Showing papers in "Journal of Intelligent Material Systems and Structures in 2000"
TL;DR: In this article, the behavior of piezoelectric elements as strain sensors is investigated and the performance of PZT and PVDF sensors compared with conventional foil strain gages is demonstrated.
Abstract: This paper investigates the behavior of piezoelectric elements as strain sensors. Strain is measured in terms of the charge generated by the element as a result of the direct piezoelectric ef- fect. Strain measurements from piezoceramic (PZT) and piezofilm (PVDF) sensors are compared with strains from a conventional foil strain gage and the advantages of each type of sensor are dis- cussed, along with their limitations. The sensors are surface bonded to a beam and are calibrated over a frequency range of 5-500 Hz. Correction factors to account for transverse strain and shear lag ef- fects due to the bond layer are analytically derived and experimentally validated. The effect of tem- perature on the output of PZT strain sensors is investigated. Additionally, design of signal condition- ing electronics to collect the signals from the piezoelectric sensors is addressed. The superior performance of piezoelectric sensors compared to conventional strain gages in terms of sensitivity and signal to noise ratio is demonstrated.
624 citations
TL;DR: In this article, a semi-active control law is used to switch the electrical shunt circuit of a piezoelectric actuator for energy dissipation in a simple mechanical system.
Abstract: In this paper, a semi-active control law is used to switch the electrical shunt circuit of a piezoelectric actuator for energy dissipation in a simple mechanical system. Switching is carried out between open-circuit (high stiffness) and short- or resistive-circuit (low stiffness) states. The actuator is held in its high stiffness state when the system is moving such that energy can be stored in the actuator. When the system’s motion would cause it to receive energy back from the actuator, the actuator is switched to a low stiffness state, dissipating the energy. In this paper, the concept is developed starting with the governing piezoelectric equations. Numerical simulation results are presented which show that the technique provides energy dissipation that is comparable to other piezoelectric shunt mechanisms, using optimal shunt resistance in each case. Finally, a brief analysis is presented in which the piezoelectric element is used in a flexible beam element to illustrate the effects of a parallel str...
334 citations
TL;DR: An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the PSS terminals as discussed by the authors.
Abstract: In the beginning, the classical one-dimensional analysis of piezoelectric active sensors is reviewed. The complete derivation for a free-free sensor is then extended to cover the cases of clamped and elastically constrained sensors. An analytical model based on structural vibration theory and theory of piezoelectricity was developed and used to predict the electromechanical (E/M) impedance response, as it would be measured at the piezoelectric active sensor’s terminals. The model considers one-dimensional structures and accounts for both axial and flexural vibrations. The numerical analysis was performed and supported by experimental results. Experiments were conducted on simple beam specimens to support the theoretical investigation, and on thin gauge aluminum plates to illustrate the method’s potential. It was shown that E/M impedance spectrum recorded by the piezoelectric active sensor accurately represents the mechanical response of a structure. It was further proved that the response of the structure...
270 citations
TL;DR: In this article, the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications was investigated using both satin and plain weave fiber architectures, and it was shown that the dominant local deformation mode was buckling of the carbon fibers on the inner surface of the bend.
Abstract: In this paper we present results on the deformation of carbon fiber reinforced shape memory polymer matrix composites for deployable space structure applications. The composites were processed using resin transfer molding or a pre-impregnated (pre-preg) laminate press, with both satin and plain weave fiber architectures. The polymer matrix glass transition temperature, Tg, was approximately 95°C. Composite specimens were bent to specific radii at T = 120°C, and cooled while constrained to a temperature of 25°C, which left them frozen in the bent state. Heating the specimens above Tg caused the composites to return to their original unbent shape with up to 95% recovery based on bend angle. The effect of constraint hold times up to 350 hours on the recoverability was found to be negligible. Microscopic investigations revealed that the dominant local deformation mode of the composites was buckling of the carbon fibers on the inner surface of the bend. Localized buckling out of the material plane lead to detr...
235 citations
TL;DR: In this article, two different damage detection schemes are combined in this methodology, which involves utilizing the electromechanical coupling property of piezoelectric materials and tracking the changes in the frequency response function data, respectively.
