bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of Kinematic Motion Deviations of Rotary Tables Based on Geometric Tolerances
Authors: Sugimura Nobuhiro , Watabiki Hitomi , Thasana Wiroj , Iwamura Koji , Tanimizu Yoshitaka
Published: July 2013

Machine tools are recognized as key components of manufacturing systems, and product quality and cost mainly depend on performances of the machine tools. Much progress has been made in the machine tool technologies, aimed at improving the performances of the machine tools from various viewpoints, such as accuracy, reliability, productivity, and flexibility. The machining accuracy is one of the most important characteristics of the machine tools. From the viewpoints of the design and the manufacturing of the machine tools and their components, one of the important issues is to clarify the relationships between the kinematic motion deviations of the machine tools and the geometric tolerances of the components, such as the guide ways and the bearings. The objective of the present research is to establish mathematical models representing the kinematic motion deviations of the machine tools, on the basis of the geometric tolerances of the components, and to apply the models to theoretical analysis of the kinematic motion deviations of the machine tool components.
Impact of Using PEM Forklifts on Manufacturing Layouts
Authors: Gosavi Abhijit , Long Suzanna , Grasman Scott , Schmidt Sean
Published: July 2013

The popularity of forklifts that use fuel cells based on proton exchange membranes (PEMs) has steadily increased with time in manufacturing industries and distribution centers. Because they potentially reduce our dependence on fossil fuels that emit carbon dioxide while generating energy, they have certain environmental benefits in comparison to forklifts driven by lead-acid batteries that are typically charged using regular sources of energy. In this paper, we study the impact of using PEM forklifts on material-handling costs and lead times, which are commonly used in measuring the cost-effectiveness of a manufacturing system’s layout. We report some initial findings in this paper. In general, we find that layouts designed for PEM forklifts tend to have lower material-handling costs, improved closeness ratings, and higher area utilization, while the shop-floor lead times tend to be shorter, leading to lower inventory and higher flexibility in responding to fluctuations in customer demand. Overall, PEM forklifts may hence improve the health of the supply chain of the product by making it more flexible and cost-effective.
Ultrasound Transducer Array Fabrication Based on Additive Manufacturing of Piezocomposites
Authors: Chabok Hamid , Zhou Chi , Chen Yong , Eskandarinazhad Arash , Zhou Qifa , Shung Kirk
Published: July 2013

Conventional methods for fabricating ultrasound imaging transducer arrays, especially for high frequency range (>20 MHz), are expensive, time consuming and limited to relatively simple geometries. In this paper, the development of an additive manufacturing (AM) process based on digital micromirror devices (DMDs) is presented for the fabrication of piezoelectric devices such as ultrasound transducer arrays. Both green-part fabrication and the sintering of fabricated green-parts have been studied. A novel two-channel design in the bottom-up projection system is presented to address the piezo-composite fabrication challenges including a small curing depth and viscous ceramic slurry recoating. A prototype system has been developed for the fabrication of green-parts with complex shapes and small features. Based on the fabricated green-parts, the challenges in the sintering process for achieving desired functionality are discussed. Various approaches for increasing the density of sintered components are presented. Dielectric and piezoelectric properties of the fabricated samples are measured and compared with those of bulk PZT samples. Based on the identified challenges in the DMD-based AM process, future work for achieving fully functional piezoelectric ceramic components is discussed.
Novel Fiber Optic Sensors and Their Application on Cutting Temperature Measurement in Rotary Ultrasonic Machining of Titanium
Authors: Zou Xiaotian , Cong Weilong , Wu Nan , Pei Z. J. , Wang Xingwei
Published: July 2013

Fiber optic temperature sensors offer unique advantages when used to measure cutting temperature in machining processes. This paper presents novel miniature fiber optic temperature sensors and their application in cutting temperature measurement in Rotary Ultrasonic Machining (RUM) of titanium. The sensors were based on a Fabry-Pérot (FP) interferometeric principle. The endface of the fiber was wet etched. A piece of borosilicate glass was thermally deposited into the cavity on the etched endface to form an FP cavity. Temperature calibration experiments were performed. During RUM, the sensor was embedded in the titanium workpiece to monitor the temperature change using different ultrasonic power. The results demonstrate the advantages of fiber optic sensors including high accuracy and resolution, superior stability and repeatability, and good durability against harsh environment.
Idle Time Treatment in the Single-Machine Scheduling Problem With Distinct Release Dates
Authors: Tanaka Shunji
Published: July 2013

The purpose of this study is to examine how idle time treatment in the single-machine scheduling problem with distinct (unequal) release dates affects schedules. For this purpose, two types of settings are considered: any idle time is permitted and unforced idle time is forbidden. In the latter setting, idle time is permitted only when no jobs are available, that is, release dates of unprocessed jobs are larger than the current time instant. Under these two idle time settings, the problem is solved both offline and online. In offline scheduling, all job information is known in advance and the schedule is optimized only once at time zero while in online scheduling, the schedule is re-optimized for only currently available jobs every time when a new job becomes available at its release date. Benchmark instances in the literature are solved by these approaches and the effect of idle time treatment on the obtained schedules is examined.
Virtual Tactile Simulation: A Novel Display and the Effects on Users’ Texture Perception
Authors: Peruzzini Margherita , Mengoni Maura , Germani Michele
Published: July 2013

