bluuebunny/crossref_metadata_2025 huggingface dataset:
Simulation of Heat Transfer in a Counterflow Porous Bed Reactor With a Thermal Non-Equilibrium Model
Authors: deLemos Marcelo J. S. , Pivem Ana C.
Published: August 2012

The objective of this work is to study the influence of physical and geometrical properties on heat transfer between solid and fluid phases in a counter-flow porous bed, for cases where the fluid moves in opposite direction with respect to the permeable matrix. For simulating the flow and heat transfer, a two-energy equation model is applied in addition to a mechanical model. Transport equations are discretized using the control-volume method. The effects of solid-to-fluid velocity ratio, permeability, porosity, ratio of solid-to-fluid thermal capacity and ratio of solid-to-fluid thermal conductivity on flow and heat transport are analyzed. Results for a counterflow, that is similar to the heat exchangers in a countercurrent, indicate that there is more heat exchange for the smaller values of the parameters analyzed resulting in more uniform heat transfer between phases along the channel.
Road-Holding and Ride Performance Optimization Using Bee’s Algorithm
Authors: Shirazi K. H. , Jaafari S. M. M. , Derakhshan M. , Shafie R.
Published: August 2012

This paper provides a method for optimal synthesis of the passenger cars suspension system to obtain the best road-holding as well as ride-comfort characteristics. The longitudinal vehicle model consists of sprung and unsprung masses, tire-ground interaction model, and suspension system kinematics. Defining the non-dimensional parameters the equations of motion of the system are derived in the non-dimensional form. Several objective functions are defined for the optimization of road-holding and ride comfort characteristics based on the transient and steady-state response of the sprung mass, respectively. The optimization variables are position of instant centers of rotation of the wheels with respect to the sprung mass. Bee’s algorithm is used to obtain the solutions of the problem. The best position for the instant centers of front and rear suspension linkages are obtained and compared with 100% anti-squat line.
Energy Efficiency Management Protocol in the Large Scale Retail
Authors: Di Palma Diego , Lucentini Marco , Rottenberg Flavio
Published: August 2012

The paper presents the results of a two years research on the field of energy management systems. These systems range from the largest ones found in industrial plants down to the smallest utilized by the residential consumers. The goal is to define an energy management system specific to supermarkets sector including hypermarkets operating in large scale retail. The need to ensure continuity and quality of energy services, the high energy consumptions, the complexity of operation and maintenance facilities and, in general, the lack of strategies in energy end uses are just some of the reasons that have oriented the research in this sector. On the other hand, the groups operating in the large-scale retail, in order to contain costs, have always walked the path of maximum standardization of plants characteristics or, in most cases, the implementation of economy of scale in purchasing and maintenance; strategies not sufficient to ensure real savings considering the rising costs of energy. The starting points of the research have been some energy efficiency actions applicable to this type of consumers: buildings and facilities design, optimization of energy purchasing, management of maintenance, monitoring and collecting energy data, promotion of best practices in end uses, energy benchmarking, etc. For the purpose an energy audit was developed in the biggest supermarket and hypermarket chain in Italy during the last two years; the results led to the implementation of an operative protocol that makes possible to achieve energy savings in excess of 20%. The large number of supermarkets analyzed, the rigorous approach to the measurement and the monitoring of energy data, the possibility to verify the results in a ongoing way and the use of simulation models and software, permit a feasible extension to similar contexts.
Artificial Neural Networks for Predicting the Performance of Novice CAD Users Based on Their Profiled Technical Attributes
Authors: Hamade R. F. , Ammouri A. H. , Artail H. A.
Published: August 2012

This paper utilizes Artificial Neural Networks (ANN) to forecast the mechanical CAD performance of novice trainees involved in formal training. We utilize 3 Artificial Neural Networks, ANN, techniques: Feed-Forward Backpropagation, Elman Backpropagation, and Generalized Regression. We also compare their predictive capabilities compared to those of linear regression techniques. For this purpose, two kinds of data are utilized as input vectors for the predictive techniques: performance data and trainee attributes data. Such data has been previously published by Hamade and coworkers. Performance data is based on the following four quantitative measures of performance: (1) construction speed of the CAD model, (2) sophistication of the constructed CAD model, and the rates of improvement of (3) construction speed and (4) model sophistication. Trainees’ attributes identified as related to building CAD competence include: (1) technical and (2) character attributes and (3) learning styles. Strong correlations have been found between many of the trainees’ profiled attributes and trainee’s actual performance throughout and upon the conclusion of the training. Generally, the ANN methods as well as the linear regression techniques were found to be successful in discriminating the trainees based on their profiled attributes. However, the findings suggest that, of the networks considered, the Generalized Regression Neural Network (GRNN) gave the best prediction results by yielding the least prediction error practically across all performance measures. Therefore, GRNN can be used to predict the performance of the novice CAD users. This capability may be used to pre-assess the development of CAD skills as training progresses and may serve as basis to develop custom CAD training programs and to improve the efficiency and effectiveness of CAD training.
Observation of Bubble Deformation Process in a Microcapsule for Developing Drug Delivery Systems Using Shock Waves and Ultrasonic Waves
Authors: Tamagawa Masaaki
Published: August 2012

