This PDF file contains the front matter associated with SPIE Proceedings Volume 7979, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Implementation of an integratable ultrasonic sensor network with associated cable connection for high temperature monitoring applications is demonstrated through application of a three-element ultrasonic sensor network for temperature measurement in a turbine stator assembly. The sensor network is composed of a piezoelectric composite film deposited on a titanium substrate with a sol-gel technique and three top electrodes deposited on the piezoelectric film. The sensor network is glued onto a selected area of the stator assembly in such a way that three subareas with different wall thicknesses are probed individually by each of the sensing elements. The ultrasonically instrumented stator assembly is first heated in a furnace to different temperatures. At each temperature and for each probed location the transit time of ultrasonic waves through assembly wall thickness is measured. Then a relationship between transit time and wall temperature is established. In a subsequent experiment, the stator assembly is heated up to 200 °C and then let cool down while the transit time in the assembly wall is being measured continuously. By using the transit time versus temperature relationship obtained earlier, the heating and cooling rates at the three probed locations are determined and then compared.

This paper presents the development and characterization of active aluminum-matrix composites manufactured by Ultrasonic Additive Manufacturing (UAM), an emerging rapid prototyping process based on ultrasonic metal welding. The primary benefit of UAM over other metal-matrix fabrication processes is the low process temperatures, as low as 25 °C. UAM thus provides unprecedented opportunities to develop adaptive structures with seamlessly embedded smart materials and electronic components without degrading the properties that make these materials and components attractive. The objective of this research is to develop UAM composites with aluminum matrices and embedded shape memory NiTi, magnetostrictive Galfenol (FeGa), and polyvinylidene fluoride (PVDF) phases. The paper is focused on the thermally induced strain response and stiffness behavior of NiTi-Al composites, the actuation properties of FeGa-Al composites, and the embedded sensing capabilities of PVDF-Al composites. We observe up to a 10% increase over room temperature stiffness for NiTi-Al composites and a magnetomechanical response in the FeGa-Al composite up to 52.4 με. The response of the PVDF-Al composite to harmonic loads is observed over a frequency range of 10 to 1000 Hz.

Wireless sensor nodes with impedance measurement capabilities, often based on the Analog Devices AD5933 impedance chip and Atmel's 8-bit ATMega 1281 microcontroller, have been demonstrated to be effective in collecting data for localized damage detection (such as for loose bolt detection) and for sensor self-diagnostics. Previouslydeveloped nodes rely on radio telemetry and off-board processing (usually via a PC) to ascertain damage presence or sensor condition. Recent firmware improvements for the wireless impedance device (WID) now allow seamless integration of the WID with SHMTools and mFUSE, an open-source function sequencer and SHM process platform for Matlab. Furthermore, SHM processes developed using mFUSE can be implemented in hardware on the WID, allowing greater autonomy among the sensor nodes to identify and report damage in real time. This paper presents the capabilities of the newly integrated hardware and software, as well as experimental validation.

In this paper, we present a series of hybrid energy configurations that are designed to provide a robust power source for embedded sensing hardware. The proper management of energy resources is a critical component in the design of any deployed sensing network. For systems that are installed in remote or inaccessible locations, or those with an operational lifespan that exceeds traditional battery technologies, energy harvesting is an attractive alternative. Unfortunately, the dependence on a single energy source (i.e. solar) can cause potential problems when environmental conditions preclude the system from operating at peak performance. In this paper we consider the use of a hybrid energy source that extracts energy from multiple sources and uses this collective energy to power sensing hardware. The sources considered in this work include: solar, vibration, thermal gradients, and RF energy capture. Methods of increasing the efficiency, energy storage medium, target applications and the integrated use of energy harvesting sources with wireless energy transmission will be discussed.

For future structural health monitoring (SHM) systems, the knowledge of past and present operational loads in the form of forces/moments at critical system interfaces will be invaluable for performing accurate prognostics and augmenting SHM capabilities. However, this information is not a direct product of traditional operational loads monitoring (OLM) techniques employed on current fleet aircraft and is not easily achieved using existing force measurement devices. In recognition of this limitation, this paper addresses the development of an accurate in-situ multiaxis force measurement system for directly monitoring dynamic operational loads at critical mechanical interfaces without altering the existing connector architecture. The proposed methodology utilizes a strain gage-based measurement technique in which a series of sensors is calibrated with a set of known loading configurations. The sensitivity matrix relating the measured strains to the loads forms the core of the system. The feasibility of the proposed technique was demonstrated both analytically and experimentally on a representative aircraft weapon store/rail interface exhibiting nonlinearity in the system. The results are conclusive in that the outlined trained network approach is able to accurately predict all six force/moment interface loads with less than 8 percent total error under various loading conditions.

