bluuebunny/crossref_metadata_2025 huggingface dataset:
Control Force Enhancement of Conical Shells Using Piezoelectric Macro-Fiber Composite
Authors: Li H. , Li H. Y. , Tzou H. S.
Published: April 2014

In piezoelectric coupled shells, the distributed actuation force usually consists of four components, including the membrane force and bending moment in the longitudinal direction, and the membrane force and bending moment in the circumferential direction. For commonly used bi-axial piezoelectric materials, such as PZT and PVDF, these four components may have phase difference of π or −π. This leads to force cancellation and reduces the overall control effectiveness. Supposing that one piezoelectric actuator is uni-axial, for example only d31 is not equal to zero, and then this actuator will generate actuation force with the first two components or the latter two, depending on the actuator configuration and the shell geometry/modes. Accordingly the force cancellation can be avoided or minimized. In this research, the Macro-Fiber Composite (MFC) actuators are used as uni-axial actuators. The dynamic equation of a conical shell is firstly given. Then the actuation force is derived based on the converse piezoelectric effect and thin shell assumptions. Three types of the MFC actuators are considered, including MFC-P1, MFC-P2 and MFC-P3. Case studies are performed to evaluate the distributed actuation forces. Both axial and transverse vibrations of the conical shell are formulated to study the force cancellation of various shell modes, and the payload effects are considered in the analysis. The results show that, by using the MFC actuators, actuation force can be enhanced because force cancellation is avoided. The force enhancement becomes even more significant for membrane dominated modes, such as axial modes of shells with heavy payloads.
Elastomer Seal With Frictional Contact: Analytical Solution
Authors: Al-Kharusi Moosa S. M. , Qamar Sayyad Zahid , Pervez Tasneem , Akhtar Maaz
Published: April 2014

Main motivation for this work is the need for performance evaluation of swelling (and inert) elastomer seals used in petroleum applications. Closed-form (analytical) solutions are derived for sealing pressure distribution along the elastomer seal as a function of material properties of the elastomer, seal geometry and dimensions, seal compression, and differential fluid pressure acting on the seal ends. Seal performance is also modeled and simulated numerically. Good agreement between analytical and numerical results gives confidence that the analytical solution can be used for reliable prediction of sealing behavior of the elastomer. Detailed investigation is then carried out to find out the effect of variation in seal design parameters on seal performance. For both analytical and numerical models, properties of the seal material at various stages of swelling are needed. Therefore, a series of experiments were also designed and conducted to study the effect of swelling on mechanical properties (E, G, K, and ν) of the sealing material.

One major finding is that sealing pressure distribution along the seal is not constant but varies nonlinearly depending on seal parameters and loading conditions, with maximum sealing pressure occurring at the center of the seal length. Longer seals are not necessarily better; after a certain seal length, sealing pressure reaches a steady value for a given set of field conditions. As expected, higher seal compression gives higher sealing pressure. Seal compression can be increased either by tubular expansion or by selecting an elastomer that swells more, or a combination of the two.

Experimental evaluation of swelling-elastomer seal performance can be very costly, and is not even possible in many cases. Numerical simulations, if validated, can be more convenient, but computational effort and cost can be high as simulations have to be run for each set of conditions. Analytical approach presented here not only gives an elegant closed-form solution, but can give reasonably accurate and much faster prediction of elastomer performance under various actual oil and gas field conditions.
Experimental Study on Evaporative Heat Sink
Authors: Kim Moo Joong , Kim Sangjin , Park Kuen Tae , Kim Hyun Jung , Kim Dong-Kwon
Published: April 2014