This paper describes development of microcapsule using underwater shock waves, especially (1) the trial of making polymer microcapsules including a bubble and disintegration tests by shock waves, (2) analysis of a bubble deformation process in a polymer capsule by pressure wave, (3) the trails of making liposome microcapsules and disintegration tests by ultrasonic waves.
Fluid Dynamics Around a Dimpled Pin-Fin
Authors: Nagar R. K. , Meyer J. P. , MahbubAlam Md. , Spedding G.
Published: August 2012

The most common and popular cooling mechanism found in various industrial applications is pin-fins. These industrial applications include cooling of heat exchangers, as well as the cooling of micro electronic equipment. With the increased heat output of these devices, new enhancement techniques have been investigated. A surface enhancement technique of using offset shallow dimples on pin-fins was found to increase the heat transfer rate by up to 30%. The insight into the mechanism is, however, not known in fluid dynamics. A numerical investigation is conducted to get insight into the mechanism, comparing fluid dynamics around a single smooth cylinder with that around a dimpled cylinder.
Preserving Stability Properties in Reduced Models of Time-Periodic Systems Using Proper Orthogonal Decomposition
Authors: Pumhoessel Thomas , Hehenberger Peter , Zeman Klaus
Published: August 2012

The necessity of providing reduced models of dynamical systems is growing continuously. Model-based control and model-based design are exemplary fields of applications. In this contribution, the reduction of a controlled drivetrain of a rolling mill using the method of Proper Orthogonal Decomposition is investigated, where the specific choice of the control law leads to equations of motion with time-periodic coefficients. Depending on amplitudes and frequency parameters of the time-periodic coefficients, artificial damping is introduced, referred to as parametric control. The maximum damping effect depends on these parameters in a nonlinear manner, as it is shown by means of a stability-parameter from Floquet theory. The reduced model set-up approximates the stability-parameter of the full model in an appropriate way within a wide range of the parameters. A measure based on the linear time-invariant system is developed that gives insight into the effect of the simulated timeseries on the properties of the reduced model.
Estimation of Creep-Fatigue Damage Through Indentation Test Method
Authors: Prakash Raghu V.
Published: August 2012

Creep, creep-fatigue damage is often estimated through in-situ metallography, tensile testing of specimens. However, these methods require specimen preparation which includes specimen extraction from critical components. Automated ball indentation testing has been used as an effective tool to determine the mechanical properties of metallic materials. In this work, the tensile properties of materials subjected to controlled levels of damage in creep, creep-fatigue is studied. It is found that the tensile properties such as yield strength and UTS deteriorates with creep damage, whereas the same specimens show an improved UTS values (at the cost of ductility) when subjected to creep-fatigue interactions.
Vibration Response of a Wind-Turbine Planetary Gear Set in the Presence of a Localized Planet Bearing Defect
Authors: Jain Sharad , Hunt Hugh
Published: August 2012

In a wind-turbine gearbox, planet bearings exhibit a high failure rate and are considered as one of the most critical components. Development of efficient vibration based fault detection methods for these bearings requires a thorough understanding of their vibration signature. Much work has been done to study the vibration properties of healthy planetary gear sets and to identify fault frequencies in fixed-axis bearings. However, vibration characteristics of planetary gear sets containing localized planet bearing defects (spalls or pits) have not been studied so far. In this paper, we propose a novel analytical model of a planetary gear set with ring gear flexibility and localized bearing defects as two key features. The model is used to simulate the vibration response of a planetary system in the presence of a defective planet bearing with faults on inner or outer raceway. The characteristic fault signature of a planetary bearing defect is determined and sources of modulation sidebands are identified. The findings from this work will be useful to improve existing sensor placement strategies and to develop more sophisticated fault detection algorithms.
Performance Investigation of a Four Stroke Diesel Engine, Using Water-Based Ferrofluid as an Additive
Authors: Daneshvar F. , Jahani N. , Shafii M. B.
Published: August 2012

In this experimental study, a four stroke diesel engine was conducted to investigate the effect of adding water-based ferrofluid to diesel fuel on engine performance. To our knowledge, Magnetic nanoparticles had not been used before. To this end, emulsified diesel fuels of 0, 0.4, and 0.8 water-based ferrofluid/Diesel ratios by volume were used as fuel. The ferrofluid used in this study was a handmade water-based ferrofluid prepared by the authors. The results show that adding water-based ferrofluid to diesel fuel has a perceptible effect on engine performance, increasing the brake thermal efficiency relatively up to 12%, and decreasing the brake specific fuel consumption relatively up to 11% as compared to diesel fuel. In addition, the results indicate that increasing ferrofluid concentration will magnify the results. Furthermore, it was found that magnetic nanoparticles can be collected at the engine exhaust using magnetic bar.
Analysis of Vibration Characteristics for Last Stage Blade With Friction Contact Surfaces of Steam Turbine
Authors: Yamashita Yutaka , Shiohata Koki , Kudo Takeshi
Published: August 2012

