bluuebunny/crossref_metadata_2025 huggingface dataset:
Practical Formula for Predicting Drill Wear in Micro-Drilling of Printed Circuit Boards Containing High Hardness Fillers
Authors: Funabiki Taiji , Hirogaki Toshiki , Aoyama Eiichi , Ogawa Keiji , Kodama Hiroyuki
Published: July 2013

This paper describes micro-drilling processes for Printed Circuit Boards (PCBs) containing fillers with high hardness and high thermal conductivity. Powered primarily by devices such as digital cameras, laptop computers, and wireless communications devices, current the electronics field today is continuously demanding smaller, lighter, and more technologically advanced high performance devices. It has been a problem from such a tendency that the increase in amount of semiconductor-generated heat has a undesirable influence on such devices. Additionally, from a viewpoint of environmental problems, electric vehicles and LEDs are developed actively. One of the principal components for building such devices is Printed Circuit Boards (PCBs). In recent years, PCBs containing alumina fillers with high thermal conductivity have been developed and begun to be widely used. However, when processing these PCBs, the drill tools severely wear because of the filler’s high hardness. We therefore examined the drill wear characteristics and derived the practical drill wear formulas from the results to develop a suitable CAM system. It can be seen that these equations are similar to Taylor’s tool life equation. We also investigated the thermal conductivity effect on temperature during drilling processes. The temperature around the drill hole was shown to be a complex phenomenon according to increasing filler content to PCBs.
Optimization on Selective Fiber Laser Sintering of Bimetallic Powder via Design of Experiments Method
Authors: Liao Hsin-Te , Le Manh Trung , Long Dinh Vuong
Published: July 2013

The objective of this study is to investigate the effect of various parameters on rapid prototyping parts for processes of sintering metallic powder mixture by using Ytterbium fiber optic laser via the design of experiments (DOE) method. Experiments based on the DOE method were utilized to determine an optimal parameter setting for achieving a minimum amount of porosities in specimens during the selective laser sintering (SLS) process. Analysis of variance (ANOVA) was further conducted to identify significant factors. A regression model predicting percentages of porosities under various conditions was developed when the traditional Taguchi’s approach failed to identify a feasible model due to strong interactions of controlled factors. The significant factors to the process were identified by ANOVA. Four controlled factors including pulse frequencies and scan rate of laser beams, laser power and scan line spacing with particle sizes of 75μm of the powder mixture base material had significant influence on the sintering process. Future investigation planned to be carried out for achieving multiple quality targets such as the hardness and the density for 3D parts. The implementation of the DOE method provided a systematic approach to identify an optimal parameter setting of the SLS process; thus, the efficiency of designing optimal parameters was greatly improved. This approach could be easily extended to 3D cases by just including additional parameters into the design. Additionally, utilization of the normality analysis on the residual data ensured that the selected model was adequate and extracted all applicable information from the experimental data.
CAD System for Utilizing Design Information and Know-How Based on Function Features
Authors: Ando Sonken , Aoyama Hideki , Sano Noriaki
Published: July 2013

Three-dimensional CAD systems contribute extensively to the detailed design processes of products. In detailed design work, designers are required not only to accurately define shapes of products but also to assign attribute information which is essential for the manufacturing process. However, it is extremely hard for inexperienced designers to determine optimum attribute values and design values. This paper introduces “Function Features” which give information on the function and role of each area of a designed part. The “Function Features” enables designers to acquire design attribute information and know-how which are related to a “Function Feature” by easy operations. A system based on the “Function Features” for the design of injection molds was developed and the results of simple design experiments confirmed the usefulness of the proposed method using “Function Features”.
Height Dependent Laser Metal Deposition Process Modeling
Authors: Sammons Patrick M. , Bristow Douglas A. , Landers Robert G.
Published: July 2013

Laser Metal Deposition (LMD) is used to construct parts in a layer-by-layer fashion. The heat transfer from the melt region to the solid region plays a critical role in the resulting material properties and part geometry. The heat transfer dynamics can change significantly as the layers increase, depending on the geometry of the sub layers. However, this effect is unaccounted for in previous analytical models, which model only a single layer. This paper develops a layer dependent model of the LMD process for the purpose of designing advanced layer-to-layer controllers. A lumped-parameter model of the melt pool is introduced and then extended to include elements that capture height dependent effects on the melt pool shape. The model dynamically relates the process inputs (e.g., laser power, material mass flow rate, and scan speed) to the melt pool morphology and temperature. A finite element analysis is then conducted to determine the effect of scan speed and track height on the solid region temperature gradient at the melt pool solidification boundary. The results of a simulation study are compared to experimental results in the literature and demonstrate that the model is able to successfully predict changes in melt pool width as track height increases, which single layer models cannot.
Simulation of Robotic Assembly With Path Optimization
Authors: Chiou Richard Y. , Kwon Yongjin (James) , Park Sang C. , Davis Bret , Kizirian Robin
Published: July 2013

