The vibration attenuation mechanisms in multi-layered metastructures, particularly the contribution from the layered architecture versus local resonance, remain a subject of debate, hindering the optimisation of the design process. This study combines experimental and theoretical analyses to systematically investigate the vibration attenuation performance of these RAMs. Four RAMs with different layer counts were designed and fabricated, simplified models predicted resonance frequencies, and systematic frequency-sweeping tests quantified acceleration responses. Additionally, supplementary simulations using steel rope springs as rubber alternatives were conducted, and an orthogonal experiment via the control variable method optimised material usage. The results confirm that rubber-based RAMs exhibit exceptional vibration attenuation capabilities. The layer count directly regulates resonant frequencies, while the number of resonators determines the number of attenuation bands. Quantitative analysis shows a positive correlation between layer count and damping efficiency. Supplementary simulations with steel rope springs validate this mechanism’s universality, and the orthogonal experiment provides a data-driven framework for material optimisation. This study clarifies the internal vibration attenuation mechanisms of multi-layered metastructures and quantitatively reveals the influence law of core structural parameters. In terms of engineering applicability, the proposed rubber-based RAMs exhibit prominent superiority for low-frequency broadband vibration suppression in civil protective structures, industrial equipment protection, and building vibration isolation scenarios.
This paper aims to investigate the free vibration characteristics of functionally graded magneto-electro-elastic (FG-MEE) porous plates resting on an elastic foundation under various different boundary conditions. The effective mechanical properties of the FG-MEE plate are assumed to vary smoothly through the plate thickness according to an improved power-law function (P-FGM), considering the effects of porosities with two distribution patterns such as even and uneven. The governing equations of motion are derived using the pb2-Ritz method based on Reddy’s third-order shear deformation theory (Reddy’s TSDT), including MEE coupling effects. The semi-analytical solution is established from the constitutive relations of MEE materials. Numerical investigations are performed to investigate the effects of applied voltage, external magneto potential, material parameters, elastic foundation stiffness parameters, and various different boundary conditions on the vibration response. The reliability and accuracy of the present semi-analytical model are verified by comparing the obtained results with available results in the literature.
This study conducts a detailed numerical investigation into the thermo-hydraulic behavior of a two-dimensional solar air heater duct equipped with a two-step transverse rib roughened absorber surface. The simulations, performed using ANSYS Fluent 2025 R2 and the RNG k-ε turbulence model, explore flow conditions corresponding to Reynolds numbers ranging from 5000 to 20,000. Twelve distinct rib configurations are examined by altering both the rib height ( e = 1.3, 1.95 and 2.6 mm ) and the rib pitch ( P = 10, 15, 20 and 25 mm ), resulting in relative roughness pitches ( P/e ) ranging from 3.84 to 19.23 and relative roughness heights ( e/D ) between 0.039 and 0.078. A mesh independence test confirms that reliable results are achieved with 142,356 elements. Model validation against the Dittus–Boelter correlation and previously published experimental data shows deviations of less than 5 % , confirming the accuracy of the numerical approach. The results provide an in-depth analysis of both average heat transfer coefficients and frictional losses for ribbed duct configurations. Under a uniform heat flux of 1000 W/m2 the findings highlight that the Reynolds number, rib pitch, and rib height play dominant roles in determining the overall thermo-hydraulic behavior. Moreover, the study identifies the optimal two-step transverse rib geometry that ensures the best compromise between enhanced heat transfer and pressure drop, thereby achieving maximum overall thermo-hydraulic performance.
