查看更多>>摘要：The classical phase field model has wide applications for brittle materials,but nonlinearity and inelasticity are found in its stress-strain curve.The degradation function in the classical phase field model makes it a linear formulation of phase field and computationally attractive,but stiffness reduction happens even at low strain.In this paper,generalized polynomial degradation functions are investigated to solve this problem.The first derivative of degradation function at zero phase is added as an extra constraint,which renders higher-order polynomial degradation function and nonlinear formulation of phase field.Compared with other degradation functions(like algebraic fraction function,exponential function,and trigonometric function),this polynomial degradation function enables phase in[0,1](should still avoid the first derivative of degradation function at zero phase to be 0),so there is no Γ convergence problem.The good and meaningful finding is that,under the same fracture strength,the proposed phase field model has a larger length scale,which means larger element size and better computational efficiency.This proposed phase field model is implemented in LS-DYNA user-defined element and user-defined material and solved by the Newton-Raphson method.A tensile test shows that the first derivative of degradation function at zero phase does impact stress-strain curve.Mode Ⅰ,mode Ⅱ,and mixed-mode examples show the feasibility of the proposed phase field model in simulating brittle fracture.
查看更多>>摘要：The total internal reflection(TIR)behavior of interface shear waves is crucial for ensuring the reliability of dielectric elastomer(DE)devices.However,due to the complex force-electric coupling and large deformation of DEs,the TIR behavior of shear waves in heterogeneous force-electric interface models is still unclear.This study modeled an elastic/DE bi-material interface to analyze the trajectory of out-of-plane shear waves.Employing Dorfmann and Ogden's nonlinear electroelastic framework and the related linear small incremental motion theory,a method has been developed to control the TIR behavior of interface shear waves.It has been found that the TIR behavior is significantly influenced by the strain-stiffening effect induced by biasing fields.Consequently,a biasing field principle involving preset electric displacement and pre-stretch has been proposed for TIR occurrence.By controlling the pre-stretch and preset electric displacement,active regulation of TIR behavior can be achieved.These results suggest a potential method for achieving autonomous energy shielding to improve the reliability of DE devices.
查看更多>>摘要：In engineering applications,the notch effect and size effect significantly influence the evaluation of fatigue performance in components,necessitating special attention in life prediction.This study proposes a new probabilistic model,based on the theory of critical distance(TCD),to predict fatigue life,with the aim of quantitatively assessing the impact of notch effect and size effect.The stress distribution on the critical plane is first characterized using a sixth-order multinomial function,and the relative stress gradient function is utilized to calculate the value of the critical distance.Furthermore,the effect of the ratio of shear strain to normal strain on fatigue life under multiaxial loading is considered.Additionally,the integration of the Weibull distribution into the TCD is employed for conducting probabilistic modeling of fatigue life.Finally,fatigue experiments are conducted on notched specimens of Q355D steel,demonstrating that the life prediction results under 50％survival probability are superior to the traditional TCD method.
查看更多>>摘要：This research explores the dynamic behaviour of horn-shaped single-walled carbon nanotubes(HS-SWCNTs)conveying viscous nanofluid with pulsating the influence of a longitudinal magnetic field.The analysis utilizes Euler-Bernoulli beam model,considering the variable cross section,and incorporating Eringen's nonlocal theory to formulate the governing partial differential equation of motion.The instability domain of HS-SWCNTs is estimated using Galerkin's approach.Numerical analysis is performed using the Haar wavelet method.The critical buckling load obtained in this study is compared with previous research to validate the proposed model.The results highlight the effectiveness of the proposed model in assessing the vibrational characteristics of a complex multi-physics system involving HS-SWCNTs.Dispersion graphs and tables are presented to visualize the numerical findings pertaining to various system parameters,including the nonlocal parameter,magnetic flux,Knudsen number,and viscous factor.