For the purpose of being competitive in the market place, manufacturing companies apply discrete event systems on their production lines. They have to continue improving the manufacturing systems in addition to the products. Due to the growing market of automation simulation software, digital production has become more and more sophisticated. Industrial companies utilize these software packages to increase profits, decrease costs and reduce the manufacturing cycle time. Research and development areas have been identified and discussed between discrete event and geometric simulators as well as between simulators and the real shop-floor. The goal of this research is to create a method of defining the optimized path of robotic assembly to meet the requirements of manufacturing scheme. The quantitative measure of optimization in this paper is completion time, as this is generally a key parameter of interest in production. The method of modeling and analyzing is performed through the use of virtual robotics simulations via PLCStudio, as well as an external optimization algorithm constructed in LabVIEW.
Robust Scheduling for Plural Lot Size Manufacturing
Authors: Kusumoto Saki , Kitamura Akira , Nakamura Masahiro
Published: July 2013

This paper describes a robust scheduling system for manufacturing processes. In this system, an adequate balance between large-lot and small-lot manufacturing can be achieved by a multi objective optimization technique, and the lead time for manufacturing large-lot products and appropriation rate for small-lot products can be improved in comparison with those used in traditional scheduling methods. In small-lot manufacturing, the change in setup time is considered by its static distribution, and thus, the productivity of small-lot products can be maximized. These effects of the robust scheduling system have been examined quantitatively by means of a numerical simulation.
Viscosity Measurement in Injection Molding Using a Multivariate Sensor
Authors: Asadizanjani N. , Gao R. X. , Fan Z. , Kazmer D. O.
Published: July 2013

Online measurement of polymer melt properties during an injection molding process is a key to provide a high quality plastic product. In-situ cavity pressure and temperature sensors are used to observe the polymer states in the mold cavity during an injecting molding process. A new multivariate sensor is introduced to measure pressure, temperature, velocity, and viscosity of polymer melt as the key parameters of the melt to improve the controlling process. This paper presents the viscosity calculating method based on melt velocity and the slope of melt pressure. The velocity is inferred using the melt temperature ramping rate; the new multivariate sensor detects melt temperature through the installed IR detector in the sensor, and the pressure is measured via the mounted piezoelectric rings. Injecting molding process of polymer melt is simulated under a range of melt velocity and temperature and the related viscosity values are inferred from simulation results and also from a set of experimental tests for a real injection molding process. Results are well matched with the expected rheological behavior of polymer.
Effect of Sodium Alginate Concentration During Laser-Assisted Printing of Alginate Tubes
Authors: Yan Jingyuan , Gudapati Hemanth , Huang Yong , Xu Changxue
Published: July 2013

For the free-form fabrication of various tissue constructs, three-dimensional (3D) additive printing technology has emerged as a promising approach for organ fabrication. This study aims to print a tube structure using a laser-assisted orifice-free printing technique and further investigate the effect of sodium alginate concentration on the tube wall thickness. Alginate tubes have been successfully printed. It is found that highly viscous materials can be laser printed into well-defined tube structures. A higher concentration solution such as the 8% sodium alginate solution leads to a thin wall, meaning a better resolution. Imaging analysis also illustrates that higher concentration solutions help develop smooth, slim jets upon the incidence of laser pulse.
Substructure Model Updating Through Iterative Convex Optimization
Authors: Zhu Dapeng , Wang Yang
Published: July 2013

In order to obtain a more accurate finite element (FE) model for a built structure, experimental data collected from the actual structure can be used to update the FE model. This process is known as FE model updating. Numerous FE model updating algorithms have been developed in the past few decades. However, most existing algorithms suffer computational challenges, particularly when applied to a large structure with dense measurements. The reason is these approaches usually operate on a relatively complicated model for the entire structure. To address this issue, a substructure updating approach is presented in this paper. The Craig-Bampton theory is adopted to condense the entire structural model into a substructure (currently being analyzed) and a residual structure. Dynamic response of the residual structure is approximated using only a limited number of dominant mode shapes. To improve the convergence of this substructure approach for model updating, an iterative convex optimization procedure is developed and validated through numerical simulation with a 200 degrees-of-freedom spring-mass model. The proposed substructure model updating is shown to successfully detect the locations and severities of simulated damage.
Wavelet-Based Online Evaluation and Classification of Wear State Using Acoustic Emission
Authors: Baccar Dorra , Söffker Dirk
Published: July 2013

