Acta Mechanica Solida Sinica最新文献

The classical-quantum analogue offers a new platform for exploring extreme dynamic control of mechanical systems. In this work, the concept of the stimulated adiabatic passage of quantum states is extended to mechanical systems for achieving unidirectional energy transportation. The mechanical analog of stimulated adiabatic passage is realized in three mechanical resonators coupled with the time-varying stiffness, which are delicately modulated to mimic the selective population of quantum states. Based on the tight-binding approximation, an analytical model for the classical-quantum analogue of the adiabatic passage effect is established to realize the one-way energy transfer control. Numerical results demonstrate that the vibration energy acquired from an initially excited resonator can be transferred to the target one via an intermediate resonator, while flow in the reverse direction is prohibited due to energy localization in the intermediate resonator. The model holds application potentials in energy suppression and harvesting, and offers promising prospects for unidirectional wave and vibration control.

In this paper, a data-driven topology optimization (TO) method is proposed for the efficient design of three-dimensional heat transfer structures. The presented method is composed of four parts. Firstly, the three-dimensional heat transfer topology optimization (HTTO) dataset, composed of both design parameters and the corresponding HTTO configuration, is established by the solid isotropic material with penalization (SIMP) method. Secondly, a high-performance surrogate model, named ResUNet-assisted generative adversarial nets (ResUNet-GAN), is developed by combining ReUNet and generative and adversarial nets (GAN). Thirdly, the same-resolution (SR) ResUNet-GAN is deployed to design three-dimensional heat transfer configurations by feeding design parameters. Finally, the finite element mesh of the optimized configuration is refined by the cross-resolution (CR) ResUNet-GAN to obtain near-optimal three-dimensional heat transfer configurations. Compared with conventional TO methods, the proposed method has two outstanding advantages: (1) the developed surrogate model establishes the end-to-end mapping from the design parameters to the three-dimensional configuration without any need for optimization iterations and finite element analysis; (2) both the SR ResUNet-GAN and the CR ResUNet-GAN can be employed individually or in combination to achieve each function, according to the needs of heat transfer structures. The data-driven method provides an efficient design framework for three-dimensional practical engineering problems.

The bulge test is a widely utilized method for assessing the mechanical properties of thin films, including metals, polymers, and semiconductors. However, as film thickness diminishes to nanometer scales, boundary conditions dominated by weak van der Waals forces significantly impact mechanical responses. Instead of sample fracture, interfacial shear deformation and delamination become the primary deformation modes, thereby challenging the applicability of conventional bulge models. To accommodate the interfacial effect, a modified mechanical model based on the bulge test has been proposed. This review summarizes recent advancements in the bulge test to highlight the potential challenges and opportunities for future research.

The development and deployment of aluminum conductor have been significantly hampered by the contradiction of yield strength, uniform elongation, and electrical conductivity. Herein, we successfully fabricated a pure aluminum (Al) clad aluminum alloy (AA) rod with hierarchical compositions and microstructures. The proposed pure Al clad AA rod showcases an optimized combination of yield strength, uniform elongation, and electrical conductivity, i.e., easing the restriction on improving yield strength, uniform elongation, and electrical conductivity. Compared to existing experiments, uniform elongation improved fourfold, while yield strength increased by 13% and electrical conductivity improved by 2% in terms of the international annealed copper standard (IACS). Microstructural characterizations and theoretical analyses revealed that the optimal performance of the Al clad AA arose from low-density low-angle grain boundaries (LAGBs) in the outer Al and high-density LAGBs with nanoscale precipitations in the inner AA. Our findings offer a compelling strategy for fabricating high-performance aluminum conductors, thereby laying a solid technical foundation for their wide application in power delivery systems.

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The debate on the effect of roughness on adhesion is crucial and open yet in contact mechanics. However, exploring the adhesive contact mechanisms of three-dimensional randomly rough surfaces coupling with elastic–plastic behaviors seems blank. This work first provides a comprehensive finite element method for analyzing the adhesive contact of three-dimensional randomly Weibull rough surfaces based on the Derjaguin approximation and the Lennard–Jones potential. The results demonstrate that roughness kills adhesion due to the contribution of inhomogeneous attractions and even repulsions. The adhesion diminishes as the scale parameter increases, the shape parameter decreases, or the thermodynamic work of adhesion decreases. Furthermore, the relationship between the decrement of pull-off force and RMS roughness is quantitatively formulated by introducing a correction parameter as a preliminary attempt from the numerical view for the open debate.

