bluuebunny/crossref_metadata_2025 huggingface dataset:
Local Buckling Behavior of 48″, X80 High-Strain Line Pipes
Authors: Suzuki Nobuhisa , Tajika Hisakazu , Igi Satoshi , Okatsu Mitsuru , Kondo Joe , Arakawa Takekazu
Published: April 2011

Two bending tests of X80-grade, 48″ high-strain line pipes pressurized to 60% SMYS were conducted to investigate local buckling behavior. The thickness and D/t ratio of the line pipes were 22.0 mm and 55.4, respectively. The mean Y/T ratio of the high-strain pipes was 0.82. A full-scale bending test apparatus was constructed to conduct the bending tests. The bending test results clarified that the pipes have the 2D average critical compressive strain of 1.51 and 1.67%, which satisfy the strain demand of 1.35%. Validation of FEA is conducted taking into account geometric properties of the pipes in terms of outside diameter and thickness and longitudinal flatness. The FEA results coincide with the test results with respect to peak load, critical displacement, critical rotation and critical compressive strain. The FEA results about the load and displacement relationship also show good agreement with the test results during post-buckling deformation. One developed wrinkle and some small wrinkles were observed on the pipe surface during post-buckling deformation, whose cross sections were fairly captured considering the geometric properties.
Challenges Faced on Cacimbas-Catu Gas Pipeline (GASCAC) Construction and the Technologies Applied to Achieve Success
Authors: Ruschi Allan , Cucco Celina , Soares Felipe , Mariot Guilherme , Loureiro Regis R.
Published: April 2011

The Cacimbas-Catu Gas Pipeline (GASCAC), part of GASENE’s Project, which was designed to connect the gas systems of the southeast to the northeast of Brazil, is the largest one constructed in the last ten years. GASCAC has a diameter of 28 inches and a length of 958km, constructed by Petrobras, one of the largest energy companies in the world. This paper aims at presenting the Construction and Assembly process of GASCAC, an ambitious project that has imposed great challenges. It also describes the strategies adopted to assure the completion of the works with quality and within the required deadline, highlighting the use of new or rarely used technologies in Brazil, such as vacuum pipe lifting, bag weights and automatic welding.
Transient Flow Assurance for Determination of Operational Control of Heavy Oil Pipelines
Authors: Cabrejo Victor , Mohitpour Mo
Published: April 2011

Most liquid pipelines design and operational control is based on steady state flow analysis. This neglects dynamic effects that occur as a result of occurrence of surges in a pipeline caused by rapid changes in pressure as a consequence of changes in the flow rate. A transient analysis of liquid pipelines on the other hand assures pipeline performance under all conditions (steady state and dynamic situations) including evaluating the following: • Impact from pump station start up, delivery restriction or shutdown (zero delivery); • Pump unit trip/failure; • Rapid mainline valve closures including Slam shut of a non-return (check) valve; • Effect of running the pipeline with minimum flow and maximum pump discharge pressure operating condition; • Variation in demand including rapid reduction/curtailment of delivery volumes; • Bubble collapse (the transition from slack-line to tight-line flow); • Unintentional changes in operational position of control valves; • Fluid property delivery conditions; • Liquid injection assessment; • Surge protection including pressure relief/control system evaluation; • Restart requirement to avoid slack-line conditions prevalent in hilly/mountainous parts right of way (ROW). Such a dynamic analysis would indicate whether liquid surges are of concern from design, as well as system operational conditions. It also would provide an evaluation of an automated control or potential automated strategies for overpressure protection. In this paper the dynamic analysis of liquid pipelines resulting in design and operational benefits will be described. Finally their benefits in application to a heavy oil pipeline facilities “Keystone” will be highlighted.
Engineering Pipelines for Transportation of CO2 With Impurities
Authors: Nahas Gabe , Mohitpour Mo.
Published: April 2011

Pipeline transportation of carbon dioxide (CO2) dates back to the early 1970’s with the construction of the Canyon Reef Carriers & Val Verde pipeline in Texas USA. Since that time about 7200 kilometers of CO2 pipeline have been built in North America (mostly in the USA), some in Asia (Turkey) and Africa and one offshore Europe. The experience of such pipelines is predominantly for the transportation of naturally occurring and relatively pure CO2 for the purpose of enhanced oil recovery (EOR).
Monitoring of Coating Disbondment by a Scanning Kelvin Probe Technique
Authors: Fu A. Q. , Cheng Y. F.
Published: April 2011

The coating disbondment and corrosion of a X65 pipeline steel under coating were studied by scanning Kelvin probe (SKP) measurements. The effects of immersion time and wet-dry cycle on the Kelvin potential profile and the corrosion behavior of the steel were investigated. Kelvin potential measured on “intact” area is shifted negatively with time, indicating an increasing water uptake under the “intact” coating. There is a more negative Kelvin potential on disbonded area than that on “intact” area, which is attributed to corrosion reaction of steel occurring under the disbonded coating. During wet-dry cycle, the thickness of solution layer trapped under disbonded coating decreases due to evaporation of water, causing a negative shift of Kelvin potential. It is associated with the reduction of oxygen solubility in the concentrated solution during drying of electrolyte.
Tensile Strain Capacity Equations for Strain-Based Design of Welded Pipelines
Authors: Kibey Sandeep , Wang Xiangyu , Minnaar Karel , Macia Mario L. , Fairchild Doug P. , Kan Wan C. , Ford Steve J. , Newbury Brian
Published: April 2011