Advanced signal processing approaches such time-frequency analysis are widely used for online evaluation, damage detection, and wear state classification. The idea of this paper is to introduce a new methodology for online examination of wear phenomena in metallic structure by means of acoustic emission (AE), Short-Time Fourier Transform (STFT) and Wavelet Transform (WT). The proposed novel low-cost system is developed for analyzing and monitoring specific signals indicating tribological effects with focus on field programmable gate array (FPGA) implementation of discrete WT (DWT). In addition, experimental results obtained from each approach are given showing the success of the introduced approach.
Characterization of Work per Volume Density of VO2-Based MEMS Actuators
Authors: Merced Emmanuelle , Zhang Jun , Tan Xiaobo , Sepúlveda Nelson
Published: July 2013

Vanadium dioxide (VO2)-coated silicon microcantilevers have gained attention due to the large stress produced during VO2’s thermally induced metal-to-insulator phase transition, which produces a curvature change of over ∼2,000 m−1. Work per volume density is an important figure of merit used to compare the performance of smart materials in micro-actuation. In this paper, the work per volume density of five fully actuated VO2-coated microcantilevers was calculated based on experimentally measured force vs. displacement curves obtained from an AFM operated in contact mode. The work per volume density for the five microactuators was found to be similar, which is around ∼1.5×104 J/m3. The work per volume density of a single microactuator was also obtained under different temperatures across the material’s transition, which exhibits the hysteretic behavior during the heating-cooling cycle.
The Quantification of Uncertainty in SHM Features Derived From Transmissibility Estimation
Authors: Mao Zhu , Todd Michael
Published: July 2013

This paper develops uncertainty models for various an estimator used in computing the frequency-domain transmissibility function for single-input-multiple-output (SIMO) linear systems. The uncertainty is assumed to come from both internal (estimator) and external (environmental, noise, etc.) sources, and it is propagated through the estimation process to arrive at closed-form probability density functions for the estimation magnitude. The models is validated on a bolted plate in the laboratory, and receiver operating characteristics (ROCs) are computed to evaluate performance in terms of meaningful metrics such as probability of detecting a structural change within the context of structural health monitoring.
Hybrid Rotary-Translational Energy Harvester for Multi-Axis Ambient Vibrations
Authors: Karami M. Amin , Inman Daniel J.
Published: July 2013

A nonlinear electromagnetic energy harvester is presented which can generate power from translational vibrations in two directions and rotational excitations. Commonly, vibrational energy harvesters are designed to generate power from only translational ambient oscillations in a specific direction. The assumption of uni-axial ambient vibrations is too idealistic. Not only the direction of the base excitations typically change in time but also the rotational excitations are as common in oscillating machinery as the translational vibrations. The proposed energy harvester is inspired by the Automatic Generating System in Seiko watches. The moving element is a magnetic pendulum. When the pendulum moves in response to the base excitations the magnetic tip passes over electromagnetic coils, positioned in a circular array in the stator. The relative motion of the tip magnet and the coil generates electricity. The paper presents an analytical representative model for the energy harvesting system. The dynamics and energy generation of the energy harvester in response to four different excitation configurations are studied. It is demonstrated that in response to large excitations the system commonly undergoes period doubling bifurcations and occasionally undergoes chaos. The study paves the way to optimal design of the hybrid rotary translational energy harvesters.
Bimorph Piezoelectric Cymbal Design in Energy Harvesting
Authors: Mo Changki , Jordan Steve , Clark William W.
Published: July 2013

This paper presents the development of a bimorph piezoelectric cymbal energy harvester that is particularly useful for extracting energy from the vibrating systems of relatively high compressive load. The bimorph cymbal harvester can be used to charge a capacitor or a battery through the piezoelectric layers fitted within the metal end caps under repeated compression or deformation.

In this work, feasibility of a bimorph piezoelectric cymbal harvester in series operation is investigated through theoretical analysis and experimental validation. The bimorph cymbal uses a composite disc of two piezoelectric layers and a steel substrate between metal end caps.

Theoretical modeling to quantify the generated energy by using bimorph cymbal design is first conducted. A parametric study is then performed to optimize generated energy with the dominant design parameters influencing energy harvesting performance for the cymbal structure. The parameters such as thickness of the end caps, radius ratio of the apex to the cavity of the end caps, cavity depth, and thickness ratio of the piezoelectric to the steel substrate are considered. Based on the optimized dimension, a cymbal harvester was fabricated and tested to validate analytically predicted open-circuit voltage on a hand jack type test rig.

