bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical Simulations of Hollow Cone Injection and Gasoline Compression Ignition Combustion With Naphtha Fuels
Authors: Badra Jihad A. , Sim Jaeheon , Elwardany Ahmed , Jaasim Mohammed , Viollet Yoann , Chang Junseok , Amer Amer A. , Im Hong G.
Published: January 2016

Gasoline compression ignition (GCI), also known as partially premixed compression ignition (PPCI) and gasoline direct injection compression ignition (GDICI), engines have been considered an attractive alternative to traditional spark ignition engines. Lean burn combustion with the direct injection of fuel eliminates throttle losses for higher thermodynamic efficiencies, and the precise control of the mixture compositions allows better emission performance such as NOx and particulate matter (PM). Recently, low octane gasoline fuel has been identified as a viable option for the GCI engine applications due to its longer ignition delay characteristics compared to diesel and lighter evaporation compared to gasoline fuel [1]. The feasibility of such a concept has been demonstrated by experimental investigations at Saudi Aramco [1, 2]. The present study aims to develop predictive capabilities for low octane gasoline fuel compression ignition engines with accurate characterization of the spray dynamics and combustion processes. Full three-dimensional simulations were conducted using CONVERGE as a basic modeling framework, using Reynolds-averaged Navier-Stokes (RANS) turbulent mixing models. An outwardly opening hollow-cone spray injector was characterized and validated against existing and new experimental data. An emphasis was made on the spray penetration characteristics. Various spray breakup and collision models have been tested and compared with the experimental data. An optimum combination has been identified and applied in the combusting GCI simulations. Linear instability sheet atomization (LISA) breakup model and modified Kelvin-Helmholtz and Rayleigh-Taylor (KH-RT) break models proved to work the best for the investigated injector. Comparisons between various existing spray models and a parametric study have been carried out to study the effects of various spray parameters. The fuel effects have been tested by using three different primary reference fuel (PRF) and toluene primary reference fuel (TPRF) surrogates. The effects of fuel temperature and chemical kinetic mechanisms have also been studied. The heating and evaporative characteristics of the low octane gasoline fuel and its PRF and TPRF surrogates were examined.
Investigation of Swirl Ratio Impact on In-Cylinder Flow in a SIDI Optical Engine
Authors: Zhuang Hanyang , Hung David L. S. , Yang Jie , Tian Shaoxiong
Published: January 2016

Advanced powertrain technologies have improved engine performance with higher power output, lower exhaust emission, and better controllability. Chief among them is the development of spark-ignition direct-injection (SIDI) engines in which the in-cylinder processes control the air flow motion, fuel-air mixture formation, combustion, and soot formation. Specifically, intake air with strong swirl motion is usually introduced to form a directional in-cylinder flow field. This approach improves the mixing process of air and fuel as well as the propagation of flame. In this study, the effect of intake air swirl on in-cylinder flow characteristics was experimentally investigated. High speed particle image velocimetry (PIV) was conducted in an optical SIDI engine to record the flow field on a swirl plane. The intake air swirl motion was achieved by adjusting the opening of a swirl ratio control valve which was installed in one of the two intake ports in the optical engine. Ten opening angles of the swirl ratio control valve were adjusted to produce an intake swirl ratio from 0.55 to 5.68. The flow structures at the same crank angle degree, but under different swirl ratio, were compared and analyzed using proper orthogonal decomposition (POD). The flow dominant structures and variation structures were interpreted by different POD modes. The first POD mode captured the most dominant flow field structure characteristics; the corresponding mode coefficients showed good linearity with the measured swirl ratio at the compression stroke when the flow was swirling and steady. During the intake stroke, strong intake air motion took place, and the structures and coefficients of the first modes varied along different swirl ratio. These modes captured the flow properties affected by the intake swirl motion. Meanwhile, the second and higher modes captured the variation feature of the flow at various crank angle degrees. In summary, this paper demonstrated a promising approach of using POD to interpret the effectiveness of swirl control valve on in-cylinder swirl flow characteristics, providing better understanding for engine intake system design and optimization.
Application of High Performance Computing for Studying Cyclic Variability in Dilute Internal Combustion Engines
Authors: Finney Charles E. A. , Edwards K. Dean , Stoyanov Miroslav K. , Wagner Robert M.
Published: January 2016

Combustion instabilities in dilute internal combustion engines are manifest in cyclic variability (CV) in engine performance measures such as integrated heat release or shaft work. Understanding the factors leading to CV is important in model-based control, especially with high dilution where experimental studies have demonstrated that deterministic effects can become more prominent.

Observation of enough consecutive engine cycles for significant statistical analysis is standard in experimental studies but is largely wanting in numerical simulations because of the computational time required to compute hundreds or thousands of consecutive cycles. We have proposed and begun implementation of an alternative approach to allow rapid simulation of long series of engine dynamics based on a low-dimensional mapping of ensembles of single-cycle simulations which map input parameters to output engine performance.