Abstract: This paper presents an integrated methodology to detect and locate structural damage. Two different damage detection schemes are combined in this methodology, which involves utilizing the electromechanical coupling property of piezoelectric materials and tracking the changes in the frequency response function data, respectively. Physical changes in the structure cause changes in mechanical impedance. Due to the electromechanical coupling in piezoelectric materials, this change in structural mechanical impedance causes a change in the electrical impedance of the piezoelectric sensor. Hence, by monitoring the electrical impedance one can qualitatively determine when structural damage has occurred or is imminent. Based on the fact that damage produces local dynamic changes, this technique utilizes a high frequency structural excitation (typically greater than 30 kHz) through the surface-bonded piezoelectric sensor/actuators. As a second step, a newly developed model-based technique, using a wave propagation ...
228 citations
TL;DR: In this paper, a cylindrical magneto-rheological (MR) seat damper is designed on the basis of the Bingham model of the MR fluid, and a skyhook controller is formulated and realized in a closed-loop control fashion.
Abstract: This paper presents vibration control of a semi-active seat suspension with a magneto-rheological (MR) fluid damper, which is applicable to commercial vehicles such as large size of trucks. A cylindrical MR seat damper is designed on the basis of the Bingham model of the MR fluid. After manufacturing the seat damper, field-dependent damping force characteristics are experimentally evaluated. A semi-active seat suspension system installed with the seat damper is then constructed and its governing equation of motion is derived. A skyhook controller to reduce vibration level at the driver’s seat is formulated and realized in a closed-loop control fashion. The control responses, such as acceleration transmissibility, are investigated in both frequency and time domains. In addition, a full-vehicle model featuring the proposed semi-active seat suspension is established and its vibration control performances are evaluated via the hardware-in-the-loop simulation (HILS).
226 citations
TL;DR: In this article, a semi-active magnetorheological (MR) fluid damper is proposed for a full-car suspension, which can be continuously controlled by the intensity of the magnetic field.
Abstract: This paper presents control characteristics of a full-car suspension featuring a semi-active magnetorheological (MR) fluid damper A cylindrical MR damper is devised and its field-dependent damping force is evaluated with respect to the piston velocity After verifying that the damping force can be continuously controlled by the intensity of the magnetic field, the MR damper is applied to a full-car model The governing equations of motions, which include vertical, pitch, and roll motions are derived and incorporated with the skyhook controller Control characteristics of the full-car suspension installed with the proposed MR damper are evaluated through hardware-in-the-loop simulation (HILS), and presented in both time and frequency domains
199 citations
TL;DR: In this paper, the authors reviewed recent achievements in the application of smart-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed-wing aircraft.
Abstract: The paper reviews recent achievements in the application of smart-materials actuation to counteract aeroelastic and vibration effects in helicopters and fixed wing aircraft. A brief review of the induced-strain actuation principles and capabilities is done first. Attention is then focused on the smart rotor blade applications. Induced twist, active blade tip, and active blade flap are presented, with emphasis on experimental results. The fixed wing aircraft applications are considered next. Experiments of active flutter control, buffet suppression, gust load alleviation, and sonic fatigue reduction are discussed. Conclusions and directions for further work are presented at the end of the paper.
193 citations
TL;DR: In this paper, the performance of three semiactive control policies, including the well-known skyhook control and two others that are referred to as groundhook and hybrid control, are studied experimentally.
Abstract: The performance of three semiactive control policies, including the well-known skyhook control and two others that are referred to as “groundhook” and “hybrid” control, are studied experimentally. The experiments use a single suspension apparatus that is commonly referred to as “quarter-car” rig, and a magnetorheological damper that is built and tuned for the purpose of this study. Upon describing the mathematics of the three semiactive control policies and the construction of the quarter-car rig, the results of a series of experiments with each control policy are presented. The transmissibility plots of the test results confirm the features of each control policy, as discussed in the past analytical studies. The results indicate that skyhook control can significantly reduce the transmissibility of the sprung mass, as compared with passive dampers. Similarly, groundhook control substantially reduces the unsprung mass transmissibility. For vehicle applications, reducing the sprung mass transmissibility oft...