The utilization of shape memory alloys (SMAs) as actuators in aerospace applications continues to show promise. These materials, when subjected to controlled changes in temperature, have the capability to provide motion while under loads that exceed thousands of times their own weight and can do so over tens of thousands of cycles. However, the rate of thermally-induced SMA transformation is significantly hindered by low thermal conductivity and latent heat effects observed in this material. The relatively long cooling times observed in SMA geometries such as beams and tubes make it difficult for controlled devices to operate with sufficiently high frequency. Therefore, the application of SMA beams as aerospace control actuators has been limited. Morphing structures such as flight control mechanisms require higher cyclic actuation frequencies than are commonly observed in SMAs, and thus have motivated the effort to increase thermal actuation rates attainable in SMA active components. This work presents an analytical study of a tapered beam actuator and discusses the possibility of using SMAs in conjunction with more conductive materials to enhance actuation performance, especially with regard to actuation cyclic frequency. The analysis involves computing the actuation work output over time of various loaded, thermally cycled active SMA beams using an accurate constitutive model implemented in a finite element framework. This set of analyses considers the solution to a transient thermomechanically coupled problem and includes the effects of latent heat of transformation on the energy balance. The study compares the effectiveness of aluminum, copper, and silver secondary material regions and their geometric configurations in altering the actuation power-to-mass ratio of the beam. An optimization scheme is used to determine the geometric distribution of each secondary material that results in the highest power-to-mass ratio. It is shown that aluminum, when optimally distributed, provides the best overall design solution of the three materials considered.

The response of a MEMS device that is exposed to a harsh environment may range from an increased noise floor to a completely erroneous output to temporary or even permanent device failure. One such harsh environment is high power acoustic energy possessing high frequency components. This type of environment sometimes occurs in small aerospace vehicles. In this type of operating environment, high frequency acoustic energy can be transferred to a MEMS gyroscope die through the device packaging. If the acoustic noise possesses a sufficiently strong component at the resonant frequency of the gyroscope, it will overexcite the motion of the proof mass, resulting in the deleterious effect of corrupted angular rate measurement. Therefore if the device or system packaging can be improved to sufficiently isolate the gyroscope die from environmental acoustic energy, the sensor may find new applications in this type of harsh environment. This research effort explored the use of microfibrous metallic cloth for isolating the gyroscope die from environmental acoustic excitation. Microfibrous cloth is a composite of fused, intermingled metal fibers and has a variety of typical uses involving chemical processing applications and filtering. Specifically, this research consisted of experimental evaluations of multiple layers of packed microfibrous cloth composed of sintered nickel material. The packed cloth was used to provide acoustic isolation for a test MEMS gyroscope, the Analog Devices ADXRS300. The results of this investigation revealed that the intermingling of the various fibers of the metallic cloth provided a significant contact area between the fiber strands and voids, which enhanced the acoustic damping of the material. As a result, the nickel cloth was discovered to be an effective acoustic isolation material for this particular MEMS gyroscope.

Adaptive Frontlighting Systems (AFS in GM usage) improve visibility by automatically optimizing the beam pattern to accommodate road, driving and environmental conditions. By moving, modifying, and/or adding light during nighttime, inclement weather, or in sharp turns, the driver is presented with dynamic illumination not possible with static lighting systems The objective of this GM-HRL collaborative research project was to assess the potential of active materials to decrease the cost, mass, and packaging volume of current electric stepper-motor AFS designs. Solid-state active material actuators, if proved suitable for this application, could be less expensive than electric motors and have lower part count, reduced size and weight, and lower acoustic and EMF noise1. This paper documents Part 1 of the collaborative study, assessing technically mature, commercially available active materials for use as actuators. Candidate materials should reduce cost and improve AFS capabilities, such as increased angular velocity on swivel. Additional benefits to AFS resulting from active materials actuators were to be identified as well such as lower part count. In addition, several notional approaches to AFS were documented to illustrate the potential function, which is developed more fully in Part 2. Part 1 was successful in verifying the feasibility of using two active materials for AFS: shape memory alloys, and piezoelectrics. In particular, this demonstration showed that all application requirements including those on actuation speed, force, and cyclic stability to effect manipulation of the filament assembly and/or the reflector could be met by piezoelectrics (as ultrasonic motors) and SMA wire actuators.