The heat sinks are used to dissipate heat from electronic and industrial systems. In the present study, in order to overcome limitation of traditional heat sink, we suggest and experimentally investigate new concept of heat sink which use evaporation of water. The heat sink is made from sintered copper plate and absorbs supplied water like sponges by capillarity-driven wetting. The absorbed water evaporates at the surface of heat sink and the surface temperature is dropped due to the latent heat of water evaporation. In this study, we experimentally compare the heat dissipation performance of the suggested heat sink with traditional heat sink. And we investigate the performance of heat sink made from the sintered copper plate with various particle radius and porosities. Finally, we find the fin spacing, at which the thermal performance is maximized.
Slurry Erosive Wear Behavior of Forged Al6061-CeO2-TiO2 Hybrid Composites
Authors: Chinnakurli Suryanarayana Ramesh , Khan Attaullah Ummar , Saheb Kumar , Kumar Apoorva , Rajput Manoj Kumar
Published: April 2014

Aluminium alloys are being widely used in naval applications owing to their excellent corrosion resistance and high formability characteristics. One of the most popular naval components is the tarpedo blade which makes use of forged aluminium alloy followed by anodizing surface treatment for corrosion protection. In recent years, there have been few attempts to replace the conventional aluminium alloys by their composites for the tarpedo blade applications. Literature review clearly says that CeO2 (Ceria) coating on aluminium and aluminium composites enhances their corrosion protection in aggressive marine environment. Further, there are reports suggesting that combination of CeO2 and TiO2 do yield better corrosion protection. However, there is no information on the work related to development of hybrid ceramic reinforced aluminium alloy matrices with CeO2 and TiO2 as particulate reinforcements for potential naval applications. In the light of above, the present work focuses on the development of novel Al6061-CeO2-TiO2 hybrid metal matrix composite by stir casting route followed by hot extrusion with an extrusion ratio of 8:1 at a temperature 550 °C and hot forging at 475 °C. The developed forged hybrid composites and the matrix alloy have been evaluated for microstructure, micro hardness and slurry erosion wear tests as per the ASTM Standards.
Wear Assessment of Large Aspect Ratio Silicon Microbearing Systems
Authors: Demiri S. , Boedo S. , Holsen L. S.
Published: April 2014

This paper addresses the wear characteristics of large aspect ratio (length-to-diameter) silicon microbearing systems using an enhanced experimental test rig. The test system is comprised of a rigid rotor which has been manually assembled onto a fixed hub to form the microbearing. CMOS-based lithographic and etching processes, including deep-reactive ion etching, are employed in the construction of the rotor and hub with length to diameter ratio of approximately 0.5 and radial clearance values in the range from 3.5 to 9.2 microns. The rotor is pneumatically driven by nitrogen gas at a constant supply pressure delivered through a rectangular microchannel.

A new methodology for measuring wear was developed by digitizing optical microscope images of the rotor system, and the rotor load was calculated from CFD models of the entire rotor-hub system. It was found that the tested silicon microbearings have an adhesion wear coefficient (based on the well-known Archard relation) which falls within a relatively narrow band bounded by previously published values for polysilicon materials tested at the macroscale and microscale.
A New Approach in Kinetic Modeling Using Thermodynamic Framework for Chemically Reacting Systems and Oxidative Ageing in Polymer Composites
Authors: Mohankumar K. V. , Kannan K.
Published: April 2014

A thermodynamic framework for chemically reacting systems is put to use in kinetic modeling of any chemical system with N species undergoing M reactions. A new approach of deriving kinetic models from a Gibbs potential, of multivariate polynomial function, is demonstrated with an example of single reaction system involving three species. Also, the usual first order kinetics is deduced as a special case in the example. The distinct advantages of the new approach lies in obtaining the evolution of concentrations of species, their individual chemical potentials and the specific Gibbs potential and is demonstrated for a single reaction system as an example. Oxidation in polymer composites is studied with a coupled reaction-diffusion model obtained using first order kinetics and is solved for a boundary value problem that predicts the concentration of species over space and time. Concentration of oxidized products is correlated with modulus of aged sample and degradation effects is calculated in case of simple torsion.
Study of Horizontal Axis Wind Turbine Blade in Virtual Wind Tunnel Simulator
Authors: Petrova Radostina , Lemu Hirpa G. , Larion Ioan
Published: April 2014

