The pseudo-Stroh formulism can transform the governing equations of multi-field coupling materials such as quasicrystals into a linear eigensystem, enabling the exact solution of multilayered structures with simply-supported boundary conditions. This provides an important reference for various numerical and experimental methods of quasicrystal beams in engineering practice. In this paper, the free vibration and bending problems of one-dimensional (1D) hexagonal quasicrystal (QC) laminated beams with functional gradients are investigated using the pseudo-Stroh formula. A simply-supported QC laminated beam is modeled, and the transfer matrix method is used to derive the exact solutions for natural frequency of free vibration and bending deformation displacements of the beam under simply-supported boundary conditions. The obtained results are compared with the existing ones to verify the accuracy and precision of the presented model. Numerical examples are provided to show the effects of high span ratio, layer thickness ratio, and functional gradient coefficient on the natural frequency, bending deformation, and mode shape of simply-supported 1D QC laminated beams under two different stacking sequences. The results show that natural frequency increases with the increase of functional gradient coefficient. Phonon displacement decreases while phason displacement increases with the increase of functional gradient coefficient under the two stacking sequences. Functional gradient coefficient and stacking sequence minimally affect phonon displacement modes but significantly impact phason displacement modes. Moreover, they notably affect phason stresses compared to phonon stresses in QC laminated beams. Thus, the optimal natural frequency and deformation displacement of a QC beam can be achieved by adjusting geometric size, stacking sequence, and functional gradient coefficient of the layered beam. These findings can provide theoretical references for various numerical methods and experimental studies on QC beams.

This study focuses on the aerothermoelastic characteristics of composite laminated panels with fully simply-supported boundaries in supersonic airflow, implementing macro fiber composites (MFCs) for active flutter-boundary control. In modeling the equation of motion, the influence of in-plane thermal load on transverse bending deflection is considered, and the aerodynamic pressure in supersonic airflow is calculated on the basis of supersonic piston theory. Motion differential equations of the structural system are derived from classical laminated plate theory and Hamilton's principle with the assumed mode method, then transformed into state space equations. By solving the state matrix eigenvalues, natural frequencies of the structural system are obtained. Aerothermoelastic characteristics of the laminated panel are analyzed via the frequency domain method, assessing the effects of ply angle and geometric parameters of the laminated panel on critical flutter aerodynamic pressure and critical buckling temperature. The proportional feedback control method is used to design the controller, and flutter boundaries of the laminated panel are computed under different control gain coefficients. Results demonstrate that the laminated panel with a ply angle of [90°/-90°/90°] exhibits the lowest aerothermoelastic stability across various aspect ratios. For larger ply angles, an increase in aspect ratio enhances the aerothermoelastic stability of the laminated panel. Adjusting MFC ply angles effectively increases critical flutter aerodynamic pressure. Moreover, the proportional feedback control method can significantly enhance flutter boundaries, but the control gain coefficient requires to be adjusted to ensure stability and performance of the control system. A control gain coefficient that is too small results in weak control, while one that is too large can destabilize the structural system.

This study investigated the dynamic response of continuous-density-graded aluminum foam sandwich tubes subjected to internal explosion loads. A finite element model for continuous-density-graded aluminum foam and sandwich tubes was established in polar coordinates using 3D-Voronoi technology. The influences of core density distributions, such as positive-gradient, negative-gradient, and V-shaped gradient including middle-high-gradient (high in the middle and low at both ends) and middle-low-gradient (low in the middle and high at both ends), core density gradient, assembly methods of tube walls and the core, and the length-to-diameter ratio of explosives on the anti-shock performance of the sandwich tube structure were analyzed. Results demonstrate that, for the same core density gradient, the maximum deformation of the outer tube in the sandwich tube with a negative-gradient core is the least, while the sandwich tube with a middle-low-gradient core exhibits the highest specific energy absorption, and the sandwich tube with a middle-high-gradient core shows the weakest anti-shock performance. As core density gradient increases, the maximum deformation of the outer tube in the sandwich tube with a negative-gradient core significantly decreases. The specific energy absorption for the sandwich tube with a middle-low-gradient core rises initially before declining, while the anti-explosion performance of the sandwich tube with a middle-high-gradient core deteriorates. Optimal bonding between tube walls and the core effectively improves the specific energy absorption of sandwich tubes with a uniform, negative-gradient, or middle-low-gradient core, but it also increases the maximum deformation of the outer tube. For varying length-to-diameter ratios of explosives, the maximum deformation of the outer tube in the sandwich tube with a negative-gradient core is smaller. The present work aims to provide valuable insights for designing such structures for protective engineering applications.