This paper presents a novel study on the simulation of material texture by means of electro-tactile stimuli and details the effects on the users’ ability to recognize and discriminate different material classes. The research exploits a novel tactile display to simulate material texture and validates the adopted simulation strategy by experimental testing. The tactile system elaborates data from real material samples and combines electrical stimuli and mechanical vibration to reproduce both roughness and texture coarseness sensations. Then, an experimental protocol based on the theory of Psychophysics is defined to carry out system calibration and tests with users. The research aims at validating the proposed simulation strategy and checking the user response on virtual tactile stimuli. Experimentations were carried out to reproduce virtual material texture and measure the users’ ability to distinguish different virtual materials and to recognize the material class. Experimental results provide interesting details about tactile perception mechanisms and validate the adopted approach for tactile signals’ recognition and material class discrimination.
Comparative Study on Thermal Behavior of Lithium-Ion Battery Systems With Indirect Air Cooling and Indirect Liquid Cooling
Authors: Yeow Kim , Teng Ho , Thelliez Marina , Tan Eugene
Published: July 2013

A comparative study is conducted on the thermal behavior of three Li-ion battery modules with two cooled indirectly with air and one cooled indirectly with liquid. All three battery modules are stacked with the same twelve 8Ahr high-power pouch Li-ion battery cells. Heat generated from the cells is dissipated through 1-mm thick aluminum cooling plates sandwiched between two cells in the module. Each of the cooling plates has an extended surface for heat dissipation. The battery heat is dissipated through the cooling fins exposed in air flow channels in the case of air cooling, and through the extended cooling plate surfaces that are in contact with a liquid-cooled cold plate in the case of liquid cooling. The cell temperatures are analyzed using a simplified Finite Element Analysis (FEA) model for battery cooling. Simulation results show that with air cooling channels structured similar to that of compact heat exchangers, the air utilization and effectiveness of air cooling can be improved significantly. With proper design of the air cooling channels (i.e. with fin inserts in the air flow channels), indirect air cooling could reach a cooling condition comparable to that of indirect liquid cooling and obtain a higher gravimetric energy density with the same cooling-related parasitic volume in the battery system as long as the cell heat rejection is < 10 W/cell.
Polystyrene in Granular Form for Fused Deposition Modeling
Authors: Singamneni Sarat , Huang Bin , Davidson Karl
Published: July 2013

Fused deposition modeling has become one of the most successful rapid prototyping technologies, and is probably the candidate for the future rapid manufacturing, challenging its traditional counterpart, injection moulding in small to medium scale production. While ABS polymer is the predominant material currently used, the filament form being a precursor, adds up to initial costs, resulting in poor economics. Alternative materials were attempted earlier, but all of them invariably undertook the filament path, necessitating the production of the filament as the first step. The current paper addresses the question if thermoplastic polymers in the granule form could directly be used for fused deposition modeling. Initial experimental results involving the extrusion of polystyrene through a portable polymer extrusion head are promising, and open up further avenues for research.
Near-Net Shape Structures Fabricated by Micro-Robotic Deposition Using Precision Extrusion Control
Authors: Hoelzle David J. , Alleyne Andrew G. , Wagoner Johnson Amy J.
Published: July 2013

This work investigates an additive manufacturing process, micro-Robotic Deposition (μRD), and its utility in fabricating advanced architecture synthetic bone grafts. The objective of this research is to develop a method to integrate different regions with different porous microstructures into a single scaffold; there is evidence that scaffolds with designed regions of specific microstructures can be used to elicit a strong and directed bone ingrowth response that improves bone ingrowth rate and quality. The key contribution of this work is integration of a control algorithm that precisely places different build materials in specified locations with a workflow that enables near-net shape fabrication, thereby the fabrication of advanced architecture scaffolds is feasible. Under previous control methods, designs were relegated to be composed of a single material with simple contours. Scaffolds with contoured forms, multiple domains with distinct porous microstructures, and hollow cavities are feasible when the developed controller is used in conjunction with a novel manufacturing workflow in which scaffolds are filled within patterned molds that support overhanging features.
Integration of On-Machine Measurements in the Force Modeling for Machining of Advanced Nickel-Based Superalloys
Authors: Henderson Andrew , Bunget Cristina , Kurfess Thomas
Published: July 2013