The article presents a 3D model analysis of a single blade for a horizontal axis wind turbine (HAWT). The analysis focuses on calculation of the wind pressure on the blade under different wind velocities and directions within the range of −45 deg. to +45 deg. using virtual wind tunnel simulators based on the Computational Fluid Dynamics (CFD) approach. Furthermore, the study deals with a linear modal analysis of the loaded blade subjected to aerodynamic loads, dead weight and angular velocity of the rotor. By modeling the blade as a thick shell, composite shell and through solid spatial finite elements (FE), a comparison of the final results regarding the modal characteristics of the blade is discussed. The objective of this comparison is to develop better understanding of the blade performance and find the best ways for computer analysis regarding the complexity of the model, computer resources and accuracy of the results. The authors consider this analysis and the corresponding conclusions as a crucial perquisite for further geometrical optimization of the flap-wise rigidity of the blade aiming reduction of the strain energy and the noise. The results of the study indicate that different solutions are possible to implement in achieving almost equal flap-wise rigidity along the blade.
Simulation of Discrete Blood Vessel Effects on the Thermal Signature of a Melanoma Lesion
Authors: Kandala Sri Kamal , Deng Daxiang , Herman Cila
Published: April 2014

The effect of the underlying blood vessel on the transient thermal response of the skin surface with and without a melanoma lesion is studied. A 3D computational model of the layers of the skin tissue with cancerous lesion was developed in COMSOL software package. Heat transfer in the skin layers and the lesion is governed by the Pennes bio-heat equation, while the blood vessel is modeled as fully developed pipe flow with constant heat transfer coefficient. The effect of various pertinent parameters, such as diameter of the blood vessel, lateral location of the blood vessel relative to the lesion, flow velocity of the blood, on the skin surface temperature distribution, have been studied in the paper. The results show significant influence of the underlying blood vessel on the temperature of the skin surface and lesion as well as on the surrounding healthy tissue. Thus, a need for development of evaluation criteria for detection of malignant lesions in the presence of blood vessels is is discussed.
Porous Media Modeling of Two-Phase Micro-Channel Cooling of Electronic Chips With Non-Uniform Power Distribution
Authors: Zhang Hua , Liu Jun Jie , Li Yubai , Yao S. C.
Published: April 2014

Compared to single phase heat transfer, two-phase micro-channel heat sinks utilize latent heat to reduce the needed flow rate and maintaining a rather uniform temperature close to the boiling temperature. The challenge in the application of cooling for electronic chips is the necessity of modeling a large number of micro channels using large number of meshes and extensive computation time. In the present study, a modified porous media method modeling of two phase flow in micro-channels is performed. Compared with conjugate CFD method, it saves computation effort and provides a more convenient means to perform optimization of channel geometry. The porous media simulation is applied to a real chip. The channels of high heat load will have higher qualities, larger flow resistances and lower flow rates. At a constant available pressure drop over the channels, the low heat load channels show much higher mass flow rates than needed. To avoid this flow mal-distribution, the channel widths on a chip are adjusted to ensure the exit qualities and mass flow rate of channels are more uniform. As a result, the total flow rate on the chip is drastically reduced, and the temperature gradient is also minimized. However, it only gives a relatively small reduction on the maximum surface temperature of chip.
Active Road Rumble Energy Harvesting Panels
Authors: Azzouz M. Salim , Chatterjee Abhishek , Rorabaugh Robert , Venegas Christopher , Duke Krista , Weller John Mark , Smith Chris
Published: April 2014

