bluuebunny/crossref_metadata_2025 huggingface dataset:
The Optimization of Time-Frequency Control: Using Non-Autonomous Time-Delay Feedback Systems as Example
Authors: Kuo Chi-Wei , Suh C. Steve
Published: February 2017

A novel time-frequency nonlinear scheme demonstrated to be feasible for the control of dynamic instability including bifurcation, non-autonomous time-delay feedback oscillators, and route-to-chaos in many nonlinear systems is applied to the control of a time-delayed system. The control scheme features wavelet adaptive filters for simultaneous time-frequency resolution. Specifically Discrete Wavelet transform (DWT) is used to address the nonstationary nature of a chaotic system. The concept of active noise control is also adopted. The scheme applied the filter-x least mean square (FXLMS) algorithm which promotes convergence speed and increases performance. In the time-frequency control scheme, the FXLMS algorithm is modified by adding an adaptive filter to identify the system in real-time in order to construct a wavelet-based time-frequency controller capable of parallel on-line modeling. The scheme of such a construct, which possesses joint time-frequency resolution and embodies on-line FXLMS, is able to control non-autonomous, nonstationary system responses. Although the controller design is shown to successfully moderate the dynamic instability of the time-delay feedback oscillator and unconditionally warrant a limit cycle, parameters are required to be optimized. In this paper, the setting of the control parameters such as control time step, sampling rate, wavelet filter vector, and step size are studied and optimized to control a time-delay feedback oscillators of a nonautonomous type. The time-delayed oscillators have been applied in a broad set of fields including sensor design, manufacturing, and machine dynamics, but they can be easily perturbed to exhibit complex dynamical responses even with a small perturbation from the time-delay feedback. These responses for the system have a very negative impact on the stability, and thus output quality. Through employingfrequency-time control technique, the time responses of the time-delay feedback system to external disturbances are properly mitigated and the frequency responses are also suppressed, thus rendering the controlled responses quasi-periodic.
Permeability Characterize of Polymeric Materials at High-Temperature and High-Pressure
Authors: Nassr Nooshin , Siddique Zahed , Keegan Jon R.
Published: February 2017

A new experimental set-up has been built to characterize the permeation of polymeric materials. The permeation of Helium through the variety of polymers under different pressure and temperature conditions was investigated. In this study, the gas permeation measurement has been performed by a high temp/high pressure gas permeation cell. Constant volume (variable pressure) procedure was considered to design this gas permeation cell. In designing the permeation cell, special consideration has been made to build a permeation cell appropriate for testing polymer samples in high pressure (up to 1200 psi) and high temperature (up to 100 °C) conditions. The permeation cell consists of two gas chambers; the high pressure side and the low pressure side. A modular plugin has been designed to place inside the gas chambers, and make the design adjustable for testing polymers with different thicknesses. Pressure change in the lower side of the set-up was measured by sensitive pressure transducer. Downstream pressure side will be used in the calculation of gas flux and gas permeation coefficient of polymers, along with differential pressure applied to polymer sample and test conditions as temperature. The results of permeability measurements for thick polymer samples at different pressure and temperature showed that the effects of increasing temperature on gas permeation are prominent compared to effect of high pressure condition.
A Method of Fracture Toughness Measurement and Effect of Partial Annealing on Monolithic Thick Cold Sprayed Aluminum 6061 Deposits
Authors: Bangstein B. , Ellingsen M. , Scholl N.
Published: February 2017

Cold spray is a solid-state material deposition method that can create thick (>10mm) metal layers that adhere metallurgically to a base part or a substrate. Numerous potential applications exist, such as returning worn mechanical parts to their original dimension, extending their service life.

For fatigue applications the fracture properties of cold spray deposited material must be known but little to no literature has been found on the fracture behavior of cold spray deposited material alone, which prompted the study presented here.

Fracture toughness specimens were manufactured by depositing thick cold-sprayed layers of powdered aluminum 6061 onto an aluminum 6061 substrate using N2 as the carrier gas. The substrate was then machined away, and monolithic miniature compact tension fracture toughness specimens were machined from the cold spray deposit itself, following ASTM E-1820.

The fracture behavior of the cold sprayed material was then experimentally determined using the elastic-plastic J-resistance method for compact test specimens described in ASTM E-1820. Two specimen conditions were successfully tested, “as-sprayed” and “partially annealed”.