155 citations
TL;DR: In this article, a non-model based technique to detect, locate, and characterize structural damage by combining the impedance-based structural health monitoring technique with an artificial neuromodel is presented.
Abstract: This paper presents a non-model based technique to detect, locate, and characterize structural damage by combining the impedance-based structural health monitoring technique with an artificial neur...
131 citations
TL;DR: The belt-rib concept for lifting surfaces with variable camber evolved at DLR recently as one of the most promising solutions for the adaptive wing as discussed by the authors, where the classical rib, which is in charge of the wing section's stiffness, is replaced by a "belt rib", which allows camber changes within given limits while leaving the remaining in-plane stiffness properties of the section widely unchanged.
Abstract: The belt-rib concept for lifting surfaces with variable camber evolved at DLR recently as one of the most promising solutions for the adaptive wing. With the belt-rib idea the adaptive wing issue is approached in a new way: instead of a “mechatronic” solution with hinges or linear bearings a “structronic” solution is chosen, where distributed flexibility allows the desired shape changes. The resulting system is not only easier to maintain due to the absence of wear, but also is structurally more reliable and substantially lighter.The new concept evolves from the classical wing structure. The classical rib, which is in charge of the wing section’s stiffness, is replaced by a “belt rib,” which allows camber changes within given limits while leaving the remaining in-plane stiffness properties of the section widely unchanged.The evolution of the belt-rib concept was accompanied by experimental tests on different prototypes. After a first development stage, in which mainly the system’s shape adaptability and t...
TL;DR: In this paper, a piezoelectric actuator is used to make use of the step-and-repeat capability of piezoric actuators, and the authors discuss pump theory, pump design and pump performance.
Abstract: A piezohydraulic pump is presented that makes use of the step-and-repeat capability of piezoelectric actuators. This work discusses piezohydraulic pumping theory, pump design, and pump performance....
TL;DR: In this paper, the magnetic forces generated by magnetostrictive transducers in response to applied magnetic fields are modeled by considering both the rotation of magnetic moments and the elastic vibrations in the transducers.
Abstract: This paper addresses the modeling of strains and forces generated by magnetostrictive transducers in response to applied magnetic fields. The magnetostrictive effect is modeled by considering both the rotation of magnetic moments in response to the field and the elastic vibrations in the transducer. The former is modeled with the Jiles-Atherton model of ferromagnetic hysteresis in combination with a quartic magnetostriction law. The latter is modeled through force balancing which yields a PDE system with magnetostrictive inputs and boundary conditions given by the specific transducer design. The solution to this system provides both rod displacements and forces. The calculated forces are used to quantify the magnetomechanical effect in the transducer core, i.e., the stress-induced magnetization changes. This is done by considering a “law of approach” to the anhysteretic magnetization. The resulting model provides a representation of the bidirectional coupling between the magnetic and elastic states. It is...
TL;DR: In this article, the fundamental analysis tools for a Single-Degree-of-Freedom (SDF) state-switchable device are presented, and the application of such a device for the purpose of vibration control in a 2-DOF system is considered.
Abstract: A system that has the capability to make instantaneous changes in its mass, stiffness, or damping may be termed a state-switchable dynamical system. Such a system will display different dynamical responses dependent upon its current state. For example, state-switchable stiffness may be practically obtained through the control of the termination impedance of piezoelectric stiffness elements. If such a switchable stiffness element is incorporated as part of the spring element of a vibration absorber, the change in stiffness causes a change in the resonance frequencies of the system, thereby instantaneously “retuning” the state-switched absorber to a new frequency. This paper briefly develops the fundamental analysis tools for a Single-Degree-of-Freedom state-switchable device, and then considers the application of such a device for the purpose of vibration control in a 2-DOF system. Simulation results indicate that state-switched vibration absorbers may be advantageous over classical passive tuned vibration...
TL;DR: In this paper, a structural damage detection method based on parameter identification using an iterative neural network (NN) technique is proposed, which is first trained off-line using an initial training data set that consists of assumed structural parameters as outputs and their corresponding dynamic characteristics as inputs.