Friction damping devices such as under platform dampers are installed for modern turbine blades to suppress dynamic vibrations of the blades. In order to secure the reliability of the blades, it is important to predict the dynamic response and friction damping characteristics accurately. In this present paper, the dynamic response and friction damping characteristics of a last stage blade (LSB) of a steam turbine with contact surfaces at the cover, tie-boss and blade root was investigated. Especially, it is focused on the effect of the non-uniform normal contact forces at the contact surface. To investigate the effect of non-uniform normal contact forces, an analysis method was developed. Analysis model of the LSB with contact surfaces was discretized by finite elements. Tangential forces at the contact surfaces were modeled by multi-DOF macro-slip modeling. The non-linear frequency responses of the LSB were obtained by using the harmonic balance method. Using this analysis method, the relationship between the contact surface behavior and the dynamic response was studied.
Analysis of Efficient Interval Field Techniques for Random Field Analysis With Uncertain Correlation Length
Authors: Verhaeghe Wim , Desmet Wim , Vandepitte Dirk , Moens David
Published: August 2012

The representation of uncertainties that give rise to a spatially distributed influence is still a topic of research in the non-probabilistic approach. The authors have developed an interval field framework to deal with multiple dependent uncertainties. Recently, the interval field method was developed to deal with random field expansions with an uncertain correlation length. The base vectors of this interval field come from a number of exact expansions of the random field in the correlation length space (e.g., Karhunen-Loe`ve expansion). The scaling interval factors are essentially a function of the correlation length. The present paper studies for the first time the convergence of an uncertain FE output (i.e. the interval on the FE output) with respect to the dimension of the base vector space, which is determined by the number of eigenvectors retained in one exact random field expansion and the number of exact random field expansions used to build the interval field representation.
Characterization of Adhesive-Bonded Sheet Metal Joints
Authors: Yan Cuifen , Wu Xin , Nassar Sayed
Published: August 2012

The bonding strength of metal-metal single-lap joints with different adhesives applied on steels and aluminum alloys were studied. The bonding strength is found to be related to the type of adhesives and the backing metal, the surface roughness, the surface scratch orientations, the adhesive layer thickness, and the loading conditions (static vs. cyclic and loading rate). SEM observation of fractured surfaces reveals some common feature of bonding strength enhancement, fracture paths and the mechanisms of fracture. The direction of the adhesive joint design is suggested.
Analysis of Plug Zones in Steady Flow in Undulating Channels
Authors: Letelier Mario F. , Svensson Pierre , Siginer Dennis A. , Stockle Juan S.
Published: August 2012

Undulating channels are important in several industrial applications related to heat transfer and also as a modeling resource for complex flow through pores or fibers. In this paper, flow of a Bingham plastic in an undulating channel is studied. An analytical model is developed which allows to determine the regions in the flow where solid (plug) or quasisolid behavior appears. The parameters considered are the dimensionless yield stress, the channel amplitude and the Reynolds number. A variety of cases are presented, in which the characteristics of the flows are described. The main results are presented by means of the streamlines, isobars, constant shear stress lines, isovelocities, and velocity profiles. Good consistency if found among all variables analyzed.
Minimum Constraint Design Analysis and Modification of a Biaxial Tensile Test Fixture for Hyperelastic Materials
Authors: Smoger Lowell , Gomes Mario , DeBartolo Elizabeth
Published: August 2012

The focus of this study is to improve the operation of a biaxial tensile test fixture for use in characterizing hyperelastic materials. The test fixture in this study was constructed based on a design developed by Brieu, et al. [1]. Due to a combination of manufacturing and design issues the original test fixture was not able to provide acceptably accurate stressstrain data. Based on visual inspection of the machine during operation, it was hypothesized that the as-built system over-constrained certain components, which resulted in binding of the specimen grips. This binding made large displacement tests inaccurate and added to the error introduced in obtaining a 1:1 equibiaxial load ratio on a test specimen. A minimum constraint design (MCD) analysis was conducted in order to establish the degree to which the original design was over-constrained, and to ensure that the newly proposed system would function properly. Due to symmetry, the design analysis of the test fixture was simplified to one half of the machine. A modified design of the test fixture was subsequently developed and built to satisfy the minimum constraint design theory. Modifications include an alignment shaft, spherical bushings, and a planar alignment plate. The new fixture design exhibits no binding and an improved biaxial load ratio. Previously, only load ratios of 0.85:1 had been achieved, but the new design achieves the desired equibiaxial loading. Tighter component tolerances have also reduced backlash when reversing from tension to compression during a test, improving the ability to obtain load-displacement data for both the load and unload paths of a specimen.
Water Reclamation From High Moisture Content Waste Heat Streams
Authors: Wang Dexin , Liss William , Bao Ainan
Published: August 2012