The results are that the Mode-I elastic-plastic stress intensity factor JI has been successfully measured for cold-spray deposited material alone, and that partially annealing a cold-spray deposit can dramatically increase its fracture toughness.
Probabilistic Reliability Evaluation of Space System Considering Physics of Failure: Case Study of Fatigue Analysis
Authors: Kiad Saeed , Pourgol-Mohammad Mohammad , Salimi Hossein
Published: February 2017

Mission assurance requires due diligence reliability for space systems taking into account limited accessibility, high uncertainty on the life data and high cost of failure. The methods based on physics of failure are promising approaches for durability evaluation of these systems. In this study, the reliability analysis is aimed for space structures, with the focus on fatigue failure. In this research, the deterministic fatigue simulation is conducted on space systems (satellite in orbit, low-level LEO1, made of aluminum 2024-T3), using models with constant and variable amplitude loading. Walker and Forman models are preliminary utilized in this study for life prediction for benchmarking with the experimental results. In the case of the variable amplitude loading, due to the amount of plastic zone in crack tip, the fatigue crack growth rate will be ceased in case of overload. Deterministic crack growth simulation was numerically simulated by using the MATLAB software and has been compared with commercial AFGROW software for verification and was observed proper match with experimental data. In the analysis of stochastic fatigue crack growth, uncertainty is analyzed by using the Monte Carlo simulation. The universal stochastic crack growth model proposed by Yang and Manning, was used for reliability analysis based on giving probabilistic method for the purpose of power and second polynomial models. In this study, these models are evaluated and three models of I) rational model, II) exponential model and III) global model are proposed. In uncertainty analysis, it is observed that by increasing the crack length, uncertainty range is widening. In case of constant amplitude loading with the same stress intensity factor range but different stress ratio, the uncertainty range was widening with increasing stress ratio. In reliability analysis, the exponential model demands less computational resources however it has a lower accuracy. The fractional model, proposed in this research, is based on the modification to Forman model. However, these models don’t consider geometric factor. The Global model, another model proposed in this research, has the capability of considering this aspect. In multiplicative stochastic factor (Yang and Manning method), accuracy of the approximation is most important. By improving the accuracy of this relation, the result accuracy is enhanced. For this purpose, for increasing efficiency of this method, the accuracy of approximation must be increased by corrections prior models or provide new accurate models.
Risk Assessment of Air Cannons at Sporting Events
Authors: Chewning-Kulick Travis G. , Lewis Marvin E. , Benson Michael J. , Keena Joshua M. , Posner Matthew A.
Published: February 2017

This study looked to determine the safety of air cannons used at public events based on experimentally collected ballistic data. Specifically, the probable injuries to bystanders resulting from being hit by various projectiles launched from air cannons were investigated. Due to the rapid deceleration of projectiles fired from air cannons as they travel through the air, this study focuses on the worst case scenario: point blank impacts. Based on data collected using a chronograph and force plate, this study asserts that it is likely an air cannon operating under the conditions of this experiment can cause significant ocular, maxillofacial, laryngeal, and extremity injuries. To mitigate the risks posed by using air cannons, this study recommends the use of safety glasses for operators, mandatory operator training, automatic trigger locking mechanisms, frequent inspections of the cannon, regulations on the projectiles that can be fired, and the establishment of a minimum firing distance between the operator and bystanders.
Exergy Analysis of a Novel Cryogenic Concept for the Liquefaction of Natural Gas Integrated Into an Air Separation Process
Authors: Tesch S. , Morosuk T. , Tsatsaronis G.
Published: February 2017

The increasing demand for primary energy leads to a growing market of natural gas and the associated market for liquefied natural gas (LNG) increases, too. The liquefaction of natural gas is an energy- and cost-intensive process. After exploration, natural gas, is pretreated and cooled to the liquefaction temperature of around −160°C.

In this paper, a novel concept for the integration of the liquefaction of natural gas into an air separation process is introduced. The system is evaluated from the energetic and exergetic points of view. Additionally, an advanced exergy analysis is conducted. The analysis of the concepts shows the effect of important parameters regarding the maximum amount of liquefiable of natural gas and the total power consumption. Comparing the different cases, the amount of LNG production could be increased by two thirds, while the power consumption is doubled. The results of the exergy analysis show, that the introduction of the liquefaction of natural gas has a positive effect on the exergetic efficiency of a convetional air separation unit, which increases from 38% to 49%.
AFM Study of Mechanical and Tribological Properties of Magnesium-Ceramics Nano-Layered Thin Films
Authors: Fialkova Svitlana , Kotoka Ruben , Yarmolenko Sergey , Sankar Jagannathan
Published: February 2017

This study aims to evaluate the wear resistance of magnesium - ceramics nano-layered thin films using atomic force microscopy technique (AFM). The magnesium - ceramics (alumina and silica) nano-layered thin films were deposited on glass substrate using DC and pulsed DC reactive magnetron sputtering process. The surface roughness and wear properties were evaluated with the single crystal diamond tip. It was observed that the surface roughness was increased with the growing of number of layers for both magnesium-ceramics films. The nano-tribology test shown a strong adhesion between Mg-ceramic layers. The results shown that alumina nanolayers more efficient to resist against wear than silica. It was also noted that magnesium-silica nanolaminates loosing wear-resistance with the increasing number of layers.
Experimental Development and Computational Optimization of Flat Heat Pipes for CubeSat Applications
Authors: Isaacs Steven A. , Arias Diego A. , Hamlington Peter E. , Hengeveld Derek
Published: February 2017