The connection conditions and vibration suppression methods of coupled shell structures have received much attention, particularly as these structures play a crucial role in aero-engine components. In this paper, the vibration characteristics of a rotating hard coating damping double-thin-walled cylindrical shell coupled structure under bolt connection conditions are studied. First, a discontinuous arc connection is constructed to simulate actual bolt connection conditions by improving the artificial spring distribution method of the continuous entire circumference. And the artificial spring technique is used to define the boundary conditions of the shell structure. Next, the strain energy of the hard-coating shell structure is determined based on Sander's shell theory. The effect of rotational speed is considered, and the Rayleigh-Ritz method is used to derive the dynamic equations of the shell structure. In addition, the efficient state space method is used for calculation. The rationality and accuracy of the theoretical methods are validated through literature comparisons and finite element analysis. Additionally, the effects of rotational speed, connection stiffness, hard-coating thickness, and boundary conditions on the traveling wave vibration characteristics of the shell structure are analyzed. The results show that the traveling wave frequency increases significantly when the connection stiffness is in the range of 10⁸～10¹⁰. Besides, the rotation leads to a separation phenomenon and an overall increasing trend in the traveling wave frequency. A greater hard coating thickness notably impacts the traveling wave frequency, exhibiting a maximum increase of 5.87% in the traveling wave frequency when the hard-coating thickness rises from 0 to 0.85 mm. These findings provide valuable theoretical insights and data support for the engineering design of hard-coating coupled double-thin-walled cylindrical shell structures.

The impact of environmental corrosion on rail service operations poses a direct safety threat. Therefore, the quantitative characterization of rail corrosion damage is of great significance for evaluating rail reliability. Uniform corrosion experiments on U71Mn hot-rolled rail samples in a 3.5 wt. % NaCl solution at room temperature were first carried out. Changes in the diameters of two samples with corrosion time were measured. According to the experimental results, the corrosion mechanism of rail samples in the 3.5 wt. % Nacl solution was analyzed. A corrosion model employing cellular automata was developed to simulate the uniform corrosion behavior of rail samples in the NaCl solution. The corrosion rate was quantified by tracking sample diameter changes through the cellular automaton simulation over varying corrosion time. A unified prediction formula for different sample diameters with corrosion time was established. Results revealed an average relative error of 8.7% between predicted and measured data, indicating the efficacy of cellular automata in accurately simulating the uniform corrosion process of U71Mn hot-rolled rail samples.

Microscale contact and friction behavior are widely present in various important industrial devices and systems. As electromechanical systems become more integrated and miniaturized, the impact of friction on devices becomes increasingly important. At the microscale, friction behavior exhibits a strong dependence on interfacial viscosity and contact size. By developing a series of modifiable potential functions to quantitatively regulate interfacial properties, friction on atomically smooth interfaces with different properties is fully simulated using molecular dynamics methods. The study first examined the influence of various interfacial potential energies on the static friction coefficient, revealing a nonlinear relationship between the static friction coefficient and interfacial potential energy intensity. Furthermore, it was found that this nonlinearity is attributed to the competition between interfacial viscosity and contact stiffness. Additionally, the study investigated the influence of contact size on static friction coefficient. The simulation results showed that as the tangential contact length of the interface increases, the peak static friction force first increases and then stabilizes. By analyzing the contact layer cloud maps obtained through post-processing, interfacial friction is observed as a “nucleation-propagation” process, influenced by different contact sizes which affect the dynamic process and lead to changes in the peak static friction force. This study provides new insights into the effects of interfacial potential energy and contact size on microscale friction through molecular dynamics simulations, it is feasible to regulate friction by changing interfacial potential energy, but attention should be paid to the nonlinear changes in the friction coefficient. Besides, solely increasing the contact size cannot infinitely increase the peak static friction force.

Lithium metal is a highly promising anode material due to its high theoretical capacity and low reduction/oxidation potential, and has received extensive attention. However, the formation and growth of lithium dendrites poses the biggest challenge to its commercialization. The use of solid-state electrolyte, instead of liquid electrolyte, has become a potential path to inhibit the growth of lithium dendrites. However, issues such as poor metal-lithium interface contact and low ionic conductivity in solid-state electrolytes persist. Composite solid-state electrolytes, prepared by combining polymers with inorganic ceramic electrolytes, have shown effectiveness in inhibiting the growth of lithium dendrites. Although these composite solid electrolytes typically have high ionic conductivity, their elastic moduli are low. Currently, the mechanism of dendrite suppression by low-modulus composite solid-state electrolytes, especially low-modulus multiphase composite solid-state electrolytes, remains incompletely clarified. Therefore, this paper considers the mechanical effects of solid electrolytes and builds a mechanical-chemical model using the phase field method. By taking poly (ethylene oxide) (PEO)-based composite-state electrolyte as an example, the study investigates the influence of composite solid electrolyte modulus on dendrite growth. The results show that the higher the electrolyte modulus, the greater the stress on the lithium metal, leading to a more uniform distribution of lithium ions on the interface between the electrolyte and the lithium anode electrode. The higher stress also tends to cause the plastic deformation of lithium dendrites, thus inhibiting their growth. This research deepens the understanding of the mechanism of inhibition of lithium dendrites by low-modulus multiphase composite solid electrolytes, and provides guidance for the design of composite solid electrolytes.

