Archive of Applied Mechanics最新文献

Upgraded Tuned Liquid Column Dampers (UTLCD) constituted by a Tuned Liquid Column Damper (TLCD) integrated into an undamped Tuned Mass Damper (TMD) have recently been introduced. A UTLCD is more efficient and straightforward than a traditional TMD in many aspects. In this paper, Multiple Upgraded Tuned Liquid Column Dampers (MUTLCD) are developed to control the vibration of buildings during earthquake loadings. Based on six different MUTLCD configurations proposed, analytical models of the building with each MUTLCD configuration are established. The Balancing Composite Motion Optimization, a potential and novel optimization algorithm, is used to search for the optimal parameters of each MUTLCD configuration based on the El Centro earthquake data. After that, the vibration control effectiveness of each optimal MUTLCD configuration is evaluated, and the best MUTLCD configuration is found. However, different earthquakes are characterized by different properties. Thus, each optimal MUTLCD configuration is also tested for different earthquakes. In addition, the influence of changes in the head-loss coefficient of UTLCDs is investigated for all MUTLCD configurations in various earthquakes. The obtained results in the present work show that most MUTLCD configurations are better than the single UTLCD case. The MUTLCD configuration with two different UTLCDs located on the top floor of the building offers the highest stability and efficiency under various earthquakes as well as changes in the physical properties of the UTLCD. The optimization approach in this study effectively identifies the most suitable MUTLCD configuration for the main structure.

This study introduces a novel thermoelastic model to advance generalized thermoelastic theory by incorporating fractional derivatives and the two-parameter Mittag–Leffler kernel. Grounded in the phase-lag concept, the model uniquely integrates spatial and temporal nonlocal effects, enabling accurate representation of microscopic interactions in elastic structures. By employing the Goufo–Caputo two-parameter fractional operator in the heat conduction equation, it significantly enhances the depiction of memory effects, illustrating how past deformations and thermal conditions influence material behavior. Applied to an infinitely long, isotropic hollow cylinder, the model reveals how spatiotemporal nonlocality and fractional scaling impact thermomechanical properties under thermal variations and structural constraints. Numerical results show that fractional-order parameters minimally affect displacement but have a stronger influence on other physical properties, such as stress and strain. Similarly, nonlocal coefficients exhibit limited effects on temperature but significantly impact other critical physical quantities, offering valuable insights into thermal and structural responses.

The three phase lag (TPL) thermoelasticity theory has been employed in this work to investigate wave propagation in a nonlocal porous medium. The governing wave-type equations are transformed into a homogeneous algebraic system, leading to non-trivial solutions that reveal the dispersion relation linked to propagation speed. From this dispersion relation, three coupled longitudinal waves (P waves, T waves, and V waves) and one transverse wave (SV-wave) are identified. The propagation speed is then plotted graphically. The effects of nonlocality, the heat flux relaxation time parameter and porosity are examined. In addition, the propagation speeds for the TPL and DPL models are examined. The influence of three phase lag (TPL) is investigated and presented via graphical representations. The already existed results in the literature are obtained by neglecting the porosity (void) parameter in the isotropic solid.

The nonlinear dynamic behavior and primary resonance of star-shaped auxetic cylindrical shells for large deformations are considered. First, the extensional and bending stiffness matrices are introduced in a closed-form relation for the star-shaped auxetic pattern. For this end, Castigliano’s theorem as well as the homogenization technique are applied. According to the classical theory of thin shells, including von Karman’s nonlinear terms, the governing equations of a star-shaped auxetic cylindrical shell are extracted. The Runge–Kutta and multiple scale methods are employed to solve the nonlinear equations of motion of the auxetic cylindrical shell for the Navier-type boundary conditions. The accuracy and stability of solutions are examined by the finite element analysis. The effects of geometrical parameters of a star-shaped auxetic cylinder on its linear and nonlinear vibrations are investigated. The presented mathematical procedure for linear and nonlinear vibration behaviors of auxetic structures can be developed for other auxetic patterns, such as honeycomb, chiral and re-entrant ones.

Light-based 3D printing techniques have recently been used to construct soft materials like hydrogels into complex architectures. However, when these extremely soft materials are printed into fine structures with feature sizes as small as microscale or even nanoscale, the resulting structures may be distorted by surface tension, which comes into play when the surface energy exceeds the material’s bulk elastic energy. In order to elucidate the basic effects of surface tension on shape distortion, we here develop a finite-element modeling method to study the difference between the resulting shape and designed shape of a photo-cured micro-strut. This method relies on a continuum framework that efficiently considers the evolution of material properties and the action of surface tension during the photo-curing process. The modeling results show that the resulting shape of the micro-strut is highly correlated with the strength of the surface tension, which can sometimes hinder the undesired deformation caused by the volume shrinkage associated with photo-polymerization. This study can provide some basic understanding for the reduction of shape distortion in printing soft materials with microscale and nanoscale features, and facilitate the design of devices with better performance.

