Journal of Intelligent Material Systems and Structures

Magnetorheological fluid is a novel functional material, of which quasistatic squeeze behavior needs to be quantitatively controlled in industrial applications. Since the quasistatic squeeze behavior has a close relation with microstructure variations, thus it is modeled from a microscopic approach. By analyzing compression of single chains, aggregation from single chains to BCT structure and compression of BCT structure, the initial stress σ 0 , yield stress σ y , yield strain ε y , and stress in post-yield stage σ are respectively modeled. It is found that they have an exponential dependence on magnetic field strength H and particle volume concentration ξ , including σ 0 ∝ ξ H 2 , σ y ∝ H 2 , and ( σ y − σ 0 ) ∝ ξ 2 , etc. By comparing predicted results with measured results, the micro-macro stress model on quasistatic squeeze behavior is well validated. This model can be used to design, manufacture, and control industrial magnetorheological devices.

In the past few years, many studies have proved the efficiency of Simple Adaptive Control (SAC) in mitigating earthquakes’ damages to building structures. Nevertheless, the weighting matrices of this controller should be selected after a large number of sensitivity analyses. This step is time-consuming and it will not necessarily yield a controller with optimum performance. In the current study, an innovative method is introduced to tuning the SAC’s weighting matrices, which dispenses with excessive sensitivity analysis. In this regard, we try to define an optimization problem using intelligent evolutionary algorithm and utilized control indices in an objective function. The efficiency of the introduced method is investigated in 6-story building structure equipped with magnetorheological dampers under different seismic actions with and without uncertainty in the model of the proposed structure. The results indicate that the controller designed by the introduced method has a desirable performance under different conditions of uncertainty in the model. Furthermore, it improves the seismic performance of structure as compared to controllers designed through sensitivity analysis.

In this paper, the authors introduce a model of a strain-based geometrically nonlinear piezoelectric beam for modeling energy harvesters. A nonlinear shear-underfomable 3-D Rayleigh’s beam theory is used to model the displacement fields and can be considered as an interesting alternative to linear and highly nonlinear models commonly presented in the literature. The nonlinearities are introduced to reproduce the behavior of the flexible structure, since moderate to large displacements can occur in response of external loading conditions. The finite element method is used to model the piezolaminated bimorph configuration. Each finite element consists of two piezoelectric energy harvesters embedded or perfectly bonded to an elastic substrate. The electromechanical coupling includes axial and flexural effects as well as additional term that comes from the nonlinearity incorporated into the strain tensor. Additionally, the authors explore briefly two topics for linear harvesters: the influence of the electric domain on the structural properties and, the performance of the harvester near resonance in term of electric power output of a purely resistive network. As a validation case, a cantilevered piezoelectric energy harvester under base excitation is modeled. Alongside, the response to gust of a harvester embedded in a wing structure is analyzed.

This paper shows how to enhance the vibration attenuation obtained by means of piezoelectric resistive shunt coupled to the use of negative capacitances. This improvement is achieved by adding an inductance in the shunt circuit. This additional inductance is not used to the usual purpose of mono-modal control, but to improve the attenuation in a broader frequency range. The benefits offered by the use of the inductance are explained by describing the shunted electro-mechanical system as a feedback control loop. The achievable attenuation improvements are highlighted in the paper at first through numerical analyses and then by means of an experimental campaign which also allows to evidence the reliability of the model employed to describe the electro-mechanical system.

Sampling fluids from the small-diameter deep pipeline is a challenging problem. In this paper, a very simple, piezoelectric-actuated inertial pump (PIP) is developed using a bionic valve to solve these problems. The PIP consists of simple components, including a cantilever beam piezoelectric actuator, a hard tube, and a bionic valve made of silicone. The fluid is driven by the inertial force generated in the vibration process of the tube. A new bionic valve inspired by a heart valve has been designed which has the advantages of small flow resistance and large flow area. The authors described the working principle of PIP in detail, established the flow characteristics model of the bionic valve, and used COMSOL Multiphysics to analyze the characteristics of the bionic valve. By comparing the response characteristics of the bionic valve with different tilt angles, the optimal Angle was obtained. Finally, the experimental and simulation results were compared, and the basic performance of PIP was tested. The experimental results showed that: When the tilting angle was 45° and the valve hole diameter was 6 mm, when the voltage was 98 V and the frequency was 24.5 Hz, the maximum output flow of the piezoelectric pump was 170.25 ml/min.

A new control method of Shape Memory Alloy (SMA) actuators based on stochastic recruitment is proposed. From the perspective of bionic control, the physiological basis of stochastic recruitment limited feedback control of artificial muscle is explained. The limited feedback control system of two-state cells and multi-state cells are established, and the limited feedback control law is deduced for these two kinds of systems. In the Simulink environment, two kinds of limited feedback control algorithms are simulated and compared, which verifies the feasibility of the algorithm. Aiming at the key problem of scaling coefficient in the system, the longitudinal and transverse comparative experiments are carried out to analyze the influence of the scaling coefficient on the system.