A new waste heat and water recovery technology based on a nanoporous ceramic membrane water vapor separation mechanism was developed, to extract the water vapor and its latent heat from low temperature high moisture content waste gas streams. For the water reclamation process, water vapor condenses inside the membrane pores and passes through to the permeate side which is in direct contact with a low-temperature water stream. Contaminants such as CO2, O2, NOx, and SO2 are inhibited from passing through the membrane by its high selectivity. The recovered water is of high quality and mineral free, therefore can be used as supplemental makeup water for almost all industrial processes. The membrane based technology has been first developed and demonstrated for industrial boiler flue gas heat and water recovery. Now it is being developed for wider applications, from residential humidification, commercial laundry, biomass production to utility boilers. The increased application areas will greatly enhance waste heat and water recovery potentials worldwide, to save both energy and water, and benefit the global environment. In this paper, the technology development process, and several demonstrations for different applications are discussed in details.
Energy Saving in a Heat Pump Air-Conditioning System Using Liquid Desiccant and Membrane Contactors
Authors: Bergero Stefano , Chiari Anna
Published: August 2012

It has been demonstrated in the literature that significant energy savings can be achieved in air-conditioning through the use of so-called hybrid systems, in which a chemical dehumidification system is combined with a vapour-compression heat pump. The advantage of such systems lies in the fact that the heat pump can operate at a higher evaporation temperature than that of a traditional system in which dehumidification is achieved through condensation, thereby achieving higher coefficients of performance. The hybrid system described in the present paper operates as follows: the air supplied to the conditioned ambient is simultaneously cooled and dehumidified in an air-solution membrane contactor. The LiCl solution is cooled by means of a vapour-compression heat pump using the refrigerant KLEA 410A. The solution is regenerated in another membrane contactor by exploiting the exhaust air and the heat rejected by the condenser. A study of the steady-state behaviour of the system in summer climatic conditions was carried out, on varying some significant operating parameters, such as the thermal efficiency of the heat exchangers, the outdoor temperature and the sensible load of the conditioned room. The performances of the hybrid system were compared with those of a traditional direct-expansion air-conditioning plant; the results of the simulations reveal that, in particular operating conditions, energy saving can exceed 50%.
Thin-Shell Response to Machining Loads
Authors: Dospeˇl Vladimi´r , Keskinen Erno
Published: August 2012

Final machining operations, such as surface grinding, play a crucial role in manufacturing of paper machine rolls. Due to developing new web-tension-measuring systems and due to demand on reduction of roll masses, a grinding operation of thin-walled rolls is required. In this paper first, delay differential equations describing the dynamics of the grinding system are introduced. The dynamic model consists of a rotating thin-walled roll and its drive and a rotating grinding stone with its drive attached to an axially moving sledge. The derivation of the cutting forces is based on wear theory. The roll is modelled in two ways for later comparison: (1) as a flexible simply supported rotor using Euler-Bernoulli beam theory and (2) as a simply supported flexible shell using Love’s equations. In both cases, a method of eigenfunctions expansion is employed for obtaining the responses. The effect of the time delay, shape error, overlapping and the PD-controller are included. The set of the delay differential equations is solved numerically. Finally, the dynamic response of the roll to the cutting forces is presented. An influence of different wall-thicknesses on the dynamic behaviour of the roll during the grinding process is studied as well. Lastly, a comparison of results obtained by using the beam theory and the shell theory are discussed.
Synthesis and Analysis of Nanoporous Material Using Microchannel
Authors: Lim Mikyung , Seo You Kyoung , Lee Seung S. , Hwang Young Kyu
Published: August 2012

Recent small electronic equipments with various functions require extreme increase of heat transfer rate per unit surface. Current small electronic equipments’ cooling abilities have limitation with its heat transfer rate. Boiling is one of the solutions for this problem since it can be applied by using microchannel and flow boiling. Also, it has much higher heat transfer coefficient than large-scale cooling system. However, boiling is not easily initiated and surface temperature often reaches high temperature even without boiling which could burn the electronic equipment. To enhance boiling, one of the best methods is coating nanoporous material on the surface. Synthesis characteristics of nanoporous material depend on both the temperature and concentration condition. Therefore, the accurate condition for the synthesis process is required but, the current synthesis method cannot control both temperature and concentration also wastes both time and resources. This research suggests a way of synthesizing nanoporous material using microchannel which can obtain accurate control of variables and save the resources. Microchannel reactor for nanoporous material synthesis is designed with channel on the SiO2 substrate. Cu-BTC solution passes through the microchannel and nanoporous material is coated on SiO2 substrate. Through time and temperature variable experiment, the procedure of growth of nanoporous material is observed within time change and transformation of crystalline structure of nanoporous material is obtained by temperature change. Most importantly, this method provides much higher synthesis rate and uniformity than the current synthesis method. The experiment on the effect of width of microchannel on synthesis rate was also performed. This has important meaning since it can be applied to the other materials which can be synthesized in microchannel and could increase their synthesis rate too. Synthesis in microchannel provides high reproducibility and helps to accomplish accurate analysis. Moreover, synthesis of nanoporous material in the microchannel is easier to fabricate and easier to be applied in the cooling system using the flow boiling. Therefore, synthesis in microchannel can make a significant improvement in cooling system of small equipments, and it contributes to miniaturization of electronic equipments.
Anti-Swing Trajectory Control of an Overhead Crane
Authors: Fung E. H. K. , Yu H. F. , Suen K. H. , Leung A. T.
Published: August 2012