Resistance spot welding (RSW) is one of the most widely used joining processes in the automotive and aerospace industries, where weld quality is critical for structural integrity and safety. Technically, the RSW quality depends on several parameters, including material properties, welding current, welding time, electrode force, and holding time. This study develops and validates a coupled-field thermo-electrical finite element model to evaluate the RSW quality of two 1.5 mm-thick SUS316 stainless steel sheets using ANSYS. Weld quality is assessed based on the weld nugget diameter, which is determined from the simulated temperature distribution by defining the nugget region as the area where the temperature reaches or exceeds the melting point of SUS316. The numerical model is validated against experimentally measured nugget diameters from a previously published study conducted under the same welding conditions, demonstrating good agreement between the simulation and experimental results. In addition, the effect of each welding parameter on the nugget diameter is examined to identify optimal process conditions. Based on the simulation results and the American Welding Society (AWS) standard, suitable welding parameters are recommended for joining two 1.5 mm-thick SUS316 sheets. These results demonstrate the effectiveness of the simulation process as a potential tool in predicting weld quality and selecting appropriate welding parameters for specific materials.
This study focuses on optimizing and analyzing the sensitivity of magnetohydrodynamic (MHD) natural convection in Cu/water nanofluids within a three-dimensional cubic enclosure with sinusoidal temperature distribution, a problem relevant for enhancing heat transfer in energy-efficient thermal systems. Advanced numerical simulations are employed using the Double Multi-Relaxation-Time Lattice Boltzmann Method (DMRT-LBM), chosen for its computational stability and efficiency in modeling complex fluid behaviors. Sensitivity analysis and optimization are performed using Response Surface Methodology (RSM) with both Central Composite Design (CCD) and Box-Behnken Design (BBD). Quantitative results demonstrate that by optimizing key parameters, including Rayleigh number (103 < Ra < 105), Hartmann number (0 < Ha < 100), nanoparticle volume fraction (0 < Φ < 0.12), and phase deviation (0 < θ < π), heat transfer efficiency is significantly enhanced. Notably, the interaction between Rayleigh and Hartmann numbers contributes the most to heat transfer improvements, while the combination of nanoparticle volume fraction and phase deviation has the least impact. Additionally, a quantitative comparison of the regression models showed that the BBD model provided a higher coefficient of determination and a lower RMSE than the CCD model, whereas the CCD model showed lower MAE and MAPE values. Therefore, the predictive performance of the two RSM designs is discussed based on multiple statistical indices rather than a general superiority claim. The optimum values for the studied parameters were almost the same for both BBD and CCD, where for maximum average Nusselt number (Ra = 105, Ha = 0 and Φ = 0.12) and Ɵ = 2.728 and 3.125 for CCD and BBD, respectively. The novel insights derived from these quantitative findings highlight the potential for developing more advanced thermal management systems by leveraging these optimized parameters.
Nanotechnology, particularly through nanoscale structures such as nanobeams, has found extensive applications in sensing, electronics, and drug delivery. Mathematical and vibrational modeling of these nanostructures is essential for predicting their behavior and achieving an optimal design. This paper undertakes a rigorous examination of the nanobeam’s nonlinear vibration behavior, accounting simultaneously for material nonlinearity and the governing mechanisms of doublet mechanics. In the doublet continuum theory, the interatomic bond length in solid materials is regarded as a characteristic length scale at the nanoscale. Hence, incorporating this concept into the study of nonlinear vibrations of nanobeams along with considering nonlinear effects rooted in both material properties and geometric deformation reflects the novelty of the present work. Accordingly, the nonlinear material behavior of the nanobeam is modeled using a nonlinear stress–strain relationship, which is coupled with the doublet mechanics framework. Moreover, the displacement field is formulated employing nonlinear geometric strain relations of the Von Kármán formulation. The nanobeam is assumed to rest on a viscoelastic support medium and is exposed to a distributed harmonic load as well as thermal and magnetic environments. Using variational mechanics, the governing nonlinear vibration model for the nanobeam is formulated, and an enhanced analytical procedure is then employed to extract the system’s dynamic response as well as its nonlinear natural frequency. The influences of various parameters, including the doublet parameter, material nonlinearity coefficient, characteristic length parameter, and other physical quantities on the vibrational characteristics such as damped and undamped natural frequencies, time responses are examined. Furthermore, the dynamic oscillation behavior of the nanobeam under the synergistic influence of intrinsic material nonlinearities and doublet mechanics is rigorously evaluated, while the concurrent impact of the doublet coefficient on the upper and lower resonance peaks is systematically analyzed. Additionally, the effect of the second mode on the first mode is thoroughly investigated. Finally, the obtained results are rigorously benchmarked against prior studies and numerical simulations to confirm the precision, and validity of the proposed model.