Various industry efforts are underway to improve or develop new methods to address the design of pipelines in harsh arctic or seismically active regions. Reliable characterization of tensile strain capacity of welded pipelines is a key issue in development of strain-based design methodologies. Recently, improved FEA-based approaches for prediction of tensile strain capacity have been developed. However, these FEA-based approaches require complex, computationally intensive modeling and analyses. Parametric studies can provide an approach towards developing practical, efficient methods for strain capacity prediction. This paper presents closed-form, simplified strain capacity equations developed through a large-scale 3D FEA-based parametric study for welded pipelines. A non-dimensional parameter is presented to relate the influence of flaw and pipe geometry parameters to tensile strain capacity. The required input parameters, their limits of applicability and simplified equations for tensile strain capacity are presented. The equations are validated through a comprehensive full-scale test program to measure the strain capacity of pressurized pipelines spanning a range of pipe grades, thickness, weld overmatch and misalignment levels. It is shown that the current simplified equations can be used for appropriate specification of weld and pipe materials properties, design concept selection and the design of full-scale tests for strain-based design qualification. The equations can also provide the basis for codified strain-based design engineering critical assessment procedures for welded pipelines.
Approaches to Qualify Strain-Based Design Pipelines
Authors: Macia Mario L. , Kibey Sandeep A. , Arslan Haydar , Bardi Francois , Ford Steve J. , Kan Wan C. , Cook Mike F. , Newbury Brian
Published: April 2011

The importance of using strain-based design pipelines is growing due to the increasing number of projects in challenging environments such as permafrost, offshore ice hazards, active seismic areas, and in high temperature/high pressure operations. To ensure pipeline integrity in environmentally sensitive areas and overall cost effectiveness, a strain-based design approach needs to consider all key interrelated design aspects including strain demand, design methods, material selection, strain capacity validation, and impact on construction and operation. To that end, significant research and development efforts have been made by the industry to facilitate the qualification of strain-based designed pipelines. This paper describes methods developed for the qualification of strain-based design pipelines, and demonstrates how recently developed strain capacity prediction tools, calibrated by full scale testing, can facilitate concept selection, material qualification and integrity verification of such pipelines.
Corrosion Assessment Method Validation for High-Grade Line Pipe
Authors: Besel Michael , Zimmermann Steffen , Kalwa Christoph , Ko¨ppe Theo , Liessem Andreas
Published: April 2011

The present paper deals with the pressure containment and deformation capacity of corroded high-grade steel line pipe. Firstly, some well established models are investigated concerning their predictive accuracy if applied to high-grade line pipe steel. In particular, it will be shown that all models under consideration tend to overestimate the remaining strength in the case of high-grade steel pipes. Afterwards, FE-analyses are performed in order to study the local evolution of plastic flow in the area of the corrosion defect; at the same time, the burst pressure is predicted applying von Mises plasticity and a simple failure criterion. Although different defect geometries are associated with well pronounced differences in the evolution of the plastic flow around the corrosion defect no significant effect on the burst pressure is found. Finally, the main results of a hydrostatic burst test performed on a pristine X100 line pipe joint are presented. It appears that the material under consideration seems to have anisotropic plastic material properties which may have effect on burst pressure.
Effects of Pipe Internal Surface Roughness on Decompression Wave Speed in Natural Gas Mixtures
Authors: Botros K. K. , Geerligs J. , Fletcher Leigh , Rothwell Brian , Venton Philip , Carlson Lorne
Published: April 2011

The control of propagating ductile (or tearing) fracture is a fundamental requirement in the fracture control design of pipelines. The Battelle two-curve method developed in the early 1970s still forms the basis of the analytical framework used throughout the industry. GASDECOM is typically used for calculating decompression speed, and idealizes the decompression process as isentropic and one-dimensional, taking no account of frictional effects. While this approximation appears not to have been a major issue for large-diameter pipes and for moderate pressures (up to 12 MPa), there have been several recent full-scale burst tests at higher pressures and smaller diameters for which the measured decompression velocity has deviated progressively from the predicted values, in general towards lower velocities. The present research was focused on determining whether pipe diameter was a major factor that could limit the applicability of frictionless models such as GASDECOM. Since potential diameter effects are primarily related to wall friction, which in turn is related to the ratio of surface roughness to diameter, an experimental approach was developed based on keeping the diameter constant, at a sufficiently small value to allow for an economical experimental arrangement, and varying the internal roughness. A series of tests covering a range of nominal initial pressures from 10 to 21 MPa, and involving a very lean gas and three progressively richer compositions, were conducted using two specialized high pressure shock tubes (42 m long, I.D. = 38.1 mm). The first is honed to an extremely smooth surface finish, in order to minimize frictional effects and better simulate the behaviour of larger-diameter pipelines, while the second has a higher internal surface roughness. The results show that decompression wave speeds in the rough tube are consistently slower than those in the smooth tube under the same conditions of mixture composition and initial pressure & temperature. Preliminary analysis based on perturbation theory and the fundamental momentum equation indicates that the primary reason for the slower decompression wave speed in the rough tube is the higher spatial gradient of pressure pertaining to the decompression wave dynamics, particularly at lower pressure ratios and higher gas velocities. The magnitude of the effect of the slower decompression speed on arrest toughness was then evaluated by a comparison involving several hypothetical pipeline designs, and was found to be potentially significant for pipe sizes DN450 and smaller.
Effects of Transverse Strains on the Measurement of the Thermal Expansion of the Composite Using FBG Sensors
Authors: Kim Hong-Il , Yoon Jae-San , Han Jae-Hung
Published: April 2011

