Despite the combination of nonlinear vibration suppression (VS) and energy harvesting (EH) has received great attention in recent years, the strategy to simultaneously improve the performance in both ...purposes and extend the operating amplitude range to low-level excitations is still an open issue. To achieve this goal, this paper proposes a tuned bistable nonlinear energy sink (TBNES) to outperform the typical bistable nonlinear energy sink (BNES). The TBNES replaces the fixed magnet that is opposite to the bistable piezoelectric beam (BPB) in the BNES by a tuning piezoelectric beam (TPB) with a movable tip magnet. On one hand, the TPB with a linear viscous damping and a piezoelectric element can improve both VS and EH performances. On the other hand, the tuning effect can dynamically reduce the elastic potential barrier of the BPB, helping it induce the initial snap-through motion and produce the strong targeted energy transfer at low-level excitations, therefore leading to the extension of its operating amplitude range. The electromechanical model and the magnetic force model are derived for both TBNES and BNES based on Hamilton’s principle and the geometrical dipole–dipole method. Parametric studies are conducted to investigate the influences of key system parameters on their VS and EH performances with three defined figure of merits. With the system parameters optimized by the presented dynamic optimization algorithm, the simulation results show that the performance of the TBNES is better than that of the BNES in VS and EH, and its operating range of excitation amplitudes can be successfully extended. The deep mechanisms for these phenomena are discussed from the aspects of 1:1 resonance, induction of nonlinearity, elastic potential energy, etc.
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•Tuned bistable nonlinear energy sink (TBNES) is proposed to outperform typical BNES.•The electromechanical model and the magnetic force model are derived for TBNES/BNES.•Parametric studies are conducted to investigate the influences of system parameters.•An algorithm is presented to optimize the system parameters of TBNES and BNES.•Improved vibration suppression and energy harvesting functions of TBNES are validated.
Pyramidal lattice sandwich structure (PLSS) exhibits high stiffness and strength-to-weight ratio which can be effectively utilized for designing light-weight load bearing structures for ranging from ...ground to aerospace vehicles. While these structures provide superior strength to weigh ratio, their sound insulation capacity has not been well understood. The aim of this study is to develop numerical and experimental methods to fundamentally investigate the sound insulation property of the pyramidal lattice sandwich structure with solid trusses (PLSSST). A finite element model has been developed to predict the sound transmission loss (STL) of PLSSST and simulation results have been compared with those obtained experimentally. Parametric studies are then performed using the validated finite element model to investigate the effect of different parameters in pyramidal lattice sandwich structure with hollow trusses (PLSSHT), revealing that the pitching angle, the uniform thickness and the length of the hollow truss and the lattice constant have considerable effects on the sound transmission loss. Finally a design optimization strategy has been formulated to optimize PLSSHT in order to maximize STL while meeting mechanical property requirements. It has been shown that STL of the optimal PLSSHT can be increased by almost 10% at the low-frequency band. The work reported here provides useful information for the noise reduction design of periodic lattice structures.
3D contour map for the distribution of absolute error in (a) learning (b) validation and (c) testing data set of GEP predictive model.
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•Re-utilization of crumb rubber (CR), gene ...expression programming has been employed has been employed.•Empirical models for prediction of mechanical properties of concrete made by using NaOH treated CR.•Compressive strength is estimated by the application of proposed simplified mathematical expressions.
To encourage the consumption of crumb rubber (CR), gene expression programming (GEP) has been exercised in this paper to establish empirical models for estimation of mechanical properties of concrete made with NaOH treated CR. An extensive and reliable database of compressive strength of concrete made with NaOH treated CR is established through a comprehensive literature review. Literature review showed that compressive strength of NaOH treated CR concrete is affected by percentage of CR used as a replacement of sand (RS%), concentration of NaOH solution (NC in %), period of NaOH pre-treatment (PTP in hours), water to cement ratio (W/C), quantity of sand (S in kg/m3) and quantity of superplasticizer (SP in kg/m3). The performance of the established model is evaluated by doing parametric analysis, applying statistical checks and comparing with regression models. The R-values in the testing phase of GEP, linear and non-linear regression (LR and NLR) equations are 0.90 and 0.77 each respectively. Furthermore, objective function (OF) of GEP model is 25%, and 33% better than LR and NLR model. Thus, results reflected that the proposed GEP model is more accurate and possess a high generalization and prediction capability than LR and NLR equations with resolved overfitting issue. The results of this research can boost the re-usage of CR for expansion of green concrete leading to environmental safety and economic advantages.