A magnetorheological fluid (MRF) device is designed to provide a static locking force caused by the operation of a controllable MRF valve. The intent is to introduce an MRF device which provides the locking force of a fifth wheel coupler while maintaining the "powerless" locking capability when required. A passive magnetic field supplied by a permanent magnet provides a powerless locking resistance force. The passively closed MRF valve provides sufficient reaction force to eliminate axial displacement to a pre-defined force value. Unlocking of the device is provided by means of an electromagnet which re-routes the magnetic field distribution along the MR valve, and minimizes the resistance. Three dimensional electromagnetic finite element analyses are performed to optimize the MRF lock valve performance. The MRF locking valve is fabricated and tested for installation on a truck fifth wheel application. An experimental setup, resembling actual working conditions, is designed and tests are conducted on vehicle interface schemes. The powerless-locking capacity and the unlocking process with minimal resistance are experimentally demonstrated.

A coupled axisymmetric finite element model is formulated to describe the dynamic performance of a hydraulically amplified Terfenol-D mount actuator. The formulation is based on the weak form representations of Maxwell's equations for electromagnetics and Navier's equation for mechanical systems. Terfenol-D constitutive behavior is modeled using a fully coupled energy averaged model. Fluid pressure is computed from the volumetric deformation of the fluid chamber and coupled back to the structure as tractions on the boundaries encompassing the fluid. Seal friction is modeled using the Lugre friction model. The resulting model equations are coded into COMSOL (a commercial finite element package) which is used for meshing and global assembly of matrices. Results show that the model accurately describes the mechanical and electrical response of the actuator under static and dynamic conditions. At higher frequencies there are some errors in the phase due to the anhysteretic nature of the Terfenol-D constitutive law. A parametric study reveals that the performance of the actuator can be significantly improved by stiffening the fluid chamber components and reducing seal friction.

Recently, the development of flexible electret based electrostatic actuator has been widely discussed. The devices was shown to have high sound quality, energy saving, flexible structure and can be cut to any shape. However, achieving uniform charge on the electret diaphragm is one of the most critical processes needed to have the speaker ready for large-scale production. In this paper, corona discharge equipment contains multi-corona probes and grid bias was set up to inject spatial charges within the electret diaphragm. The optimal multi-corona probes system was adjusted to achieve uniform charge distribution of electret diaphragm. The processing conditions include the distance between the corona probes, the voltages of corona probe and grid bias, etc. We assembled the flexible electret loudspeakers first and then measured their sound pressure and beam pattern. The uniform charge distribution within the electret diaphragm based flexible electret loudspeaker provided us with the opportunity to shape the loudspeaker arbitrarily and to tailor the sound distribution per specifications request. Some of the potential futuristic applications for this device such as sound poster, smart clothes, and sound wallpaper, etc. were discussed as well.

This paper presents two approaches to developing improved check valves for high frequency fluid rectification in a smart material electro-hydraulic actuator: a single reed-type design and an array of miniaturized valves. The multiphysics software COMSOL was used to study the 3-D fluid-structure interaction between the valve and hydraulic fluid during pump operation, and the results were validated utilizing an instrumented valve to measure in-situ tip displacement. The added mass effect of the fluid on the valve was experimentally characterized. To improve the frequency response of the valves, an array of miniature reed valves were designed for the high frequency and high pressure environment in the pump. A fabrication method was developed for the miniaturized valves utilizing micromachining processes. The performance of the two types of valves was compared through static and dynamic experiments.