Abstract: A structural damage detection method based on parameter identification using an iterative neural network (NN) technique is proposed in this study. The NN model is first trained off-line using an initial training data set that consists of assumed structural parameters as outputs and their corresponding dynamic characteristics as inputs. The structural parameters are assumed with different levels of reduction to simulate various degrees of structural damage. The concept of orthogonal array is adopted to generate the representative combinations of parameter changes, which can significantly reduce the number of training data while maintaining the data completeness. A modified back-propagation learning algorithm is proposed which can overcome possible saturation of the sigmoid function and speed up the training process. The trained NN model is used to predict the structural parameters by feeding in measured dynamic characteristics. The predicted structural parameters are then used in the FE model to calculate ...
TL;DR: In this paper, the authors presented a novel work on developing fiber optic micro-sensors and integrating them into soldiers' uniforms, which can be used to sense various battlefield hazards in re...
Abstract: This paper presents novel work on developing fiber optic micro-sensors and integrating them into soldiers’ uniforms. These fiber optic sensors can be used to sense various battlefield hazards in re...
TL;DR: In this paper, the behavior of piezoceramic sheet actuators under different types of excitation and mechanical loading was investigated, and a phenomenological model to predict this behavior was developed and validated.
Abstract: This paper investigates the behavior of piezoceramic sheet actuators under different types of excitation and mechanical loading. The research especially focuses on the application of these actuators to the development of smart rotor systems. The free strain response of the actuators under DC excitation is experimentally investigated along with the associated drift of the strain over time. Effect of tensile stress on the free strain response is examined. The magnitude and phase of the free strain response of the actuator under different excitation voltages and frequencies is measured, and a phenomenological model to predict this behavior is developed and validated. The power consumption of the free actuator and a pair of actuators surface bonded to a host structure is calculated by the impedance method and validated by measurement. Additionally, depoling of the actuators is discussed, along with the feasibility of recovering performance by repoling in the event of accidental depoling.
TL;DR: In this article, the authors discuss the process for impact location detection in which the generated acoustic signals are detected by PZT using the improved neural network paradigms, and apply the Levenberg-Marquardt algorithm and the generalization methods to improve the accuracy and reliability of a neural network based impact identification method.
Abstract: Low-velocity impact damage is a major concern in the design of structures made of advanced laminated composites, because such damage is mostly hidden inside the laminates and cannot be detected by visual inspection. It is necessary to develop the impact monitoring techniques providing on-line diagnostics of smart composite structures susceptible to impacts. In this paper, we discuss the process for impact location detection in which the generated acoustic signals are detected by PZT using the improved neural network paradigms. To improve the accuracy and reliability of a neural network based impact identification method, the Levenberg-Marquardt algorithm and the generalization methods were applied. This study concentrates not only on the determination of the location of impacts from sensor data, but also the implementation of time-frequency analysis such as the Wavelet Transform (WT) to measure the characteristic frequencies of acoustic emission waves for the determination of the occurrence and the estima...
TL;DR: In this article, a field-controllable, semi-active magneto-rheological fluid (MRF) shock absorber for high-payload, off-highway vehicles is presented.
Abstract: This paper presents the study of a field-controllable, semi-active magneto-rheological fluid (MRF) shock absorber for high-payload, off-highway vehicles. A MRF damper is developed that is tailored for ground vehicles which undergo a wide range of dynamic loading. The MRF damper also has the capability for different rebound and compression characteristics. The new MRF shock absorber emulates the original equipment manufacture shock absorber behavior in its passive-off mode. Theoretical and experimental studies are performed to examine this MRF damper. The Bingham Plastic theory is employed to model the nonlinear behavior of the MRF. A fluid-mechanics-based theoretical model along with a three-dimensional finite element electromagnetic analysis is utilized to predict the MRF damper performance. The theoretical and experimental results are demonstrated to be in good agreement.
TL;DR: In this article, a constitutive model and a finite element formulation were developed for predicting the thermomechanical response of SMA hybrid composite structures subjected to combined thermal and mechanical load.
Abstract: A constitutive model and a finite element formulation are developed for predicting the thermomechanical response of SMA hybrid composite structures subjected to combined thermal and mechanical load...