An analytical model is developed for a prismatic SMA beam with rectangular cross section subjected to alternating bending at temperature below the austenitic transformations. The loading path consists in a loading-unloading cycle under bending and then under reversed bending. Two opposite martensitic variants take place, whose volume fractions evolve linearly with the axial stress. Different Young’s moduli are taken for the austenitic and martensitic phases. As the bending moment is increased, the martensitic transformation starts from the top and bottom and then it extends inwards. If the maximum applied bending moment is large enough, then the complete Martensitic transformation takes place at the upper and lower parts of the cross section. During unloading and the following reversed bending, reorientation of the Martensite variant into the opposite one takes place starting from the boundary between the fully martensitic region and the intermediate transforming region. Special attention is devoted to calculate analytically the axial stress and Martensite variant distributions within the cross section at each stage of the process. A closed form moment-curvature relation is provided for loading and elastic unloading and in integral form for the rest of the process. The approach is then validated by comparison with analytical results available in the literature.

The road-base usually deteriorate during service time due to factors such as cyclical traffic loads and road-base fouling. Currently the monitoring method for road-base quality is quite limited. This paper proposes a real-time Monitoring method for Road-Base Quality (MRBQ) based on a soil dynamic model and piezoelectric sensors buried in road-base. The soil dynamic model was extended with a piezoelectric equation to calculate the voltage in the road-base generated by a moving traffic load. Then, a model test was conducted to measure the output voltage of the piezoelectric sensors buried in the road-base. Finally, the road-base modulus was back-calculated through the soil dynamic model with the measured voltage. The back-calculated modulus was compared with the modulus measured by resonance column test (RCT) to validate this method. The unique relationship between the peak voltage and the road-base modulus at various depths was identified for different traffic load amplitudes and speeds, and the feasibility and accuracy of the MRBQ was demonstrated. This study reveals that the sensitivity of the piezoelectric sensors can reach 2 V/MPa, and the error to measure the road-base modulus is less than 20%. The proposed MRBQ demonstrates a good application potential in health monitoring of transportation facilities.

The energy scavenged from a vibrating building installed with distributed electromagnetic energy harvesters under random excitation is analyzed. Each harvester is connected to an energy harvesting circuit made of a full-wave bridge rectifier connecting a resistor in parallel with a capacitor. Statistical linearization is adopted to estimate the stationary response of the harvester-structure system. As an illustrative example, a 20-story building equipped with 16 harvesters on each story is examined. Results show that the scavenged energy mainly concentrates at the higher stories. The vibration mitigation and energy scavenging performance of the harvesters can be enhanced simultaneously with the proper design of harvesters and circuits. Gradient ascent approach with the first-order perturbation approximation is proposed to determine the optimal design of distributed harvesters with nonlinear circuits that maximizes the total mean output power. Results show that output power decreases due to circuit nonlinearity. The maximum total mean output power obtained from the 20-story building under wind excitations with mean speed of 5 m/s is around 1.32–2.17 kW for harvesters having short-circuit damping coefficient ranging 100–300 kNs/m. These results show that scavenging energy from structural vibration is a feasible technology even considering the negative effect of circuit nonlinearity.

The demand for life-time power supply in Internet of Things (IoT) nodes is a challenge issue. Piezoelectric energy harvesting (PEH) is expected to meet the demand by harvesting vibration energy and converting it into electricity for the IoT nodes. This article presents a novel PEH power improvement circuit with thermoelectric energy assistance. The proposed circuit can extract energy from thermoelectric generator (TEG) to assist the PEH. Simulation and experimental platforms are built for testing the power generation performance of the proposed circuit. With the thermoelectric assistance of 0.1 V and 0.2 V, the harvested power can reach 3.4 times and 4 times that of the standard energy harvesting (SEH) circuit when the piezoelectric transducer (PZT) original open circuit voltage V_oc,org = 8 V, respectively. The harvested power can be increased by 13.3% and 33.3% with the thermoelectric assistance of 0.1 V and 0.2 V, respectively.

The structure health monitoring (SHM) system with Lamb waves technique is studied numerically and experimentally in this paper. A damage shape recognition algorithm (DSRA) is developed for the hole on aluminum alloy plate specimen. The proposed DSRA is established based on the two arrival time difference method (2/ATDM) and Lagrangian optimization method. This method captures the damage shape by describing the coordinates of the reflection point from the piezoelectric ceramic lead zirconate titanate (PZT) transducers to the damage edge. 2/ATDM provides a way to obtain coordinate points by the arrival time which is determined by Lamb waves. And the coordinate points are optimized by the Lagrangian optimization method. A numerical model is established to simulate the proposed experiment process. Its convergence rate of mesh size and time steps is investigated, and the numerical results are verified by these of experiment. Hence, the shape recognition of damage occurring at an arbitrary position and that of irregular damage are studied by the proposed numerical and experiment methods.

