1,721,035 research outputs found
A multivariate adaptive regression splines based damage identification methodology for web core composite bridges including the effect of noise
No full text A novel computationally efficient damage identification methodology for web core fiber-reinforced polymer composite bridges has been developed in this article based on multivariate adaptive regression splines in conjunction with a multi-objective goal-attainment optimization algorithm. The proposed damage identification methodology has been validated for several single and multiple damage cases. The performance of the efficient multivariate adaptive regression splines-based approach for the inverse system identification process is found to be quite satisfactory. An iterative scheme in conjunction with the multi-objective optimization algorithm coupled with multivariate adaptive regression splines is proposed to increase damage identification accuracy. The effect of noise on the proposed damage identification algorithm has also been addressed subsequently using a probabilistic framework. The multivariate adaptive regression splines-based damage identification algorithm is general in nature; therefore, in future it can be implemented to other structures. </jats:p
On-demand contactless programming of nonlinear elastic moduli in hard magnetic soft beam based broadband active lattice materials
No full textEngineered honeycomb lattice materials with high specific strength and stiffness along with the advantage of programmable direction-dependent mechanical tailorability are being increasingly adopted for various advanced multifunctional applications. To use these artificial microstructures with unprecedented mechanical properties in the design of different application-specific structures, it is essential to investigate the effective elastic moduli and their dependence on the microstructural geometry and the physics of deformation at the elementary level. While it is possible to have a wide range of effective mechanical properties based on their designed microstructural geometry, most of the recent advancements in this field lead to passive mechanical properties, meaning it is not possible to actively modulate the lattice-level properties after they are manufactured. Thus the on-demand control of mechanical properties is lacking, which is crucial for a range of multi-functional applications in advanced structural systems. To address this issue, we propose a new class of lattice materials wherein the beam-level multi-physical deformation behavior can be exploited as a function of external stimuli like magnetic field by considering hard magnetic soft beams. More interestingly, effective property modulation at the lattice level would be contactless without the necessity of having a complex network of electrical circuits embedded within the microstructure. We have developed a semi-analytical model for the nonlinear effective elastic properties of such programmable lattice materials under large deformation, wherein the mechanical properties can be modulated in an expanded design space of microstructural geometry and magnetic field. The numerical results show that the effective properties can be actively modulated as a function of the magnetic field covering a wide range (including programmable state transition with on-demand positive and negative values), leading to the behavior of soft polymer to stiff metals in a single lattice microstructure according to operational demands
Uncertainty quantification of residual strength post lightning strike: a coupled stochastic thermal-electrical-mechanical simulation framework for composite laminates
No full textThe strength of composite laminates can be significantly impacted by the damage caused due to lightning strikes. Quantifying such impact of lightning strikes, taking the inevitable compound influence of material and lightning current uncertainty into consideration, is of utmost importance to ensure the operational safety and serviceability in critical composite structural applications such as aircraft and wind turbines. We introduce a machine learning-enabled stochastic framework of hybrid thermal–electrical–mechanical simulations for the uncertainty quantification of residual strength post lightning strike in composite laminates. A comprehensive probabilistic analysis is presented for accurately assessing the uncertainty associated with the residual tensile strength of carbon/epoxy laminates considering stochastic temperature-dependent material properties and lightning current waveform. The results reveal that source uncertainty of the unprotected laminates significantly influences the structural strength with considerable stochastic variability. The machine learning models are exploited further for conducting global sensitivity analysis to examine the relative impact of the influencing parameters on the residual strength after lightning strikes. Seamless coupling of the Gaussian process-driven machine learning model in the finite element based multi-physical lightning strike analysis, integrating multi-stage computationally intensive simulations, leads to an efficient quantification of uncertainty for complete probabilistic characterization of the residual strength and subsequent serviceability analysis
Mixed‐mode multidirectional Poisson's ratio modulation in auxetic 3D lattice metamaterials
No full textIf a conventional material is compressed in one direction, it tries to expand in the other two perpendicular directions and vice versa, indicating a positive Poisson's ratio. Recently auxetic materials with negative Poisson's ratios, which can be realized through artificial microstructuring, are attracting increasing attention due to enhanced mechanical performances in multiple applications. Most of the proposed auxetic materials show different degrees of in-plane auxeticity depending on their microstructural configurations. However, this restricts harnessing the advantages of auxeticity in 3D systems and devices where multidirectional functionalities are warranted. Thus, there exists a strong rationale to develop microstructures that can exhibit auxeticity both in the in-plane and out-of-plane directions. Herein, generic 3D connected double loop (3DCDL) type periodic microstructures are proposed for multi-directional modulation of Poisson's ratios. Based on the bending dominated behavior of elementary beams with variable curvature, mixed-mode auxeticity following the framework of multimaterial unit cells is demonstrated. The proposed 3DCDL unit cell and expanded unit cells formed based on their clusters are capable of achieving partially auxetic, purely auxetic, purely nonauxetic and nullauxetic behavior. Comprehensive numerical results are presented for the entire spectrum of combinations concerning the auxetic behavior in the in-plane and out-of-plane directions including their relative degrees.<br/