The effects of the transverse strain on the fiber gratings to the wavelength shift of the FBG (fiber Bragg grating) sensor were investigated. A new FBG model including the strain transmissibility coefficients along the longitudinal and transverse directions was proposed. The finite element method was applied to obtain the strain transmissibility coefficients of the interface between FBG sensor and base structure surface. The wavelength shift of each FBG sensor was calculated for the assumed strain condition of the base structures. Simulated core strains based on both conventional 1-DOF model and the present model were compared. The numerical results showed that the surface strains could be well predicted using the proposed FBG model while the conventional 1-DOF model gave large errors when the transverse strain of the base structure was significant as in composite structures under thermal loadings.
Online Tracking of Structural Parameters Based on Recursive Subspace Identification
Authors: Weng Jian-Huang , Loh Chin-Hsiung
Published: April 2011

An important objective of structural health monitoring (SHM) for civil infrastructure is to identify the state of the structure and to detect these changes when it occurred. The changes of features in a structural system may due to the nonlinear inelastic response of structure or due to the structural damage subjected to severe external loading. Therefore, damage detection in large structural system, such as buildings and bridges, can improve safety and reduce maintenance costs and the design of damage detection system is one of the goals of SHM. The objective of this paper is to develop an on-line and almost real-time system parameter estimation and damage detection technique from the response measurements through using the Recursive Subspace identification (RSI) or Recursive Stochastic Subspace Identification (RSSI) approaches. Verification of the proposed method by using data from both numerical simulation and the shaking table test of a steel structure with abrupt change of inter-story stiffness are discussed. With the implementation of forgetting factor in RSSI/RSI methods the ability of on-line damage detection of structural system can be enhanced.
Nonlinear Vibration Analysis of Shear Deformable Functionally Graded Ceramic-Metal Plates Using an Improved Higher Order Theory
Authors: Talha Mohammad , Singh B. N.
Published: April 2011

In the present study, an improved higher order theory in conjunction with finite element method (FEM) is presented and is applied to study the nonlinear vibration analysis of shear deformable functionally graded material (FGMs) plates. The present structural model kinematics assumes the cubically varying in-plane displacement over the entire thickness, while the transverse displacement varies quadratically to achieve the accountability of normal strain and its derivative in calculation of transverse shear strains. The theory also satisfies zero transverse strains conditions at the top and bottom faces of the plate, and the geometric nonlinearity is based on Green-Lagrange assumptions. All higher order terms appearing from nonlinear strain displacement relations are incorporated in the formulation. The material properties of the plates are assumed to vary smoothly and continuously throughout the thickness of the plate by a simple power-law distribution in terms of the volume fractions of the constituents. A C0 continuous isoparametric nonlinear FEM with 13 degrees of freedom per node is proposed for the accomplishment of the improved elastic continuum. Numerical results with different system parameters and boundary conditions are accomplished, to show the importance and necessity of the higher order terms in the nonlinear formulations.
Augmented Adaptive Control of Flexible Structures Using Residual Mode Filters
Authors: Balas Mark , Frost Susan A.
Published: April 2011

Flexible structures containing a large number of modes can benefit from adaptive control techniques which are well suited to applications that have unknown modeling parameters and poorly known operating conditions. In this paper, we focus on a direct adaptive control approach that has been extended to adaptively reject persistent disturbances. This theory will be extended to accommodate troublesome modal subsystems of a plant that might inhibit the adaptive controller. In some cases the plant in does not satisfy the adaptive controller requirements of Almost Strict Positive Realness. Instead, there maybe be a modal subsystem that inhibits this property. In this paper we will modify the adaptive controller with a Residual Mode Filter (RMF) to compensate for the troublesome modal subsystem, or the Q modes. This paper addresses leakage, or propagation, of the disturbances into the Q modes. We will apply the above theoretical results to a flexible structure example to illustrate the behavior with and without the residual mode filter.
Fabrication, Oxidation and Characterization of Shark Skin Inspired Riblet Structures as Aerodynamically Optimized High Temperature Coatings for Blades of Aeroengines
Authors: Bu¨ttner Claudia C. , Schulz Uwe
Published: April 2011