Due to the compact and modular nature of CubeSats, thermal management has become a major bottleneck in system design and performance. In this study, we outline the development, initial testing, and modeling of a flat, conformable, lightweight, and efficient two-phase heat strap called FlexCool, currently being developed at Roccor1. Using acetone as the working fluid, the heat strap has an average effective thermal conductivity of 2,149 W/m-K, which is approximately four times greater than the thermal conductivity of pure copper. Moreover, the heat strap has a total thickness of only 0.86 mm and is able to withstand internal vapor pressures as high as 930 kPa, demonstrating the suitability of the heat strap for orbital environments where pressure differences can be large. A reduced-order, closed-form theoretical model has been developed in order to predict the maximum heat load achieved by the heat strap for different design and operating parameters. The model is validated using experimental measurements and is used here in combination with a genetic algorithm to optimize the design of the heat strap with respect to maximizing heat transport capability.
Hydrodynamic and Thermal Modeling of Circulating Fluidized Bed Solar Receivers
Authors: Bilyaz Serhat , Tari Ilker
Published: February 2017

The riser tube solar receiver of a circulating fluidized bed solid particle absorption solar thermal energy system was numerically modeled for analyzing hydrodynamic and heat transfer behaviors of the solid particles in the riser. Hydrodynamics of the model is validated by comparing radial distribution of void fractions with an experimental study. For the heat transfer from the opaque walls of the receiver that is heated to high temperatures by the solar rays concentrated by the heliostat field, a simple fractional model is used in which radiative transfer is neglected and total heat flux is distributed to phases according to the instantaneous volume fractions at the boundary cells. MFIX: Multiphase Flow with Interphase eXchanges code of NETL is used with a 2.5D Eulerian-Eulerian computational model for transient simulations. The 2.5D grid is a combination of planar cells and cylindrical cells with the determined optimum fraction of planar cells of 0.15. For the solar receiver riser, transient and time averaged results of void fraction and gas and solid phase temperature distributions were numerically obtained and analyzed.
Conventional Locomotive Coupling Tests
Authors: Llana Patricia , Jacobsen Karina , Tyrell David
Published: February 2017

Research to develop new technologies for increasing the safety of passengers and crew in rail equipment is being directed by the Federal Railroad Administration’s (FRA’s) Office of Research, Development, and Technology. Crash energy management (CEM) components which can be integrated into the end structure of a locomotive have been developed: a push-back coupler and a deformable anti-climber. These components are designed to inhibit override in the event of a collision. The results of vehicle-to-vehicle override, where the strong underframe of one vehicle, typically a locomotive, impacts the weaker superstructure of the other vehicle, can be devastating. These components are designed to improve crashworthiness for equipped locomotives in a wide range of potential collisions, including collisions with conventional locomotives, conventional cab cars, and freight equipment.

Concerns have been raised in discussions with industry that push-back couplers may trigger prematurely, and may require replacement due to unintentional activation as a result of service loads. Push-back couplers are designed with trigger loads meant to exceed the expected maximum service loads experienced by conventional couplers. Analytical models are typically used to determine these required trigger loads. Two sets of coupling tests are planned to demonstrate this, one with a conventional locomotive equipped with conventional draft gear and coupler, and another with a conventional locomotive equipped with a push-back coupler. These tests will allow a performance comparison of a conventional locomotive with a CEM-equipped locomotive during coupling. In addition to the two sets of coupling tests, car-to-car compatibility tests of CEM-equipped locomotives, as well as a train-to-train test are also planned. This arrangement of tests allows for evaluation of the CEM-equipped locomotive performance, as well as comparison of measured with simulated locomotive performance in the car-to-car and train-to-train tests.

This paper describes the results of the coupling tests of conventional equipment. In this set of tests, a moving locomotive was coupled to a standing cab car. The coupling speed for the first test was 2 mph, the second test 4 mph, and the tests continued with the speed incrementing by 2 mph until the last test was conducted at 12 mph. The damage observed resulting from the coupling tests is described. The lowest coupling speed at which damage occurred was 6 mph. Prior to the tests, a one-dimensional lumped-mass model was developed for predicting the longitudinal forces acting on the equipment and couplers. The model predicted that damage would occur for coupling speeds between 6 and 8 mph. The results of these conventional coupling tests compare favorably with pre-test predictions. Next steps in the research program, including future full-scale dynamic tests, are discussed.
Dielectrophoretic Interactions and Chaining of Ellipsoidal Particles in a Microchannel
Authors: Hossan Mohammad Robiul , Gopmandal Partha P. , Dutta Prashanta , Dillon Robert
Published: February 2017