Double-arm rhombus-type compliant displacement amplification mechanisms are widely employed in piezoelectric actuation, precision positioning, and micro-manipulation because of their compact geometry, structural symmetry, and convenient integration. Most existing analytical models are derived under small-deformation assumptions and simplify or neglect axial-force/bending coupling, limiting their ability to predict load-dependent changes in displacement amplification, input stiffness, and output stiffness. This study develops a load-dependent static model for a previously reported double-arm rhombus mechanism. A stiffness-matrix formulation is established as the linear reference, after which a beam-constraint formulation is introduced to account for axial-force/bending coupling. Closed-form expressions for the three static performance indicators are derived and evaluated against geometrically nonlinear ANSYS finite-element simulations. Across the investigated geometric parameters, analytical and finite-element deviations remained below approximately 14
This study investigates the thermal performance of double-glazed windows incorporating phase change material (PCM) under the hot-arid summer conditions of Al-Diwaniyah, Iraq. A two-dimensional numerical model based on the enthalpy formulation method was developed and solved using the Finite Volume Method (FVM) to evaluate how PCM thermophysical properties, namely, density, specific heat, fusion temperature, thermal conductivity, and latent heat, influence the thermal behavior of the glazing system. The results show that raising PCM density to ≈1000 kg/m3 strengthens thermal inertia, lowering peak inner-surface temperatures by up to 0.4 °C. Increasing specific heat delays the thermal response and stabilizes temperatures, although gains diminish beyond 2 kJ/(kg K). Fusion temperatures of 40–45 °C produce the longest time lags (up to 4.5 h) and the smallest decrement factors under the studied climate. Thermal conductivity exerts the greatest influence, with a 6.37 °C peak-temperature difference at 0.10–0.30 W/(m K). Latent heat of up to 300 kJ/kg extends the time lag to 5.5 h and lowers the decrement factor to 0.770. Together, these results form a parametric basis for selecting PCM properties suited to hot climates with large diurnal swings, supporting energy-efficient envelope design. The reported quantitative results were obtained using a validated two-dimensional, conduction-based enthalpy model and applied to the studied glazing configuration and climatic conditions; extending them to other geometries or climates should therefore be done with appropriate caution.
This paper presents an analytical investigation of Love-type wave propagation in a layered mechanical system consisting of a viscous liquid on top of a flexoelectric medium embedded on a flexomagnetic half-space. The study investigates the effect of height and density of the viscous layer, flexomagnetic and flexoelectric coefficients under the magnetic and electric open and short circuit boundary conditions. The study derives a dispersion relation using an analytical method. The graphs are plotted to show the effects of key physical parameters like the thickness and density of the viscous layer, the thickness of the flexomagnetic layer, and the elastic coefficients using MATLAB. The results reveal that the height and density of viscous liquid decrease the phase velocity with increasing wave number. In contrast, the thickness of the flexoelectric layer accelerates the phase velocity. The presence of piezoelectric and piezomagnetic effects shows a decrease in the phase velocity for all the cases considered. The findings highlight the importance of different parameters on wave propagation, further useful in the design and optimisation of wave-based sensors and fluid-loaded waveguides.
This study investigates a thermoelastic diffusive rod with micro concentrations subjected to gradually increasing internal heat generation and a laser pulse. The rod is fixed at both ends with thermally insulated and chemically impermeable boundaries. The laser pulse provides localized heating at the rod center, generating thermal waves that propagate through the medium. The governing one-dimensional equations are solved using the Laplace transform method, and numerical inversion yields expressions for displacement, stress, temperature, concentration, micro concentration, and mass diffusion flux moment. Results, presented in 2D and 3D graphs, show that the laser pulse creates intense localized temperature and concentration peaks that decay through diffusion, while the gradually increasing internal heat generation (modeling scenarios such as nuclear decay or autocatalytic reactions) contributes to background field evolution. The strong thermodiffusion coupling produces similar patterns in temperature and concentration fields. Microstructural diffusion mechanisms reveal complex behavior distinct from macroscopic fields.