Vehicles traveling through busy roads and highways waste a huge portion of their kinetic energy. Up to five percent of the car’s energy is lost due to braking. In an effort to save energy it is possible to harvest some of this lost energy through a mechanical device built into the road. With over 1 billion cars, there is a huge potential for a man made untapped energy to be collected and harvested. This presentation focuses on designing a mechanical system that collects the energy of cars passing over a depressible flapping road rumble panel. As the car passes over the flap, the panel depresses and turns a directional shaft. The energy of many panels is collected and is summed up in a continuously turning flywheel. The collected mechanical energy can then be converted into electrical energy. The panels would be located where car drivers encounter deceleration ramps, when approaching a stop sign or entering a toll plaza. The analysis of this active road rumbles concept involved 1) designing a prototype using a computer drawing software such as SolidWorks, then 2) modeling the system mathematically to figure out all the important and intervening parameters factoring in the expression of the equation of motion of such systems, and then finally 3) building a physical prototype to analyzes the performances of such systems. The SolidWorks drawings for the model have been created. The dynamical model used free body diagrams and Newton’s second laws to determine the different loads and the equation of motion of the road rumble system. The mathematical model took into consideration the parameters of a shock absorber with a spring/mass/damper system. The kinematic equations of the shaft and flywheels were used to determine the speed and acceleration of the power train. A physical prototype was tested manually for time and frequency responses. It has been found that the energy collecting flywheel is lightly damped and loses a small part of its energy to friction. A feasibility study was conducted to evaluate the economic viability of such system. The harvested energy was estimated by measuring the RPM of the flywheel, and it was found that such system have an acceptable return on the investment. It is envisioned that such harvesting energy systems can be used in many ways one of them is to empty a huge offshore silo tank filled with sea water and producing peak electrical energy by allowing the sea water back into the silo through a hydraulic turbine.
Bioreactor Development for Cultivating Tenocytes on Collagen Foils Supported by Constitutive Modelling
Authors: Willenberg Wolfgang , Stoffel Marcus , Weichert Dieter
Published: April 2014

For medical applications, it is desirable to cultivate tendon cells. In addition to the many biochemical requirements for successful cultivation, mechanical stimulation also plays an important role. Especially, it is well known that tendon cells de-differentiate quickly if they are not put under physiological conditions. For this reason, a new bioreactor for the investigation and cultivation of tenocytes is developed, in which tenocytes are seeded on a carrier material. To be able to identify the real loads the tenocytes are subjected to, the material properties of the carrier material are found by performing material tests followed by a numerical analysis.
Energy Transport and Thermal Stress Formation in Hybrid Laser-MIG Welding
Authors: Zhou Jun , Khalilollahi Amir , Tsai Hai-Lung
Published: April 2014

This study is focusing on understanding the thermal stress formation in hybrid laser-MIG welding which has been gaining a lot of interests due to its many advantages over laser welding. Thermal stress formation is tightly associated with heat and mass transfer in hybrid laser welding, so accurate analysis of heat transfer process in the welding process is critical to correctly predict thermal stress information and residual stress in hybrid laser welds. In this study, a comprehensive heat and mass transfer model analyzing the energy, mass, and momentum transport processes in hybrid laser-MIG welding is successfully integrated with a mechanical model to study thermal stress formation in hybrid laser-MIG welding and residual stress in final welds as well. High compressive stress is found to exist on the top surface of the weld which might cause irregular welds topology and high tensile residual stresses were found in some locations in the final weld. This proposed study can be used as a foundation to further understand the thermal stress formation mechanisms in welding and to provide an efficient way to optimize the hybrid laser-arc welding process.
Study of Combined Heat and Mass Transfer From Fins Using Non-Dimensional Finite Element Formulation
Authors: Pashah Sulaman , Zubair Syed M. , Arif Abul Fazal M.
Published: April 2014