Nickel-based superalloys are specially designed for applications where high strength, creep resistance, and oxidation resistance are critical at high temperatures. Many of their applications are the hot gas sections of turbo-machinery (e.g. jet engines and gas turbines). With greater demands on the performance and efficiency of these types of machines, the firing temperatures are reaching higher levels and nickel-based superalloys are being utilized more because of their excellent mechanical qualities at extreme temperatures. However, the properties that make them attractive for these applications present difficult challenges for the manufacture, particularly machining, of the components that are made from these materials. Considering the extreme environment that these components operate in, part quality, in particular surface quality, is paramount. The damage and stresses introduced to the surfaces of these components during manufacture needs to be well understood and controlled in order to ensure that premature component and machine failures do not occur. With improved process models and on-machine measurement capabilities, the in-process cutting forces and temperatures can be better understood and therefore subsurface damage can be better controlled. Since cutting forces and temperatures are direct contributors to subsurface damage, better control of these aspects would then lead to better control of subsurface damage. This paper discusses the use of on-machine touch probes to measure wear on milling tools and using those measurements to update a mechanistic force model for more accurate prediction of the cutting forces incurred during the milling of nickel-based superalloys.
Review on Powder-Based Electron Beam Additive Manufacturing Technology
Authors: Gong Xibing , Anderson Ted , Chou Kevin
Published: July 2013

This paper presents a thorough literature review of the powder-based electron beam additive manufacturing (EBAM) technology. EBAM, a relatively new additive manufacturing (AM) process, can produce full-density metallic parts directly from the electronic data of the designed part geometry. EBAM has gained broad attentions from different industries such as aerospace and biomedical, with great potential in a variety of applications. The paper first introduces the general aspects of EBAM. The unique characteristics, advantages and challenges of EBAM are then presented. Moreover, the hub of this paper includes extensive discussions of microstructures, mechanical properties, geometric attributes, which impact the application ranges of EBAM parts, with focus on commonly used titanium alloys (in particular, Ti-6Al-4V). In the end, modeling work of the EBAM process is discussed as well.
Remote Non-Contact Solar Cell Surface Monitoring
Authors: Chiou Richard , Mauk Michael , Davis Bret
Published: July 2013

This paper discusses the design and implementation of a remote non-contact solar cell surface roughness monitoring system as well as resulting data in solar energy manufacturing. The process solution set represents an integrated suite that provides solar cell manufacturing process monitoring, tool and fixture design, visualization, quality analysis, and automation through a remote robotic control system. An experimental study of surface roughness effect on laser light scattering from textured surfaces is described. The results and the system proposed are useful in implementing laser light scattering instruments for on-line monitoring of solar cell manufacturing processes which produce surface roughness patterns.
Wave Propagation in Periodic Piezoelectric Elastic Waveguides
Authors: Piliposyan D. G. , Ghazaryan K. B. , Piliposian G. T. , Avetisyan A. S.
Published: July 2013

The prorogation of electro-magneto-elastic coupled shear-horizontal waves in one dimensional infinite periodic piezoelectric waveguides is considered within a full system of the Maxwell’s equations. Such setting of the problem allows to investigate the Bloch-Floquet waves in a wide range of frequencies. Two different conditions along the guide walls and three kinds of transmission conditions at the interfaces between the laminae of waveguides have been studied. Stop band structures have been identified for Bloch-Floquet waves both at acoustic and optical frequencies. The results demonstrate the significant effect of piezoelectricity on the widths of band gaps at acoustic frequencies and confirm that it does not affect the band structure at optical frequencies. The results show that under electrically shorted transmission conditions Bloch-Floquet waves exist only at acoustic frequencies. For electrically open interfaces the dynamic setting provides solutions only for photonic crystals. In this case the piezoelectricity has no effect on band gaps.
Simulation of Interaction Between Lamb Waves and Cracks for Structural Health Monitoring With Piezoelectric Wafer Active Sensors
Authors: Shen Yanfeng , Giurgiutiu Victor
Published: July 2013

In this paper, the detection for two kinds of cracks is studied: (1) linear notch crack; (2) nonlinear breathing crack. A pitch-catch method with piezoelectric wafer actives sensors (PWAS) is used to interrogate an aluminum plate with a linear notch crack and a nonlinear breathing crack respectively as two cases. The inspection Lamb waves generated by the transmitter PWAS, propagate into the structure, interact with the crack, acquire crack information and are picked up by the receiver PWAS. The linear notch crack case is investigated through: (1) analytical model developed for Lamb waves interacting with a general linear damage; (2) finite element simulation. The breathing crack, which acts as a nonlinear source, is simulated using two approaches: (1) element activation/deactivation technique; (2) contact model. The theory and solving scheme of the proposed element activation/deactivation approach is discussed in detail. The signal features of different damage severities are analyzed. Crack opening, closing, stress concentration, surface collision phenomena are noticed for the breathing cracks. Mode conversion is noticed for both crack cases. The generation mechanism and mode components of the new wave packets are investigated by studying the particle motion through the plate thickness. A damage index is proposed based on the spectral amplitude ratio between the second harmonic and the excitation frequency for the breathing crack. The damage index is found capable of estimating the presence and severity of the breathing crack. The paper finishes with summary and conclusions.
Technology Developments Towards a Practical SMA Aero Engine Application
Authors: Webster John
Published: July 2013

