To concurrently achieve low-frequency vibration absorption and high-frequency vibration isolation in high-static-stiffness applications, this study proposes a hybrid passive vibration isolator that integrates a lever mechanism with a Halbach array negative stiffness mechanism. The lever mechanism reduces the natural frequency by increasing the system’s effective mass and introduces an anti-resonance frequency. Additionally, the negative stiffness amplified by the lever counteracts the positive stiffness, leading to the substantial reduction in the dynamic stiffness with only a small amount of negative stiffness required. Both theoretical and experimental results indicate that the synergistic integration facilitates the broad isolation bandwidth and effective low-frequency absorption while keeping the added mass minimal and the negative stiffness low. The comparative analysis of several magnetic array configurations demonstrates that, when the isolator dimensions and added mass are held constant, the Halbach array configuration reduces both resonance and anti-resonance frequencies while preserving high-frequency transmissibility. The integrated strategy enables the development of a compact and lightweight isolator, providing an effective solution for low-frequency vibration suppression in scenarios where mass and space are limited.

The mixed elastohydrodynamic lubrication (EHL) behavior of a smooth, rigid, insulating cylindrical indenter in contact with transversely isotropic piezoelectric half-planes possessing Gaussian-distributed surface roughness is analyzed. Three distinct surface topographies are considered: longitudinally oriented, isotropic, and transversely oriented. The lubricant is assumed to exhibit non-Newtonian flow characteristics, and its density and viscosity are modeled to be pressure-dependent. A modified Reynolds equation, incorporating both pressure and shear flow factors, is utilized to compute the hydrodynamic pressure distribution within the lubricating film. An iterative computational scheme is developed for the coupled resolution of the modified Reynolds equation, flow rheology equations, asperity contact pressure equation, load balance equation, and film thickness equation. Parametric investigations are conducted to examine the influence of the total normal load, entrainment velocity, hydrodynamic roughness parameter, slide-to-roll ratio, contact roughness parameter, and surface pattern parameter on the film thickness, asperity contact pressure, and fluid hydrodynamic pressure. The results obtained may provide valuable insights for mitigating surface degradation at piezoelectric contact interfaces and enhancing the operational reliability of associated electromechanical systems.

Bioinspired micropillar-arrayed surfaces have been widely adopted across diverse applications because they enable tunable adhesion enhancement. Although prior studies have examined their load-sharing efficiency and adhesion enhancement, the rate-dependent effects remain largely unexplored. Here, we investigate the rate dependence of the load-sharing efficiency and adhesion enhancement by extending an elastic array model to the viscoelastic case through the Lee-Radok correspondence principle. Our results show a pronounced drop in the load-sharing efficiency at intermediate loading rates, which can be attributed to a reduced effective stiffness ratio between the backing layer and the micropillars, leading to a larger count of deformation accommodated by the backing layer. The extent of the intermediate-rate reduction scales positively with the array size, and decreases with the increasing pillar spacing and pillar length. In terms of adhesion performance, the array designs that enhance adhesion relative to a smooth interface in the static limit do not necessarily retain this advantage once the rate effects are considered. This degradation is particularly pronounced for the dense arrays of slender micropillars, for which the maximum pull-off force ratio relative to a smooth surface can drop much more markedly than in the quasi-static case, thereby necessitating careful evaluation. The findings provide guidance for the design and reliability assessment of bioinspired micropillar interfaces under rate-dependent loading conditions.

Pre-strain and pre-stress in soft materials have significant effects on their adhesive behavior, thereby influencing their functions and applications. Whereas prior theoretical studies on the adhesion of pre-strained elastomers predominantly rely on fracture mechanics frameworks based on the assumption of short-range forces, this study models surface interactions using the Lennard-Jones potential, thereby elucidating more intricate details of the adhesive behavior. The results of the proposed model are initially validated through finite element simulations and the analytical models in the literature. Subsequently, the effects of substrate pre-stretch on the adhesive behavior, including the pull-off force, JKR-Bradley transition, jump-in and jump-out instabilities, surface profile, and pressure distribution, are revealed by the proposed model. Based on the ‘semi-rigid’ theory (SRT), an analytical solution is derived to predict the displacement and central gap at the jump-in point. A modified Tabor parameter that incorporates the substrate pre-stretch effect is also proposed. The JKR-Bradley transition characterized by this modified parameter coincides with the unstretched case. This study offers new insights into understanding the adhesive behavior of pre-stretched elastomers.