This paper deals with the study of different structuring methods for high temperature nickel alloys, which are used for compressor and turbine blades in aeroengines. The ideal structured surface combines high oxidation resistance with low drag in a hot gas flow. The effect of drag reduction due to riblet structured surfaces was originally inspired by the shark scales, which have a drag reducing riblet structure. Riblets were successfully produced on a NiCoCrAlY coating by picosecond laser treatment. This method is suitable for larger structures within the range of some tens of micrometers. Furthermore, experiments were performed by depositing different materials through polymer and metal masks via electrodeposition and physical vapor deposition. All fabricated structures were oxidized at 900–1100°C for up to 100 h to simulate the temperature conditions in an aeroengine. The resulting shape of the riblets was characterized using scanning electron microscopy. The most accurate structures were obtained by using photolithography with a subsequent electrodeposition of nickel. This method is suited for single digit micrometer structures. The reduction of the wall shear stress was measured in an oil channel. The riblet structures prior to oxidation showed a reduction of the wall shear stress of up to 4.9%.
Effects of CNT Doping Level and Water/Cement Ratio on the Piezoresistivity of CNTS/Cement Composites
Authors: Han Baoguo , Yu Xun , Ou Jinping
Published: April 2011

The carbon nanotubes (CNTs)/cement composites with different doping levels of multi-walled carbon nanotubes (MWNTs) and water/cement ratios are fabricated. By comparing the responses of electrical resistance of these CNTs/cement composites to compressive stress, the effects of MWNT doping level and water/cement ratio on the piezoresistive sensitivity of composites are investigated. Experimental results indicate that the piezoresistive sensitivities of CNTs/cement composites with 0.05 wt. %, 0.1 wt. % and 1 wt. % of MWNTs firstly increase and then decrease with the increase of CNT doping levels. The electrical resistance of CNTs/cement composites 0.6 water/cement ratio is more sensitive to compressive stress than that of composites with 0.45 water/cement ratio.
A Computational Model for Structural Evolution of Protein Fibrils
Authors: Cheng Liang , Oates William S. , Englander Ongi , Paravastu Anant
Published: April 2011

A phase field modeling framework is developed to quantify structure evolution of protein fibrils in solution. The modeling framework employs a set of multi-physics constitutive relations to predict time dependent protein fibril structural evolution. The balance relations include chemical potential relations, microforces that govern local protein structure evolution, linear momentum and conservation of mass. Anisotropic formation of protein fibrils is controlled by protein monomer microforces and chemical fluxes to obtain long fibril growth from small seed particles. The theoretical model is implemented numerically using a nonlinear finite element phase field modeling approach which couples nonlinear mechanics with microscopic protein fibril structure evolution and chemical behavior. For comparisons to the model, the self-healing RADA16-I protein fibrils are characterized using transmission electron microscopy before and after ultrasonic radiation. Comparisons illustrate quantitative model predictions that govern spontaneous protein fibril self-healing that is predicted on the time scale of several hundred hours. The underlying physical mechanisms associated with self-assembly of the protein fibrils are discussed.
Performance Evaluation of the Pre-Stressed Piezoelectric Unimorph Using Nonlinear Piezoelectric Properties
Authors: Kang Lae-Hyong , Han Jae-Hung
Published: April 2011

Piezoelectric actuators operate when the electric field (voltage) is applied to them. This piezoelectric behavior is defined using piezoelectric strain coefficients which are generally assumed to be constant. However, when high electric fields are applied to the piezoelectric actuators the piezoelectric strain constant may increase up to more than twice of the nominal value and, thus, cannot be considered as a constant value. Besides, in case of the pre-stressed piezoelectric unimorph actuators, the stress conditions inside piezoelectric actuators can affect piezoelectric behaviors. For reasons mentioned above, actuation performance of PUMPS actuator, which is one of the pre-stressed piezoelectric actuators developed by present authors, cannot be predicted accurately without consideration of piezoelectric nonlinearities such as voltage and stress effects. Generally, the piezoelectric behavior is mainly affected by the piezoelectric strain coefficient and the elastic modulus. Therefore, the voltage and stress effects on the piezoelectric strain coefficient and the elastic modulus of piezoelectric layer were investigated, and the results were used for prediction of actuation performance of PUMPS. Taking the nonlinear material properties of the piezoelectric layer into account, the actuation performance of PUMPS was accurately predicted in this study.
Active Vibration Isolation System Using the Piezoelectric Unimorph With Mechanically Pre-Stressed Substrate
Authors: Lee Dae-Oen , Kang Lae-Hyong , Han Jae-Hung
Published: April 2011