SMAs have been demonstrated for many actuation applications and found a few commercial applications, generally for small components with ambient temperature actuation. A study into their use for an adaptive geometry exit nozzle for a large aero gas turbine started around 2001. SMA mechanisms offer significant advantages in weight, complexity and aerodynamic form which can be achieved. It quickly became clear however that virtually all aspects of the material, form availability, mechanism, design methods, actuation and application assessment would need significant further development. This paper will describe the work which has been done on those aspects which have been necessary to move the concept towards a practical reality and wind tunnel demonstration of a prototype component. A relatively simple structure has been pursued, but this has led to the unusual need for large sheet materials at higher temperatures than the materials which were available at the time. Unique processing and characterisation methods have been developed in parallel with the materials to provide a practical process which can be applied to provide predictable stable operation within a structure where the loading is predominantly in tension. The structure also allows more rapid cooling of the SMA which has been identified as an issue in many studies, although our solution does require increased heat input for actuation. The design of any engineering component is a series of compromises around parameters such as weight, efficiency and cost. SMA seems to offer a major opportunity in all of these areas. Safety is clearly paramount in any aircraft application and the compromises must be made without any detrimental effect on this. All of these issues are covered by standard industry procedures. The characteristic of SMA which are different to conventional actuation offer major advantages, but also significant challenges in achieving acceptance.
Time Dependent Polarization and Strain Evolution Around a Circular Hole in Ferroelectrics
Authors: Liu Q. D.
Published: July 2013

The simulation of inhomogeneous creep around a circular hole in the center of ferroelectric plate is presented aiming for understanding the birefringence measurements around the hole. The time dependent fields of strain and polarization around the hole in response to its concentrated electric field effect can be determined using the finite element method. It was found that the electric field concentration factor by a hole can achieve 6 times of the applied loads and shows slightly time dependence; the creep of polarization and strains process is controlled by the local electric field magnitude, which governs the saturation of remnant polarization and strain. The result of geometric principal strain difference contours around the hole agrees with that of birefringence observation. The remnant polarization increased in a power-law relation with electric field magnitude, while the principal strain difference developed quadratically with the total electric displacement. Both experimental and numerical results suggest that the strain distributes around the hole and changes with time, which is controlled by both the local electric field magnitude and the saturation process. Although the inhomogeneities enhance fields locally, the saturated values of strain and polarization decrease with an increase in the defect volume.
The Effect of the Configuration of the Amplification Device on the Power Output of a Piezoelectric Strip
Authors: McCarthy Jesse M. , Deivasigamani Arvind , John Sabu J. , Watkins Simon , Coman Floreana
Published: July 2013

We investigated the behaviour of a polyvinylidene-fluoride piezoelectric strip (‘stalk’) clamped at the leading edge, and hinged to an amplification device (‘leaf’) at the trailing edge. Flutter of this cantilevered system was induced within smooth, parallel flow, and an AC voltage was generated from the PVDF strip. A polypropylene, triangle comprised the leaf. Two leaf parameters were varied so as to quantify their effect on the power output of the system: 1) the area, and 2) the aspect ratio. It was found that the highest power output was realised with the 2nd-largest leaf across a range of wind speeds, but the variation in power measurements was large. Thus, the 3rd-largest leaf was found to give the highest power output with the lowest power variation. This leaf area was then fixed and the aspect ratio varied. It was found that the largest aspect ratio-leaf rendered the highest power output, but had a relatively high start-up wind speed.
Compliant Articulation Structure Using Superelastic NiTiNOL
Authors: Liu Jiening , Hall Benjamin , Frecker Mary , Reutzel Edward W.
Published: July 2013

A device that can provide articulation to surgical tool tips is needed in natural orifice transluminal endoscopy surgery (NOTES). In this paper, we propose a compliant articulation structure that uses superelastic NiTiNOL to achieve a large deflection angle and force in a compact size. Six geometric parameters are used to define this structure, and constraints based on the fabrication process are imposed. Using finite element analysis, a family of designs is evaluated in terms of the free deflection angle and blocked force. The same family of designs is evaluated for both NiTiNOL and stainless steel. It can be seen that significant benefits are observed when using NiTiNOL compared to 316 stainless steel; a maximum free deflection angle of 64.8° and maximum blocked force of 24.7 N are predicted. The designs are refined to avoid stress concentrations, and design guidelines are recommended. The meso-scale articulation structure is fabricated using both a Coherent Avia Q-switched, 355 nm laser and a Myachi Unitek 200 W single mode pulsed fiber laser with active water cooling. Select fabricated structures are then tested to validate the finite element models.
Development of Robust Control Algorithms for Shape Memory Alloy Bending Actuators
Authors: Crews John H. , Smith Ralph C. , Hannen Jennifer C.
Published: July 2013