The semi-active vibration isolator (SAVI) has the characteristics of dynamic adjustable stiffness and damping, which can achieve high-efficient broadband vibration isolation. However, the issue of the energy supply constraints on its application in engineering. A novel self-powered semi-active vibration isolator (SPSAVI) with adjustable stiffness is proposed to achieve vibration reduction and energy harvesting. The piezoelectric materials are adhered onto the buckling beam structure to gather the electrical energy generated by vibration, which can supply the energy demand of the piezoelectric actuator for achieving the self-supply capability. An electromechanical coupling dynamic model of the SPSAVI is established under Newton’s second law. The vibration reduction and self-powered effect of the SPSAVI are analyzed by the harmonic balance method. The results indicate that the SPSAVI can effectively improve the vibration isolation performance and achieve the self-powered effect. When the external excitation is 0.65g in which g is the gravity acceleration, the SPSAVI can achieve a stable self-powered effect.

The strength and damage tolerance of additively manufactured (AM) alloys are significantly influenced by their heterogeneous microstructures. However, establishing quantitative relationships between these microstructural characteristics and the resulting mechanical properties remains a challenge. Here, a microstructure-based mechanical model is established based on the heterogeneous grain distribution within the melt pool, with particular emphasis on the strain gradient effect arising from the deformation incompatibility between distinct grain regions. The strengthening mechanisms and local deformation response of AM alloys are elucidated with the finite element method (FEM). The strain gradient effect generated by the deformation incompatibility between the columnar and equiaxed grain regions enhances the local stress near the equiaxed-columnar interface, which is an important reason for the overall work hardening. Concurrently, the local stress concentration makes it easier to reach the critical stress for microcrack nucleation at the interface, leading to failure and a lack of synergy between the strength and damage tolerance. The prediction of the crack initiation location based on the simulation results is consistent with the previous experiments. By further quantitatively predicting the comprehensive effects of melt pool size on strength, strain hardening, and damage rate, small-melt-pool structures produce high strength, but microcracks originate early, whereas large-melt-pool structures have weak strengthening effects but fast damage evolution in the later stages of deformation. This study provides a pathway to predict the optimal melt pool size for achieving superior combinations of strength and damage tolerance in AM alloys.

Light-driven self-excited soft swimming systems based on liquid crystal elastomers (LCEs) offer a promising route toward autonomous motion. However, existing designs commonly rely on non-equilibrium oscillatory actuation and large-area or spatially distributed illumination. Here, we present a light-powered self-propelling boat actuated by a self-rotating LCE rod that operates around a steady-state equilibrium under static parallel illumination. While swimming, parallel light continuously irradiates the rod without the need for large-area coverage or moving illumination. A coupled theoretical model incorporating heat conduction and photomechanical response is developed to elucidate the self-propulsion mechanism. Analytical expressions for the light-induced lateral curvature and driving moment are derived to characterize the self-rotating dynamics. Numerical simulations reveal how the rod radius, light intensity, and support span influence the self-rotation angular velocity and self-propulsion speed. Experiments validate the theoretical predictions and demonstrate autonomous self-propulsion under static parallel illumination without moving light fields. The proposed system establishes a new physical mechanism for light-driven locomotion and provides design principles for scalable, untethered soft swimming robots, light-powered microtransport platforms, and adaptive micromotors.

The bending behavior of microbeams in micro-nano devices exhibits significant size effects, making accurate prediction of their mechanical behaviors crucial for device reliability. This paper employs the modified couple stress theory (MCST) and derives the governing equations for the Reddy beam theory (RBT) via the principle of virtual work. By considering the load equivalence, the analytical solutions for the bending problem are derived and expressed as the functional relations based on the Euler-Bernoulli beam model. Once the Euler-Bernoulli beam solution is obtained, the exact solution for the corresponding Reddy beam can be directly determined through these functional relations and boundary conditions. Analytical solutions for the doubly simply-supported (S-S), clamped-free (C-F), and clamped-clamped (C-C) boundary conditions are derived and validated through comparison with the results of previous studies. This study clarifies the analytical relationship between the two beam theories at the micro-scale, enabling exact mechanical solutions for higher-order shear deformation beams without solving complex higher-order governing equations.