Using high strength materials in concrete filled steel tube (CFST) columns is expected to achieve better structural performance and fulfil the requirements of sustainable construction. To study the ...mechanical behaviour of eccentrically loaded high strength concrete filled high strength square steel tube (HCFHSST) stub columns, this paper describes 12 tests with different eccentricity ratios and steel ratios. The cubic strength of high strength concrete under investigation was 110.5 MPa, and the yield strength of the high strength steel was about 434 MPa. Curves of load-lateral deformation were presented, along with values of ductility index, and the minimum ductility index based on the steel ratio of columns was suggested. Finite element analysis (FEA) software ABAQUS was applied to simulate HCFHSSTs. The analytical results were in good agreement with the experimental ones. The load-lateral deformation curve was divided into four stages: elastic, elastic-plastic, plastic hardening and descending. The confinement effect of steel tube at various stages was analysed. The parametric studies were carried out to evaluate the influences of the eccentricity ratio, concrete compressive strength, steel yield strength and steel ratio on the strength reduction factor (SRF), concrete contribution ratio (CCR), P-M and P/Pu-M/Mu interaction curves of the HCFHSST members. The bending moments at balanced points of P/Pu-M/Mu curves calculated by the plastic stress distribution models (PSDM) and FEA models were compared. The ultimate bearing capacities obtained from the tests and the values calculated from the AISC 360, GB 50936 and CECS 28: 90 design codes were compared. Finally, the formulas were proposed to predict the P/Pu-M/Mu curves for the HCFHSST stub columns subjected to eccentric load. The proposed formulas’ predictions agreed well with the test results.
•Eccentric compression tests were performed on HCFHSST stub columns.•The minimum ductility index was suggested.•The confinement effect of steel tube was investigated by FEA models.•Parametric studies were carried out to study the mechanical behaviour of HCFHSSTs.•Formulas were put forward to predict the P/Pu-M/Mu curves.
•Developed a CFD approach for heating induced thermal runaway incorporating heat dissipation.•Predictions established the critical temperature to trigger TR for the current LIB as 131–132 °C.•Filled ...important experimental gaps on heat generation of the different decomposition reactions.•Analysis demonstrates effective prevention of TR propagation needs to be implemented prior to TR.
Combined numerical and experimental studies have been carried out to investigate thermal runaway (TR) of large format 21700 cylindrical lithium-ion battery (LIB) induced by different thermal abuse. Experiments were firstly conducted with the Extend Volume Accelerating Calorimetry (EV-ARC) using both the heat-wait-seek (HWS) protocol and under isothermal conditions. The kinetic parameters were derived from one of the HWS EV-ARC tests and implemented in the in-house modified computational fluid dynamics (CFD) code OpenFOAM. For the subsequent CFD simulations, the cell was treated as a 3-D block with anisotropic thermal conductivities. The model was verified by the remaining two HWS tests not used in the derivation of the kinetic parameters and validated with newly conducted isothermal EV-ARC tests. Further laboratory tests and model validation were also subsequently conducted using Kanthal wire heaters. The validated model was also used to fill the experimental gaps by predicting the onset temperature for TR in simulated EV-ARC environment, heat generation rate due to different abuse reactions, the influence of heating power and heating arrangement as well as the effect of heat dissipation on TR evolution and the implications for battery thermal management. The present study has identified the TR onset temperature of the considered 21700 LIB to be between 131 and 132 °C. The predicted heat generation rate due to the decompositions of SEI and anode were found to follow similar patterns while that from cathode increase sharply near the maximum cell surface temperature, indicating the possibility of delaying TR onset temperature by optimising the cathode material. The time to maximum cell surface temperature decreases rapidly with the increase of the heating power.
The use of piezoelectrically controlled bistable composite laminates for morphing applications has received increased attention in recent years. So far, most existing investigations have explored the ...possibility to trigger snap-through using large-sized piezoelectric Macro Fibre Composite (MFC) actuators bonded at the centre of the bistable laminate. However, bonding large-sized MFCs at the centre of the plate leads to flattening of the midsection of the laminate, which can result in the loss of bistability. This study presents an alternative approach of bonding distributed smaller MFCs over the entire surface of the laminate and investigate the resulting stable shapes and the change in snap-through voltages. Self-resetting piezoelectrically controlled active laminates where the MFC patches are distributed over the laminate surface have been investigated. A semi-analytical model using the Rayleigh–Ritz technique is developed to account for the distributed actuation system. Results from the proposed semi-analytical framework are verified using a corresponding finite element model. The bistable shapes, as well as the snap-through and snap-back voltages, are calculated for different distributed MFC configurations and are compared with a single MFC laminate system. Snap-through voltage predictions from the proposed semi-analytical formulation and the finite element model are compared with the experimental results for a single MFC patch available from the literature. Further, the possibility to tailor the snap-through voltages of the proposed laminate-MFC configuration is explored by replacing conventional cross-ply laminates with variable stiffness (VS) laminates generated from curvilinear fibre alignments. A finite element parametric study is performed by tailoring the VS fibre orientation parameters to achieve a bistable laminate-MFC configuration with lower snap-through requirements where the designed laminate is actuated with distributed MFC patches.