In this paper, we present a systematic approach to developing robust control algorithms for a single-tendon shape memory alloy (SMA) bending actuator. Parameter estimation and uncertainty quantification are accomplished using Bayesian techniques. Specifically, we utilize Markov Chain Monte Carlo (MCMC) methods to estimate parameter uncertainty. The Bayesian parameter estimation results are used to construct a sliding mode control (SMC) algorithm where the bounds on uncertainty are used to guarantee controller robustness. The sliding mode controller utilizes the homogenized energy model (HEM) for SMA. The inverse HEM compensates for hysteresis and converts a reference bending angle to a reference temperature. Temperature in the SMA actuator is estimated using an observer, and the sliding mode controller ensures that the observer temperature tracks the reference temperature. The SMC is augmented with proportional-integral (PI) control on the bending angle error.
Model Reduction of Piezoelectric Energy Harvesters Subject to Band-Limited, Stochastic Base Excitation
Authors: Wickenheiser Adam M.
Published: July 2013

In many scenarios where vibration energy harvesting can be utilized — particularly those involving bio-motions or environmental disturbances — energy sources are broadband and non-stationary. On the other hand, design procedures have been predominantly developed for harmonic or white noise excitation, specifically for single degree of freedom approximations of the transducer. In this paper, a general approach for design optimization of cantilevered, piezoelectric energy harvesters in the presence of band-limited, white-noise excitation is outlined. For this study, human and vehicular motions are considered; these complex waveforms are distilled into a small set of dominant features with regard to their impact on the power output of the device. Criteria based on modal participation factors, including pre-filtering of the disturbance, are used in guiding the reduction of the input and plant degrees of freedom in order to make the design optimization problem tractable. This process determines the error in assuming a low-order model for the transducer in the presence of broadband noise that may excite multiple modes of vibration. Furthermore, this study considers the quantitative impact of charge cancellation in higher modes and the benefits of inserting multiple electrodes along the length. To illustrate these methods, energy harvesters are designed for acceleration data collected from walking and car idling. It is shown that a simple method that is a generalization of naïve approaches that assume harmonic or white noise excitation and a single degree of freedom can determine which simplifications are appropriate and the inaccuracies that can be expected from them.
Development of a Miniaturized Clamping Device Driven by Magnetic Shape Memory Alloys
Authors: Schlüter Kathrin , Blumenthal Philipp , Raatz Annika
Published: July 2013

This article deals with the potential of magnetic shape memory (MSM) actuators for the use in micro applications and in particular in clamping devices. The most common actuator concepts are introduced briefly, including the so called push-push concept. Subsequently, an overview of clamping technology is given and the advantages of mechanical clamping are pointed out. It is proposed to use the push-push actuation concept for the development of an energy-efficient clamping device driven by magnetic shape memory alloys. Hence, the design of the MSM clamping device and the dimensioning of its magnetic circuits are presented. Finally, the characteristics of the device are experimentally examined and the results are summarized.
Inverse-Motion-Based Modeling for Electromechanics With Application to Electrostrictive Polyurethane
Authors: Ask Anna , Denzer Ralf , Menzel Andreas , Ristinmaa Matti
Published: July 2013

In this work the inverse motion problem for electroelasticity is considered. For given loads and boundary conditions, and a given deformed shape of the electro elastic body, the initially unknown undeformed configuration is sought. The boundary-value problem for the inverse motion is obtained by reparameterization of the forward motion equations in terms of the inverse deformation map. In order to account for incompressibility, a mixed formulation is adopted. The finite element method is used to calculate the undeformed configuration for an electro-active gripper application.
Towards Hyper-Redundant and Super-Configurable Articulated Structures
Authors: Swensen John P. , Dollar Aaron M.
Published: July 2013

In this paper, we describe preliminary analysis for a method of constructing homogeneous actuated electromechanical composite structures from many smaller electromechanical “active cells”. The preliminary cell design consists of a contractile shape memory alloy (SMA) elements (Nitinol) connecting two electrically conductive terminals. The composite structure is actuated by applying a gross electrical potential across the entire structure. This causes connected cells to activate through resistive heating. The material properties of the ensemble structure can be varied by changing the properties of the binding material, enabling a wide range of stiffness and damping properties. A structure made from these cells can be easily fabricated in a nearly arbitrary shape — simply by producing an appropriate mold — and would be highly redundant and robust to localized cell failures. The primary focus of this paper is to perform a static analysis of the connectivity of arrays of active cells and the associated power dissipation in the individual cells.
Experimental Optimization of Electrode Composition for Ionic Polymer Transducers in Sensing
Authors: Kocer Bilge , Weiland Lisa Mauck
Published: July 2013