Experimental result indicates that the measured open-circuit voltage from the bimorph cymbal harvester is less than that of analytically predicted. However, it shows that the bimorph piezoelectric cymbal structure is an alternative cymbal design that is useful for harvesting energy from the source of relatively high load.
Effect of Filler Materials on the Performance of Conformal Load-Bearing Spiral Antennas
Authors: Daliri Ali , John Sabu , Wang Chun H. , Galehdar Amir , Rowe Wayne S. T. , Ghorbani Kamran , Callus Paul J.
Published: July 2013

The slots in spiral antennas induce stress concentrations and hence may adversely affect the load-carrying capacity of the structural antenna. To minimise the detrimental effect of the slots, appropriate fillers are required to provide structural reinforcement without compromising the radar performance of the antenna. This paper presents an investigation of the effects of electrical and mechanical properties of potential filler materials on the performance of slot spiral antennas. Finite element analysis is carried out for a slot spiral that is designed to work in the C-Band range of frequencies (4–8 GHz). Computational simulations performed using commercial software packages ANSYS® and HFSS® show that by using commercially available filler materials the stress concentration factor of the spiral slot can be reduced by 20%. The results from this research enhance the previously introduced advantages of this type of conformal load-bearing antenna structure (CLAS). This CLAS concept provides a promising solution of replacing conventional externally mounted antennas, thus reducing aircraft weight and aerodynamic drag.
Self-Sensing Photoactive Thin Films for Monitoring Space Structures
Authors: Ryu Donghyeon , Loh Kenneth J.
Published: July 2013

Reusable and on-orbit space structures endure harsh operating conditions and can sustain damage due to impact by micrometeoroids and orbital debris. Thus, it is necessary to develop and implement suitable sensing technologies for monitoring space structure performance, detecting damage, and preventing catastrophic failure from occurring. The challenge however is to tailor these sensors for operating in such unique environments and constraints. One such limitation is the amount of energy available for powering onboard sensing systems. Thus, the objective of this study is to design and characterize the properties of a novel self-sensing photoactive thin film. Self-sensing is encoded by designing the films to generate a photocurrent in response to illuminated light so that no electrical energy is needed for powering the sensor, and photocurrent generated varies with applied strain. First, the self-sensing thin films were fabricated using poly(3-hexylthiophene) (P3HT) and double-walled carbon nanotubes (DWNT). Two different sets of films, ones with and without DWNTs, were fabricated. Second, photocurrent generation was validated. Then, tensile tests were conducted for characterizing their strain sensing performance. Lastly, current-voltage measurements were also obtained for characterizing thin film shunt and series resistance relationships to applied strains. The results showed that photocurrent varied linearly with applied tensile strains, and this was mainly due to the effects of P3HT alignment and shunt resistance changes of the photoactive thin films.
Combined Squeeze-Shear Properties of Magnetorheological Fluids: Effect of Pressure
Authors: Spaggiari Andrea , Dragoni Eugenio
Published: July 2013

Several applications of magnetorheological (MR) fluids are nowadays present in the industrial world, however sometimes system requirements require better material properties. In technical literature an interesting previous work shows that MR fluids exhibit a pressure dependency called squeeze strengthen effect. Since a lot of MR fluid based devices are rotary devices, this paper investigates the behaviour of MR fluids under pressure when a rotation is applied to shear the fluid. The system is designed in order to apply both the magnetic field and the pressure following a Design of Experiment method. The experimental apparatus comprises a cylinder in which a piston is used both to apply the pressure and to apply a prescribed rotation. The magnetic circuit is designed to provide a nearly constant induction field in the MR fluid. The experimental apparatus measures torque as a function of the variables considered and the yield shear stress is computed. A statistical analysis of the results shows that there is a positive interaction between magnetic field and pressure, which enhance the MR fluid performances more than two times.
Solvent Induced Shape Memory Behaviour of Sulfonated Poly Ether Ether Ketone (SPEEK)
Authors: Anand V. S. , Vimal K. V. , Varughese Susy
Published: July 2013

Shape memory polymers (SMPs) are a widely studied class of materials due to their numerous applications in various fields of engineering. They find applications in deployable structures, biomedical devices, adaptive optical devices, sensors and actuators, in textiles etc. Recent studies have shown shape memory behavior in many polymers. Sulfonated poly ether ether ketone (SPEEK) is an ionic polymer which is being extensively studied for its application in fuel cells as a Proton Exchange Membrane (PEM) polymer due to its relatively higher thermal and mechanical stability over other PEMs in addition to proton transport. Recent studies on a sulfonated ionomer, Nafion® which has only one broad reversible phase transition, can show tunable, multiple shape memory effects by deforming the polymer at different temperatures without compromising the shape fixity (Rf). This paper reports, for the first time, the swelling (in solvents) induced shape memory behavior observed in SPEEK. The study was motivated by the preliminary observations of the response of SPEEK to solvent stimulus. SPEEK samples of varying degrees of sulfonation (DS) were prepared by the sulfonation of poly ether ether ketone (PEEK). The shape fixation and recovery rates (Rr) of the polymer under different temperatures and solvent conditions are reported. A comparative study of the shape memory response of the material with varying DS was also carried out. We also report for the first time the potential use of the parallel plate geometry of a rheometer for estimating the force during the shape recovery process. Visual demonstration of the shape memory effect is carried out using solvents at different temperatures.
Modeling of Hybrid Shape Memory Alloy Composites Incorporating MAX Phase Ceramics
Authors: Lester Brian T. , Lagoudas Dimitris C.
Published: July 2013

