International Journal of Non-Linear Mechanics最新文献

This paper analyzes the delay-independent stability and harvesting performance of a tri-stable vibrational energy harvester (TVEH) with time-delayed feedback control. The dynamical model of the controlled electromechanical TVEH is established, and the method of multiple scales is employed to derive the steady-state response near the primary resonance. The delay-independent stability conditions of the TVEH are obtained using Routh Hurwitz criterion and classical Sturm criterion. The influences of time-delayed feedback control on the TVEH's output and jump phenomena are discussed through the steady-state response. Furthermore, appropriate choices of feedback gains and time delays can ensure the system stability and enhance the output power. The theoretical results are validated through numerical simulations, demonstrating the effectiveness of the proposed control strategy.

The bifurcation problem of a circular Euler–Bernoulli rod subject to a uniform radial force distribution is investigated under three distinct loading conditions: (i.) hydrostatic pressure, (ii.) centrally-directed, and (iii.) dead load. Previous studies on this apparently ‘familiar’ structural problem have yielded controversial results, necessitating a comprehensive clarification. This study shows that results previously labelled as ‘correct’ or ‘wrong’ simply refer to different external constraints, whose presence becomes necessary only for the two latter loads, (ii.) and (iii.). Moreover, the paper presents the first experimental realization of a circular rod subjected to centrally-directed loads. The experimental findings align with the theoretical predictions and show the exploitation of a new type of load acting on a continuous structural element. The feasibility of this load is demonstrated through the use of inextensible cables and opens the way to applications in flexible robotics when cables are used for actuation.

The Winkler foundation model is often used to analyze the wrinkling of a film/substrate bilayer under compression, and it can be rigorously justified when both the film and substrate are homogeneous and the film is much stiffer than the substrate. We assess the validity of this model when the substrate is still homogeneous but the film has periodic material properties in the direction parallel to the interface. More precisely, we assume that each unit cell is piecewise homogeneous, and each piece can be described by the Euler–Bernoulli beam theory. We provide analytical results for the critical compression when the substrate is viewed as a Winkler foundation with stiffness modeled either approximately (as in some previous studies) or exactly (using the Floquet theory). The analytical results are then compared with those from Abaqus simulations based on the three-dimensional nonlinear elasticity theory in order to assess the validity of the Euler–Bernoulli beam theory and the Winkler foundation model in the current context.

To quantify the impact of hybrid uncertainty (random and interval parameters) on the frequency-domain nonlinear dynamic response, the multi-scale method (MSM) and the random interval moment method (RIMM) are combined to establish a new uncertainty propagation analysis method, called the multi-scale random interval moment method (MS-RIMM). RIMM is used to describe the hybrid uncertainty, while MSM is used to determine the frequency-domain nonlinear dynamic response. The statistical characteristics (i.e., the expectation value and variance) of the amplitude-frequency response of the nonlinear system with hybrid uncertainties are derived. Furthermore, the accuracy and effectiveness of the proposed method are verified by comparing the results with those obtained using the multi-scale Monte Carlo simulation method (MS-MCSM). Overall, the results of this study can serve as a useful reference for the hybrid uncertainty propagation analysis of nonlinear systems and for predicting the frequency-domain nonlinear dynamic response.

Research is conducted on the dynamic modeling of a rotating functionally graded (FG) cylindrical shell subjected to magnetic and temperature fields. Based on the elasticity theory and generalized Hooke's law on the physical neutral surface, nonlinear geometric equations and thermoelastic constitutive relations are determined. According to the Kirchhoff-Love theory, variational formulas of strain energies for deformation, temperature, and centrifugal force are obtained. Considering the rotational effect, the kinetic energy and its variational formula are derived. The electromagnetic force model incorporating magnetization effect of the ferromagnetic FG shell is established by utilizing the electromagnetic theory. Subsequently, the magneto-thermoelastic dynamic model of the rotating FG shell is developed by adopting the Hamilton's principle. The model can reveal the coupling mechanisms of the interaction and superposition of multi-physical fields. Finally, taking the primary resonance as example, detailed numerical analyses are performed to investigate the effects of different parameters on vibration response and dynamical stability.

Convection induced by internal heating and adverse temperature gradient in a porous medium has various real-world applications, such as solar energy collectors, solar-based drying and cooking. Thus, it is crucial to analyze such flows to understand the physics behind the flow and analyze heat transfer through the system. We assume that volumetric heating occurs within the fluid phase due to radiation exposure from an overhead source or a stratified arrangement of heat-generating materials. For modeling convenience, we further assume that internal heating diminishes exponentially with the depth of the porous layer and fluctuates sinusoidally over time, affecting the mean value. Solid and fluid phases of the porous layer are considered out of thermal equilibrium. Floquet theory is employed to determine the linear instability bound of the system. By analyzing the eigenvalue spectrum, we identify the critical Rayleigh number that marks the onset of instability. Subsequently, a weakly nonlinear analysis is carried out using a truncated Fourier series expansion of the physical quantities to analyze the heat transfer within the system. The effect of governing nondimensional parameters on the system’s stability and heat transport is graphically illustrated and thoroughly discussed. The effect of modulation amplitude and volumetric heat is to enhance heat transfer, whereas depth coefficient and modulation frequency suppress heat transfer.