In this paper, a pre-stressed piezoelectric unimorph made by a new fabrication method in room temperature, and an active vibration isolation system using the pre-stressed unimorph actuators are introduced. The fabricated piezoelectric unimorph, called PUMPS (piezoelectric unimorph with mechanically pre-stressed substrate), is an actuator in which actuation level is enhanced by displacement amplification mechanism that converts piezoelectric extension and contraction to large bending/pumping motion without sacrificing the actuation force. Preliminary vibration tests were performed to check the performance of PUMPS as actuators for active vibration control in a lab environment. Two feedback control schemes, the positive position feedback (PPF) and negative velocity feedback (NVF), were applied for active vibration control. Using a smart vibration isolation system with improved load capacity obtained by stacking pre-stressed piezoelectric unimorph actuators, about 10dB vibration reduction of the system was achieved near the resonant frequency region. With the preliminary vibration test results showing promising performance of PUMPS actuator in active vibration control, an integrated active vibration isolation system composed of PUMPS actuators is developed. The developed system contains compact analogue circuits and a sensor for PUMPS actuation and control, and power is supplied by Li-Polymer battery which means the system is completely standalone and portable. In addition, an integrated jitter isolation demonstration system was developed to demonstrate the degrading effect of jitter and the effectiveness of the developed integrated active vibration isolation system in improving the performance of optical payloads. Comparison of image qualities taken before and after the operation of vibration control system indicates that effective suppression of vibration disturbances can be achieved using the developed vibration isolation system with PUMPS actuators.
A Ferromagnetic Shape Memory Foil Actuator
Authors: Kohl Manfred , Krevet Berthold , Yeduru Srinivasa R. , Ezer Yossi , Sozinov Alexei
Published: April 2011

This paper presents experimental and simulation results on the performance of a new kind of linear actuator making use of the magnetic shape memory (MSM) effect. The actuation material is a Ni-Mn-Ga foil of 200 μm thickness that has been fabricated from a bulk Ni-Mn-Ga (100) single crystal consisting of 10 M martensite variants at room temperature. Stress-strain experiments on tensile test structures demonstrate that the stress needed for reorientation of martensite variants is about 1.2 MPa. The low twinning stress allows magnetic-field induced variant switching, the basic mechanism of MSM actuation. A Ni-Mn-Ga foil actuator is fabricated by lithography and hybrid integration. The actuator shows a maximum magneto strain of 4.9%, which is limited by the constraints of fixation and loading. Upon tensile loading at 1.5 MPa, linear actuation cycles are generated with an actuation stroke of 2.2%. The linear actuator is used as a benchmark system for modeling the coupled magneto-mechanical behavior of MSM actuation. We present finite element simulations based on a thermodynamic Gibbs free energy model that describes the observed tensile stress-dependence of magneto strain in many respects.
Fractal-Inspired Multi-Frequency Structures for Piezoelectric Harvesting of Ambient Kinetic Energy
Authors: Castagnetti D.
Published: April 2011

The investigation of energy harvesting devices, able to convert freely-available ambient energy into electrical energy, has significantly improved. To this aim, the most suitable form of ambient energy is the kinetic one, being almost ubiquitous and easily accessible. Among the available conversion technologies, piezoelectric energy harvesting devices are one of the most promising, due to their simple configuration and high conversion efficiency. The most demanding task is to identify simple and efficient multi-frequency structures in the ambient vibration range. To this aim, this work proposes four fractal-inspired structures for piezoelectric energy harvesting. Through computational analysis, their frequency response is calculated up to 100Hz. The structures are examined both in the micro and macro scale and the effect of the iteration level of the fractal geometry is also assessed. By considering the bending strain associated to each mode shape, a quantitative criterion to assess the harvesting efficiency of the proposed structures is introduced.
Fabrication and Testing of a Simple “Bionic Arm” Demonstrator
Authors: Peel Larry D. , Ball Charles
Published: April 2011

Artificial or “bionic” limbs have been the subject of considerable research, TV shows, and dreams by children. The “Six Million Dollar Man” show was about a man who received artificial limbs after his own were lost in an accident. To get students interested in practical engineering, the current work showcases a simple artificial arm that produces greater force than a typical man, demonstrates the capability of Rubber Muscle Actuators (RMA), and provides a portable “arm wrestling platform” for student recruitment efforts. The actuators for “Kingsville Arm One & Two” are McKibben-like actuators made from fiber-reinforced elastomeric composites. These actuators offer excellent strength-to-weight ratios and contract similar to a human muscle. RMAs produce greater force and have less “blow-outs” than typical McKibben actuators because of optimized braid angles and ends that transfer loads through the braid fibers. Kingsville Arm One (KA1) was developed in just two weeks. It consisted of carbon/fiberglass/epoxy composite tubular bones, a metal clevis “elbow” and four RMAs. With considerable effort, a very large student was able to overcome the force generated in an “arm wrestling” contest. KA1’s actuators had end attachments that transferred loads well and enabled flexibility, but easily tore and had air leaks. Kingsville Arm Two (KA2) had new “bones” and RMAs. Although slightly smaller diameters, the KA2 RMAs produced comparable forces to the KA1 RMAs and had molded end attachments. The rigid ends did not allow as much rotation as expected and necessitated using just 2 RMAs. With only two RMAs, KA2 produced approximately the same “arm strength” as KA1. Future work will focus on flexible but durable RMA molded ends, life-like skins and a realistic “hand.”
The Strain Rate- and Temperature-Dependent Mechanical Behavior of Veriflex-E in Tension
Authors: McClung A. J. W. , Tandon G. P. , Baur J. W.
Published: April 2011