A new hybrid shape memory alloy (SMA)-ceramic composite is being developed for use in extreme environments. The proposed composition is intended to address past issues with brittle failure in the ceramic phase by generating a compressive residual stress state in that phase. This biasing load takes advantage of the superior mechanical properties of ceramics when loaded in compression. Past investigations of SMA composites with an elasto-plastic second phase have shown that such a residual stress state may be developed in the second phase through the generation of irrecoverable, plastic strains. To take advantage of this characteristic, a class of ceramics known as the MAX phases are being used. These ceramics have a unique response characterized by the formation of kink bands which can allow for both recoverable and irrecoverable inelastic strains. A model of the hybrid composite incorporating this response and the effects of the microstructure is developed to explore the ability of this material system to generate such stress states. To this end, an approximation of the MAX phase response is introduced to describe the irrecoverable kink band formation. The effects of the microstructure are accounted for through the generation of a finite element mesh from microtomography results of the considered composite. Finite element simulations of the hybrid composite are performed using the assumed MAX phase response and a recent 3D phenomenological SMA constitutive model. The effective stress-temperature response of the composite is determined and the interaction of the different phases is discussed. Specifically, it is shown that composite still exhibits a hysteretic response although with a decreased hysteresis height and shifted transformation temperatures. The effect of the microstructure on the composite response is discussed. Finally, it is shown that through an actuation loading path a compressive residual stress state is developed in the ceramic phase.
Modeling and Experimental Validation of Shape Memory Alloy Bending Actuators
Authors: Haigh Casey D. , Crews John H. , Wang Shiquan , Buckner Gregory D.
Published: July 2013

In this paper, we develop a computational model that can be used to investigate and optimize the performance of shape memory alloy (SMA) bending actuators. These actuators (approximately 7–21 mm in length) consist of curved SMA wires embedded within elastic sleeves and are intended for positioning and anchoring robotic catheters inside blood vessels during clinical treatments. Each SMA wire is shape-set to an initial curvature and inserted along the neutral axis of a straight elastic member (cast heat-resistant silicone with varying section modulus). The elastic member preloads the SMA (or produces a stress-induced phase transformation), reducing the equilibrium curvature of the composite actuator. Temperature-induced phase transformations in the SMA (via Joule heating) enable strain recovery and increased bending (increased curvature) in the composite actuator. The homogenized energy framework is utilized to model the behavior of this composite actuator, and the effects of several critical design parameters (initial SMA curvature and section modulus of the elastic member) on the deactivated and activated curvatures are investigated. Experimental results validate the model, enabling its use as a design tool for bending performance optimization.
Cooling Strategies for a SMA Wire Actuator in a Feed Axis
Authors: Meier Horst , Pollmann Jan , Czechowicz Alexander
Published: July 2013

Shape memory alloys (SMA) are smart materials which can be activated thermally. They are suitable for the use as actuators due to their ability to remember an imprinted shape through thermal activation. In addition, actuators based on shape memory alloys offer a higher work output in relation to their volume compared to other actuator concepts. Other advantages of using SMA in actuation applications include the ability to design lightweight systems and the comparatively low material costs.

On the other hand, designing an SMA actuator poses a challenge in case a specific rate of feed has to be achieved. These difficulties become especially apparent if the actuator is used to create a defined displacement not only in its activation direction, but in the returning (deactivation) direction as well. This might occur, for example, while devising an SMA-driven feed axis.

During the activation of the SMA, the speed of the actuator and therefore the speed of the axis can be influenced by choosing a specific thermal energy transfer method. For instance, when using the intrinsic resistance for heating purposes, the speed can be controlled by changing the electrical current running through the SMA. However, after the deactivation (end of the heating phase) of the shape memory alloy, the transformation needs a considerably longer time. For an exemplary SMA wire actuator, the transformation time in room temperature can be five times higher than the activation time. For usage in a feed axis, the actuator should produce similar speeds in both the activation and deactivation direction.

To achieve this, different strategies for cooling the SMA after cutting off the current are investigated. These strategies include an active air cooling system with different flow characteristics and the operation of the actuator in a cooling fluid.