Ionic Polymer Transducers (IPTs), also known as Ionic Polymer Metal Composites (IPMCs), are a promising group of intelligent materials which exhibit electromechanical coupling behavior in both actuation and sensing. They are composed of an electroactive ionomer, inserted between metallic electrodes. In this study, IPTs are experimentally examined as a sensor in the aspect of electrode composition optimization. Sensors with electrodes having several volumetric percentages of metallic powder, ruthenium dioxide -RuO2-, are tested in bending under different step displacement inputs to explore the output current response. Optimum metallic powder content in the electrode solution for a sensor generating maximum current output is determined. Furthermore, the magnitude of the tip deflection’s effect on sensitivity is examined. The IPTs used in the experiments are fabricated via Direct Assembly Process which enables direct control over the electrode architecture.
A Practical Power Maximization Design Guide for Piezoelectric Energy Harvesters Inspired by Avian Bio-Loggers
Authors: Shafer Michael W. , Bryant Matthew , Garcia Ephrahim
Published: July 2013

Vibrational energy harvesting has been the subject of significant recent research, and has even begun commercial deployment. Despite the research community’s understanding of the fundamental mechanics of piezoelectric systems under base excitation, proper design methods and guidelines for applied systems are nonexistent. This leaves engineers with the options of either using non-ideal beams, or developing complex heuristic computational design programs. Such options are untenable given the state of research. We seek to answer a relatively simple question: Given mass, frequency, and size requirements, what would be the dimensions of the ideal bimorph harvester? By using approximations for the first natural frequency and mode shape, we are able to determine the unknown beam dimensions and modal parameters in terms of the system requirements and material properties. The result is a power equation that only depends on relative piezoelectric material thickness, and the mechanical damping ratio. With only two dependent variables, the equations can be swept in order to find the ideal beam geometry for any given damping ratio. In addition to presenting this method, two design case studies are provided as examples.
Cellular Honeycomb-Like Structures With Internal Buckling and Viscous Elements for Simultaneous Load-Bearing and Dissipative Capability
Authors: Barbarino Silvestro , Pontecorvo Michael E. , Gandhi Farhan S.
Published: July 2013

Cellular structures with hexagonal unit cells show a high degree of flexibility in design. Based on the geometry of the unit cells, highly orthotropic structures, structures with negative Poisson’s ratios, structures with high strain capability in a particular direction, or other desirable characteristics may be designed. Much of the prior work on cellular structures is based on hexagonal honeycomb-like unit cells, without any inclusions. A companion paper to the current paper presented a vision of cellular honeycomb-like structures with diverse inclusions or internal features within the unit cells (such as contact elements resulting in stiffening behavior, buckling beams resulting in softening behavior, bi-stable elements producing negative stiffness or viscous dashpots producing dissipative behavior). That paper further went into details on linear springs as the most fundamental of inclusions.

In the present paper, a buckling beam and viscous dashpots are used as inclusions in the basic pin-jointed rigid-walled hexagonal unit cell. The buckling beam provides the cell with a high initial stiffness and load carrying capability. At loads beyond the critical buckling load, the unit cell softens (while still retaining the ability to carry a “design” load), and undergoes large deformation under incremental load. The viscous dampers undergo a correspondingly large stroke resulting in high dissipative capability and loss factor under harmonic or transient disturbance beyond the design load. In the paper, an analysis and design study of the cell behavior with variation in unit cell geometric parameters, buckling beam parameters and viscous dashpot parameters is presented. The analytical results in the paper are validated against ANSYS Finite Element results. Further, a prototype unit cell with an aluminum internal buckling beam and viscous dashpots is fabricated and tested under static and dynamic loads in an Instron machine. Good correlation is observed between the tests, the FE results and the analytical simulations when accounting for the non-linear behavior of the viscous dashpot used in the tests.
Design and Characterization of a Soft Electroactive Adaptive Structure for Legged Robotic Motion
Authors: Newton Jason , Hays Michael , Clark Jonathan , Oates William S.
Published: July 2013

Legged robotics exhibit mobility over complex terrains that overcomes many of the challenges experienced with traditional wheeled robots. This includes the ability to traverse rough terrain, climb obstacles, and in some robotic platforms, even scale walls. It is known from bio-locomotion research that humans and other animals adjust the stiffness of their muscles to accommodate differences in the terrain. Methods to implement changes in the passive mechanical stiffness on a legged robotic platform have included geometric changes to the leg configuration, complex mechanical linkages and gears, or thermally induced modulus changes in polymers. Each of these cases are limited in their dynamic response and efficiency. As an alternative, we have developed a leg module that changes its stiffness by application of an electric field. This is achieved by applying a large voltage to the dielectric elastomer VHB. Previous studies have demonstrated up to a 92% stiffness reduction. The goal of this work is to identify the electromechanical dynamic responses of those elements to understand limits in adaptability from abrupt changes in terrain. We quantify the structural dynamic behavior and electromechanical limits governing rapid stiffness changes in our legged VHB module. Structural vibration characterization is presented to illustrate transient dynamic changes when the VHB material is exposed to a step input voltage change. The results are analyzed and compared to the system dynamics required for the iSprawl legged robot.
Micromechanics Modeling of Multiphase Piezoelectric Composites
Authors: Malakooti Mohammad H. , Sodano Henry A.
Published: July 2013