This study introduces a multifunctional hybrid sandwich plate that integrates an auxetic honeycomb (AH) core with laminated functionally graded carbon nanotube-reinforced composite (FG-CNTRC) face sheets, hereafter referred to as the AH-FGCNTRC sandwich plate. By combining the negative Poisson’s ratio characteristics of auxetic cores with the stiffness-tailoring capability of CNT-reinforced graded laminates, the proposed configuration enables simultaneous lightweight design, enhanced load-carrying capacity, and improved vibration performance. An accurate and computationally efficient analytical model is developed within the framework of Reddy’s third-order shear deformation theory (RTSDT), allowing precise representation of transverse shear effects without the need for empirical correction factors. The governing equations are derived using Hamilton’s principle and solved through a Navier-type analytical procedure. The formulation is validated against benchmark solutions to demonstrate its reliability for engineering analysis and design. A comprehensive parametric investigation is conducted to evaluate the influence of auxetic geometric parameters, CNT distribution patterns (UD, FG-V, FG-X, FG-O), nanotube orientation, and laminate stacking sequences on the static deflection and natural frequencies of the hybrid plate. The results demonstrate that coordinated tuning of core topology and face-sheet gradation provides significant flexibility in controlling stiffness, weight efficiency, and vibration characteristics.
Triangular and trapezoidal velocity profiles are widely used in industrial servo-controlled motion systems because of their intuitive phase-based timing structure and compatibility with commercial motion controllers. However, their classical piecewise formulations contain acceleration discontinuities at phase transitions, which may cause impulsive jerk and reduce the reliability of analytical dynamic evaluation in multibody dynamic simulations. Existing smooth trajectory-planning methods can overcome this limitation, but they often modify the original industrial timing semantics or require numerical construction. This study proposes a polynomial standardization framework for reconstructing industrial triangular and symmetric one-third trapezoidal velocity profiles in closed analytical form. The triangular profile is reformulated using a normalized fifth-order displacement polynomial, while the symmetric one-third trapezoidal profile retains its constant-velocity phase and replaces the acceleration and deceleration phases with polynomial-shaped boundary phases. The resulting motion laws provide closed-form displacement, velocity, acceleration, and feasible duration expressions under prescribed velocity and acceleration limits. The proposed profiles are evaluated through a computer-aided-design-based multibody dynamic simulation of a gantry robot integrated with a transport system. The results show that the standardized symmetric one-third trapezoidal profile requires a longer cycle time, but reduces the root-mean-square velocity, acceleration, and vertical actuator driving force compared with the standardized triangular profile. However, the peak-to-peak vertical driving-force envelope remains nearly unchanged. These findings show that the symmetric one-third trapezoidal profile mainly reduces time-averaged dynamic intensity, whereas the triangular profile remains advantageous when shorter cycle time is required.
This work presents a vibration and dynamic stability analysis of rotating functionally graded porous (FGP) shafts using Timoshenko beam theory (TBT) combined with the p -version finite element method ( p -FEM). The formulation simultaneously captures shear deformation, rotary inertia, gyroscopic coupling, rigid disk inertia, and linear bearing stiffness/damping, while explicitly modeling both symmetric and non-symmetric porosity distributions in the shaft. Material gradation and porosity are represented through continuous radius-dependent variations of Young’s modulus, shear modulus, and density, calibrated to the effective behavior of open-cell metallic foams. Convergence studies and comparisons with benchmark solutions for homogeneous beams, FGP cylindrical shafts, and rotating shafts confirm the accuracy and robustness of the model. Using Campbell diagrams and extensive parametric studies, the proposed framework systematically quantifies how porosity level and pattern, geometric slenderness/thickness ratios, and support stiffness and damping jointly affect natural frequencies, forward/backward whirl separation, and critical speeds. The results reveal that symmetric porosity can enhance the effective stiffness-to-mass ratio and thereby improve dynamic stability, whereas non-symmetric porosity consistently degrades it. Additionally, stiffer bearings, lighter disks, and high-modulus ceramics increase critical speeds, while strong external damping reduces them. The findings provide practical guidelines for tailoring porosity patterns, geometric parameters, and support conditions in lightweight, high-speed FGP rotors for aerospace, power generation, and advanced turbomachinery applications.