In a nutshell, the paper compares different ways of cooling an SMA wire actuator to increase the transformation speed after deactivation. The aim is to make the deactivation speed as manageable as the activation speed.
Investigation of Host Structure Compliance in Aeroelastic Energy Harvesting
Authors: Bryant Matthew , Tse Ricky , Garcia Ephrahim
Published: July 2013

This paper experimentally investigates the interactions between host structure compliance and natural frequency and the behavior of a fluttering piezoelectric energy harvester. Unlike the base excitation case where a piezoelectric energy harvester extracts energy from a vibrating base structure, the aeroelastic flutter energy harvester generates limit cycle oscillations from an ambient fluid flow. The flow induced oscillatory motion of the energy harvester can transfer energy into the host mounting structure, and may introduce significant vibrations in the structure as well affect the behavior of the energy harvester itself. The energy harvester motion and electrical output is compared for a rigid host structure, as well as a flexible host structure, and the vibrations induced in the host structures are also be examined. The results show significant effects on the energy harvester cut-in wind speed, power output, flutter limit cycle oscillation frequency, and optimal electrical load as a result of the host structure compliance.
Active Twist Blades: Electromechanical Damping
Authors: Riemenschneider Johannes , Schulz Martin , Pohl Martin
Published: July 2013

Active Twist Rotor Blades for helicopter main rotors have been developed for the use in secondary control such as higher harmonic control (HHC) and individual blade control (IBC). The basic principle of such blades is the implementation of piezoelectric actuators into the blades causing the blades to twist. At the DLR such types of active twist blades have been designed for quite some years. Several model scale blades have been manufactured to demonstrate the feasibility of such systems. This paper presents a new set of rotor blades (4 m diameter) which is designed to go into a wind tunnel experiment within the “STAR” consortium. In this paper it is discussed, what kind of other applications for such blades — equipped with piezoceramic actuators — can be considered. Besides the capability to twist at frequencies of 1 through 6/rev, there is always the option of statically changing the pretwist of the blade, which will influence the figure of merrit. The idea is to use blade integrated actuators as part of electromechanical absorbers has been discussed recently. Using certain electrical networks, the structural behavior of the rotor blade can be significantly influenced. The effectiveness of such systems was experimentally investigated using a twist blade. In this paper results of a rotating blade with aerodynamic damping is shown for the first time. Different types of shunt networks have been investigated as presented in [1] before: At first an oscillating circuit was established coupling the capacitive piezoelectric actuators with an inductivity. If the setup is tuned right, this results in a significant decrease of the amplitues of a single frequency, e.g. torsional eigenfrequencies. In a next step a virtual “negative capacity” was used to dissipate the vibrating energy in the electrical circuit. Such an element shows the same amplitude response as the capacity, but the phase is shifted by 180 deg compared to a “regular capacity”. The advantage of this method is the effectiveness over a broad frequency range. That way several modes can be influenced at the same time. Finally, a first evaluation of the influence of these measures on the vibration level of a complete rotor was carried out.
On a Physics-Based Model for Nonlinear Sensing in Ionic Polymer Metal Composites
Authors: Aureli Matteo , Porfiri Maurizio
Published: July 2013

In this paper, we propose a physics-based model of ionic polymer metal composites (IPMCs) charge dynamics in response to dynamic mechanical deformation by developing a perturbation solution of a particular form of the Poisson-Nernst-Planck equations. We derive an equivalent nonlinear circuit model whose components are directly controlled by the imposed mechanical deformation. We show results for a variety of loading scenarios to gather insight on the nonlinear characteristics of IPMC electrical response and its potential application in sensors and energy harvesting devices.
Sliding Mode Control of the Human Vestibular System
Authors: McCarty Rachael , Mahmoodi S. Nima , Williams Keith
Published: July 2013

An original sliding mode controller is designed, based on an existing mathematical model for response control of the human vestibular system. The human vestibular system is located in the inner ear and significantly contributes to the functions of detecting head motion, maintaining balance and posture, and realizing gaze stabilization. The vestibular system sends signals to the brain to tell it how the head and body are moving, and the brain reacts by changing eye position accordingly. The nonlinearities of the vestibular system are not completely understood. The biggest nonlinearity is the nystagmus, a bouncing of the eyes to compensate for quick head movement. Another nonlinearity is that the quick phase does not start until head movement reaches a certain frequency. Considering these nonlinearities as well as the uncertainties of the system, sliding mode control a good choice for controlling the system. Several mathematical models of the human vestibular system are considered for use in the control design. The best model of those considered is chosen based on the models’ consideration of nonlinearities and their levels of complexity. The mathematical model used in this paper is a nonlinear transfer function. The output is controlled with a robust sliding mode controller. Results demonstrate the need to increase control parameters as frequency of the sinusoidal input increases to minimize overshoot error. However, since the human head cannot tolerate an infinitely large frequency input, control parameters also will necessarily be limited. Therefore, results show that the designed sliding mode robust controller is an effective mechanism for controlling the mathematical model of the human vestibular system.
The Variations in Active Panel Location and Number for a Bioinspired Aircraft Gust Alleviation System
Authors: Blower Christopher J. , Wickenheiser Adam M.
Published: July 2013