This paper investigates the thermoelastic dynamic response of a functionally graded piezoelectric rod, accounting for thermal conduction memory and size-dependent effects. Unlike conventional models, this one permits thermal waves to propagate at a finite speed, with the Moore–Gibson–Thompson equation being a key component. By incorporating two additional relaxation times into the thermal conduction equation and introducing Klein–Gordon-type nonlocal elastic theory in the constitutive equation, the model effectively captures small-scale interactions. Using this model, the one-dimensional thermo-mechanical response of a piezoelectric rod was analyzed. Analytical expressions for the transformed thermophysical fields were derived in the Laplace transform domain. Numerical inversion methods were then applied to obtain solutions in the physical domain, elucidating the effects of various physical parameters. These findings are applicable to the development of various pyro/piezoelectric devices, such as sensors and gyroscopes with piezoelectric components.

As an inertial element, the inerter has a large inertance-to-mass ratio and a small installation volume which makes it have important prospect in the suspensions of the heavy vehicles. Based on the dynamic vibration absorber (DVA) and inerter, the inerter-based active vibration–absorption suspension (IBAVAS) is proposed. The parameters of IBAVAS are configured with the multi-objective NSGA-II algorithm, and the control strategy selects the sky-groundhook algorithm. In the frequency domain, it is proved that the movement performance of IBAVAS is superior to those of traditional passive suspension (TPS) and sprung-DVA passive suspension (SDVAPS). In addition, the mode shapes and parameter sensitivity analysis of IBAVAS are investigated. The engineered configuration of IBAVAS (i.e., EIBAVAS) employs a fluid inerter to generate inertial force with the generation of the parasitic damping force. Configure parameters for EIBAVAS, and then it can be proved that the performance of EIBAVAS has not degraded significantly compared with IBAVAS and is not sensitive to the value range of the parasitic damping coefficient. In summary, EIBAVAS can widen the adjustment bandwidth of active suspension for road excitation frequency and is reasonable and easy to implement in engineering, thus providing a theoretical basis for the future experiment.

This study investigated the dynamic stress distribution of an elliptical inclusion embedded in a two-dimensional inhomogeneous medium under shear horizontal wave incidence. The inhomogeneity of the medium was characterized by a continuous density variation expressed as a polynomial function. The governing equation, developed based on this inhomogeneity, was solved analytically using the complex function method. By solving the governing equation, an incident wave at an arbitrary angle was constructed, and complete expressions for the displacement and stress fields in the inhomogeneous medium were obtained. The conformal mapping method was then applied to transform the elliptical inclusion into a unit circle, and the boundary conditions were formulated accordingly. Finally, the undetermined coefficients in the scattering and standing waves were obtained using the orthogonal Fourier series expansion method, and the dynamic stress concentration factor (DSCF) at the inclusion was calculated. Comprehensive dimensionless parameters were considered to analyze the dynamic stress distribution around the inclusion. The effect of various parameters on the DSCF was examined. Overall, this research provides theoretical references for wave propagation problems in solid mechanics and materials science.

The welding processes generate residual stress in structures. Finite element methods are widely used to determine residual stresses, but this method has some problems due to the movement of the welding nozzle. In this research, numerical solution based on element-free Galerkin (EFG) method is extended to predict the temperature distribution and residual stresses due to welding. Thermal and mechanical analysis based on thermal-elastoplastic method is done in two stages. To reach the final nodal distribution, the shape and size of the support domain, influence domain size, different weight function and distance between nodes were studied. To validate the results, laser thermometer and the hole-drilling strain-gauge method have been used for the results of temperature field and residual stress, respectively. A good agreement has been obtained between the results of numerical solution and experimental methods, which indicates the accuracy of the presented formulation and the effectiveness of the parameters investigation method. Accordingly, a new application for the thermo-elastoplastic equation based on the EFG method to prediction of the temperature distribution and determination of residual stresses has been presented.

In the context of combining analytical models with data driven, this paper aims to establish an appropriate computational process for constructing hybrid formulas to predict the transverse effective conductivity of uniaxial composites. Specifically, the paper predicts the geometric parameter r, which represents the size of a pattern shape in the generalized self-consistent approximation model and could characterize the complexity of the material structure. For the case of a random suspension of fibers, the parameter (r) can be represented by a ReLU function that allows variation from 1 to 0 as the structure transitions from sparse (central symmetry) to dense (hexagonal structure). For ordered structured configurations, database are constructed for two cases: square and hexagonal arrays. Then, a calculation strategy is proposed based on the genetic programming model to find the most suitable analytical formula for each structure. The resulting models show excellent agreement with both numerical and analytical results, even in cases where the volume fraction approaches the theoretical maximum of 99.9% and the conductivity of the inclusions tends toward infinity. The method is also validated with available experimental data in the most extreme case and further extended to the polydisperse scenario, producing stable and accurate results. The computational process thus holds great potential for extension to various models and different types of composite materials.