Recent experimental studies report that the understanding of dielectrophoretic (DEP) interactions and chaining of irregularly shaped particles, particularly ellipsoidal shaped particle, are critical for development of smart materials, engineered biological cellular structure and tissue formation. This paper presents a comprehensive numerical investigation of direct current (DC) dielectrophoretic (DEP) chaining and interactions of ellipsoidal particles in a microchannel. A hybrid immersed boundary-immersed interface method is employed to explain the fundamental mechanism of DEP interactions and chaining of ellipsoidal particles. Electric field equations are solved by the immersed interface method while the immersed boundary method is employed to solve fluid equations. The DEP force was estimated by using Maxwell’s stress tensor (MST) and the Cauchy stress tensor (CST) was employed to evaluate hydrodynamic force. The results show that the electrical properties of fluid and particles are the main deciding factor on the final orientation of ellipsoidal particles. However the size, shapes and initial positions and orientations have significant impact on interaction time spans. Results also show that if the interacting particles are electrically similar i.e. having same electrical conductivity then they always form a chain parallel to the applied electric field, otherwise they form a chain which is orthogonal to the applied electric field. In parallel chaining, particles rotate in a clockwise direction, while in orthogonal (to the applied electric field) chaining, particles rotate in counter-clockwise direction to reach to the final orientation. Results also indicate that the ellipsoidal particles go through an electro-orientation process if initially the major axis of the ellipsoidal particles is not in perfect alignment with the applied electric field. The electro-orientation and DEP interaction take place simultaneously to reach to final stable orientation. This study provides critical insight on the mechanism of DEP interactions and chaining of ellipsoidal shaped particles.
Effect of Uncertainties in the Estimation of Dynamic Coefficients on Tilting Pad Journal Bearings
Authors: Ruiz Rafael O. , Diaz Sergio E.
Published: February 2017

It has been identified that small variations in the pad clearance and preload of a Tilting Pad Journal Bearing lead to important variations in their dynamic coefficients. Although this variation trend is already identified, a more robust statistical analysis is required in order to identify more general tendencies and quantify it. This work presents a framework that helps to identify the relation between the manufacturing tolerance of the bearing (reflected in the pad clearance and preload) and the expected variations on the dynamic coefficients. The procedure underlies the adoption of a surrogate model (based on Kriging interpolation) trained by any deterministic model available to predict dynamic coefficients. The pad clearance and preload are considered uncertain parameters defined by a proper probability density function. All statistical quantities are obtained using stochastic simulation, specifically adopting a Monte Carlo simulation employing the surrogate model. The framework is illustrated through the study of a five pad bearing.
Thermal Performance of a Fin Operating Under Dehumidifying Operating Conditions
Authors: Pashah Sulaman
Published: February 2017

The use of extended surfaces or fins is very common for enhancing the heat transfer between a prime surfaces and surrounding environment. The applications cover both scenarios where the prime surface is either at a higher or at a lower temperature than the surrounding environment. In the first case, only sensible heat transfer occurs whereas the latter is typical for refrigeration and air conditioning applications where both sensible and latent heat transfer occur.

The performance of a fin is well described through a dimensionless parameter called fin efficiency. The efficiency is represented graphically in form of charts as a function of another dimensionless parameter called the fin parameter. The objective of the dimensionless presentation is that it provides the solution to a class of problems. However, this is true only for the dry fins because such charts for wet fins are for a set of particular operating conditions (i.e. temperature and psychrometric data). Thus, a separate chart is required if operating conditions are changed. The objective of present study is to investigate the possibility of developing the fin efficiency charts in the form which are independent of the operating conditions, thus a single chart covering all possible operating conditions. The finite element formulation is used to account for the actual nonlinear psychrometric relationships.
Very Low Reynolds Number Flow Over Non-Spherical Particles: Applications to Pollen Aerodynamics
Authors: Grega Lisa
Published: February 2017