The use of dimensional analysis and dimensionless parameters is very common in the field of heat transfer. The paper presents a non-dimensional finite element capable of modeling combined heat and mass transfer from fins. The aim of the formulation is to get solution of the fin problems that do not have a closed form solution. The performance of a fin is described through its efficiency and numerous closed form solutions for fin efficiency under combined heat and mass transfer are available in the literature. Deriving a closed form solution for geometric or material complexities is somewhat a difficult task. An example is variable profile composite fin. A composite fin is composed of base material or substrate with a coating layer. Finite element approach can handle such complexity with relatively ease, Therefore the main objective is to developed formulation for mass transfer problems. The formulation is derived in dimensionless form to extend the applicability of finite element results to a class of problems with same governing dimensionless parameters. The derived formulation is then applied to study the combined heat and mass transfer for variable profile composite fins under fully wet condition.
Sound Radiation Analysis of a Longwall Cutting Drum
Authors: Yang Junyi , Camargo Hugo E. , Yantek David S.
Published: April 2014

Operators of longwall mining systems experience sound levels of 93–105 dB(A) and receive noise exposures that place them at risk of noise-induced hearing loss. To address the problem, the National Institute for Occupational Safety and Health (NIOSH*) Office of Mine Safety and Health Research (OMSHR) has conducted research to develop engineering noise controls for longwall systems. In previous field surveys, the sound radiated by the cutting drums was identified as a major hazard, especially considering their close proximity to the operators. Cutting drums are complex structures consisting of curved metal pieces welded together, and NIOSH has used modeling and simulation to characterize the acoustic properties of this structure. Based on a finite element (FE) model of the drum, the boundary element method (BEM) was used to predict the sound radiated from the vibrating drum due to an excitation force applied to one of the cutting bits. Simulations were used to examine the following with respect to the radiated sound power: (1) the ramifications of adding the welds to the model rather than assuming direct attachment between the metal components; (2) the effect of weld stiffness; (3) the relative contributions of the vanes and the cylindrical part of the drum; and (4) the sensitivity to the direction of the applied force. Parametric studies have shown that including the weld in the finite element model has a significant effect on the predicted sound power level, while varying the weld Young’s modulus by 20% does not radically change the sound radiation. Panel contribution analysis indicates that the vanes contribute much more to the total sound power level, as compared to the cylindrical part of the drum. Consequently, it is expected that damping treatments would be most effective at controlling noise radiation if applied to the vanes rather than to the cylindrical portion. Finally, case study results show that the sound power levels are most sensitive to the tangential and bending forces above 500 Hz. For frequencies below 500 Hz, the sound power level is most sensitive to axial and bending forces.
Design of a Damper for a Suspension System via Evolutive Optimization
Authors: Duchanoy Carlos A. , Moreno-Armendáriz Marco A. , Cruz-Villar Carlos A.
Published: April 2014

In this paper a dynamic optimization methodology for designing a passive automotive damper is proposed. The methodology proposes to state the design problem as a dynamic optimization one by considering the nonlinear dynamic interactions between the damper and the other elements of the suspension system, emphasizing geometry, dimensional and movement constraints. In order to obtain realistic simulations of the suspension, a link between a Computer-Aided Engineering Model (CAEM) and a multi-objective dynamic optimization algorithm is developed. As design objectives we consider the vehicle safety and the passenger comfort which are represented by the contact area of the tire and the vibrations of the cockpit respectively. The damper is optimized by stating a set of physical variables that determine the stiffness and damping coefficients as independent variables for the dynamic optimization problem, they include the spring helix diameter, the spring wire diameter, the oil physical characteristics and the bleed orifice diameters among others. The optimization algorithm that we use to solve the problem at hand is a multi-objective evolutive optimization algorithm. For this purpose we developed a parameterized model of the damper which is used to link the CAE tools and the optimization software, thus enabling fitness evaluations during the dynamic optimization process. By selecting the physical characteristics of the damper as design variables instead of the typical stiffness and damping coefficients, it is possible to consider important design constrains as the damper size, movement limitations and anchor points. As result of the proposed methodology a set of blueprints of non dominated Pareto configurations of the damper are provided to the decision maker.
Validations of Virtual Animal Model for Investigation of Shock/Blast Wave TBI
Authors: Tan X. G. , Przekwas Andrzej J. , Long Joseph B.
Published: April 2014