The connection holes in aircraft load-bearing components are susceptible to stress concentration, which initiates fatigue cracks and accelerates fatigue failure. This has become a bottleneck problem that severely compromises the safety performance of aircraft. In response to the insufficient fatigue performance of load-bearing components with holes, this study focuses on 7050 aluminum alloy specimens and enhances the fatigue performance of such components through the split mandrel hole expansion method. Hole expansion experiments were conducted under different conditions. Subsequently, comparative fatigue tests were conducted on the unexpanded and expanded specimens to reveal the mechanism by which expansion times affect fatigue performance. The research findings reveal that the median fatigue lives of specimens undergoing once and twice expanded strengthening are 1.52 and 1.73 times greater than those of the unexpanded, respectively. Moreover, the wider the fatigue striations and the higher the stress intensity factor at the crack tip, the shorter the fatigue life of the specimen. Conversely, the larger the crack propagation zone and the larger the toughness dimples, the longer the fatigue life.
Non-circular beveloid gears (NBGs) combine the prescribed variable transmission ratio of non-circular gears with the axial tooth-thickness variation of beveloid gears, resulting in spatial meshing and nonlinear vibration characteristics that differ from those of ordinary non-circular spur gears and conventional beveloid gears. To clarify these characteristics, this paper investigates the nonlinear vibration response of an NBG transmission system under coupled multi-parameter excitation. First, the tooth-surface equations of the NBG are derived through coordinate transformation, and a three-dimensional solid model is established. Then, time-varying meshing stiffness obtained from finite-element contact analysis, variable transmission ratio, time-dependent backlash, meshing damping and transmission error are introduced into an eight-degree-of-freedom translation-torsion nonlinear dynamic model. The governing equations are solved numerically, and bifurcation diagrams, maximum Lyapunov exponents, three-dimensional phase portraits and Poincare sections are used to identify periodic, multi-periodic, quasi-periodic and chaotic responses under variations in excitation frequency, excitation amplitude, damping and stiffness. Unlike previous studies that mainly focus on geometric modelling or single-excitation dynamics of non-circular gears, this study emphasizes the coupled influence of NBG-specific spatial geometry and multiple internal excitations on nonlinear vibration. Experimental results obtained from an NBG transmission platform show the same response trends as the numerical prediction, providing trend-level validation of the proposed model. The results provide theoretical guidance for parameter selection, vibration suppression and dynamic design of NBG transmission systems.
This study investigates heat transfer in an annular fin with a triangular profile, constructed from functionally graded material (FGM). The material properties vary radially following a power-law distribution. The heat transfer problem is first solved for a homogeneous material (HM) using the Frobenius series method to address the complexity of the governing equations. Subsequently, the first analytical solution for triangular annular functionally graded fins using Kummer functions under power-law grading is derived. The findings reveal that FGMs exhibit higher temperature distribution and efficiency compared to HMs, as expected. Furthermore, it is observed that increasing the inhomogeneity parameter (β) and the radii ratio (ω) enhances heat transfer, while an increase in the dimensionless thermo-geometric parameter (Γ) reduces it. These trends provide valuable guidance for designing and optimizing fins in practical applications. The analytical solution developed in this study provides a reliable analytical approach for understanding the heat transfer behavior of both homogeneous and functionally graded fins. It provides a reliable benchmark for validating both numerical simulations and experimental results, which helps advance thermal management strategies in engineering systems.