Recent work on multifunctional materials has shown that a functionally graded interface between the fiber and matrix of a composite material can lead to improved strength and stiffness while simultaneously affording piezoelectric properties to the composite. However the modeling of this functional gradient is difficult through micromechanics models without discretizing the gradient into numerous layers of varying properties. In order to facilitate the design of these multi-phase piezoelectric composites, accurate models are required. In this work, multi-inclusion models are extended to predict the effective electroelastic properties of multiphase piezoelectric composites. The presented formulation will provide a general framework for modeling other coupled fields of heterogeneous materials. To evaluate the micromechanics modeling results, a three dimensional finite element model of a four-phase piezoelectric composite was created in the commercial finite element software ABAQUS with different volume fractions and aspect ratios. The simulations showed excellent agreement for predicting the electroelastic properties of the multiphase piezoelectric composites.
Gas Accumulation Detection in a Water Tank Using Lamb Waves
Authors: Yu Lingyu , Tian Zhenhua , Zhao Liuxian
Published: July 2013

According to U.S. Nuclear Regulatory Commission (NRC) Generic Letter 2008, the gas accumulation in the nuclear emergency core cooling systems is concerned since it may critically damage pipes, pumps and valves. There is a need to detect the inside gas accumulation including the quantification of gas location and volume. In this paper, we propose a in-situ technique for gas detection in a gas tank by using Lamb waves. Lamb wave propagation in a plate-like structure is affected by the boundary conditions. For structures in air or submerged in liquid, wave propagations are different. When the structure is in contact with liquid such as water, wave energy leaks into it from the solid material. Therefore, the way of gas detection is related to the detection of change in wave propagation characteristics. Experimental tests in a steel water tank were conducted and shown the Lamb wave’s response to the water presence. Theoretical study of Lamb waves propagation on a free plate in air and on a plate with one surface submerged in liquid were then conducted and compared. Further investigation to understand the change in Lamb wave propagation when water is present was conducted with frequency-wavenumber analysis. In the frequency-wavenumber space, it was found that a new plate wave mode, quasi-Scholte wave showed up. A0 Lamb mode showed a decreased propagation while S0 Lamb wave showed no changes. The change in the Lamb wave propagation is found to be frequency dependent.
Underwater Tracking and Size-Estimation of a Moving Object Using an IPMC Artificial Lateral Line
Authors: Abdulsadda Ahmad T. , Tan Xiaobo
Published: July 2013

Motivated by the lateral line system of fish and amphibians, arrays of flow sensors have been proposed as a new sensing modality for underwater robots. Most existing studies on such artificial lateral lines have been focused on the localization of a vibrating sphere, also known as a dipole source. In this paper we investigate the problem of tracking a moving but non-vibrating cylindrical object and estimating its size and shape using an artificial lateral line system. Based on a nonlinear analytical model for the moving object-induced flow field, a two-stage extended Kalman filter is proposed to estimate the location, velocity, size, and shape of the object. Simulation results on tracking a cylinder with ellipsoidal cross-section are presented to illustrate the approach. On the experimental side, we demonstrate the use of an artificial lateral line prototype comprising six ionic polymer-metal composite (IPMC) flow sensors in the tracking and size estimation of a moving circular cylinder.
Nonlinear Guided Waves for Structural Health Monitoring: Numerical Algorithm and Application to Railroad Track
Authors: Nucera Claudio , Lanza di Scalea Francesco
Published: July 2013

The University of California at San Diego (UCSD), under a Federal Railroad Administration (FRA) Office of Research and Development (R&D) grant, is conducting research to develop a system for in-situ measurement of the rail Neutral Temperature in Continuous-Welded Rail (CWR). It is known that CWR can break in cold weather and can buckle in hot weather. Currently, there is a need for the railroads to know the current state of thermal stress in the rail, or the rail Neutral Temperature (rail temperature with zero thermal stress), to properly schedule slow-order mandates and prevent derailments.

UCSD has developed a prototype for wayside rail Neutral Temperature measurement that is based on non-linear ultrasonic guided waves. Numerical models were first developed to identify proper guided wave modes and frequencies for maximum sensitivity to the thermal stresses in the rail web, with little influence of the rail head and rail foot. Experiments conducted at the Large-scale Rail NT Test-bed indicated a rail Neutral Temperature measurement accuracy of a few degrees. Field tests are planned at the Transportation Technology Center (TTC) in Pueblo, CO in June 2012 in collaboration with the Burlington Northern Santa Fe (BNSF) Railway.
Implementation of a Variable Stiffness Actuator Based on Dielectric Elastomers: A Feasibility Study
Authors: Berselli Giovanni , Vertechy Rocco , Babič Mitja , Parenti Castelli Vincenzo
Published: July 2013