This paper presents the development of a biomimetic closed-loop flight controller that integrates gust alleviation and flight control into a single distributed system of feather-like panels over the upper and lower surfaces. This bio-inspired gust alleviation system (GAS) mimics the techniques used by birds to respond to turbulent and gusting airflow. The GAS design replicates the profile of a bird’s wing through the installation of feather-like panels across the upper and lower surfaces of the airfoil, and replacement of the trailing-edge flaps. While flying through gusts, the flight controller uses a linear quadratic regulator to perform continuous adjustments to the local states through active deflection of electromechanical feathers. This system consequently offers a wide range of flap configurations that enable the vehicle to perform gust response maneuvers unachievable by standard aircraft. The GAS is developed using a 2D adaptive panel method that enables analysis of the airfoil’s aerodynamic performance during all flap configurations. The airfoil’s dynamic model is simulated to calculate the disturbances incurred during gusting flows. The flight controller tracks the vehicles velocity, angle of attack and position, and continuously performs adjustment to the orientation of each flap to induce the corrective responses to inbound gusts. The replacement of standard single trailing edge profile with the integration of a dual trailing edge (DTE) configuration offers a reduction of the aircraft’s deviation from the target flight path through the introduction of aero-braking during strong longitudinal gusts. The introduction of 6 additional surface flaps offers new flap configurations capable of minimizing the disturbances in the aircraft’s global states. Non-linear and linear dynamic models of the 8-flap GAS are compared to a traditional single control surface baseline wing and the DTE configuration. The feedback loops synthesized depend on the inertial changes of the global states; however, variations in flap configuration are compared. The integration of an 8-flap GAS provides enhancements to maneuverability and stability in turbulent intensive environments.
Piezoelectric Energy Harvesting Through Fluid Excitation
Authors: Truitt Andrew , Mahmoodi S. Nima
Published: July 2013

Piezoelectric energy harvesters have recently captured a lot of attention in research and technology. They employ the piezoelectric effect, which is the separation of charge within a material as a result of an applied strain, to turn what would otherwise be wasted energy into usable energy. This energy can then be used to support remote sensing systems, batteries, and other types of wireless MEMS devices. Such self powered systems are particularly attractive where hardwiring may not be feasible or numerous battery sources unreasonable. The source of excitation for these systems can include direct actuation, natural or mechanical vibrations, or fluid energy (aerodynamic or hydrodynamic). Fluid based energy harvesting is increasingly pursued due to the ubiquitous nature of the excitation source as well as the strong correlation with other types of excitation. Vortex-induced vibrations as well as vibrations induced by bluff bodies have been investigated to determine potential gains. The shape and size of these bluff bodies has been modeled in order to achieve the maxim power potential of the system. Other studies have focused on aeroelastic fluttering which relies on the natural frequency of two structural modes being achieved through aerodynamic forces. Rather than a single degree of freedom, as seen in the VIV approach, aeroelastic flutter requires two degrees of freedom to induce its vibrational state. This has been modeled through a wing section attached to a cantilevered beam via a revolute joint. To accurately model the behavior of these systems several types of dampening must be considered. Fluid flow excitation introduces the component of dampening via fluid dynamics in addition to structural dampening and electrical dampening from the piezoelectrics themselves. Air flow speed modifies the aerodynamic dampening and it has been shown that at the flutterer boundary the aerodynamic dampening dissipates while the oscillations remain. However, such a system state exhibits a decaying power output due to the shunt dampening effect of the power generation itself. Research in energy harvesting is quickly progressing but much has yet to be discovered. The focus of this paper will be fluid as a source of excitation and the development that has followed thus far. Configurations and applications of previous works will be examined followed by suggestions of new research works to move forward in the field.
Piezoelectric-Property Adjustment of Cellular Ferroelectrets by Foam-Structure and Geometry Variations
Authors: Sborikas Martynas , Wegener Michael
Published: July 2013

Piezoelectric materials are the active elements in e.g. ultrasound transducers and thus widely used in sensor and actuator systems. The rather recent addition to ultrasonic transducer materials are the so-called ferroelectrets, voided piezoelectric-active polymer films. One type among the most studied ferroelectrets is cellular polypropylene. The properties of ferroelectrets, such as low elastic stiffness, high piezoelectric activity, good matching with air makes them suitable as ultrasonic transducer material. Here, we demonstrate the controlled adjustment of the piezoelectric properties, especially of the resonance frequency of cellular polypropylene films by means of transducer-structure modifications.
Study of Aerospace Structures With Bonded Piezoelectric Strips Subjected to Unsteady Aerodynamic Loads for Structural Health Monitoring
Authors: Han Yong , Mateescu Dan , Misra Arun K.
Published: July 2013