Complementary to animal testing and analysis of clinical data, a validated anatomy and physiology based mathematical models can provide capabilities for a better understanding of blast wave brain injury mechanisms, animal-human injury scaling, assessing and improving protective armor. We developed the 3D “virtual” animal models for multi-scale computational simulations of blast induced injury. A multi-scale modeling tool, CoBi, has been adopted for the analysis of blast wave primary TBI mechanisms and coupled biomechanics events. The shock wave over a rat in a shock tube was modeled by the CFD method. The primary biomechanics FEM study uses anatomic based animal geometry with a high resolution brain model. The virtual rat model has been validated against recently collected data from shock tube tests on rodents, including pressure time history in the free-stream and inside the rat brain. The model has been used to conduct parametric simulations to study the effect of animal placement location in the shock tube, and different loading orientations on the rat response. We also compared the rat brain biomechanical response between simulations of a free-to-move and a protected or constrained rat under the same shock tube loading to identify the role of body protection and head movement and on the rat TBI. The implications of these results suggest that virtual animal model could be used to predict the biomechanical response in the blast TBI event, and help design the protection against the blast TBI.
Enhancing Model Reuse Through 3D Annotations: A Theoretical Proposal for an Annotation-Centered Design Intent and Design Rationale Communication
Authors: Dorribo-Camba Jorge , Alducin-Quintero Gerardo , Perona Pascual , Contero Manuel
Published: April 2014

The long term goals of this research are to study the effectiveness of CAD 3D annotation techniques to support the explicit communication of design intent and rationale, and to analyze the impact of the annotations in the alteration and reutilization of 3D models in a product design context. Towards these goals, we are initially examining the formal annotation practices defined by model-based standards such as ASME Y14.41-2012 and ISO 16792:2006, and their implementation in current CAD systems. This paper presents a prototype implementation of a module to automatically extract textual information from annotated 3D CAD models. Automated extraction of data annotation can be used to analyze both the content and the quality of the annotations with the purpose of determining what makes annotations effective and ultimately communicating design intent. The architecture of a system designed to manage and manipulate this information is also described and analyzed.
Driveline Dynamics Simulation and Analysis of the Dry Clutch Friction-Induced Vibrations in the Eek Frequency Range
Authors: Senatore Adolfo , Hochlenert Daniel , D’Agostino Vincenzo , von Wagner Utz
Published: April 2014

Vibrations that arise during the slip phase of the clutch in the driveline of a motor vehicle yield to poor ride quality and result in discomfort and noise. The control systems in modern automated manual transmission systems couldn’t provide good improvement of vehicle longitudinal dynamics during gearshifts without a deep knowledge of the driveline model and its stiffness and damping parameters, along with the frictional conjunction between its main subparts.

In this paper an original 5-degree of freedom mathematical model of the dry clutch mechanism is presented with the intention of studying the excitation in a passenger car driveline of torsional vibration by frictional actions during the slip phase of the engagement. Furthermore, the analysis aims to deepen about the coupling between pressure plate wobbling and torsional motions in order to improve the current understanding of the excitation mechanisms in the frequency region of the so-called “eek noise”, 250–500 Hz. The results of this work substantiate that enhancing of torsional motion in the characteristic frequency range of the “eek sound” occurs even regardless of the rigid wobbling motion of the pressure plate and underline the need to include the non-linear characteristic of the clutch cushion spring in the simulation of such a phenomenon.
Optimization of Wind Turbine Airfoil With Good Stall Characteristics by Genetic Algorithm Using CFD and Neural Network
Authors: Djavareshkian Mohammad H. , Latifi Amir
Published: April 2014