Diesel engines remain the backbone of the rail cargo sector, where maximizing fuel efficiency is critical for sustainability. This study optimizes the fuel injection strategy of a high-power locomotive engine, representative of those operating on 900 km rail corridors in Brazil, by investigating the synergy between fuel injection timing and spray angle ( β ). Numerical simulations were performed at a constant engine speed of 996 revolutions per minute (RPM) using computational fluid dynamics with the Extended Coherent Flame Model 3-Zones (ECFM-3Z) and the κ - ζ -f turbulence model. A parametric study of 25 configurations was conducted, varying the spray angle from 153.0 to 167.0 ^∘ and injection timing from 698 to 706 Crank Angle (CA) degrees, referenced against a 160.0 ^∘ /702 CA baseline. Results demonstrate that advancing injection to 698 CA enhances Indicated Power and Brake Mean Effective Pressure (BMEP) by up to 2.92 β = 167.0 ^∘ ) resulted in spray-bowl misalignment, increasing soot by up to 168 ^∘ ) improve mixing through higher turbulent kinetic energy, delaying injection to 706 CA with a 160.0 ^∘ angle yields a simultaneous reduction in NO (22.3
The paper presents the response of an infinite fibre-reinforced photo-thermoelastic plate of width 2d, loaded with non-viscous fluid layers of widths h1 and h2 on the upper and lower sides, respectively. An internal heat source of constant magnitude and a focused laser beam (photothermal excitation) are acting in the plate. The photo-thermoelastic effect considers the plasma-generated electron density field coupled with the thermoelastic waves. The analytical expressions of displacement, stresses, temperature field, and carrier density (plasma waves) are obtained by normal mode analysis technique. The numerical values of the expressions are evaluated using MATLAB. The graphical results are presented to show the effect of different photo-thermoelastic theories with and without reinforcement and with varying plasma-thermal coupling parameters.
To address the issues of multi-fault feature coupling, single-domain feature incompleteness, and poor fixed-threshold adaptability in rolling bearing compound fault diagnosis, this paper proposes an intelligent method integrating multi-source feature fusion, three-stage feature screening, heterogeneous ensemble learning, and dynamic threshold optimization. First, time-domain, frequency-domain, and time–frequency domain features are fused to overcome the limitations of single-domain features. A three-stage screening strategy combining variance thresholding, mutual information, and recursive feature elimination is adopted to construct a low-redundancy, high-discriminability feature set. A heterogeneous ensemble learning framework integrating Convolutional Neural Network with Attention mechanism (CNN-Attention), Densely Connected Networks (DenseNet), and CNN-Long Short-Term Memory (CNN-LSTM) is established, with an improved attention-CNN as the final classifier. A dynamic threshold mechanism is introduced to adaptively adjust decision boundaries based on validation set statistics. On the Case Western Reserve University (CWRU) dataset, the proposed method achieves an average accuracy of 99.74
The influence of fiber distribution on the mechanical response of unidirectional composites remains insufficiently quantified, particularly across a wide range of fiber volume fractions. This study develops a micromechanical finite element framework based on representative volume elements to compare the elastic behavior and crack initiation of composites with regular and random fiber arrangements from low to high fiber contents. Effective transverse elastic modulus, shear modulus, and Poisson’s ratio are evaluated using periodic boundary conditions and homogenization. Crack initiation is investigated using the extended finite element method coupled with matrix plasticity and cohesive modeling of the fiber-matrix interface. Results show that regular fiber arrangements yield higher transverse elastic modulus due to more uniform load transfer, whereas random distributions exhibit higher shear modulus and Poisson’s ratio as a result of fiber clustering, matrix-rich regions, and heterogeneous strain fields. Crack initiation occurs at lower global displacement in random microstructures, originating in highly stressed matrix ligaments between closely spaced fibers. Increasing fiber volume fraction accelerates crack initiation for both distributions. These findings demonstrate that fiber distribution strongly governs shear response and damage initiation, and that regular microstructural idealizations can underestimate crack initiation at high fiber contents.