This paper details the use Titan at the Oak Ridge Leadership Computing Facility to investigate CV in a gasoline direct-injected spark-ignited engine with a moderately high rate of dilution achieved through external exhaust gas recirculation. The CONVERGE™ CFD software was used to perform single-cycle simulations with imposed variations of operating parameters and boundary conditions selected according to a sparse grid sampling of the parameter space. Using an uncertainty quantification technique, the sampling scheme is chosen similar to a design of experiments grid but uses algorithms designed to minimize the number of samples required to achieve a desired degree of accuracy. The simulations map input parameters to output metrics of engine performance for a single cycle, and by mapping over a large parameter space, results can be interpolated from within that space. This interpolation scheme forms the basis for a low-dimensional ‘metamodel’ (or model of a model) which can be used to mimic the dynamical behavior of corresponding high-dimensional simulations.

Simulations of high-EGR spark-ignition combustion cycles within a parametric sampling grid were performed and analyzed statistically, and sensitivities of the physical factors leading to high CV are presented. With these results, the prospect of producing low-dimensional metamodels to describe engine dynamics at any point in the parameter space will be discussed. Additionally, modifications to the methodology to account for nondeterministic effects in the numerical solution environment are proposed.
Managing Geohazards in Hard Conditions: Monitoring and Risk Assessment of Pipelines That Crosses Amazonian Jungles and the Andes
Authors: Moya John Erick Malpartida
Published: January 2016

The hydrocarbon transmission system that belongs to Transportadora de Gas del Perú (TGP), comprise two parallel pipelines: a natural gas (NG) pipeline, which runs from the upstream facilities at Malvinas, in the Amazonian jungle of Cusco-Peru, to a reception station at Lurín (south of Lima); and a natural gas liquid (NGL) pipeline, which transports the condensed liquids from Malvinas to Pisco, on the coast of Peru. The right-of-way (ROW) crosses the Peruvian jungle with both pipelines in its first 200 kilometers, after climbs over the Andes Mountains at an elevation of 4860 masl, and descends steeply toward the coast along the Pacific Ocean.

TGP’s Pipeline Integrity Management System (PIMS) has identified the Weather and Outside Forces such as main threat which increases the risk of the integrity of its pipelines in jungle and mountains areas. In pipelines with particular characteristics such as pipeline which crosses the Andes and the Amazonian jungle, this threat can cause even a greater number of failures than other threats such as Corrosion or TPD. This threat caused the 70% of the leaks of our NGL pipeline. The geotechnical and geologic conditions were key factors in the risk level of the system since the beginning of the operation.

The PIMS of TgP has achieved an important development in the use and suitable handling of the information provided by diverse techniques of pipeline mechanical and the geotechnical inspection and monitoring of the ROW. Different alternative techniques of monitoring have to be taken into account. It is important also to take into account alternative assessment methodologies in order to determine the pipeline exposure, resistance and mitigation to this threat. By integrating these inspections, monitoring and particular assessments as part of PIMS, we have been able get accurate risk assessments in order to mitigate and/or minimize the occurrence of failures. In this way we are able to optimize efforts to preserve the integrity of our system and in addition minimize personal, environmental and business impact.

Risk Assessment is an essential part of the Integrity Management System. Our company developed a very comprehensive and detailed Risk Assessment Model based on the guidelines of API 1160 and ASME B31.8S. The probability model is based on logic trees instead indexing models (the most commonly used), that is because we want to reflect in the result all the variables and factors: Exposition, Resistance and Mitigation Factors.

By means of the pipeline Integrity Management System developed by TGP, we are able to mitigate risks due to outside forces. We have been able to act before any event becomes critical: TGP NGL pipeline’s failure rate due to WOF (number of failures per 1000 kilometers-years) decreases substantially from 5.39 to 1.26 in ten years of operation. For the whole system that rate decreases from 2.33 to 0.46.
Analytical Modelling of Rolamite Mechanism Made of Shape Memory Alloy for Constant Force Actuators
Authors: Spaggiari Andrea , Dragoni Eugenio
Published: January 2016

This paper analyses the Rolamite architecture exploiting shape memory alloys as power element to obtain a solid state actuator. The Rolamite mechanism was discovered in the late sixties, initially as precision and low friction linear bearing. The most common Rolamite configuration consists of a flexible thin metal strip and two rollers mounted between two fixed parallel guide surfaces. The system can roll back and forth without slipping guided by the plates along its so called sensing axis. The system presents another relevant advantage in addition to low friction coefficient, which is the possibility to provide force generation in a quite simple way. In the original literature works the force was provided thanks to cutouts of various shape in the strip, though this method does not allow the Rolamite to be considered a proper actuator, but only a force generator. In this paper we developed the idea of exploiting the shape memory alloy as Rolamite power element and therefore to use the shape memory effect to change the elastic properties of the strip and to provide the actuation force. The mechanical analyses and the equations where the martensite-austenite transition is modelled in a simplified way, show that this application is feasible, mainly thanks to the initial precurvature of the SMA strip. The discussion of the results highlights some important merits of this architecture such as long stroke, constant force and compactness.
Design and Characterization of a Continuous Rotary Minimotor Based on Shape Memory Wires and Overrunning Clutches
Authors: Scirè Mammano Giovanni , Dragoni Eugenio
Published: January 2016