The Monte Carlo simulation (MCS) technique is quite simple in concept and the most accurate for seismic reliability analysis (SRA) of structures involving nonlinear seismic response analysis, considering the effect of the stochastic nature of earthquakes and the uncertainty of various structural parameters. However, the approach needs to execute several repetitive nonlinear dynamic analyses of structures. The metamodeling technique has emerged as a practical alternative in such a scenario. In SRA, the dual metamodeling approach is typically adopted to deal with the stochastic nature of earthquakes following a lognormal seismic response assumption. In contrast, a direct metamodeling approach of SRA can avoid such prior assumptions. Adaptive training near the limit state is important in the metamodeling-based SRA. However, its implementation is quite challenging for SRA due to the record-to-record variation of earthquakes. In this context, an adaptive sparse Bayesian regression-based direct metamodeling approach is developed for SRA, where an active learning-based algorithm is proposed for adaptive training of metamodels for approximating nonlinear seismic responses. As the sparse Bayesian regression is computationally faster than Kriging due to the sparsity involved in sparse Bayesian learning, the overall performance of the proposed approach is expected to be better than the adaptive Kriging-based SRA approach. The effectiveness of the proposed approach is illustrated by numerical examples.

Hard-magnetic soft materials (HMSMs) are a class of magnetoactive smart polymers capable of sustaining a high residual magnetic flux density and can undergo large actuation strains under an external magnetic excitation. Due to these exceptional characteristics, soft actuators based on HMSMs hold enormous potential for remote-controlled applications. The temperature and viscoelasticity considerably influence the performance of these materials during the operation. This work aims to develop an analytical framework for modeling the dynamic behavior of a planar hard-magnetic soft actuators (HMSA) considering temperature and viscoelastic effects. The constitutive behavior of the viscoelastic HMSA is described by employing an incompressible neo-Hookean model in conjunction with a Zener rheological model and the Rayleigh dissipation function. The dynamic governing differential equations of motion are derived by utilizing the non-conservative form of the Euler–Lagrange equation. This study delves into the collective influence of temperature and viscoelastic properties on the stability, periodicity, and resonance characteristics of nonlinear vibrations exhibited by HMSM-based planar actuator subjected to dynamic magnetic loading, presenting the findings through time-history responses, Poincaré maps, and phase-plane plots. The presented results can help in the efficient and robust design of HMSM-based actuators and can also serve as an initial step toward the development of advanced actuators exposed to dynamic loading under variable temperatures for diverse applications in the fields of engineering and medicine.

The nonlinear energy harvesting systems of the forced vibration with an electron-mechanical coupling are widely used to capture ambient vibration energy and convert mechanical energy into electrical energy. However, the nonlinear response mechanism of the friction induced vibration (FIV) energy harvesting system with multiple stability and stick-slip motion is still unclear. In the current paper, a novel nonlinear energy harvesting model with multiple stability of single-, double- and triple-well potential is proposed based on V-shaped structure spring and the belt conveying system. The dynamic equations for the energy harvesting system with multiple stability and self-excited friction are established by using Euler-Lagrangian equations. Secondly, the static characteristics of the nonlinear restoring force, the friction force, and the potential energy surfaces are obtained to show the nonlinear stiffness, multiple equilibrium points, discontinuous behaviors and multiple well responses. Then, the equilibrium surface of bifurcation sets for the autonomous system is given to show the third-order quasi zero stiffness (QZS3), fifth-order quasi zero stiffness (QZS5), double well (DW) and triple well (TW). The co-dimension bifurcation sets of the self-excited vibration system are analyzed and the corresponding phase portraits for the coexistent of multiple limit cycles are obtained. Furthermore, the analytical formula of amplitude frequency response of the approximated system are obtained by the complex harmonic method. The response amplitudes of charge, current, voltage and power of the forced electron-mechanical coupled vibration system for QZS3, QZS5, DW and TW are analyzed by using the numerically solution. Finally, a prototype of FIV energy harvesting system is manufactured and the experimental system is setup. The experimental works of static restoring forces, damping forcse and the electrical outputs are well agreeable with the numerical results, which testified the proposed FIV energy harvesting model.

Thanks to their properties of superelasticity and shape memory effects, SMA wires are often considered for the design of damping devices or actuators coupled to pulleys. In order to dimension such devices for commercialization, it is necessary to develop reliable, robust and fast numerical tools. To this end, simplifying the management of the wire/pulley contact using an Arbitrary Lagrangian–Eulerian (ALE) formulation is an original and effective solution. In this work, the wires are modeled by three-dimensional truss thermo-mechanical finite elements associated with a superelastic law. For each node, the curvilinear abscissa is used as an additional degree of freedom in order to deal with material flow from one element to another. After presenting the ALE formalism and the necessary precautions (advection of variables), as well as the material behavior and thermo-mechanical contact laws at the pulleys, elementary validation tests are studied. Finally, two devices taken from the literature are modeled using the ALE formalism. The results obtained demonstrate the relevance and effectiveness of the approach adopted, as well as the importance of not neglecting friction at the pulleys and thermal effects on the material mechanical response.