The production of car body panels are defective in succession of process fluctuations. Thus the produced car body panel can be precise or damaged. To reduce the error rate, an intelligent deep drawing tool was developed at the Fraunhofer Institute for Machine Tools and Forming Technology IWU in cooperation with Audi and Volkswagen. Mechatronic components in a closed-loop control is the main differentiating factor between an intelligent and a conventional deep drawing tool. In correlation with sensors for process monitoring, the intelligent tool consists of piezoelectric actuators to actuate the deep drawing process. By enabling the usage of sensors and actuators at the die, the forming tool transform to a smart structure. The interface between sensors and actuators will be realized with a closed-loop control. The content of this research will present the experimental results with the piezoelectric actuator. For the analysis a production-oriented forming tool with all automotive requirements were used. The disposed actuators are monolithic multilayer actuators of the piezo injector system. In order to achieve required force, the actuators are combined in a cluster. The cluster is redundant and economical. In addition to the detailed assembly structures, this research will highlight intensive analysis with the intelligent deep drawing tool.

The Department of Energy and the Sandia National Laboratories Wind Power Technology Department have initiated a number of wind turbine blade sensing technology projects with a major goal of understanding the issues and challenges of incorporating new sensing technologies in wind turbine blades. The projects have been highly collaborative with teams from several commercial companies, universities, other national labs, government agencies and wind industry partners. Each team provided technology that was targeted for a particular application that included structural dynamics, operational monitoring, non-destructive evaluation and structural health monitoring. The sensing channels were monitored, in some or all cases, during blade fabrication, field testing of the blade on an operating wind turbine, and lab testing where the life of the blade was accelerated to blade failure. Implementing sensing systems in wind turbine blades is an engineering challenge and solutions often require the collaboration with a diverse set of expertise. This report discusses some of the key issues, challenges and lessons-learned while implementing sensing technologies in wind turbine blades. Some of the briefly discussed topics include cost and reliability, coordinate systems and references, blade geometry, blade composites, material compatibility, sensor ingress and egress, time synchronization, wind turbine operation environments, and blade failure mechanisms and locations.

The loads on wind turbine components are primarily from the blades. It is important to control these blade loads in order to avoid damaging the wind turbine. Rotor control technology is currently limited to controlling the rotor speed and the pitch of the blades. As blades increase in length it becomes less desirable to pitch the entire blade as a single rigid body, but instead there is a requirement to control loads more precisely along the length of the blade. This can be achieved with aerodynamic control devices such as flaps. Morphing technologies are good candidates for wind turbine flaps because they have the potential to create structures that have the conflicting abilities of being load carrying, light-weight and shape adaptive. A morphing flap design with a highly anisotropic cellular structure is presented which is able to undergo large deflections and high strains without a large actuation penalty. An aeroelastic analysis couples the work done by aerodynamic loads on the flap, the flap strain energy and the required actuation work to change shape. The morphing flap is experimentally validated with a manufactured demonstrator and shown to have reduced actuation requirements compared to a conventional hinged flap.

Wind turbines are frequently located in remote, hard-to-reach locations, making it difficult to apply traditional oil analysis sampling of the machine's critical gearset at timely intervals. Metal detection sensors are excellent candidates for sensors designed to monitor machine condition in vivo. Remotely sited components, such as wind turbines, therefore, can be comfortably monitored from a distance. Online sensor technology has come of age with products now capable of identifying onset of wear in time to avoid or mitigate failure. Online oil analysis is now viable, and can be integrated with onsite testing to vet sensor alarms, as well as traditional oil analysis, as furnished by offsite laboratories. Controlled laboratory research data were gathered from tests conducted on a typical wind turbine gearbox, wherein total ferrous particle measurement and metallic particle counting were employed and monitored. The results were then compared with a physical inspection for wear experienced by the gearset. The efficacy of results discussed herein strongly suggests the viability of metallic wear debris sensors in today's wind turbine gearsets, as correlation between sensor data and machine trauma were very good. By extension, similar components and settings would also seem amenable to wear particle sensor monitoring. To our knowledge no experiments such as described herein, have previously been conducted and published.