An attractive but little explored field of application of the shape memory technology is the area of rotary actuators, in particular for generating endless motion. This paper presents a miniature rotary motor based on SMA wires and overrunning clutches which produces high output torque and unlimited rotation. The concept features a SMA wire tightly wound around a low-friction cylindrical drum to convert wire strains into large rotations within a compact package. The seesaw motion of the drum ensuing from repeated contraction-elongation cycles of the wire is converted into unidirectional motion of the output shaft by an overrunning clutch fitted between drum and shaft. Following a design process developed in a former paper, a six-stage prototype with size envelope of 48×22×30 mm is built and tested. Diverse supply strategy are implemented to optimize either the output torque or the speed regularity of the motor with the following results: maximum torque = 20 Nmm; specific torque = 6.31×10−4 Nmm/mm3; rotation per module = 15 deg; free continuous speed = 4 rpm.
Application of the Shape Memory Effect to Restore Smoothness
Authors: Braden Paul , Gainer Kaitlyn
Published: January 2016

A major worldwide industry is the display and preservation of historical and rare documents, paintings, canvases, tapestries and other works of art. Many private collectors and museums pay large amounts, such as the $23 million for the U.S. National Gallery and $8 million for the U.S. National Archives. There is an even greater demand for many consumers who desire an affordable way to safely maintain their images in top condition for viewing and enjoyment. Another industry where the smoothness of the paper documents is important is in the shipping and delivery business. Here, many shipments are done with cylindrical tubes that cause the paper to appear bent and not flat. In some cases, this can pose a major problem for scanning and electronic devices which need a flat surface for optimal performance. A novel new alternative to traditional conservation methods is the use of Shape Memory Alloys (SMA’s) to remove wrinkles and other surface anomalies.

SMA’s use a thermoelastic property called the Shape Memory Effect (SME) to recover large strains by phase transformation. In this process, the SMA is stretched until the polycrystalline microstructure is detwinned Martensite. Then, energy in the form of heat is applied to the SMA which causes the phase transformation to the more compact Austenite. Thus, a reverse method is the proposed solution for the complex problem faced by art preservation experts. Instead of using large clamps and having to wait for results, we demonstrate how embedded SMA wires in a robust picture frame can provide a continuous restorative force that maintains the picture’s smoothness. Using proper simple wiring from the SMA wires to the picture, it is possible to remove the strains in the paper and hold the picture to the proper smoothness long term. We provide experimental results and offer suggestions for the future use of SMA’s in this new field of art restoration.
Nonlinear Modal Interactions to Improve the Broadband Transduction of Vibratory Energy Harvesters
Authors: Chen Li-Qun , Jiang Wen-An , Panyam Meghashyam , Daqaq Mohammed F.
Published: January 2016

This article exploits nonlinear modal interactions, namely, a two-to-one internal resonance energy pump to improve the steady-state bandwidth of vibratory energy harvesters. To demonstrate the enhanced performance, an L-shaped cantilevered structure laminated with a piezoelectric patch and augmented with frequency tuning magnets is considered. The magnets serve to adjust the first two modal frequencies of the structure such that the second modal frequency is twice that of the first mode activating a nonlinear energy transfer mechanism. The structure is then subjected to a harmonic excitation with a frequency close to the first modal frequency of the structure. The voltage frequency-response curves are generated for different excitation levels, illustrating an improved bandwidth and output voltage over a case involving no nonlinearly-interacting modes.
Electrohydraulic Modeling of a Fluidic Artificial Muscle Actuation System for Robot Locomotion
Authors: Chapman Edward , Macleod Marc , Bryant Matthew
Published: January 2016

Fluidic artificial muscles have the potential for a wide range of uses; from injury rehabilitation to high-powered hydraulic systems. Their modeling to date has largely been quasi-static and relied on the operator to adjust pressure so as to control force output and utilization while little work has been done to date to analyze the kinematics of the driving-systems involved in their operation. This paper establishes a combined electro-hydraulic model of a fluidic artificial muscle actuated climbing robot to establish a method for studying the relationships between muscle size, robot size and function, and system design. The study indicates a strong relationship between appropriate system component selection and not only system efficiency but individual component effectiveness. The results of the study show that robot mass, operating pressure, muscle size, and motor-pump selection have noteworthy impacts on the efficiency and thereby longevity of the robot for performing its task.
Electromechanical Performance of Viscoelastic Dielectric Elastomer Actuator Undergoing Temperature Variation
Authors: Sheng Junjie , Li Shuyong , Zhang Yuqing , Liu Lei
Published: January 2016