In this study, the inelastic deformation behavior of Veriflex-E, a thermally-triggered shape memory polymer resin, was investigated. The experimental program was designed to explore the influence of strain rate on monotonic loading at various temperatures. In addition, the creep behavior of specimens at various temperatures was evaluated. The time-dependent mechanical behavior of the Veriflex-E resin is strongly influenced by the temperature as well as the deformation rate. Thermally-actuated shape memory polymers can be thought of as having two phases separated by the glass transition temperature (Tg). At temperatures well below the Tg (room temperature), the Veriflex-E exhibits a high elastic modulus and positive, nonlinear strain rate sensitivity in monotonic loading. Likewise, the room temperature creep response is significantly influenced by the prior strain rate. The Poisson’s ratio at room temperature is independent of the strain rate, but dependent upon the strain magnitude. As the temperature is increased, the strain rate sensitivity in monotonic loading decreases. Well above the Tg, the elastic modulus drops by several orders of magnitude, and strong strain rate sensitivity is no longer observed in the path of the stress-strain curve. In this high temperature region, the material achieves strain levels well above 100% and the Poisson’s ratio is constant at 0.5 regardless of strain rate or strain magnitude. The creep strain, on the other hand, is significantly influenced by the prior strain rate at the elevated temperature. A slight hysteresis is observed during unloading, while recovery following unloading shows a permanent strain.
Design, Manufacturing and Test of a High Lift Secondary Flight Control Surface With SMAPBP (Shape Memory Alloy Post-Buckled Precompressed) Actuators
Authors: Sinn Thomas , Barrett Ron
Published: April 2011

This paper discusses the design, manufacturing and test of a new kind of adaptive airfoil with Shape Memory Alloy actuation. An antagonistic arrangement of SMA wires is used in a Post-buckled Precompressed (PBP) kind of actuator that is being employed in an adaptive flap system. SMA actuators are typically used either antagonistically and/or arranged to move structural components with linearly varying resistance levels, like springs. This generally means that large percentages of strain energy are spent doing work on passive structure (rather than performing the task at hand, like moving a flight control surface or resisting air loads etc.). Post-Buckled Precompressed (PBP) actuators on the other hand are arranged so that the active elements do not waste energy fighting passive structural stiffnesses. Most (if not all) of the PBP actuators of the past have used piezoceramic elements and are highly prone to tensile failure on convex faces. Because SMA actuators are far more tolerant of tensile stresses than piezoceramics, a switch of actuator type is a natural progression of technology. With the Post-buckled Precompressed mechanism, the power consumption to hold deflections is reduced by one if not two orders of magnitude. Because aircraft often require flight control surfaces to be held in a given position for extremely long times to trim the vehicle, conventional SMA’s are essentially non-starters for many classes of aircraft. For the reason that PBP actuators balance out air and structural loads, the steady-state load on the SMAs is essentially negligible, when properly designed. Experiments showed that the SMAPBP actuator shows tip rotations on the order of 45° which is nearly triple the levels achieved by piezoelectric PBP actuators. The paper opens with a short survey on the history of flap systems actuated by adaptive materials and delves into actuation theory. In the following the author gives a detailed explanation of the design concept and the manufacturing of the airfoil. A NACA0012 airfoil with a chord length of 150 mm was used to prove the concept of the adaptive flap system. The paper continues with a description of the test setup, the CFD model assumptions and the results of wind tunnel tests. The architecture and the employment of a closed loop position feedback system to overcome the nonlinear behavior of the SMA material and the PBP mechanism is also discussed.
Energy Scavenging Combining Piezoelectric and Pyroelectric Effects
Authors: Erturun Ugur , Waxman Rachel , Green Christopher , Richeson Matthew Lee , Mossi Karla
Published: April 2011

The piezoelectric effect is well known and used for vibration energy harvesting applications. The pyroelectric effect is also used to generate electrical power if there is an environment that has cyclic temperature changes. In this study, increasing generated electrical power by use of a combination of piezoelectric and pyroelectric effects is investigated. As a sample case it is aimed to utilize this piezoelectric and pyroelectric effect for a new sensor application. The results of the tests indicate that energy from vibrations and heat can have a significant interaction depending on the frequencies at which each effect occurs. In some cases, energy from vibrations and energy from heat can be detrimental when combined. Therefore both parameters have to be tuned properly to optimize scavenging energy. It was determined that at the best tested parameters the rate of charge increases by approximately 12%.
Force Characterization of Hygroscopic Liquid Crystal Elastomers
Authors: Hays Michael R. , Wang Hongbo , Oates William S.
Published: April 2011