Flows at the very low Reynolds number regime (<10) typically have application to the understanding of the dispersion of micro-scale particulates in the atmosphere, as well as microorganisms. Most particulates are non-spherical, requiring specialized studies in order to determine their settling velocities, drag forces, or interactions. The present study considers flow over saccate pollen with the goal of better understanding their flight dynamics. The pollen grains of several gymnosperm groups consist of a main body and one to three air-filled bladders, or sacci, forming ellipsoidal lobes. Previous studies have demonstrated that sacci increased the resistance coefficient of the grain compared to one without sacci, thereby improving its aerodynamic efficiency by increasing dispersal distance. In order to better quantify the effect of sacci position, size, and orientation on pollen dispersion, scaled-up physical models were created based on electron microscopy images. Furthermore, surface ornamentation or texture could be added to the models, adding a higher degree of realism. The models were suspended inside of a glycerin-filled tank capable of translating at very low speeds, producing Reynolds numbers as low as 0.05. Particle Image Velocimetry (PIV) was used to measure velocity fields in the wake of the pollen models. This experimental arrangement facilitated the ability to produce both steady and unsteady (i.e. accelerating or decelerating) flows. Differences among the wake flowfields were related to previously made measurements of pollen shape factors. These studies suggested that both sacci size, orientation or relative position on the main body, as well as surface texture affected this shape factor. The PIV measurements are capable of resolving wake details which demonstrate a wide stagnant flow region behind the main body and between the sacci. This is in contrast to a typical spherical or ellipsoidal geometry, which would be characterized by a single stagnation streamline at the aft, with the flow remaining attached and no wake present when Re<1. At these low Reynolds numbers, there does not appear to be evidence of flow reversal between the sacci; however rapid flow deceleration was capable of producing such reversals.
Shape Recovery Characteristics of 3D Printed Soft Polymers and Their Composites
Authors: Liu Wenbo , Wu Nan , Pochiraju Kishore
Published: February 2017

Shape memory polymers can be triggered to assume memorized shapes from temporarily deformed forms using thermal stimuli. This paper focuses on the characterization of the shape memory behaviors observed in selected 3D printable photo-cured polymer parts and filament with specified fillers. The shape recovery ratio and recovery time were analyzed using 3D printed specimens with 90° bends. Parts with the mixture of selected commercially available polymers — a rigid polymer (RP) and two digitally mixed polymer blends (DB-A and DB-B) were 3D-printed on a multi-material 3D printer capable of producing digital materials with variable mix ratios. The recovery ratios were determined after thermal triggering and after long-term creep (self-recovery) without thermal triggering. The 3D printed parts were heated to above their glass transaction temperature to train temporary shapes and the recovery of original shapes after a thermal trigger was monitored using a high-resolution camera. Long-term self-recovery (non-triggered) was also studied by observing the parts after temporary shape has been trained, as the try to regain their original shape over several days of slow recovery. The recovery of bending angles was quantitatively recorded from the images taken during the shape recovery process. The recovery due to thermal triggers was monitored under a high resolution microscope by reheating with hot water at 90°C. Experiments of long-term self-recovery at room temperature included monitoring of several parts by taking periodic images of the specimens using a resolution camera. The effect of inclusion of fillers on the shape recovery characteristics was also investigated. Silicon Carbide (SiC) with different weight fractions were mixed into PLA powders. Continuous filaments were extruded using a single screw extruder. The recovery time of thermal activation recovery was then characterized to determine the effect of addition of the fillers. The effect of material-mix ratio, initial printed orientation, filler type on the recovery ratio and recovery time are described in this paper.
Performance Analysis for Pressure Retarded Osmosis: Experimentation With High Pressure Difference and Varying Flow Rate, Considering Exposed Membrane Area
Authors: Tran Thomas T. D. , Park Keunhan , Smith Amanda D.
Published: February 2017

Pressure retarded osmosis (PRO) is a process for renewable energy conversion that makes use of a salinity gradient between two bodies of water. A semipermeable membrane separates two solutions: the draw solution, with higher salinity, and the feed solution, with lower salinity. In this study, three system design choices for bench-scale PRO systems were investigated: mesh spacer opening area, hydraulic pressure difference, and relative flow rates. Mesh spacers provide mechanical support to the membrane, but can reduce the water flux. Moreover, the water flux behavior at high hydraulic pressure difference is shown to be nonlinear, departing from the theoretically predicted water flux, which is based on a linear model. The ratio of feed solution flow rate to draw solution flow rate also determines PRO performance. Experimental data from a bench-scale system is used to present design-relevant information for optimizing PRO systems toward higher power densities.
Tuning and Implementation of a Feedback Control Strategy for Drying Process Based on IAE Minimization
Authors: Lugo Ana M. , Audivet Durán Cinthia , Sanjuán Marco E.
Published: February 2017

Agricultural products contain a significant amount of moisture during the harvesting stage. The presence of this moisture increases the deterioration rate of the products during storage, handling, and processing periods; drying is one of the most suitable processes that can be applied to these by-products before using them as cattle feed or soil conditioner. This process is certainly one of the most energy consuming found in industry. The selection of an appropriate process control strategies can minimize production and maintenance cost, maximize product quality and reduce environmental pollution. Rotary dryers are normally employed to dry agricultural products because it can give high production rate and high drying uniformity.

