obvious difference between the bare cylinder and the PMC3 in terms of flow patterns. Another important result is that the coating effect is explicitly exhibited by the increase in Reynolds numbers. As explained by the velocity values, these zones moved away from the bodies due to the decrement of Reynolds numbers. As a parameter, Reynolds number is considerably dominant on the cluster positions. Similar patterns have been approximately observed for PMC1, PMC2 and PMC4 in terms of Reynolds stress correlations.

This study introduces a simulated method for detecting matrix cracking and assessing its density in cross-ply laminated composites by using guided Lamb wave propagation and surface-mounted fiber Bragg grating (FBG) sensors. A cross-ply laminated composite with a [0₂/90₆]_s lay-up under antisymmetric guided Lamb wave propagation was simulated using the finite element method. The Lamb wave-induced strain field was obtained along a specified path in the FE models of both intact and damaged composites with matrix cracks. This strain field served as input for the models developed in the FBG-SiMul software, where the time response diagrams of the reflected spectrum from surface-mounted FBG sensors were analyzed. The spectrum parameters, including the oscillation amplitude of the wavelength shift, the mean peak width variation, and the oscillation amplitude of the peak width variation, increased by up to 1000% at an excitation frequency of 200 kHz in the damaged specimen compared to the intact one. The proposed simulated method, combining Lamb wave propagation and FBG sensors, effectively detects matrix cracking damage and assesses its density in laminated composites.