Viscoelasticity causes a time-dependent performance and affects the conversion efficiency of VHB-based dielectric elastomers actuator (DEA), when subject to voltage and temperature. However, few reports focus on the effect of temperature on the viscoelastic electromechanical performance on the DEA. The viscoelastic performance of a VHB film in a circular actuator configuration undergoing temperature variation is studied both theoretically and experimentally. Subjected to temperature variation and voltage, viscoelastic creep and higher deformation at higher temperature are obtained using thermodynamics models. Subsequently, an experiment was designed to validate the simulation and the results indicate that DEA creeps with time due to the viscoelasticity and a bigger deformation can be achieved at a higher temperature, which shows well consistent with the experimental results.
Thermal Actuation Through Bimaterial Lattices
Authors: Toropova Marina M. , Steeves Craig A.
Published: January 2016

The goal of this study is to examine the theoretical capability of bimaterial lattices as thermally driven actuators. The lattices are composed of planar non-identical cells. Each cell consists of a skewed hexagon surrounding an irregular triangle; the skew angles of the hexagon and the ratio of the coefficients of thermal expansion (CTEs) of the two component materials determine the overall performance of the actuator. Such a cell has three tailorable CTEs along the lines connecting the points where adjoining cells are connected. Each individual cell and a lattice consisting of such cells can be strongly anisotropic in terms of thermal expansion. While these lattice cells have been used as stress-free connectors for components with differing CTEs, they have not been explored for their actuation capacity. This paper develops models for bimaterial lattices that can be used as mechanical actuators for valves, switches and differential motion. A general procedure for lattice design includes drawing of its skeleton, which identifies the points at which a lattice cell is connected to other cells or substrates; calculation of three CTEs in each cell depending upon the functionality desired; choosing lattice materials; and finding of the skew angles for each cell as solutions of three nonlinear algebraic equations. By changing materials and geometry, we can determine the change of their configuration when the temperature changes. This paper illustrates the concepts with several examples: a two-cell lattice that is connected to a substrate that functions as a lever in a switch; a three-cell lattice that serves as a valve; and a lattice that controls the maximum total deflection of two adjoining parts of a structure.
Numerical Analysis on Thermo-Mechanical Behavior of Shape Memory Alloy Strip With Two-Way Shape Memory Effect
Authors: Hao Lin , Qiu Jinhao , Ji Hongli , Nie Rui
Published: January 2016

Phenomenological model on thermo-mechanical response of shape memory alloy (SMA) strip is presented in this paper. Thermal response and transformation accompanied deformation are described by the proposed model. Newly transformation expansion tensor is defined to describe the relationship between the transformation-induced deformation of the strip and the temperature. The model is then implemented into ABAQUS by using the user-defined subroutine. Finally, the proposed model is verified by the comparison between the finite element simulation and experiment.
Adaptive State Feedback to Maximize the Power Capture and Reduce the Tower Motion of Wind Turbine in Partial Loading Operation
Authors: Thapa Magar Kaman , Balas Mark J.
Published: January 2016

A direct adaptive control approach is used to track the tip speed ratio of wind turbine to maximize the power captured during the below rated wind speed operation. Assuming a known optimum value of tip speed ratio, the deviation of actual tip speed ratio from the optimum one is mathematically expressed as tip speed ratio tracking error. Since the actual tip speed ratio is not a measurable quantity, this expression for tip speed ratio tracking error is linearized and simplified to express it in terms of wind speed and rotor speed, where rotor speed can easily be measured whereas an estimator is designed to estimate the wind speed.

Important results from stability and convergence analysis of the proposed adaptive controller with state estimation and state feedback is also presented. From the analysis it was observed that the adaptive disturbance tracking controller can be combined with adaptive state feedback to achieve other control objectives such as reducing the wind turbine structural loading. Hence, an adaptive state feedback scheme is also proposed to reduce wind turbine tower fore-aft and side-side motions.
Thermo-Responsive Shape Memory Self-Healing Polyurethanes and Composites With Continuous Carbon Fiber Reinforcement
Authors: Heo Yunseon , Sodano Henry A.
Published: January 2016

Thermally responsive self-healing polyurethanes (1DA1T, 1.5DA1T, and 2DA1H) with shape memory property were developed and the fully reversible Diels-Alder (DA) and retro Diels-Alder (rDA) reactions were employed for the healing mechanism. The transition temperatures of the DA and rDA reactions were confirmed through a differential scanning calorimetry and the molecular level of analysis on the reversibility and the repeatability between the DA and rDA reactions were completed though a variable temperature proton nuclear magnetic resonance at the reaction temperatures. Also, compact tension specimens were made to observe the healing efficiencies. These specimens were healed without the use of external forces to close the crack surfaces after testing for the repeatable healing ability with three cycles. As a result, the average first healing cycle efficiencies of 80%, 84%, and 96% for 1DA1T, 1.5DA1T and 2DA1H, respectively, were achieved and small drops for the second and third healing cycles were observed. Then, using two of the self-healing polyurethanes as resins, continuous carbon fiber fabric reinforced polymer matrix composites (C1.5DA1T and C2DA1H) were fabricated and short beam shear testing was conducted to determine the healing capability on the delamination. Accordingly, the first healing efficiencies of 88% and 85% were measured without any additional treatments on the fibers; however, an external pressure was applied during the composite healing process.
Straight Shape Setting of Nitinol Wires by Using a Laser Beam
Authors: Biffi Carlo Alberto , Coduri Mauro , Casati Riccardo , Tuissi Ausonio
Published: January 2016