To gain a deeper understanding of the constraint effect from double crack tips and accurately characterize it, this study focuses on non-collinear parallel double cracks in a homogeneous plate. It examines the stress and strain fields associated with these double cracks, employing the ABAQUS finite element analysis software. Particular attention is paid to their behaviors at various horizontal distances (s) and vertical distances (h). Additionally, by leveraging the unified constraint parameter A_p, the constraints of double crack tips are compared with those of coalesced single crack tips. The findings reveal significant differences in the distributions and magnitudes of stress and strain at double crack tips compared to coalesced single crack counterparts. The conventional method of calculating the constraints from double cracks based on the stress or strain field at a crack tip, as done for single cracks, would lead to inaccurate results. Comparison of A_total, A_inside, and A_outside with A_single shows that considering both inside and outside crack tip strain fields aligns the variation trend of A_total more closely with A_single, with a remarkably narrow fluctuation. The constraint magnitude for coalesced single cracks ranges from 0.10 to 0.30 of the total strain field (A_total). This approach demonstrates a degree of universality, unaffected by whether the double cracks coalesce or not. It can be directly applied to quantify the constraints imposed by double cracks, regardless of their coalescing status. This study offers valuable insights into the constraint effect of double crack tips and presents a novel method for characterizing the constraints associated with double cracks. In summary, this novel approach offers a more comprehensive and accurate understanding of the complex constraints from double cracks, providing scientific support for evaluating structural integrity with double and multiple cracks.

The material properties of quasicrystals are significantly affected by defects due to high brittleness. Understanding the fracture behavior of quasicrystals is crucial for material applications. In this paper, the fracture mechanics of one-dimensional hexagonal quasicrystals with periodic Type-III multiple cracks emanating from a nanoscale hole is investigated theoretically. Based on complex elasticity theory and the Gurtin-Murdoch surface elasticity theory, stress fields of a nano-hole with periodic multiple cracks, considering surface effects, are obtained using boundary value problems of analytic function theory and the conformal transformation technique. Analytical expressions for stress intensity factors and energy release rates of the phonon field and phase field at the crack tip under the same conditions are further derived. The effects of aperture size, number of periodic cracks, crack-length/aperture ratio, coupling coefficient between phonon field and phase field, and applied loads on dimensionless stress intensity factors and dimensionless energy release rate are discussed. Results indicate that the coupling coefficient, applied loads, and aperture size do not affect dimensionless stress intensity factors without surface effects. Larger aperture sizes show stronger size dependence on dimensionless stress intensity factors and dimensionless energy release rate when considering surface effects. An obvious coupling effect between the phonon field and the phase field is observed. The influence of the number of periodic cracks on dimensionless stress intensity factors and energy release rate is restricted by defect size. The effects of phonon field loads and phase field loads on dimensionless stress intensity factors and energy release rate differ. This work reveals the specific influence of surface effects on the fracture behavior of multi-cracks at the hole edge, offering significant academic insights into quasicrystal fracture mechanics.

Compared to conventional mechanical testing methods, the indentation method offers the advantages of simple manufacturing of samples and in-situ testing. This study proposes an alternative to deriving material mechanical parameters solely from indentation load-depth curves. It introduces an effective method for deducing metal plastic mechanical parameters based on residual indentation morphology and neural network learning. An Instron universal material testing machine was used to conduct spherical indentation tests on Cu, Mg, and Fe, followed by scanning their residual indentation morphology through the contour morphology system. The extracted morphology features served as the basis for further analysis. Data processing techniques such as amplification, rounding, binarization, and high-order digit supplementation were applied to the acquired data. Through Abaqus software and numerical simulations, residual indentation depth data associated with various material parameters were automatically extracted for neural network learning. Selections of activation function, neural network parameter initialization and updating mode, loss function, parameter optimization strategy, and neural network structure were carefully conducted to ensure effective learning. The plastic mechanical parameters of Cu, Mg, and Fe were obtained based on the residual indentation morphology feature data from indentation tests and the neural networks after learning. Additionally, the related plastic mechanical parameters of Cu, Mg, and Fe were also acquired through conventional uniaxial tensile tests and characterization using the Instron machine. By comparing the neural network learning results with tensile test data, relative errors in plastic mechanical parameters were identified. The effectiveness of the proposed method in obtaining metal plastic mechanical parameters based on neural network learning and residual indentation morphology was validated. This method can be expanded for characterizing mechanical properties and acquiring plastic parameters of other metal/alloy materials.