Mechanical metamaterials are artificial materials that control their macroscopic properties using repetitive units rather than chemical constituents. Through rational design and spatial arrangement of the unit cells, mechanical metamaterials can realize a range of counterintuitive properties on a larger scale. In this work, a type of mechanical metamaterial unit cell is proposed, exhibiting both compression-twist coupling behavior and bistability that can be programmed. The design involves linking two cylindrical frames with topology-designed inclined beams. Under uniaxial loading, the structure undergoes a compression-twist deformation, along with buckling at two joints of the inclined beams. Through a rational design of the unit's geometric parameters, the structure can retain its deformed state once the applied displacement surpasses a specified threshold, showing a programmed bistable characteristic. We investigated the influence of the involved parameters on the mechanical response of the unit cells numerically, which agrees well with our experimental results. Since the inclined beams dominate the elastic deformation of unit cells, the two cylindrical frames are almost independent of the bistable response and can therefore be designed in any shape for various arrangements of unit cells in multi-dimensional space.

The silicon-graphite (Si–C) composite electrode is considered a promising candidate for next-generation commercial electrodes due to its high capacity. However, lithium-ion batteries with silicon electrodes often experience capacity fading and poor cyclic performance, primarily due to the mechanical degradation of the solid-electrolyte interphase (SEI). In this work, we present a homogenized constitutive model for Si–C composite electrodes under finite deformation, incorporating lithium-ion concentration-dependent properties. We perform a wrinkling analysis and systematically examine the influence of key parameters, such as modulus and thickness ratios, on the critical conditions for instability. Additionally, we investigate the ratcheting effect across varying silicon contents. Our findings reveal that maintaining the silicon content within an optimal range effectively reduces plastic accumulation during charge–discharge cycles. These insights provide crucial guidance for optimizing the design and fabrication of Si–C electrode systems, enhancing their durability and performance.

3D printing has emerged as an advanced manufacturing technique for carbon fiber reinforced composites and relevant structures that endure significant dynamic loads in engineering applications. The dynamic behavior of these materials, primarily influenced by the dynamic fiber pullout interface strength necessitates investigation into the rate-dependent fiber/matrix interfacial strength. This study modifies a Hopkinson tension bar to conduct dynamic pullout tests on a single fiber bundle, utilizing a low-impedance bar and an in-situ calibrated semiconductor strain gauge to capture weak stress signals. Stress equilibrium analyses are performed to validate the transient dynamic loading on single fiber bundle specimens. The results reveal that the fiber/matrix interfacial strength is rate-dependent, increasing with the loading rate, while remaining unaffected by the embedded length. Fracture microstructural analyses show minimal fiber pullout due to high interfacial stresses induced by longer embedded lengths. Lastly, suggestions are made for the efficient design of fiber pullout experiments.

The propagation of solitary waves in fiber-reinforced hyperelastic cylindrical shells holds tremendous potential for structural health monitoring. However, solitary waves under external forces are unstable, and may break then cause chaos in severe cases. In this paper, the stability of solitary waves and chaos suppression in fiber-reinforced compressible hyperelastic cylindrical shells are investigated, and sufficient conditions for chaos generation as well as chaos suppression in cylindrical shells are provided. Under the radial periodic load and structural damping, the traveling wave equation describing the single radial symmetric motion of the cylindrical shell is obtained by using the variational principle and traveling wave method. By employing the bifurcation theory of dynamical systems, the parameter space for the appearance of peak solitary waves, valley solitary waves, and periodic waves in an undisturbed system is determined. The sufficient conditions for chaos generation are derived by the Melnikov method. It is found that the disturbed system leads to chaotic motions in the form of period-doubling bifurcation. Furthermore, a second weak periodic disturbance is applied as the non-feedback control input to suppress chaos, and the initial phase difference serves as the control parameter. According to the Melnikov function, the sufficient conditions for the second excitation amplitude and initial phase difference to suppress chaos are determined. The chaotic motions can be successfully converted to some regular motions by weak periodic perturbations. The results of theoretical analyses are compared with numerical simulation, and they are in good agreement. This paper extends the research scope of nonlinear elastic dynamics, and provides a strategy for controlling chaotic responses of hyperelastic structures.

We study the axisymmetric frictionless indentation problem of a piezoelectric semiconductor (PSC) thin film perfectly bonded to a semi-infinite isotropic elastic substrate by a rigid and insulating spherical indenter. The Hankel integral transformation is first employed to derive the general solutions for the governing differential equations of the PSC film and elastic substrate. Then, using the boundary and interface conditions, the complicated indentation problem is reduced to numerically solve a Fredholm integral equation of the second kind. Numerical results are given to demonstrate the effects of semiconducting property, film thickness as well as Young’s modulus and Poisson’s ratio of the substrate on the indentation responses. The obtained findings will contribute to the establishment of indentation experiments for PSC film/substrate systems.