查看更多>>摘要：A local design scheme for origami energy dissipation braces was proposed by combining local Miura units at both ends and a straight segment in the middle.This design was implemented to address the issue of uneven axial stiffness observed in global origami braces.Globally and locally designed origami braces were simulated and compared under cyclic loading to validate the advantages of the proposed design scheme in terms of hysteretic properties.Additionally,an analysis was conducted on the designed braces with varying straight segment lengths,geometric angles,and origami plate thicknesses for comparison.Results indicate that the local design significantly increases the tensile bearing load,enhances the anti-buckling capability,and improves the energy dissipation performance compared to the global design.The positive impact on bearing capacity and energy dissipation performance was observed with increased straight segment length,geometric angles,and origami plate thickness.However,excessively large parameter values result in brace buckling under compression,diminishing energy dissipation capacity.
查看更多>>摘要：By incorporating two different fracture mechanisms and salient unilateral effects in rock materials,we propose a thermo-mechanical phase-field model to capture thermally induced fracture and shear heating in the process of rock failure.The heat conduction equation is derived,from which the plastic dissipation is treated as a heat source.We then ascertain the effect of the non-associated plastic flow on frictional dissipation and show how it improves the predictive capability of the proposed model.Taking advantage of the multiscale analysis,we propose a phase-field-dependent thermal conductivity with considering the unilateral effect of fracture.After proposing a robust algorithm for solving involved three-field coupling and damage-plasticity coupling problems,we present three numerical examples to illustrate the abilities of our proposed model in capturing various thermo-mechanically coupled behaviors.
查看更多>>摘要：In this study,analytical and numerical methods are applied to investigate the dynamic response of an axially moving plate subjected to parametric and forced excitation.Based on the classical thin plate theory,the governing equation of the plate coupled with fluid is established and further discretized through the Galerkin method.These equations are solved using the method of multiple scales to obtain amplitude-frequency curves and phase-frequency curves.The stability of steady-state response is examined using Lyapunov's stability theory.In addition,numerical analysis is employed to validate the results of analytical solutions based on the Runge-Kutta method.The multi-value and stability of periodic solutions are verified through stable periodic orbits.Detailed parametric studies show that proper selection of system parameters enables the system to stay in primary resonance or simultaneous resonance,and the state of the system can switch among different periodic motions,contributing to the optimization of fluid-structure interaction system.
查看更多>>摘要：Since dielectric elastomers(DEs)exhibit obvious nonlinear visco-hyperelasticity,and remarkable temperature dependence,it is difficult to accurately predict the cyclic deformation of DEs at various temperatures.To address this issue,an improved visco-hyperelastic constitutive model is proposed here to reproduce the complex temperature-dependent cyclic deformation of DEs.In the improved model,the Ogden model is chosen to provide the strain energy density representing the hyper-elastic response,a nonlinear viscosity evolution equation is used to depict the strong viscosity of DEs,and specific temperature-dependent parameters are incorporated to describe the cyclic deformation of DEs at various temperatures.Finally,the prediction capability of the proposed visco-hyperelastic model is validated by reproducing the cyclic deformation of VHB 4910 DE observed in experiments at different temperatures.This study provides a theoretical basis for the rational design of DE devices.
查看更多>>摘要：In this paper,we investigate the existence of strange nonchaotic attractors(SNAs)in a slender rigid rocking block under quasi-periodic forcing with two frequencies.We find that an SNA can exist between a quasi-periodic attractor and a chaotic attractor,or between two chaotic attractors.In particular,we demonstrate that a torus doubling bifurcation of a quasi-periodic attractor can result in SNAs via the fractal route before transforming into chaotic attractors.This phenomenon is rarely reported in quasiperiodically forced discontinuous differential equations and vibro-impact systems.The properties of SNAs are verified by the Lyapunov exponent,rational approximation,phase sensitivity,power spectrum,and separation of nearby trajectories.
查看更多>>摘要：Skin tissue is a kind of complex biological material abundant with fibers.A new constitutive model,relating macroscopic responses with microstructural fiber configuration alteration,is developed to investigate the stress softening behaviors of skin tissue observed during cyclic loading-unloading tests.Two influential factors are introduced to describe the impact of fiber configuration change and stretch-induced damage.The present model achieves good agreement between predicted stress distribution of human skin and corresponding ex vivo experimental data obtained from the literature,affirming its capability to effectively capture the characteristic softening behaviors of human skin under cyclic loading conditions.
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