Imprecise positioning and swing of load of overhead crane cause prolonged transportation time. Some researchers tried to achieve suppression of swing angle and fast transfer simultaneously. But, the hoisting motion is usually ignored which can cause greater swing angle. Hence, a physical 2-DOF overhead crane model which consists of horizontal motion and hoisting motion is set up for this study. The total kinetic energy and the total potential energy are derived to obtain dynamic equations of motion by using Lagrangian method. Secondly, fuzzy logic control (FLC) has been adopted to control positioning of horizontal and hoisting motion and to suppress swing angle during transportation. Moreover, to minimize total transportation time, proportional (P) controller is added to the system forming the switching P+FLC controller. Finally, the proposed methods are evaluated by simulations and experiments. The overall results show that fuzzy logic controller combined with P controller (P+FLC) can effectively reduce the transportation time with a little increase in the swing angle.
Nanoporous Membrane Tube Condensing Heat Transfer Enhancement Study
Authors: Bao Ainan , Wang Dexin , Lin Cheng-Xian Charlie
Published: August 2012

A Transport Membrane Condenser (TMC), made from nanoporous membrane tube bundles, was developed by Gas Technology Institute (GTI) to recover the water vapor and its significant amount of latent heat from boiler flue gases to improve boiler efficiency and save water. Water vapor condensing phenomenon inside membrane pores is different in two aspects from surface condensation when the membrane pore size is in the nanometer scale. First, based on the pore capillary condensation mechanism—Kelvin equation, pore condensation can occur when local gas stream relative humidity is well below 100%, so more water condensation is possible at the same surface temperature compared with surface condensation. Second, as membrane heat exchanging surface continues evacuating condensed water to the permeate side, no water will be accumulated on the condensing surface, which eliminates the additional heat transfer resistance caused by the condensed liquid film (or droplets) for a conventional impermeable condensing surface. Experiments have been carried out to study the phenomena for both a nanoporous membrane tube bundle and an impermeable stainless steel tube bundle with the same characteristic dimensions. Flue gas streams with a water vapor mass fraction 11.3%, temperature ranges from 65°C to 95°C were used for the experimental study, which covers the typical TMC waste heat recovery application parameter range. Results show the convection Nusselt number of the membrane tube bundle is 50 to 80% higher than that of the impermeable stainless steel tube counterpart at typical condensation heat transfer conditions. More parameter study was also done to study a wider range of parameters. The condensing heat transfer enhancement effect gives a good perspective for using nanoporous membrane surface to design high efficiency condensing heat exchangers to recover both water vapor and its substantial amount of latent heat from high moisture content low grade waste heat streams.
Experimental Investigation of the Complex Flow Behavior in a Hard Disk Drive Model
Authors: Shirai Katsuaki , Bu¨ttner Lars , Czarske Ju¨rgen , Shiga Nobuo , Obi Shinnosuke
Published: August 2012

Flow inside a hard-disk drive (HDD) is investigated using a simplified 3.5″ HDD model with shroud opening and read-and-write arm (RWA). The model is designed to serve as a benchmark of HDD flow study both in experiments and in numerical simulations. The complex flow behavior in the narrow disk-to-disk space is focused with the RWA inserted into the space. The velocity statistics are acquired at totally 8 different locations using a velocity profile sensor with a spatial slot resolution of 30 μm along the axial direction. The measurement was carried out at the disk Reynolds number Red = 2.4×105 which corresponds to the rotation speed of 7700 rpm at a real 3.5″ HDD for desktop computers. The resulting mean velocities and Reynolds stress components are influenced by the shroud opening and especially by the RWA, compared to an axisymmetric model without an RWA. The highly sheared flow between the RWA and adjacent upper/lower disk was successfully captured in the experiment.
Simulation of Red Blood Cell Passing Through Constrictions Using Modified Moving Particle Semi-Implicit Method
Authors: Firoozbakhsh K. , Ahmadian M. T. , Hasanian M.
Published: August 2012