TL;DR: In this article, a new interconnection technique has been developed that allows versatile multiple strand connections between microsensors, sensor arrays, and chips designed for wire bonding, which can be used for wireless sensor arrays.
Abstract: A new interconnection technique has been developed that allows versatile multiple strand connections between microsensors, sensor arrays, and chips designed for wire bonding. The new technique has ...
TL;DR: In this article, a steady-state analysis of piezohydraulic and piezopneumatic frequency rectification with a steady state model of work and energy transfer is presented.
Abstract: Piezohydraulic and piezopneumatic frequency rectification is analyzed with a steady-state model of work and energy transfer. In this paper, piezohydraulic actuation is defined as the use of incompressible fluid to rectify the oscillatory motion of a piezoelectric device into unidirectional motion; piezopneumatic actuation is the use of a compressible gas such as air. The steady-state analysis is based on the definition of two efficiency metrics. The mechanical efficiency is defined as the ratio of mechanical work transferred to the load to the total mechanical work performed by the actuator, and the electrical efficiency is defined as the ratio of electrical energy expended to the peak energy required. The analysis demonstrates that piezohydraulic rectification is inherently more efficient than piezopneumatic rectification due to the assumption of fluid incompressibility. The mechanical efficiency is 100% when using incompressible fluid (ideal) but drops to below 40% when using compressible gas. The maxim...
TL;DR: In this paper, a force/displacement actuator with high output power and time response can be fabricated from shape memory wires or ribbons using Ni-Ti shape memory alloys.
Abstract: Force/displacement actuators with the high output power and time response can be fabricated from shape memory wires or ribbons. Typically Ni-Ti shape memory alloys are used as an active material in...
TL;DR: In this article, the concept of sensitivity enhancing control (SEC) is proposed to aid in damage detection in smart structures through both experimental and simulation evaluation, and an initial proof-of-concept laboratory experiment demonstrating enhancement of modal frequency shifts due to tip mass damage in a cantilevered beam is reported.
Abstract: This paper demonstrates the concept of sensitivity enhancing control (SEC) to aid in damage detection in smart structures through both experimental and simulation evaluation. Methods of implementing state estimate feedback using point measurements of strain along the structure are described, and an initial proof-of-concept laboratory experiment demonstrating enhancement of modal frequency shifts due to tip mass damage in a cantilevered beam is reported. Simulation results focus on applying state feedback control to finite-element models of a cantilevered structure with slot, through-surface crack, or surface crack damage. The simulation analysis ascertains the ability to enhance sensitivity of modal frequency shifts due to realistic damage cases that are difficult to evaluate experimentally. The simulation also ascertains the potential for using the same sensors and actuators for implementing both sensitivity enhancing control laws and vibration damping control laws that are insensitive to damage. In the control model with which SEC laws are designed, damage consists of simple reductions in thickness over a small area of the structure. Finite-element models to which control laws are applied are developed using commercial software (ABAQUS TM ) that more accurately models stiffness damage by releasing element connections or by using line spring elements to model fatigue cracks. Experimental results show that enhancement in sensitivity of modal frequencies to damage can be achieved using a single piezoceramic actuator and multiple piezoelectric strain sensors along the beam. Simulation results indicate that feedback control laws can be designed for either sensitivity enhancement or vibration suppression using identical hardware, providing for multifunctional smart structures. In addition, analysis demonstrates that commercial finite-element software is useful for model-based simulation of damaged controlled structures.
TL;DR: In this paper, the authors propose that passive vibration absorbers reach their limits in advanced technical systems such as aircrafts, space structures and automobiles, since they have to combine high performance with low weight.
Abstract: Since advanced technical systems, such as aircrafts, space structures and automobiles, have to combine high performance with low weight, passive vibration absorbers reach their limits. This is why ...
TL;DR: In this paper, the design of a current controlled switching power amplifier to drive a piezoelectric actuator is formulated as a continuous optimization problem, where the objective function is chosen to be the weight of the inductor.