The aim of this research is to improve the performance of a feedback control strategy for a drying process, based on the implementation design of experiment; this approach allows finding specifics tuning parameters and potential operation conditions that will traduce in a more robust process. The selected criterion to evaluate the performance of the strategy is the integral absolute of the error (IAE) and the analysis is based on a dynamic model of a rotary dryer. The objective of the process improvement is to find an operation region, function of the controller gain, the integral time and derivative time, in which IAE parameter is minimized, this will lead to enhancement of equipment performance and reduction of the wear of the final control element. Once the controlled strategy is described, the methodology states an exploratory stage, for process characterization, establishment of a regression model, to describe the relation between experiment significant factors and response variable, maximum ascent route, exploration of a possible curvature, definition of a new regression model and finally determination of a new optimum operating point.
Knowledge Based Engineering and Ontology Engineering Approaches for Product Development: Methods and Tools for Design Automation in Industrial Engineering
Authors: Furini Francesco , Rossoni Marco , Colombo Giorgio
Published: February 2017

The study illustrated in this paper aims at analyzing the knowledge management issue related to product development. Especially, the focus is on the domains in which Knowledge-based Systems (KBE) and Design Automation (DA) tools could be adopted. In the past various studies, a lot of KBE and DA systems have been developed in multiple fields such as automotive, aerospace, energy, materials and manufacturing: the information treated in these studies are about data relatives to specific design, for example, of automotive engine components, aircraft structures, energy plants, advanced material and manufacturing or assembly lines. In all of these domain the organization and formalization of the knowledge is a critical issue. The adoption of a good strategy to manage data and information relative to products and processes involves benefits in the product development process. Different methodologies are described in literature. The two of the most used are the Object-Oriented (OO) and Ontology Engineering (OE) approaches. The former is one of the most common and adopted in the industrial domain, including a lot of implementations in the recent past years. The latter is more commonly used in other fields, like bio-engineering, used with the scope of management of experimental data; few implementation in industrial engineering have been considered. The article considers a brief description of the state of the art about Knowledge Based Engineering and Ontology Engineering. A case studies will be described and the benefits and disadvantages due to the use of the different methodologies will be discussed.
Damage Identification Using a Continuously Scanning Laser Doppler Vibrometer System
Authors: Chen Da-Ming , Xu Y. F. , Zhu W. D.
Published: February 2017

A continuously scanning laser Doppler vibrometer (CSLDV) system is capable of rapidly obtaining spatially dense operating deflection shapes (ODSs) by continuously sweeping a laser spot from the system over a structure surface. This paper presents a new damage identification methodology for beams that uses their ODSs under sinusoidal excitation obtained by a CSLDV system, where baseline information of associated undamaged beams is not needed. A curvature damage index (CDI) is proposed to identify damage near a region with high values of the CDI at an excitation frequency. The CDI uses the difference between curvatures of ODSs associated with ODSs that are obtained by two different CSLDV measurement methods, i.e., demodulation and polynomial methods; the former provides rapid and spatially dense ODSs of beams, and the latter provides ODSs that can be considered as those of associated undamaged beams. Phase variables are introduced to the two methods for damage identification purposes. The proposed damage identification methodology was experimentally validated on a beam with damage in the form of machined thickness reduction. The damage and its region were successfully identified in neighborhoods of prominent peaks of CDIs at different excitation frequencies.
A Novel Design of Thermostat Based on Fishing Line Muscles
Authors: Saharan Lokesh , Tadesse Yonas
Published: February 2017

Recently reported fishing line muscles are soft actuators which can be fabricated by twist insertion in commercially available Nylon 6 monofilament fibers under certain amount of tension. Annealing and Training are needed to retain the twist inserted to complete the fabrication process. These actuators are soft polymeric materials with high stresses, large strain, relatively high power to weight ratio when compared to conventional actuators apart from being cost effective. Though the performance of the muscles is largely dependent on parameters of fabrication, these actuators deform linearly in response to thermal gradient. Actuation can be triggered by varying temperature by any means such as blowing hot fluid or resistive (Joule) heating. The response of the muscles depends on the rate of change of temperature, magnitude of temperature, and applied load. We recognized the potential application of the muscle as a mechanical thermostat as a new design or for use in opening and closing a control valves. Mostly the working range for this muscle is 50–150°C, which is the working range of a wide variety of devices and instruments. This study presents a novel design, fabrication, working principle and preliminary experiments of the thermostat device that is light in weight, simple to manufacture and cost effective.
A Modified Stochastic Subspace Identification Method for Estimating Natural Frequencies
Authors: Dai Kaoshan , Wang Ying , Huang Yichao , Zhu W. D. , Xu Y. F.
Published: February 2017