During the circulation of RBC it undergoes elastic deformation as it passes through micro-capillaries where the inner diameter of the constriction can be about 3 micro meters. It means RBC shape must be changed in order to pass through these narrow channels. The role of mechanical behavior of RBC and the deformability traits of RBC are observed with the several experimental studies [1]. Several methods were implemented to simulate the mechanical behavior of RBCs in micro-capillaries [1, 2]. One of the most recent methods is Moving Particle Semi-implicit method (MPS) which is a Lagrangian method with semi-implicit algorithm that guaranties the incompressibility of the fluid. MPS method was implemented for simulation of RBC motion through parallel plates by Tsubota et al. 2006 [3]. Due to small Reynolds number and the Diffusion number restrictions, implementation of small time step size would be necessary which leads to long time simulation. By the way in case of complex geometries or FSI problems, standard MPS method has a delicate pressure solver which leads to diverge the solution. So in these cases using a small time step can help to overcome the problem. Some studies have applied a new approach for time integration and the fractional time step method is employed to overcome the noticed problem. Yohsuke Imai and coworkers (2010) have developed the former studies with two main new approaches [4]. Firstly, evaluation of viscosity is upgraded and secondly boundary condition is assumed to be periodic. Although the developments are really impressive and MPS method has turned into a practical method for simulation of RBC motion in micro-capillaries, but still there are some considerations about using large time steps and error of the velocity profile consequently.
Simulations of Power Transfer Through Water via Piezoelectric Transducers
Authors: Wilt K. R. , Radziemski L. J. , Scarton H. A.
Published: August 2012

Recently, the efficient ultrasound transmission of power through a water barrier has been modeled using principles developed from modeling transmission through metal walls. The bulk of the latter effort was focused on a solution using two coaxially aligned piezoelectric transducers on opposite sides of the metallic transmission barrier to create an ultrasonic power delivery channel. In this work, a similar physical channel configuration is adopted, but with water replacing metal as the transmission media. Finite element models of several channels are presented which begin to quantize the possible transfer efficiencies of this type of power transmission channel. In these models, the effects of various different nominal operating frequencies on the efficiency of the system are considered, as well as the effects due to differences between the transmitting and receiving transducer diameters. Experiments with ultrasound transducers in water have illuminated the strengths of the current model and directions for improvements.
Application of Finite Strip Method in Vehicle Design: Part 1 of 2—Linear Buckling Analysis of Thin Walled Structures
Authors: Gandhi Umesh , Roussel Stephane , Furusu K. , Nakagawa T.
Published: August 2012

In automotive body design use of AHSS (advanced high strength steel) has been rapidly increasing in the past few years. AHSS which has higher yield strength offers opportunity to reduce gage and hence weight reduction of the body structure. However, it is also known that for the flat thin walled members, as the stress increases and gage gets thinner, the tendency of local instability such as buckling, increases. In this presentation we will discuss finite strip method to estimate linear buckling load for thin walled sections. The finite strip method is simpler version of finite element method, it can be applied on 2D sections, requires limited computer resources and little training to use. Cross section studies based on finite strip method are compared with traditional section analysis as well as finite element method. The results indicates that, the finite strip method is equivalent to finite element method in predicting local buckling of prismatic structures, which is better estimates of the section load capacity compared current methods in CATIA based on fully plastic stress distributions.
Correlation of Electrochemical Impedance to Pool Boiling Behavior on Copper
Authors: Glavin Nicholas R. , Hunter Chad N. , Check Michael , Turner David , Fisher Timothy S.
Published: August 2012

Pool boiling studies were performed on roughened copper in a dilute saline solution while incorporating a three electrode electrochemical monitoring system. Electrochemical impedance at a frequency of 1000 Hz was monitored during nucleate boiling and through the transition point from nucleate to film boiling. During nucleate boiling, a steady increase in impedance was observed as the solid-vapor contact area increased. Impedance monitoring lead to the discovery of a critical impedance vector magnitude (|Z|) between the range of 1.85 kΩ-cm2 and 2.35 kΩ-cm2 where critical heat flux was most likely to occur. At the critical point just after nucleate boiling and beginning transition film boiling, an impedance vector magnitude spike was observed from approximately 2 kΩ-cm2 to 100 kΩ-cm2, due to the formation of a current impeding vapor layer encompassing the substrate surface. A phase angle decrease at this boiling regime transition point from −2.25 degrees to −30 degrees provides insight into a change in electrochemical circuit phenomena from a purely resistive to a somewhat capacitive electrochemical system.
Application of Finite Strip Method in Vehicle Design: Part 2 of 2—Post Buckling Analysis of Thin Walled Structures
Authors: Gandhi Umesh , Roussel Stephane , Furusu K. , Nakagawa T.
Published: August 2012

Thin walled parts of high strength steel, under compressive loads are likely to buckle locally, and then depending on geometry and material properties the section may continue to carry additional load. For the post buckling conditions the deformations are large but finite. Therefore we need to consider geometrical non linearity in the calculations. In this paper we are extending the linear finite strip element formulation to include geometrical non linearity. Method to derive secant and tangent stiffness matrix for non linear finite strip element is developed and then the element formulation is verified for inplane and center load on a plate using Newton Raphson solver. The new non linear finite strip element can be useful in estimating maximum load capacity (including post buckling) of thin walled structures from 2D data.
A Comparison Study of Power Minimizing Controllers for Active Magnetic Bearings
Authors: Yoo Seong-yeol , Noh Myounggyu
Published: August 2012