Abstract: The formulation and solution of an optimization problem for the design of a current controlled switching power amplifier to drive a piezoelectric actuator is the subject of this paper. The design is formulated as a continuous optimization problem. A detailed model that includes the anhysteretic nonlinearity between the electric field and polarization is developed and is coupled with a dynamic model of the amplifier. The design specifications are formulated as optimization constraints. The objective function is chosen to be the weight of the inductor. Optimization results are presented to demonstrate the efficiency of the proposed design methodology.
TL;DR: In this paper, the authors proposed a health monitoring method based on the changes of the resonant frequencies of flexible structures, which can be used as information sources for realizing the health monitoring and diagnosis.
Abstract: How to access the health situation of civil infrastructures is a brand-new challenge that scientists and civil engineers faced up to. Therefore, the method of health monitoring and diagnosis for flexible structures is a very active area of both academic and industrial research and development. For the large flexible structures, the mini cracks, which are the premise to induce the large cracks and damages in the structures, exert a little influence on the resonant frequencies of the structures. So the health monitoring method based on the changes of the resonant frequencies need that the cracks are so large that it can influence the resonant frequencies. However the mini cracks would change the vibration amplitude determined through monitoring the strain near the cracks, which can be used as the information sources realizing the health monitoring and diagnosis. It is a pity that the random external disturbances would influence the vibration amplitude, which can influence the effectiveness of the method tha...
TL;DR: In this article, the authors present the formulation of a new experimental procedure to employ in problems of damage analysis of structural elements, based on the acquisition and comparison of Frequency Response Functions (FRFs) of the monitored structure before and after damage occurred.
Abstract: The purpose of this work is to present the formulation of a new experimental procedure to employ in problems of damage analysis of structural elements. The proposed method is based on the acquisition and comparison of Frequency Response Functions (FRFs) of the monitored structure before and after damage occurred. Structural damages modify the dynamic behaviour of the structure and consequently its FRFs making possible calculation of a representative “Damage Index.” The experimental activity was carried on using two prototypes of magnetostrictive actuators developed within the European Commission funded project named MADAVIC (Magnetostrictive Actuators for Damage Analysis and VIbration Control). Three kinds of damages have been simulated on two beam-like structures: little mass disturbances, partial cuts of the beam sections and constraint yielding. Two expressions of damage indices were calculated and analysed. The main target of the work was to assess the reliability of the damage identification by using...
TL;DR: In this article, using three coupons representative of radome structures, several non-destructive evaluation (NDE) methods have been adapted to composite sandwich structures in order to detect damage, in particular impact induced damage.
Abstract: Non-Destructive Evaluation (NDE) methods have been adapted to composite sandwich structures in order to detect damage, in particular impact induced damage. Using three coupons representative of radome structures, several techniques were tested: ultrasonics, the Electromagnetic/InfraRed method (EMIR), stimulated shearography and stimulated infrared thermography. The extension of the measured damaged area was taken as a criterion, showing that stimulated shearography and ultrasound are the most sensitive methods. Moreover, two integrated Health Monitoring Systems (HMS) were tested, based on the one hand on microbending sensitive fibres and Optical Time Domain Reflectometry (OTDR), and on the other hand on Fibre Bragg Grating (FBG) sensors. The experiments demonstrated that HMS can detect damage with sensitivity comparable to that of the external NDE techniques.
TL;DR: In this article, a novel shape memory alloy (SMA) actuator with high frequency responses is described. And the authors describe the development of a novel SMA actuator using Peltier modules as heat pumps for heating and cooling.
Abstract: This paper describes the development of a novel shape memory alloy (SMA) actuator with high frequency responses. By applying Peltier modules as heat pumps for heating and cooling of SMAs, the actuator is expected to have higher frequency responses comparing with conventional ones. Thermomechanical properties of the actuators; such as the deformation of SMAs and recovery forces generated during the phase transition of SMAs, were investigated first. Then, response tests of the actuators were carried out in the complete thermal cycles for cases with and without Peltier modules respectively. Based on results from numerical simulations and experiments, the transient behavior of the actuator subjected to continuous actuations has been discussed. The results show that the actuator has dramatically enhanced frequency responses. In cases where the heating and cooling are controlled by electric current sequences, the thermal instability of the actuator occurs due to the accumulation of Joule heat in Peltier modules...