A system identification method for estimating natural frequencies is proposed. This method developed based on the stochastic subspace identification method can identify modal parameters of structures in operating conditions with harmonic components in excitation. It benefits wind turbine tower structural health assessment because classical operational modal analysis methods can fail as periodic rotation excitation from a turbine introduces strong harmonic disturbance to tower structure response data. The effectiveness, accuracy and robustness of the proposed method were numerically investigated and verified through a lumped-mass system model.
Configuration Analysis and Design of a Wind Turbine With Hydrostatic Transmission System
Authors: Deldar Majid , Izadian Afshin , Anwar Sohel
Published: February 2017

This paper presents a methodology for designing and dimensioning of hydrostatic transmission system (HTS) configurations for wind turbines. HTS provides an alternative method to the gearbox in wind power applications. It decouples the turbine and the generator such that the generator can be driven at synchronous speed regardless of wind speed variation. A comparison of different HTS configurations shows that the functionality and performance of the proposed system depends on proper dimensioning of hydraulic components and the circuit configuration. Practical constraints of wind turbine and hydraulic technologies are considered in the design to configure an industrial scale system. The design objectives include obtaining the maximum system efficiency at the rated and high efficiency at partial load. Different hydrostatic systems were designed and simulated to show potentials for improving the overall efficiency of wind power using HTS. It was shown that the larger swept area and moderate speed generator improve efficiency of hydrostatic drivetrain. Optimization of the entire HTSWT can improve output power from a HTSWT to an extent that its annual energy production (AEP) becomes closely equal to AEP of a geared WT.
Mechanical Strength Responses of Poled Lead Zirconate Titanate Under Extreme Electric Field and Various Temperature Conditions
Authors: Wang Hong , Matsunaga Tadashi , Zhang Kewei , Lin Hua-Tay , Wereszczak Andrew A.
Published: February 2017

PZT (lead zirconate titanate), particularly PZT-5A, is used in a variety of critical actuation and sensing systems because of its high Curie temperature and large piezoelectric coefficients. However, PZT is susceptible to mechanical failure. The evaluation of the mechanical strength of the material under the target working conditions is very important. This study presents part of the recent experimental developments in mechanical testing and evaluation of PZT materials at Oak Ridge National Laboratory. Ball-on-ring and four-point bending testing setups were used, with modifications made to account for testing requirements from high-level electric field and elevated temperature. The poled PZT-5A or equivalent material was tested under various specimen and testing conditions. The parameters of the distribution of strengths (characteristic strength and Weibull modulus) are discussed in relation to the testing conditions. Fractographic results based on scanning electron microscopy are also presented and discussed. The related data can serve as input for the design of piezoceramic devices, not only those used in energy systems like fuel injectors in heavy-duty diesel engines, but also those used in structural health monitoring, energy harvesting, and other critical systems in aerospace and civil engineering.
Refinement and Scaling Effects on Peridynamic Numerical Solutions
Authors: Dipasquale Daniele , Oterkus Erkan , Sarego Giulia , Zaccariotto Mirco , Galvanetto Ugo
Published: February 2017

One of the most common methods to implement peridynamics numerically is based on the discretization of the whole body by means of a structured and regular grid of nodes and a constant horizon size. That leads to an inefficient use of computational resources as well as to the impossibility to explore the multi-scale capabilities of peridynamics within a unique framework. Adaptive grid refinement and scaling seem to be a promising strategy to reduce those limitations, allowing to increase the resolution of the analysis and to reach the interested length-scale only in the desired regions. The application of such an approach in the peridynamic solutions requires certainly to be investigated, in particular, this is done by the comparison of numerical peridynamic solutions with the analytical solutions of classic linear elasticity theory.
Review of Hazards and Assessment of Safety Features for Agricultural Equipment
Authors: Kornuta Jeffrey A. , Kennedy Eugenia
Published: February 2017

Agriculture has been considered one of the most hazardous industries in the U.S., with studies showing that the worker fatality rate in agriculture is over seven times higher in 2011 than the fatality rate for all private industry workers. According to the U.S. Department of Labor Occupational Safety and Health Administration (OSHA), many of the fatalities and injuries that occur each year are preventable based on the use of protective equipment. Hazards associated with agricultural equipment such as farm tractors have been known for a number of years, and safety features have been introduced to mitigate, or in some cases, eliminate hazards associated with operation of this type of equipment. This paper presents a historical analysis of fatal and nonfatal injury data to identify potential effects of these safety features once introduced. The risks agricultural workers face, with an emphasis on hazards presented by farm equipment, is identified and quantified from data in recent years, specifically for farm tractors. For context, an introduction to the regulations and industry standards relevant to agricultural equipment is given, including the introduction of certain safety features such as roll-over protective structures (ROPS), which have been an industry standard requirement on tractors manufactured since the mid-1980s. Overall, recent data show continual reductions in the number of fatal injuries in the agricultural industry, particularly for farm tractors. However, further research is needed to clearly correlate the specific effects of safety mitigation devices on injuries associated with equipment in this industry.
Static and Dynamic Pull-In of Electrically Actuated Circular Micro-Membranes
Authors: Sajadi Banafsheh , Alijani Farbod , Goosen Hans , van Keulen Fred
Published: February 2017