This study designs, fabricates and tests a piezoelectric pump with the structure of a polystyrene ball check valve. The structure of the check valve consists of three layers of specially designed polymethylmethacrylate plates and six polystyrene balls, which forms a particular three-layer constraint mechanism to limit the lateral and vertical displacement of the balls. The assembly of the ball valve can be completed with a simple placing operation, which simplifies the assembly process of the entire pump. The balls are lightweight, which is beneficial for working at high frequencies. The current design adopts two compressible spaces, and the equivalent analogue circuit of compressible spaces is established and analysed. Experimental results indicate that compressible spaces can alleviate the burden in the actuator and smoothen the flow rate pulsation in the long flow channel. The theoretical analysis and experimental tests reveal that this new piezoelectric pump is self-priming. A high flow rate of 99.6 mL/min and the maximum back pressure of 15.3 kPa are obtained when the pump is driven with a sinusoidal voltage of 448 V_pp at the resonant frequency of 790 Hz.

In this paper, the primary purpose is to have a complete understanding of the importance of fibers in dielectric elastomers due to the influence of fiber orientation in decreasing the applied voltage to simulate the structure and improving mechanical performance. Fibers will also reduce the chance of failure like Wrinkling instabilities and increase the response rate under electric displacement. Implementing the dielectric elastomers with anisotropic structure, despite their great potential, has not adequately analyzed in previous researches. Therefore, based on nonlinear continuum mechanics and large inelastic deformations, the constitutive relationships and equations governing the behavior of viscoelastic dielectric elastomers under harmonic electrical loading are extracted and analyzed in different states. The numerical results, such as phase and frequency-amplitude diagrams and the oscillation, illustrate the dynamic behavior of an anisotropic dielectric elastomer with different fiber orientations. To describe the viscoelasticity behavior of the material, hyperelastic models and the rheological model, are used in conjunction with electrical coupling. Using the theory of anisotropic dielectric elastomers, a geometrically nonlinear formulation under finite deformations is developed by the Euler-Lagrange equations and solved mathematically.

As a novel fiber-based piezoelectric composite material, macro fiber composites (MFC) affords notable advantages of good flexibility, high deformability, and large actuation ability. However, the intrinsic hysteresis behavior of the MFC decreases the positioning precision and performance of the flexible structure actuated by MFC actuators. A bias bipolar Prandtl-Ishlinskii (BBPI) model is presented to describe the bias bipolar hysteresis nonlinearity of a MFC-actuated flexible cantilever. The BBPI hysteresis model is composed of two parts: a superposition of the weighted play operators of the classical Prandtl-Ishlinskii (PI) model is employed to characterize the symmetric hysteresis. And a superposition of the weighted dead-zone operators is cascaded to deal with the bias bipolar behavior. Experimental identification results demonstrate that the presented BBPI model exhibits better modeling performance than the classical PI model. A feedforward compensation strategy based on the inverse BBPI hysteresis model is proposed. Experiments on trajectories tracking subject to a triangular wave, sinusoidal wave, and triangular wave with random amplitudes are carried out. Experimental results demonstrate the feasibility and effectiveness of the proposed BBPI model and the inverse feedforward compensator.

Shape Memory Alloys (SMA) have become a material with great application prospects because of their unique characteristics and superior properties. A phenomenological constitutive model for SMA is constructed in the current paper. The proposed constitutive model is based on the phenomena observed in the experiment, and Artificial Neural Networks (ANN) are used to simulate part of the characteristics of SMA. The parameter identification method is also proposed, where Back-Propagation (BP) algorithm and the nonlinear optimisation algorithm are used at the same time. The numerical experiment has been carried out, which can well capture the constitutive relationship curve obtained from uniaxial tension and compression experiments of SMA, thus the model can be verified. The model can also describe the phase transformation characteristics of SMA well.

The pH-sensitive hydrogels are a unique class of three-dimensional hydrophilic polymers containing ionic pendant groups on their polymeric network. In response to the external pH variation, these materials span the volume of an aqueous/biological solution and swell without dissolution. Nowadays, the pH-sensitive hydrogels have attracted the growing interest of many researchers in various fields of researches such as drug delivery, tissue engineering, soft actuators, etc. which makes the simulation of their behavior crucial for optimum utilization. The essential prerequisite for the simulation of these materials is the swelling theory. In this article, we present a review of the fundamental phenomena in swelling theories of the pH-sensitive hydrogels. We also classify the swelling theories into two groups including the monophasic and multiphasic theories. Then, we briefly examine the most highlighted swelling theories in each group. The experimental data is essential for material parameters estimation as well as verification of the constitutive equations. Thus, we introduce and discuss the most highlighted experiments on the swelling and deswelling behavior of the pH-sensitive hydrogels as well.