The actuation forces of a hydrophilic liquid crystal elastomer (LCE) in response to water vapor was tested and modeled. These materials exhibit asymmetric swelling as water vapor is absorbed into one side of the elastomer film. This gives rise to deflection away from the water source. Deformation due to water vapor has shown to be on the order of seconds and is reversible which provides unique sensing and actuation characteristics for elastomer films. The constitutive behavior is modeled by using nonlinear continuum mechanics to predict internal changes in density of the liquid crystal elastomer and subsequent deformation by correlating moisture exposure with changes in the elastomer’s density. In order to compare the model and obtain a set material parameters, a micro-Newton measuring device was designed and tested to quantify the forces generated in the liquid crystal elastomer under bending. Forces ranging between 1 to 8 μN were measured as a function of the location of the water vapor source. The results provide important insight into chemical force response and sensing for a number of biomedical and microfluidic applications.
A Dexterous Surgical Manipulation Tool Using Self-Sensing Magnetoelectric Actuators
Authors: Wang Yezuo , Atulasimha Jayasimha
Published: April 2011

In this paper, a dexterous surgical manipulation tool is developed, and characterized using a magnetoelectric self-sensing actuator. The magnetoelectric actuator is made up of three magnetoelectric cantilevers, which are mounted in a specific configuration. Each of the magnetoelectric cantilevers is composed of Galfenol and PZT-5H. The device consists of a single larger magnetoelectric cantilever that is capable of producing an up-down movement upon remote application of a magnetic field to the magnetostrictive layer. Towards one of the ends of this actuator two smaller magnetoelectric cantilevers are attached that are capable of producing a deflection in a side-ways direction making them well suited for gripping action. The shape-anisotropy of the magnetostrictive layers is designed to ensure a controlled sequence of gripping action and up-down movement when these cantilevers are actuated via a remote magnetic field which induces bending in them. The electrical signal generated by the piezoelectric layer is used to provide a sensing signal for both tactile sensing (and gripping) and deflection. This can be used in a closed loop control system.
Modeling and Simulation of Light Activated Shape Memory Polymers
Authors: Sodhi Jaskirat S. , Rao I. Joga
Published: April 2011

This paper focuses on developing a model for light activated shape memory polymers (LASMP’s) undergoing deformation using the framework based on multiple natural configurations and simulating results for boundary value problems. LASMP’s are novel polymeric materials that are different in many ways from the first generation thermally controlled Shape Memory Polymers (SMP’s). Instead of using phase change to produce a mechanism, LASMP’s have photosensitive molecules grafted on their polymer chains. These photosensitive molecules, when exposed to light at certain wavelengths, form covalent bonds that act as crosslinks to give this class of SMP’s their temporary shape. By virtue of their different mechanism, LASMP’s provide a wide array of advantages such as remote activation and selective exposure, thus opening new doors as a potential for vast applications in the biomedical and aerospace industries [1].
Electromechanical Properties of Novel Carbon-Nanofiber/Polypyrrole Composite Bending Sensors and Actuators
Authors: Zhang Shuai , Kim Cheol
Published: April 2011

An electrochemical polymerization method has been developed newly to fabricate a single layer polypyrrole (PPy) film and some single layer carbon-nanofiber (CNF)/PPy films with several different weight ratios of CNF such as 3%, 5%, 7%, and 10%. The CNF/PPy composite material was newly fabricated first time for this research. PPy was fabricated by oxidation of pyrrole monomer in a mixed solution of propylene carbonate and LiTFSI (Bis(trifluoromethane)sulfonamide lithium salt). Ni sheets were used as working and counter electrodes during polymerization. SEM images were taken on surfaces and cross-sections of the CNF/PPy composite samples. Conductivity is shown to be improved much from 77.93S/cm to 124.3S/cm due to the high conductivity of CNF. Experimental results show that conductivity increases approximately linearly. Actuation strain was measured. The strain of a PPy film was 12.6% and for a 10% CNF/PPy film, the strain was 8.6%. It was noticed from experiments as the strain of samples was reduced as CNF weight ratio increased. Bending motions were observed for both PPy and CNF/PPy films when subjected to electric currents. The tip deflections of the films varied from 0.5mm to 2mm. Mechanical properties such as Young’s modulus and strength were tested and it was shown that the CNF enhanced the strength of the composite samples greatly. The CNF/PPy films show a great potential to be a good candidate for good sensor and actuator material.
Cyclic Behavior of Concrete Confined by Active and Passive Jackets
Authors: Choi Eunsoo , Kim Yeon-Wook , Chung Young-Soo , Kim Hong-Taek , Cho Baik-Soon
Published: April 2011

Shape memory alloy (SMA) wire jackets for concrete are distinct from the conventional jackets of steel or FRP since they provide active confinement that can be easily archived due to the shape memory effect of SMAs. This study uses NiTiNb SMA wires of 1.0 mm diameter to confine concrete cylinder with the dimension of 300 mm × 150 mm (L × D). The NiTiNb SMAs have a relative wider temperature hysteresis than NiTi SMAs and, thus, are more applicable for severe temperature-variation environment which civil structures are exposed to. Steel jackets of passive confinement are also prepared to compare the cyclic behavior of active and passive confined concrete cylinders. For this purpose, monotonic and cyclic compressive loading tests are conducted to obtain axial and circumferential strain. The both of strains are used to estimate volumetric strains of concrete cylinders. Also, plastic strains from cyclic behavior are also estimated. For the NiTiNb SMA jacketed cylinders, the monotonic axial behavior differs from the envelope of cyclic behavior; this should be studied in future. The plastic strains of the active confined concrete show a similar trend to those of the passive confinement. The trend of plastic strain of this study does not match with that of CFRP (Carbon Fiber Reinforce Polymer) jackets. For the volumetric strain, the active jackets of the NiTiNb SMA wires provide more energy dissipation than the passive jacket of steel.
Signal Quality Evaluation of Embedded Antennas in Composite Panels
Authors: Sulic Edin , John Sabu , Pell Brendan , Rowe Wayne , Ghorbani Kamran , Gupta Rahul , Zhang Kefei
Published: April 2011