Dielectric Elastomers (DE) seem to be a promising technology for the implementation of light and compact Variable Stiffness Actuators (VSAs), thanks to their large power densities, low costs and shock-insensitivity. Nonetheless, the development of DE-based VSA is not trivial owing to the relevant dissipative phenomena that affect the DE when subjected to rapidly changing deformations. In this context, the purpose of the present paper is to investigate the practical feasibility of DE-based VSA. As a case study, two conically-shaped actuators, in agonistic-antagonistic configuration, are modeled accounting for the visco-hyperelastic nature of the DE films. The model is then linearized and employed for the design of a stiffness controller. The control algorithm requires the knowledge of the actuator configuration (via a position sensor) and of the force exchanged with the environment (via a force sensor). An optimum full-state observer is then implemented, which enables both accurate estimation of the DE time-dependent behavior and adequate suppression of sensor measurement noise. At last, experimental results are provided together with the description of an effective electronic driver that allows an independent activation of the agonistic-antagonistic DE membranes.
Tunable Band-Pass Filters Employing Stretchable Electronic Components
Authors: Slipher Geoffrey A. , Mrozek Randy A. , Shumaker Justin L.
Published: July 2013

This paper describes some of the recent results of an ongoing U.S. Army research program examining the electronic behavior of hyperelastic stretchable capacitor, resistor, and inductor networks for which the conductor material employed is stretchable. As with traditional rigid analog components, stretchable electronic components exhibit frequency-dependant behavior. Unlike their rigid counterparts, stretchable electronic components may also exhibit dramatic strain-dependent behavior. In this way stretchable circuit networks may be viewed as controllable spatio-temporal filters. Resistance, capacitance, and inductance all change to varying degrees depending on the specific set of spatio-temporal inputs. These variations may be harnessed to create an adaptive circuit element that is controllable. This paper describes the results of integrating stretchable components into a tunable band-pass filter. Center frequency, bandwidth, and gain can be varied in a controllable way by varying the capacitance or resistance of specific circuit elements by stretching them. Biaxially stretchable components are described that are subjected to equibiaxial strain-states as high as 100% area strain. We examine the influence that the type of compliant conductor has on tunable circuit properties and on control authority.
Experimental Investigations in Embedded Sensing for Structural Health Monitoring of Composite Components in Aerospace Vehicles
Authors: Ghoshal Anindya , Ayers James , Gurvich Mark , Urban Michael , Bordick Nathaniel
Published: July 2013

This paper summarizes the experimental investigations for smart embedded sensing in rotorcraft composite components. The overall objective of this effort was to develop smart embedded sensor technologies for condition based maintenance (CBM) for composite components in Army rotorcraft. This paper presents the results of experimental investigations related to development and maturation of different types of embedded sensing solutions for structural health monitoring of composite components including Fiber Bragg Grating (FBG) sensors, phased and discrete piezoelectric sensor arrays. A discussion is provided relative to embedment of optical fibers into composites, and the results from embedded FBG sensors in a rotorcraft flexbeam subcomponent test specimen with seeded delamination subjected to dynamic loading. Likewise, results are analyzed of surface mounted phased array and embedded smart piezoelectric sensors in the flexbeam subcomponent test specimen with embedded delamination, subjected to fatigue cyclic loading. The paper also summarizes the lessons learned from efforts to nucleate and propagate delamination within composite components under dynamic cyclic loading.
Integrated Bioderived-Conducting Polymer Membrane Nanostructures for Energy Conversion and Storage
Authors: Sundaresan Vishnu-Baba , Salinas Sergio
Published: July 2013

Conducting polymers are ionic active materials that can perform electro-chemo-mechanical work through redox reactions. The electro-chemo-mechanical coupling in these materials has been successfully applied to develop various application platforms (actuation systems, sensor elements and energy storage devices (super capacitors, battery electrodes)). Similarly, bioderived membranes are ionic active materials that have been demonstrated as actuators, sensors and energy harvesting devices. Bioderived membranes offer significant advantages over synthetic ionic active materials in energy conversion and the scientific community has put forward various system level concepts for application in engineering applications. The biological origins of these material systems and their subsequent mechanical, electrical and thermal properties have served as a key deterrent in applications. This article proposes a novel architecture that combines a conducting polymer and a bioderived membrane into an integrated material system in which the charge gradients generated from a biochemical reaction is stored and released in the conducting polymer through redox reactions. This paper discusses the fabrication and topographical characterization of the integrated bioderived-conducting polymer membrane nanostructures. The prototype comprises of an organized array of fluid-filled three-dimensional containers with an integrated membrane shell that performs energy conversion and storage owing to its multi-functional microstructure. The bioderived membrane is self-assembled into a hollow spherical container from synthetic membranes or bilayer lipid membranes with proteins and the conducting polymer membrane forms a wrapper around this container resulting in a three-dimensional assembly.