Probing the chirality-dependent elastic properties and crack propagation behavior of single and bilayer stanene
No full textStanene, a quasi-two-dimensional honeycomb-like structure of tin belonging to the family of 2D-Xenes (X = Si, Ge, Sn) has recently been reported to show promising electronic, optical and mechanical properties. This paper investigates the elastic moduli and crack propagation behaviour of single layer and bilayer stanene based on molecular dynamics simulations, which have been performed using the Tersoff bond order potential (BOP). We have parameterized the interlayer van der Waals interactions for the bilayer Lennard-Jones potential in the case of bilayer stanene. Density functional calculations are performed to fit the Lennard-Jones parameters for the properties which are not available from the scientific literature. The effect of temperature and strain rate on the mechanical properties of stanene is investigated for both single layer and bilayer stanene in the armchair and zigzag directions. The results reveal that both the fracture strength and strain of stanene decrease with increasing temperature, while at higher loading rate, the material is found to exhibit higher fracture strength and strain. The effect of chirality on the elastic moduli of stanene is explained on the basis of a physics-based analytical approach, wherein the fundamental interaction between the shear modulus and Young's modulus is elucidated. To provide a realistic perspective, we have investigated the compound effect of uncertainty on the elastic moduli of stanene based on an efficient analytical approach. Large-scale Monte Carlo simulations are carried out considering different degrees of stochasticity. The in-depth results on mechanical properties presented in this article will further aid the adoption of stanene as a potential nano-electro-optical substitute with exciting features such as 2D topological insulating properties with a large bandgap, the capability to support enhanced thermoelectric performance, topological superconductivity and a quantum anomalous Hall effect at near-room-temperature.</p
Semi-analytical atomic-level uncertainty quantification for the elastic properties of 2D materials
No full textInherent stochasticity in the nanostructural geometry and molecular mechanics properties of lattice-like two-dimensional (2D) materials can significantly deviate the predicted elastic properties that are widely reported in a deterministic framework. Such uncertainties can be attributed to inevitable fabrication uncertainties and random error in parameterizing the atomic-level constants depending on the accuracy of highly complicated nanoscale experiments. Generalized high-fidelity analytical models are developed in this article to quantify the influence of these source-uncertainties on the basis of first- and second-order perturbation theories coupled with nanoscale continuum mechanics. The proposed stochastic mechanics–based analytical framework is further validated using the baseline Monte Carlo simulation–assisted probabilistic approach. To provide comprehensive numerical insights, four different 2D materials with uniform and non-uniform atomic distributions are considered covering the monoplanar as well as multiplanar nanostructural configurations (graphene, hexagonal boron nitride, stanene and molybdenum disulfide). The perturbation-based approach is further extended to quantify the relative sensitivity of different nanostructural and molecular mechanics parameters on the elastic moduli of 2D materials. The proposed analytical approach leads to a significant level of computational efficiency by alleviating the necessity of carrying out thousands of molecular dynamics simulations to obtain deep computational insights concerning uncertainty quantification and sensitivity analysis, which would assume a crucial role to ensure robust analysis and design of technologically demanding multifunctional devices and systems across the length-scales.</p
Programmed out-of-plane curvature to enhance the multi-modal stiffness of bending-dominated composite lattices
No full textConventional bending-dominated lattices exhibit less specific stiffness compared to stretching-dominated lattices while showing high specific energy absorption capacity. This article aims to improve the specific stiffness of bending-dominated lattices by introducing elementary-level programmed curvature through a multi-level hierarchical framework. The influence of curvature in the elementary beams is investigated here on the effective in-plane and out-of-plane elastic properties of lattice materials. The beam-like cell walls with out-of-plane curvature are modeled based on 3D degenerated shell finite elements. Subsequently, the beam deflections are integrated with unit cell level mechanics in an efficient semi-analytical framework to obtain the lattice-level effective elastic moduli. The numerical results reveal that the effective in-plane elastic moduli of lattices with curved isotropic cell walls can be significantly improved without altering the lattice-level relative density, while the effective out-of-plane elastic properties reduce due to the introduction of curvature. To address this issue, we further propose laminated composite cell walls with out-of-plane curvature based on the 3D degenerated shell elements, which can lead to holistic improvements in the in-plane and out-of-plane effective elastic properties. The proposed curved composite lattice materials would enhance the specific stiffness of bending-dominated lattices to a significant extent, while maintaining their conventional multi-functional advantages
Multi-physically programmable tubular origami metamaterials: exploitable nexus of geometry, folding mechanics and stimuli-responsive physics
No full textProgrammable shape morphing: unleashing the potential of satially graded derivatives of miura architecture
No full textPartial mode cloaking via axial-shear coupling in piezoelectrically tuned mechanical metamaterials
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