Shape setting is a fundamental step in the production route of Nitinol Shape Memory Alloys (SMAs) for the fixing of the functional properties, such as the shape memory effect and the pseudo-elasticity. The conventional method for making the shape setting needs the use of furnaces.

In this work laser technology was adopted for performing the straight shape setting on commercially available Nitinol thin wires. The laser beam was moved along the wire length for inducing the functional performances. Calorimetric and pseudo-elastic response of the wires, laser annealed, were studied; high energy X-Rays diffraction was done for studying the evolution of the microstructure texture. It can be stated that the laser technology can realize the shape setting of thin SMA wires with pseudo-elastic properties; the wire performances can be modulated in function of the laser power.
Active Artificial Hair Cells for Use in Fluid Environments
Authors: Joyce Bryan S. , Tarazaga Pablo A.
Published: January 2016

Artificial hair cells (AHCs) are sensors inspired by biological hair cells. These devices often have lower sensitivities and poorer frequency resolutions than their biological counterparts. This is especially true when AHCs are placed in fluid. In the authors’ previous work, active AHCs were developed which used nonlinear feedback control to mimic the cochlea’s nonlinear amplifier. Incorporating this nonlinear control law can improve the AHC’s sensitivity, frequency selectivity, and dynamic range. This work examines an active artificial hair cell partially submerged in water. The fluid loading on the sensor adds inertia and significantly increases damping. A model of the sensor in air is developed and then modified to incorporate the added inertia and damping from the fluid. Simulation and experimental results show that the active artificial hair cell can overcome the added fluid inertia and damping to amplify oscillations due to low input levels and create a sharper frequency response. The resulting sensor is better suited to operate in fluid environments for flow sensing than an otherwise passive device. These sensors could potentially develop into replacements for damaged hair cells in the fluid-filled cochlea.
Synchronization of Cantilevers Arranged in Line of a Piezoelectric Energy Harvester
Authors: Spornraft Max , Schwesinger Norbert , Berger Shlomo
Published: January 2016

Synchronization opens further ways to improve cantilever-based energy harvesting arrays in view of power output, easier rectification and scaling. Objective of this study is to investigate the synchronization behavior of a cantilever-array based energy harvesting systems. Thereby, synchronization is achieved by mechanical coupling through a so-called “overhang”. Nakajima et al. [1] and Wang et al. [2] already verified this principle for the synchronization of two and three cantilevers, but at constant vibrational excitation. Regarding energy harvesting, no application of this method is presently available. In this paper, we investigate the synchronization behavior of a piezoelectric cantilever-line energy harvester in airflow. The design of the energy harvester bases upon a piezoelectric cantilever-line and a common bluff body, arranged upstream. To investigate synchronization of the cantilevers, three commonly available piezoelectric bimorphs were employed to study synchronization. Mounted on a common bluff body, the effect of overhang material and position was studied. Therefore, different constellations were examined by impulse excitation as well as vortex-induced vibration in a wind channel. In several measurements, we found arrangements and parameters allowing for an in-phase synchronization of neighborly cantilevers of the line. The knowledge gained allows for a direct electrical connection of piezoelectric cantilevers with just one single rectifier unit. Cantilevers coupled with overhangs arranged in the right order oscillate with the same frequency and phase, i.e. without any charge cancellations. This knowledge opens ways to develop basic design rules for the synchronization of cantilevers.
Developing a Generalized Harmonic Balance Method for Accurate Identification of Crack Depth in a Continuous Shaft-Disc System
Authors: Khorrami Hamid , Sedaghati Ramin , Rakheja Subhash
Published: January 2016

In this work, the effect of a crack on the vibrational properties of a shaft-disc system has been studied applying a generalized harmonic balance method. In the reviewed literature, the reported methods to find the unbalance response of a continuous shaft-disc system provide only the first harmonic component of the response; whereas, the presented method gives the super-harmonic components as well. The shaft-disk system consists of a flexible shaft with a single rigid disc mounted on rigid short bearing supports. The shaft contains a transverse breathing crack (fatigue crack). The main concept for crack detection in vibration-based methods is basically the investigation of crack-induced changes in the selected vibrational properties. Shaft critical speeds and harmonic and super-harmonic components of the unbalance lateral response have been used as typical vibrational properties for crack detection in a rotating shaft system. A generalized harmonic balance method has been developed to efficiently investigate changes in vibrational properties due to the effect of crack properties, depth and location. The results of the developed analytical model have been compared with those obtained from the finite element model and close agreement has been observed.
Design and Experimental Analysis of a Biomedical Prosthetic Knee With Magnetorheological Fluid
Authors: Nguyen The , Suarez Alan , Bapat Saurabh
Published: January 2016