In this paper, an attempt is made to evaluate signal performance of an antenna embedded in a viscoelastic thermoset composite polymer commonly known as Sheet Moulding Compound (SMC). Signal quality is investigated by studying the impedance matching and radiation pattern results of an embedded antenna. The investigation was done experimentally and using simulation software CST Microwave Studio. Two types of antenna have been investigated. One being planar inverted conical antenna (PICA) that operates in the range of about 850 MHz to about 10 GHz and the second one being slot dipole antenna that operates in the range of 1.2 GHz to 1.4 GHz. The signal quality was evaluated at four different antenna configurations. Configuration 1 – antenna with 0° angle deformation, configuration 2 – antenna with 22° angle, configuration 3 – antenna with 45° angle and configuration 4 – 90° angle. The effect of these four configurations on signal quality of each antenna is discussed and simulation results are compared to experimental results.
Damage Assessment Using Hyperchaotic Excitation and State-Space Geometry Changes
Authors: Torkamani Shahab , Butcher Eric A. , Todd Michael D. , Park Gyuhae
Published: April 2011

The current study explores the use of a steady-state hyperchaotic signal to probe a system for state-space geometry changes used for structural health monitoring applications. This is an extension of a previous chaotic interrogation technique approach that exploited the intrinsic high sensitivity of chaotic systems to subtle changes of the parameters. The enhanced technique proposed in this paper explores a novel structural excitation, namely a hyperchaotic excitation, which exhibits a chaotic behavior wherein at least two Lyapunov exponents are positive due to stretching of the phase space in multiple directions. A feature called average local attractor variance ratio (ALAVR), which is based on attractor geometry, is used to compare the geometry of a baseline attractor to a test attractor. The enhanced technique is applied to analytically and experimentally analyze the response of an 8-degree-of-freedom system to the hyperchaotic excitation for the sake of damage assessment. A comparison between the results obtained from current hyperchaotic excitation vs. a chaotic excitation highlights the higher sensitivity of the hyperchaotic excitation. Thus, hyperchaotic interrogation can be used as an alternative damage assessment technique when increased sensitivity to small amounts of damage is required.
Shape Memory Polymers: A Potential Material for Future’s Changing Shape
Authors: Leng Jinsong , Liu Yanju , Du Shanyi
Published: April 2011

Shape memory polymers (SMPs) undergo significant macroscopic deformation upon the application of an external stimulus. As a novel and promising kind of smart materials, they have been widely researched since the 1980s. SMPs present many potential technical advantages that surpass those of shape memory alloys and shape memory ceramics such as good shape recoverability, low density, ease in processing and in tailoring of properties (e.g., transition temperature, stiffness, bio-degradability, and ease of functionally grading), programmability and controllability of recovery behavior, and most importantly, low cost. This paper aims to provide a comprehensive review of SMPs, encompassing a fundamental understanding of the shape memory of SMPs. The synthesis of SMPs is presented firstly. In order to realize the actuation of SMPs for a special application, the investigation of actuations in multi ways are performed, namely electroactive SMPs, light-responsive SMPs, magnetism-induced SMPs, and chemo-responsive SMPs. These novel actuation approaches play a critical role in the development of multifunctional materials that not only exhibit the shape memory effect but also perform particular functions. Based on the unique properties of such materials, primary applications are also listed, and the potential directions and applications of SMPs are proposed to be developed in future research.
Electromechanical Modelling and Experiments of a Bistable Plate for Nonlinear Energy Harvesting
Authors: Arrieta Andres F. , Hagedorn Peter , Erturk Alper , Inman Daniel J.
Published: April 2011

Vibration based energy harvesting has received extensive attention in the engineering community in the past decade. It has been mainly focused on linear electromechanical devices excited close or at resonance, where these systems operate optimally. Although much progress has been achieved in this research direction, real harvesting devices would seldom operate in environment with such idealized conditions. Recently, the idea to use nonlinearity to enhance the performance for energy harvesters has been introduced. Nonlinear devices have been shown to have the potential to operate over a wider band of frequencies and deliver higher power. Bistable composites are a new type of composites exhibiting two stable states so far considered for morphing applications. In this paper, we propose to exploit the nonlinear behaviour of a bistable composite plate with bonded flexible piezoelectric patches to obtain a nonlinear energy harvesting device. The response of the structure is investigated revealing several large amplitude nonlinear phenomena over a wide range of frequencies. Resistor sweeps are conducted for representative dynamic regimes giving the optimal electrical load for each type of oscillations. The observed characteristics give the proposed device the potentiality for broadband energy harvesting.