This paper studies the aeroelastic oscillations of wing-like structures with the aim to detect at an incipient stage the presence of structural cracks. Such oscillations occur normally in certain flight evolutions of aircraft or can be excited by piezoelectric actuators bonded on the wing structure. These oscillations can be used to detect at an early stage the presence of cracks by monitoring the response of several piezoelectric sensors bonded on both sides of the structure during the aeroelastic oscillations. The proposed method of crack detection uses pairs of piezoelectric strip sensors bonded on the opposite sides of the structure and is based on the fact that the presence of a crack causes a difference between the strains measured by the two sensors of a pair. The structural analysis presented in this paper uses a nonlinear model for the cracks and a finite element formulation for the piezoelectric strips coupled with the structure. A 3D panel method developed by the authors is used to determine the unsteady aerodynamic loads acting on the oscillating wing structure. The dynamic analysis in the time domain is performed for the oscillating structures with piezoelectric strips subjected to unsteady aerodynamic loads. In the present work, the efficiency of this crack detection method is studied in realistic situations, by considering the aeroelastic oscillations in flexion and torsion of a wing-like structure which are excited in one of the following modes: (i) the aeroelastic oscillations excited by a pair of piezoelectric actuators bonded on the opposite sides of the structure; (ii) the aeroelastic oscillations excited by the harmonic oscillation of the angle of attack corresponding to the flight in atmospheric turbulence (harmonic gust); (iii) the aeroelastic oscillations generated by a sudden change in the angle of attack or in the airplane velocity due to a pilot control input. The numerical simulations for these cases have been performed by the simultaneous solution of the coupled equations of unsteady fluid flow and of the structure deformation motion, by using a finite element method for the dynamic of the structures with cracks and bonded piezoelectric strips, and a 3D panel method developed by the authors for the calculation of the unsteady aerodynamic loads. These numerical simulations have shown that the presence of a crack in the structure can be efficiently detected at an early stage by monitoring the response of the pairs of piezoelectric sensors.
Lamb Wave Propagation Study Using Frequency-Wavenumber Analysis
Authors: Tian Zhenhua , Yu Lingyu
Published: July 2013

Lamb waves are dispersive and multi-modal. Various wave modes make the interpretation of Lamb wave signal very difficult. It is desired that different modes can be separated for individual analysis. In the this paper, we present our studies on the multimodal Lamb wave propagation and wave mode extraction using frequency-wavenumber analysis. Wave spectrum in the frequency-wavenumber domain shows clear distinction among Lamb wave modes being present. This allows separating them or extracting a desired Lamb wave mode through a novel filtering strategy. Thus a single mode Lamb can be identified and extracted for certain types of damage detection in structural health monitoring (SHM). These concepts are illustrated through experimental testing. A scanning laser Doppler vibrometer is used to acquiring the time-space wavefield regarding the multimodal Lamb wave propagation. Then the recorded wavefield was analyzed in frequency-wavenumber domain and decomposed into different wave modes.
Modeling of a Vibration-Based Piezomagnetoelastic Energy Harvesting System by Using the Duffing Equation
Authors: Westermann Henrik , Neubauer Marcus , Wallaschek Jörg
Published: July 2013

This article illustrates the modeling of a piezomagnetoelastic energy harvesting system. The generator consists of a piezoelectric cantilever with a magnetic tip mass. A second oppositely poled magnet is attached near the free end of the beam. Due to the nonlinear magnetic restoring force the system exhibits two symmetric stable equilibrium positions and one instable equilibrium position. The equation of motion is derived and it is shown that the system can be modeled as Duffing oscillator. An analytical approach is given to derive the Duffing parameters from the system parameters. The Duffing equation is solved for an oscillation around both equilibrium positions by using the harmonic balance method. For small orbit oscillations the equation of motion is solved by applying the fourth-order multiple scales method.
Electrospinning and Characterization of Nafion Nanofiber Membranes
Authors: Zhang Fenghua , Zhang Zhichun , Liu Yanju , Leng Jinsong
Published: July 2013

This study seeks to assess the morphology of Nafion nanofiber membranes produced by electrospinning technology. The effects of solution concentration, electrode separation and applied voltage on diameter are investigated. The morphology of Nafion nanofibers measurements for different concentration and operating conditions are acquired by scanning electron microscopy (SEM). The thermal performance is also analyzed by TGA and DSC. Results show that the bead-free nanofibers are electrospun from 0.3 wt%∼0.7 wt% PEO in 5 wt% Nafion solution at the electrode separation of 16 cm ∼ 20 cm, an applied voltage of 20 kV ∼ 50 kV and an electrode bar rotation rate of 0.9 rpm. The mean dimeters of Nafion increase with increasing PEO content and electrode separation. The mean dimeters of Nafion decrease with increasing applied voltage. The formation of continuous smooth nanofiber is related to solution viscosity and electrospinning conditions. In addition, glass transition temperature of the Nafion nanofibers increases with increasing PEO concentration and Nafion nanofibers show a good thermal stability.