Current prosthetic legs rely on technology that is inefficient. Electric motors used today require high amounts of current to operate. Prostheses utilizing smart materials, including magnetorheological fluid (MRF), require less power to operate effectively. In this study, the MR fluid knee was designed for above the knee amputees. The design was in the family of MR fluid brake/clutch as it provides simple design and good MR fluid uniformity. However, this MR knee design is different from any existing MR brake, featuring a novel non-circular rotor. Three fourths of the rotor, considered circular, has the same radius, and the remaining quarter has a varying radius to provide a variable gap size between the rotor and stator. This feature allows the MR fluid to experience a stronger magnetic field as the knee rotates, resulting in a variable braking torque. At this stage of research, the first working prototype of the proposed MR fluid knee was built and tested to determine the braking torque profile. Corresponding theoretical models were also created. The calculated torque was used to predict the performance of the MRF knee. The experiments has been conducted to examine the MRF knee performance and to compare with the theoretical model. The knee was expected to use less power to operate and provided the necessary braking torque required by an average male human body. An improved design was planned for weight reduction and optimization to allow the commercialization of the MRF knee.
Computationally Efficient Analysis of SMA Sensory Particles Embedded in Complex Aerostructures Using a Substructure Approach
Authors: Bielefeldt Brent , Hochhalter Jacob , Hartl Darren
Published: January 2016

The Digital Twin concept represents an innovative method to monitor and predict the performance of an aircraft’s various subsystems. By creating ultra-realistic multi-physical computational models associated with each unique aircraft and combining them with known flight histories, operators could benefit from a real-time understanding of the vehicle’s current capabilities. One important facet of the Digital Twin program is the detection and monitoring of structural damage. Recently, a method to detect fatigue cracks using the transformation response of shape memory alloy (SMA) particles embedded in the aircraft structure has been proposed. By detecting changes in the mechanical and/or electromagnetic responses of embedded particles, operators could detect the onset of fatigue cracks in the vicinity of these particles. In this work, the development of a finite element model of an aircraft wing containing embedded SMA particles in key regions will be discussed. In particular, this model will feature a technique known as substructure analysis, which retains degrees of freedom at specified points key to scale transitions, greatly reducing computational cost. By using this technique to model an aircraft wing subjected to loading experienced during flight, we can simulate the response of these localized particles while also reducing computation time. This new model serves to demonstrate key aspects of this detection technique. Future work, including the determination of the material properties associated with these particles as well as exploring the positioning of these particles for optimal crack detection, is also discussed.
Enhancement of Digital Self-Powered Energy-Harvesting for 2DOF Mixed-Mode Vibrations
Authors: Yamamoto Yuta , Makihara Kanjuro , Yoshimizu Kenji
Published: January 2016

The digital self-powered energy harvesting method that we propose is a switching-type vibration energy harvesting method that has a circuit that is functionally integrated with a digital processor. The main feature of the proposed harvester is that the digital processor is driven by energy harvested from vibration. Therefore, other electrical power sources, such as batteries, are not required to power it. The self-powered digital processor automatically changes the states of the harvester circuit using a switching control method. The switching is synchronized with the vibration phase, which is conducive to the effective conversion of vibrational energy. The proposed harvester is programmable and easily implements different types of control schemes based on its various parameters. This study has two objectives regarding the digital self-powered harvesting method. The first objective is to evaluate the power generation performance of the self-powered harvester for multimodal vibrations. Several experiments employing an experimental apparatus with two degrees of freedom (2DOF) are conducted. The second objective is to apply a new switch control scheme to our proposed harvesting method. The scheme is designed for moderate energy harvesting: it intentionally pauses the harvesting action so as to increase the amount of energy generated later. This method is different from the former method of switch control. We confirm the usability of the new control scheme in a digital self-powered system.
Multiphysics Equivalent Circuit of a Thermally Controlled Hydrogel-Micro Valve
Authors: Voigt Andreas , Marschner Uwe , Richter Andreas
Published: January 2016