Lightweight sandwich annular plates with honeycomb cores (HCCs) and carbon-nanotube-reinforced face sheets have been widely used in aerospace and energy structures where the high stiffness-to-weight ratio and the buckling reliability are required. In this paper, an integrated thermo-mechanical buckling model is presented for such plates resting on a radially graded modified Winkler-Pasternak (MWP) elastic foundation. The interlaminar shear deformation and the layerwise displacement continuity are accurately represented with the refined zigzag theory (RZT), while the carbon nanotube (CNT) agglomeration effects are considered with the Mori-Tanaka homogenization scheme. The governing equations are solved with the generalized differential quadrature method (GDQM). The results indicate that the CNT dispersion quality is more decisive than the CNT volume fraction, and the severe agglomeration reduces the critical buckling load by approximate 50%. A proper honeycomb design, particularly with a cell angle of approximate 30°, a wall thickness ratio within the range of 0.1 to 0.15, and a compact cell configuration, markedly enhances the structural stability. The radially graded foundation stiffness interaction increases the buckling capacity by 6%–15%, whereas temperatures of 300 K–400 K slightly reduce the capacity.

Shortly after the middle of the past century, a comprehensive presentation of continuum mechanics was written under the supervision of Clifford Ambrose Truesdell III in two volumes of Siegfried Flügge’s Handbuch der Physik; a first volume in 1960 with Richard Toupin on The Classical Field Theories (the monster), including an Appendix on Tensor Analysis by Jerald LaVerne Ericksen, and a second volume in 1965 with Walter Noll on The Non-Linear Field Theories of Mechanics (the monsterino). Both nicknames were due to Truesdell. These contributions were gradually taken as turning points by the mechanics community worldwide, due to the completeness of the analysis and the profoundness of the documentation. However, the vastness of the treatment acted as a shield against careful reasoning on delicate but basic notions. In the wake of some 19th-century scholars, these notions were taken to be worthy of belief and incorporated into the presentation with a valuable historical background. A lack of engineering perspective discouraged the necessary caution when addressing a number of issues. Scholars in continuum mechanics, fascinated by the monumental work conceived and carried out by Truesdell and his associates, did not dare to make any accurate revisions. The analysis is here centered on unsatisfactory formulations that are presently disseminated in the literature by followers of Truesdell’s magnum opus. The geometric approach in four-dimensional (4D) Euclidean spacetime adopted here is self-contained even in the classical context, providing clarity of notions, methods, and results unachievable via the more familiar but less powerful and error-prone three-dimensional (3D) treatment.

Orbital dynamics is a fundamental problem in celestial mechanics, yet its governing equations are characterized by irrational terms and denominator-type nonlinearities. Traditional numerical methods, which are locally discrete, may lead to ambiguities near singularities (e.g., x=y=z=0), thereby limiting the numerical stability and accuracy. To address these challenges, we propose a Lie derivative algorithm that constructs discrete iterative schemes based on the Lie series expansion. Unlike local schemes, this approach discretizes the vector field in a global manner, effectively avoiding singular inconsistencies while ensuring stable long-term integration. Numerical experiments demonstrate that, when compared with a high-accuracy reference solution under uniform step-size settings, the proposed approach not only achieves higher accuracy but also improves computational efficiency by up to 47% in the two-body problem and 67% in the circular restricted three-body problem, relative to classical second-order schemes. These results indicate that the Lie derivative algorithm provides an efficient and practical alternative for high-precision orbital dynamics computations.

The high-order targeted essentially non-oscillatory (TENO) scheme, known for its innovative weighting strategy, has demonstrated strong potential for complex flow predictions and applications. This study extends the TENO weighting approach to develop a family of central TENO (CTENO) schemes for unstructured meshes. The CTENO schemes employ compact directional stencils, which increase the likelihood of finding all stencils within smooth regions. The design is intentionally compact to simplify the implementation of directional stencils. An effective scale-separation strategy is adopted via an essentially non-oscillatory (ENO)-like stencil selection method, which employs large central stencils in smooth areas to achieve high-order accuracy, and employs smaller directional stencils near discontinuities to improve shock-capturing capability. Extensive tests involving central weighted essentially non-oscillatory (CWENO), TENO, and CTENO family schemes are conducted to assess their performance in terms of accuracy, parallel scalability, and computational efficiency. The applications to shock-driven flows indicate that the proposed schemes deliver high-order accuracy, lower numerical dissipation, and excellent shock-capturing performance in several practical flow cases such as shock reflection, bubble dynamics, explosion, and particle flow problems.