The single-layer reticulated shell with aluminium alloy gusset (AAG) joints is an innovative space structure system, and has been widely used in the building engineering. According to the bending ...behaviour of AAG joints obtained from the theoretical formulae, the finite element (FE) models of K6 AAG joint shells were established in the ANSYS program. The buckling performance of K6 shells with semi-rigid and rigid joints was discussed. It is indicated that the semi-rigid behaviour of AAG joints had a significant effect on the buckling performance of K6 shells. To develop a further understanding, parametric studies were performed, varying the span-to-thickness ratio, height-to-span ratio, ring, member section, joint bending behaviour, joint stiffness model, material property, load distribution, support condition and initial geometric imperfection. It is found that the effects of these parameters on the elasto-plastic stability of K6 shells with rigid and AAG joints were different obviously. At last, to predict the elasto-plastic buckling load of AAG joint shells, theoretical formulae were proposed on the basis of the FE results of more than 8000 shell models.
•The finite element models of K6 AAG joint shells were established.•The behaviour of AAG joints affects the buckling performance of K6 shells greatly.•To develop a further understanding of K6 shells, parametric studies were performed.•To predict the buckling load of K6 shells, theoretical formulae were proposed.
This paper describes a comprehensive testing and numerical simulation investigation into the material properties, membrane residual stresses and compression capacities of S690 high strength steel ...welded I-section stub columns. The testing programme was performed on eight welded I-sections fabricated from 5 mm thick S700MC high strength steel hot-rolled plates by means of gas metal arc welding, and included material tensile coupon tests, membrane residual stress measurements, initial local geometric imperfection measurements, and sixteen concentrically loaded stub column tests. A membrane residual stress distribution model for S690 high strength steel welded I-sections was firstly proposed, based on the experimentally measured results. In conjunction with the structural testing, a numerical modelling study was carried out, in which finite element models were initially developed and validated against the experimental results, and afterwards employed to conduct parametric studies, aiming at generating further structural performance data over a broader range of cross-section sizes. The obtained experimental and numerical data were used to evaluate the accuracy of the slenderness limits (for classifications of plate elements and cross-sections) and design rules for S690 high strength steel welded I-section stub columns, as set out in the European, American and Australian standards. The results of the evaluation revealed that the codified slenderness limits are accurate for the plate element and cross-section classifications of S690 welded I-sections in compression, and the established local buckling design provisions in the considered three codes result in precise and consistent cross-section compression resistance predictions for both non-slender and slender S690 welded I-section stub columns.
•Material properties, residual stresses and compression capacities of S690 welded I-section stub columns were studied.•Longitudinal and transverse tensile coupon tests and residual stress measurements on S690 welded I-sections were conducted.•A total of sixteen concentrically loaded S690 welded I-section stub column tests were carried out.•FE models were developed and validated against experimental results, and then utilised to perform parametric studies.•The codified local buckling design rules for S690 welded I-section stub columns was assessed, indicating accuracy.
Due to its wide applicability, vortex-induced vibration (VIV) from wind and water flow has been explored for piezoelectric energy harvesting. However, the broadband VIV energy harvesting at low wind ...speeds is still a great challenge. In this paper, an auxetic nonlinear VIV energy harvester (ANVEH) is proposed. For the first time, the advantages of monostable softening behavior using magnetic attraction are investigated. It is found theoretically and experimentally that the monostable softening can broaden the working wind speed range whereas decreasing the peak energy output. Thus, the auxetic structure is proposed to compensate the decrease of peak energy output with the monostable softening due to its negative Poisson’s ratio and high stress distribution. Utilizing the experimentally validated theoretical model, parametric investigations are undertaken to examine the effects of various factors, including the magnetic separation distance, the stiffness and mass of the harvester, the dimension of the bluff body, the connected resistance, and the electromechanical coupling coefficient. Results show that no matter how the system parameters vary, the ANVEH has the superior performance than the plain nonlinear VIV energy harvester (PNVEH).
•Advantages of monostable softening in broadband VIV energy harvesting are explored.•Auxetic structure is proposed to compensate the decreased peak power with monostability.•Theoretical and experimental investigation are performed to validate the assumption.•Deep system mechanisms are investigated through dynamics and parametric studies.•Superior performance of the proposed system exists no matter how parameters vary.
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