Micro-Electro-Mechanical devices have shown enormous popularity in engineering devices as sensors and actuators. In this paper, the instability, i.e. the dynamic pull-in behavior, of an electrically actuated circular micro-membrane is studied. In order to investigate the periodic solutions, detect bifurcations and follow branches of the solution, the non-linear equation of motion is derived using an energy approach, and, is solved by using a pseudo arc-length continuation and collocation technique. It has been shown that, both hardening and/or softening nonlinear responses could emerge depending on the applied DC voltage. The results indicate that the critical load parameters, namely DC and AC voltages and the excitation frequency, have a major influence on the pull-in characteristics of the micro-membrane. The results reveal different dynamic pull-in mechanisms. In addition, they accurately show the decrease of the pull-in voltage due to dynamic loading.

The proposed approximate solution is very fast and robust for detecting the pull-in instability. It allows observation of both global and local softening behavior even close to dynamic pullin, where the resonance frequency is almost equal to zero.
Analysis and Modifications of Turbulence Models for Wind Turbine Wake Simulations in Atmospheric Boundary Layers
Authors: Antonini Enrico G. A. , Romero David A. , Amon Cristina H.
Published: February 2017

Computational Fluid Dynamics (CFD) simulations of wind turbine wakes are strongly influenced by the choice of the turbulence model used to close the Reynolds-averaged Navier-Stokes (RANS) equations. A wrong choice can lead to incorrect predictions of the velocity field characterizing the wind turbine wake, and consequently to an incorrect power estimation for wind turbines operating downstream. This study aims to investigate the influence of different turbulence models on the results of CFD wind turbine simulations. In particular, the k–ε, k–ω, SSTk–ω, and Reynolds stress models are used to close the RANS equations and their influence on the CFD simulations is evaluated from the flow field generated downstream a stand-alone wind turbine. The assessment of the turbulence models was conducted by comparing the CFD results with publicly available experimental measurements of the flow field from the Sexbierum wind farm. Consistent turbulence model constants were proposed for atmospheric boundary layer and wake flows according to previous literature and appropriate experimental observations. Modifications of the derived turbulence model constants were also investigated in order to improve agreement with experimental data. The results showed that the simulations using the k–ε and k–ω turbulence models consistently overestimated the velocity in the wind turbine wakes. On the other hand, the simulations using the SSTk–ω and Reynolds stress models could accurately capture the velocity in the wake of the wind turbine. Results also showed that the predictions from the k–ε and k–ω turbulence models could be improved by using the modified set of turbulence coefficients.
Investigation of Heavy Truck Restraint System Effectiveness Through Finite Element Computer Simulations in Frontal Crashes
Authors: Schulz Nathan , Silvestri Dobrovolny Chiara , Mohanakrishnan Abhinav
Published: February 2017

Computer finite element simulations play an important role in reducing the cost and time taken for prediction of a crash scenario. While interior crash protection has received adequate attention for automobiles, very little is known for commercial vehicle such as heavy trucks. The understanding of injury types for heavy trucks occupants in relation to different crash scenarios would help mitigation of the injury severity.

Finite element computer models of the heavy truck cabin structure, interior cabin components, anthropomorphic test device (ATD) (also called dummy) and passive restraint systems were developed and assembled to simulate head-on crash of a heavy truck into a rigid barrier. The researchers developed a computer simulation parametric evaluation with respect to specific seat belt restraint system parameters for a speed impact of 56.3 km/h (35 mph). Restraint parameter variations within this research study are seat belt load limiting characteristics, inclusion of seat belt pretensioner, and variation of seat belt D-ring location. Additionally an airbag was included to investigate another restraint system. For each simulated impact characteristic and restraint system variation, the occupant kinematics were observed and occupant risks were assessed.

Within the approximations and assumptions included in this study, the results presented in this paper should be considered as preliminary guidance on the effectiveness of the use of seat belt as occupant injury mitigation system.
Effect of Key Variable Combinations on the Vibration-Induced Loosening of Preloaded Fasteners
Authors: Lee Joon Ha , Mahmood Khalid , Nassar Sayed A.
Published: February 2017

This study investigates the effect of key variable combinations on the loosening performance of a preloaded threaded fastener system under harmonic transverse vibrations, using a software for bolt loosening analysis. The software is based on a mathematical model of the standard Junker test for vibration loosening. Studied variable combinations include the fastener initial tension, thread pitch, bearing and thread friction coefficients, bolt stiffness, and joint stiffness. Generated data on bolt loosening performance is analyzed for trends and relative significance of variables, and variable combinations.