This paper presents the performance of a variety of structural health monitoring (SHM) techniques, based on the use of piezoelectric active sensors, to determine the structural integrity of a 9m CX-100 wind turbine blade (developed by Sandia National Laboratory). First, the dynamic characterization of a CX-100 blade is performed using piezoelectric transducers, where the results are compared to those by conventional accelerometers. Several SHM techniques, including Lamb wave propagations, frequency response functions, and time series based methods are then utilized to analyze the condition of the wind turbine blade. The main focus of this research is to assess and construct a performance matrix to compare the performance of each method in identifying incipient damage, with a special consideration given the issues related to field deployment. Experiments are conducted on a stationary, full length CX-100 wind turbine blade. This examination is a precursor for planned full-scale fatigue testing of the blade and subsequent tests to be performed on an operational CX-100 Rotor Blade to be flown in the field.

Increasing demand and deployment of wind power has led to a significant increase in the number of wind-turbine blades manufactured globally. As the physical size and number of turbines deployed grows, the probability of manufacturing defects being present in composite turbine blade fleets also increases. As both capital blade costs, and operational and maintenance costs, increase for larger turbine systems the need for large-scale inspection and monitoring of the state of structural health of turbine blades during manufacturing and operation critically increase. One method for locating and quantifying manufacturing defects, while also allowing for the in-situ measurement of the structural health of blades, is through the observation of the full-field state of deformation and strain of the blade. Static tests were performed on a nine-meter CX-100 composite turbine blade to extract full-field displacement and strain measurements using threedimensional digital image correlation (3D DIC). Measurements were taken at several angles near the blade root, including along the high-pressure surface, low-pressure surface, and along the trailing edge of the blade. The overall results indicate that the measurement approach can clearly identify failure locations and discontinuities in the blade curvature under load. Post-processing of the data using a stitching technique enables the shape and curvature of the entire blade to be observed for a large-scale wind turbine blade for the first time. The experiment demonstrates the feasibility of the approach and reveals that the technique readily can be scaled up to accommodate utility-scale blades. As long as a trackable pattern is applied to the surface of the blade, measurements can be made in-situ when a blade is on a manufacturing floor, installed in a test fixture, or installed on a rotating turbine. The results demonstrate the great potential of the optical measurement technique and its capability for use in the wind industry for large-area inspection.

Percolation threshold (PT) phenomena, existing in filler filled systems, play a central role in the insulator-to-conductor transition of electrical properties. While PT problem is important for mathematical-physical search, it also contributes to the sharp transition of other properties. In works published in previous researches in this issue, all PT problems were investigated the role in the transition of properties from experiential profile. In this paper, a mathematical model is developed to study the percolation of composites filled with randomly oriented particles. Special emphasis is given to found the dependence of the PT on unit cells (UCs) partition. Moreover, developed model agrees quite well with the experimental results and is expected being applicable to predict PT of composites using the motion coefficient as a fitting parameter. An important advance to the subject matter is done to study the dependence of anisotropic electrical properties on UCs partition with motion coefficient.

Of the factors that mainly affect the efficiency of the wing during a special flow regime, the shape of its airfoil cross section is the most significant. Airfoils are generally designed for a specific flight condition and, therefore, are not fully optimized in all flight conditions. It is very desirable to have an airfoil with the ability to change its shape based on the current regime. Shape memory alloy (SMA) actuators activate in response to changes in the temperature and can recover their original configuration after being deformed. This study presents the development of a method to control the shape of an airfoil using SMA actuators. To predict the thermomechanical behaviors of an SMA thin strip, 3D incremental formulation of the SMA constitutive model is implemented in FEA software package ABAQUS. The interactions between the airfoil structure and SMA thin strip actuator are investigated. Also, the aerodynamic performance of a standard airfoil with a plain flap is compared with an adaptive airfoil.

In many condition and health monitoring applications, it is necessary to be able to differentiate between response characteristics that result from structural and sensor specific damage types. An investigation is presented in this paper that considers the effectiveness of sensor self-diagnostic techniques for piezoelectric-based transducers that operate in harsh temperature environments. The motivation behind this work is to develop a method for interrogating sensor health when embedded within high-cost research systems. The theoretical basis for this approach is first presented, along with several analytical test cases in which temperature effects are examined within models of the piezoelectric transducer. Following this, a series of experiments are presented in which transducers with varying types and degrees of damage are subject to repeated temperature cycling from cryogenic to room temperature. The results of this study indicate that capacitive-based self-diagnostic techniques are capable of detecting both sensor delamination and cracking at room and liquid nitrogen temperatures.