This paper describes a comparison study of power consumption of power minimizing controllers for active magnetic bearing (AMB) system. AMB system usually used bias currents in order to linearize force-current nonlinear relation. Using linearization with bias currents, AMB system achieves better dynamic performance and system linearity while bias currents always have to be consumed. The ohmic loss caused by them is one of the major energy losses of magnetic bearing systems. There are several researches to reduce constant power consumption by bias current. However, they all claim to reduce the power consumption of AMBs compared to the conventional PD-type controller, no study has been to compare these techniques. In this paper, we studied and implement previous researches with identical system frame for reasonable comparison. For comparison study, we derived simulation models using identical frame work and also built 2 degree-of-freedom (DOF) test bed.
Influence of Tibial Eminence Size on the ACL Injury
Authors: Bhuiyan Ariful I. , Hashemi Javad , Breighner Ryan E. , Slauterbeck James R.
Published: August 2012

The geometry of the tibial plateau as well as the femoral condyles are emerging as key parameters to be studied as anterior cruciate ligament (ACL) injury risk factors. In this paper, we study the role of tibial eminence size as a potentially important characteristic of the tibial plateau in loading and or protecting the ACL from injury. The volume of Tibial eminence in 52 uninjured controls (32 women and 20 men) and 44 anterior cruciate ligament-injured cases (23 women and 21 men) were measured using magnetic resonance images and 3-d image reconstruction using commercial software Analyze 9.0. We hypothesized that the Individuals with a small tibial eminence are at increased risk of suffering an anterior cruciate ligament injury compared with those with larger tibial eminences. Based on t-tests, we established that the uninjured controls had larger tibial eminences (p<0.05) compared with the injured cases. Biomechanically speaking a larger tibial eminence could prevent excessive medio-lateral movement of femur with respect to the tibia. A larger eminence could also protect the knee from large magnitude rotational movements. We suggest that future studies are needed to confirm this relationship and to evaluate the potential role of the tibial eminence size in the risk of ACL injury.
Application of the Poor Man’s Navier–Stokes Equations to Real-Time Control of Fluid Flow
Authors: Polly James B. , McDonough J. M.
Published: August 2012

Control of fluid flow is an important, and quite underutilized process possessing significant potential benefits ranging from avoidance of separation and stall on aircraft wings and reduction of friction factors in oil and gas pipelines to mitigation of noise from wind turbines. But the Navier–Stokes (N.–S.) equations governing fluid flow consist of a system of time-dependent, multi-dimensional, non-linear partial differential equations (PDEs) which cannot be solved in real time using current, or near-term foreseeable, computing hardware. The poor man’s Navier–Stokes (PMNS) equations comprise a discrete dynamical system that is algebraic—hence, easily (and rapidly) solved—and yet which retains many (possibly all) of the temporal behaviors of the full (PDE) N.–S. system at specific spatial locations. In this paper we outline derivation of these equations and present a short discussion of their basic properties. We then consider application of these equations to the problem of control by adding a control force. We examine the range of PMNS equation behaviors that can be achieved by changing values of this control force, and, in particular, consider controllability of this (non-linear) system via numerical experiments. Moreover, we observe that the derivation leading to the PMNS equations is very general, and, at least in principle, it can be applied to a wide variety of problems governed by PDEs and (possibly) time-delay ordinary differential equations such as, for example, models of machining processes.
Fasteners at Low Temperatures: Characterization and Methods for Design
Authors: Stephan Melanie , Weber Jens O. , Wuttke Ulrich , Berger Christina
Published: August 2012

Bolted joints are a major part of wind energy plants. Due to climatic conditions, they are often exposed to temperatures far below the freezing point. Together with the multiaxial state of stress, which results from the notch effect of the thread, and possible dynamic overloads during operation, sufficient ductility of the material is needed. The state of the art method to investigate the ductile behavior of fasteners is the Charpy pendulum impact test with a V-notched specimen. According to international standard DIN EN ISO 898-1 [1] respectively ASTM F568M-07 [2], fasteners made of carbon steel and alloy steel with a body centered cubic lattice structure can be used for temperatures down to 223 K (−50°C, −58°F) as long as a minimum impact energy of 27 J at 253 K (−20°C, −4°F) is met. As there are several disadvantages in using this test method for fasteners, a detailed examination of existing test methods and design concepts is necessary to find alternatives to the Charpy pendulum impact test. Extensive quasi-static and dynamic material tests were conducted on fasteners with property classes 5.6, 10.9 and 12.9 in a temperature range between 203 K (−70°C, −94°F) and room temperature 293 K (20°C, 68°F). Both mechanical properties and the influence of different specimen geometries were evaluated. Analytical concepts for the description of the low temperature applicability of different steels were analyzed.
Growing Large Nanostructured Superlattices by Sequential Activation of Self-Assembly
Authors: Zhao Zhouzhou , Lu Wei
Published: August 2012