Hydrogels consist of a network of cross-linked polymers that swell when put into water. For temperature-sensitive smart hydrogels the equilibrium hydrogel size depends on the temperature of the liquid. These hydrogels are used to build temperature-controlled fluidic valves. Here we present an equivalent circuit model of such a hydrogel valve. The transient behavior is based on the model by Tanaka with three additional assumptions: 1. Only the fundamental mode of the deformation field, i.e. the slowest-decaying exponential temporal behavior, is relevant. 2. There are distinct equilibrium sizes for the swollen and the de-swollen state. 3. As observed in experiment, the swollen gel and the de-swollen gel have different elastic moduli, which affect the time constants of swelling vs. de-swelling. The resulting network model includes three physical subsystems: the thermal subsystem, the polymeric subsystem and the fluidic subsystem. The thermal subsystem considers the temperature of the heater, of the adhesive and of the hydrogel. It is assumed that adhesive, housing and hydrogel act as heat capacities in combination with heat resistors. The modeled polymeric subsystem causes in addition time delays for swelling and de-swelling of first order with different delay constants. The fluidic subsystem basically includes the fluidic channel between hydrogel and housing with time varying cross section, which is modeled as controlled source. All subsystems are described and coupled within one single circuit. Thus the transient behavior of the hydrogel can be calculated using a circuit simulator. Simulation results for an assumed hydrogel setup are presented.
Damping Properties of Steel, Copper and NiTi for Use in Industrial Circular Saws
Authors: Theiß Ralf , Dymel Benjamin , Langbein Sven , Nürnberg Tobias
Published: January 2016

Circular saws are a common tool for cutting a variety of materials like stone, wood or alloys. Cutting results are significantly influenced by vibrations occurring during processing. Negative consequences are for example increased cutting width and noise emissions. Vibration results from impulses generated at the entrance of the tool teeth into the work piece, from axial run of the cutting tool as well as vibrations transmitted from the machines drive. Therefore, the implementation of effective and cost efficient damping measures is of significant interest. Passive damping approaches are favored because of their low costs.

One approach to dampen vibrations in circular tools and tool flanges passively is the use of shape memory alloys (SMA) as damping elements. SMA and especially NiTi are able to convert large amounts of mechanical stress into heat energy by a stress induced austenite-martensite phase transformation providing the potential to dampen vibrations with more compact damping elements in contrast to other common damping materials like steel or copper used in circular saws. SMA are suitable for damping low frequencies at high amplitudes, e.g. during earthquakes and the damping of single or repetitive shocks, such as those occurring in positioning. The attenuation of higher-frequency vibrations caused by machining with fast rotating cutting tools has so far been considered inadequate but has not been sufficiently investigated in relevant frequency ranges for industrial circular saws.

This paper compares the damping properties of NiTi to those of copper and steel for industrial circular saws. Therefore, the first chapter introduces different sources and types of vibrations in industrial cutting processes while the second chapter describes exemplarily the vibrations occurring in an industrial circular saw. Based on this, the third chapter illustrates common approaches to modify the static and dynamic behavior of circular saws. The fourth chapter gives a brief description of internal damping mechanism, especially the damping mechanism of SMA. The experimental methodology and evaluation of NiTi, steel and copper is in the focus of the fifth chapter. The paper concludes with a summary of findings and an outlook on following work packages.
Airflow Sensing With Arrays of Hydrogel Supported Artificial Hair Cells
Authors: Sarlo Rodrigo , Leo Donald
Published: January 2016

The hair cell is a biological sensor that uses microscopic hair-like structures to detect delicate motions of surrounding fluid. Inspired by this principle, we have created an artificial hair cell (AHC) sensory method based on biomolecular transduction for sensing spatial variations in air flow. The key feature of this method is the use of one-dimensional arrays built from modular AHC units which measure local velocity at different points in a flow profile. Each of the AHC units uses thinly extruded glass fibers as mechanical receptors of air velocity. Hair vibrations are converted to current via hydrogel-supported lipid bilayer membranes through their mechanocapacitive properties. Preliminary tests with linear arrays of three AHC units attempt to measure the air source profile with varying position and intensity. Each unit was fabricated with a hair of different length, giving it a unique vibrational response. This technique was inspired by how organisms use hair cells with tuned responses to mechanically process flow stimuli. A significant challenge in processing the sensors’ output was the limitation of one input channel on the current measurement unit, thus each sensor output had to be sent over the same channel. When several AHC units are excited simultaneously by an airflow, the resulting signal is a superposition of each sensor’s individual response. To separate the signals back into their individual measurements, the Hair Frequency Response Decomposition method is developed, which maps the spectral content of a combined output to the location of excitation in the array. This method takes advantage of the AHC’s high signal-to-noise ratio (compared to other membrane-based AHCs) and linear output response to flow velocity. Results show that the bilayers’ consistent spectral responses allow for an accurate localization of sensor excitation within the array. However, temporal variations in bilayer size affect sensitivity properties and make accurate flow velocity estimation difficult. Nevertheless, under stable bilayer conditions the measured velocity profiles matched closely with theoretical predictions. The implementation of the array sensing method demonstrates the sensory capability of bilayer-based AHC arrays, but highlights the difficulties of achieving consistent performance with bio-molecular materials.
Nonlinear Vibration Reduction in Smart Structures Using Nonlinear Integral Resonant Controller
Authors: Omidi Ehsan , Mahmoodi Nima
Published: January 2016