We propose a mechanism to grow a large superlattice of phase domains from a continuum homogenous binary film by sequential activation of self-assembly. Self-assembly was initiated in a small mobile region, where atoms could diffuse, to form a seed pattern, Then the mobile region was shifted gradually. This process led to the formation of a long-rang ordered superlattice, regardless whether the seed was perfect or not. The pattern quickly improved to a perfect superlattice along with the sequential activation. We found that the scanning velocity can effectively control the domain pattern when the system is in a bistable state, which refers to a window of average concentration where two different superlattices can both stabilize. We demonstrated two schemes for large-scale high speed fabrication: alternation between scanning directions, using the superlattice created in each previous step as a large seed; and two dimensional growth.
Vehicle Concept Model Abstractions for Integrated Geometric, Inertial, Rigid Body, Powertrain, and FE Analyses
Authors: Osborne Gary , Prater Glen , Lesiv Rostyslav , Lamb David , Castanier Matthew
Published: August 2012

Vehicle analysis models of any kind have their basis in some type of physical representation of the design domain. Rather than describing three-dimensional continua of a collection of components as is done in detail-level CAD models, an architecture-level abstraction describes fundamental function and arrangement, while capturing just enough physical detail to be used as the basis for a meaningful design space representation and eventually, analyses that permit architecture assessment. The design information captured by the abstractions is available at the very earliest stages of the vehicle development process, so the model itself can function as a “design space for ideas”. In this paper we describe vehicle architecture abstractions appropriate for integrated model extractions suitable for geometric, inertial, rigid body, acceleration, braking, fuel efficiency, structural, and NVH assessments. Additionally, we discuss the requisite level of information required for each analysis type.
Optimized Expanding Microchannel Geometry for Flow Boiling
Authors: Miner Mark J. , Phelan Patrick E. , Odom Brent A. , Ortiz Carlos A. , Sherbeck Jonathan A. , Prasher Ravi S.
Published: August 2012

This study discusses the simulation of flow boiling in a microchannel and the predicted effects of channel geometry variation along the flow direction. Recent experimental studies have generated interest in expanding the cross-section of a microchannel to improve boiling heat transfer. The motivation for this geometry change is discussed, constraints and model selection are reviewed, and Revellin and Thome’s critical heat flux criterion is used to bound the simulation of separated flow in a heated channel, via MATLAB. Expanding channel geometry permits higher heat rates before reaching critical heat flux.
Finite Element Modeling and Analysis of Magnetorheological Dampers
Authors: Case David , Taheri Behzad , Richer Edmond
Published: August 2012

A magnetorheological fluid consists of a suspension of microscopic magnetizable particles in a non-magnetic carrier medium. In the absence of a magnetic field, the fluid behaves in a roughly Newtonian manner. When a magnetic field is produced in the same space, the microscopic particles suspended in the fluid become oriented and form chains along the magnetic flux lines, changing the fluid’s rheology. The orientation of these particle chains is crucial to producing the Bingham plastic behavior necessary for high strength-to-weight ratio magnetorheological dampers and actuators. This project uses COMSOL Multiphysics finite element software to examine the magnetic flux lines, field intensity, and non-Newtonian fluid flow within a magnetorheological damper. Several established and novel damper configurations are examined and modified to improve performance while minimizing power draw of the electromagnet.
Polymer-Based Flapping-Wing Robotic Insects: Progresses in Wing Fabrication, Conception and Simulation
Authors: Vanneste Thomas , Bontemps Alexandre , Bao Xiao Qing , Grondel Se´bastien , Paquet Jean-Bernard , Cattan Eric
Published: August 2012

This paper reports our recent progresses on the conception of polymer-based flapping-wing robotic insect, which involves the design, fabrication and characterization of novel all-polymer wing as well as their aeroelastic simulation. Accomplished MEMS technology allows the production of artificial wing with complex geometry as well as complete prototype with material mimicking the insect one. Key innovation of our design is the flexible resonant wing on an active bending mode coupled with passive torsion. Structural optimizations are reported aiming to increase the wing kinematics and the associated aerodynamic forces. Simultaneously to improve prediction and optimization of wing aerodynamic performance, a novel aeroelastic model is introduced using finite element method coupled with the quasi-steady analysis of insect flight. Although only basic wing shapes are here considered, the aeroelastic model exhibits promising capabilities for the evaluation of more realistic wing.
Derivation of Rigid Body Analysis Models From Vehicle Architecture Abstractions
Authors: Lesiv Rostyslav , Prater Glen , Osborne Gary , Lamb David , Castanier Matthew
Published: August 2012

Vehicle analysis models of every type have their basis in some type of physical representation of the design domain. Rather than describing three-dimensional continua of a collection of components as is done in detail-level CAD models, an architecture-level abstraction describes fundamental function and arrangement, while capturing just enough physical detail to be used as the basis for a meaningful representation of the design, and eventually, analyses that permit architecture assessment. The design information captured by the abstractions is available at the very earliest stages of the vehicle developing process, so the model itself can function as a “design space for ideas”. In this paper we describe a generalized process for analysis model extraction from vehicle architecture abstractions, and then apply that process to the specific case of rigid body response models. We also discuss implementation of a rigid body analysis engine that forms part of the analysis suite of a software package supporting all aspects of vehicle architecture design.