This paper discusses a new nonlinear controller for vibration reduction in nonlinear vibrating smart structures. Nonlinear Integral Resonant Controller (NIRC) applies additional damping to the closed-loop system of a nonlinear vibrating system, and reduces the vibration amplitude in a wide range of frequency domain. An approximate solution is obtained using a multi-layer implementation of the Method of Multiple Scales, steady-state amplitude-frequency response is obtained and closed-loop stability is examined. Effects of different controller parameters on system response are investigated, in addition to numerical simulation results. In contrast to the Positive Position Feedback approach, the closed-loop response of the controlled system via NIRC does not show any high-amplitude peak in the neighborhood of the suppressed resonant frequency. This makes the closed-loop system robust to variations in excitation frequency.
Development of an Extended Kalman Filter for Self-Sensing Application of Shape Memory Alloy Wire Actuator
Authors: Gurung H. , Karmakar S. , Banerjee A.
Published: January 2016

This paper presents the development of an Extended Kalman Filter (EKF) for self-sensing application of Shape Memory Alloy (SMA) wire actuator. The EKF is used to estimate the end displacement of a SMA wire actuated compliant link using the electrical resistance variation of SMA. The model of the system is developed by coupling the stress-deformation relation of the link along the direction of the SMA actuator with the phenomenological model of the SMA wire. In EKF, the stress and temperature of SMA comprise the state vector and its electrical resistance is considered as output. The developed EKF is validated, by comparing the estimated system response with that of the model for a given input signal. The effects of the process and measurement noise on the estimation error have also been studied. An experimental setup is developed to measure the change in electrical resistance of the SMA wire, voltage drop across the same, and the associated end-displacement of the compliant link. Using the measured data, the end-displacement of the link is estimated using EKF and compared with the experimentally measured end-displacement. Significant qualitative agreement is observed. It is noted, that the convective heat transfer coefficient significantly affects the quantitative discrepancy. Thus the coefficient of convective heat transfer is determined, so as to minimize the gap between the two responses for a particular applied voltage. The coefficient is then used for different set of experiments, revealing the true potential of the EKF based approach to harness the self-sensing capability of SMA.
Cumulative Second Harmonics in a Nonlinear Transversely Isotropic Plate
Authors: Zhao Jinling , Chillara Vamshi K. , Cho Hwanjeong , Qiu Jinhao , Lissenden Cliff J.
Published: January 2016

The problem of second harmonic guided wave generation in transversely isotropic plates is investigated from a theoretical and numerical standpoint. The strain energy function of transversely isotropic materials is written down using five invariants in terms of the Green-Lagrange strain tensor and contains five linear terms and nine nonlinear terms.

Theoretical investigations reveal that second harmonics in a weakly nonlinear transversely isotropic plate are cumulative only when the phase matching and nonzero power flux criteria are satisfied. Also, only cumulative secondary symmetric Lamb wave modes can be generated — a conclusion in line with what is observed for isotropic plates. Finally, numerical simulations are carried out to examine the cumulative second harmonic generation from the S0 mode and the results obtained are discussed in the light of the theory.
Design of a Reconfigurable SMA-Based Solar Array Deployment Mechanism
Authors: Wheeler Robert , Saunders Robert , Pickett Kelli , Eckert Cullen , Stroud Hannah , Fink Tyler , Gakhar Kanika , Boyd James , Lagoudas Dimitris
Published: January 2016

Shape memory alloys (SMAs), are a class of metals that possess the capability to recover substantial deformations resulting from applied mechanical loads through a solid-solid phase transformation. Typical deployment systems for solar arrays on microsats only allow for one-way deployment. However, by using an SMA actuator in place of a conventional deployment system, repeatable deployment and retraction can be achieved. Relative to conventional actuators, SMA-based solid state actuators offer a reduction in the weight, volume, and overall complexity of the system. In this study, a design of an SMA-based solar panel deployment mechanism for a typical microsat is presented. In this design, a conventional actuation system is replaced with a system of SMA torsional actuators, which allows for a deployed and stowed phase to be reached independent of environmental conditions. This design study illustrates that an SMA-based solar array deployment system can provide a viable replacement for a conventional deployment system while significantly reducing the deployment system weight, volume, and complexity.
Sensorless Force Control Interface for DEAP Stack-Actuators
Authors: Hoffstadt Thorben , Maas Jürgen
Published: January 2016

Transducers based on dielectric electroactive polymers (DEAP) offer an attractive balance of work density and electromechanical efficiency. For example in automation and haptic applications, especially multilayer transducers are used to scale up their absolute deformation and force. Depending on the application different transducer controls have to be realized to match the specifications of the particular application. However, analogous to conventional electromechanical drive systems an inner sensor-less force control can be realized for DEAP transducers, too. For this force control the nonlinear relations between voltage and electrostatic pressure as well as the electromechanical coupling have to be considered. The resulting open-loop force control can be used for superimposed motion controls, such as position, vibration and impedance controls. Therefore, within this contribution the authors propose a model-based feedforward force control based on an overall model of the transducer that does not require any force measurement. Finally, the derived open-loop force control interface is experimentally validated using in-house developed DEAP stack-transducers and driving power electronics.