In this research, optimization of a wind turbine airfoil is done by Genetic Algorithm (GA) as optimization method, coupled with CFD (Computational Fluid Dynamics) and Artificial Neural Network (ANN). A pressure-based implicit procedure is used to solve the Navier-Stokes equations on a nonorthogonal mesh with collocated finite volume formulation to calculate the aerodynamic coefficients. The boundedness criteria for the numerical procedure are determined from Normalized Variable Diagram (NVD) scheme and the k–ε eddy-viscosity turbulence model is utilized. ANN has been used as surrogate model to reduce computational cost and time. Single objective and multi objective optimization of wind turbine airfoil have been performed and the results of optimization are presented. To reduce the number of design variables and producing a smooth shaped airfoil, modified Hicks-Henne functions are used. In this process, the Eppler E387 airfoil has been applied as the base airfoil. Angle of attack varies from 0 to 20 degrees and Reynolds number of the flow is 460000.
CO2-Filled Vertical Geothermal Boreholes: Modeling and Application
Authors: Eslami-Nejad Parham , Ouzzane Mohamed , Aidoun Zine
Published: April 2014

In the context of extremely cold or hot climates, ground coupled heat pumps offer several environmental and energy efficiency advantages over conventional methods for heating and cooling of buildings and they are increasingly used in most near-zero and net-zero energy buildings. However, the high initial cost of the ground loop portion (geothermal boreholes) has often raised the question on the economical competitiveness of the system. In the present study, a geothermal borehole is proposed in which two-phase carbon dioxide (mixture of liquid and vapor) exchanges heat with the ground to improve the thermal performance of the borehole and thus to reduce borehole length. Carbon dioxide shows several cost and environmental advantages. Moreover, it offers superior thermophysical properties and heat transfer characteristics.

A numerical model has been developed to study the complex thermal behavior of a two-phase CO2-filled vertical geothermal borehole. The model can handle both two-phase and single-phase conditions along the borehole length. An explicit solution for fully coupled conservation equations of mass, momentum and energy as well as an equation of state are applied. The model accounts for the thermal interaction among the pipes and it predicts the fluid temperature, pressure and two-phase quality profiles. It is used to assess the thermal performance of the CO2-filled secondary loop geothermal borehole operating in heating mode. Results indicate that the proposed borehole offers superior performance due to the relatively high two-phase heat transfer characteristics of CO2.
An Adaptive-Grid Projection Method for High Density Ratio Interfacial Flows
Authors: Gómez Pablo , Zanzi Claudio , Palacios Julián , Hernández Julio , López Joaquín
Published: April 2014

A graded-adaptive grid projection method to solve the Navier-Stokes equations for incompressible interfacial flows characterized by large density ratios is presented. The numerical model is similar to the one we proposed in [7] and extended to 3D problems in [8].

The free surface is described using a level set method. A Godunov-type method and a Crank-Nicholson temporal discretization scheme are used to solve the advection equation of the level set function and to update of the momentum equation. The reinitialization procedure of the distance function is based on solving a hyperbolic equation to steady state using third-order Runge-Kutta and fifth-order WENO schemes.

The conservation equations are discretized on a rectangular adaptive grid with an octree data structure and the pressure stored at the grid cell vertices. In order to avoid spurious pressure oscillations, the velocity components are stored at the cell edges. This new storage scheme combines the advantages of vertex-based schemes, in which the nodes where the pressure is stored are aligned, and cell center-based schemes, which avoid pressure-velocity coupling problems.

The numerical model incorporates a continuous surface tension model based on the balanced-force algorithm proposed in [6]. A special treatment of T-nodes (nodes located at vertices, edges or faces of cells belonging to two different refinement levels) is proposed that considerably improves the efficiency of the method.

Several tests in two and three dimensions have been carried out to assess the accuracy and efficiency of the proposed method. In this work we present some numerical results for a 3D kinematic test, which are compared with those obtained by other authors. We also present results for the impact of a drop of water onto a liquid surface, which are compared with experimental visualization results.
A Novel Additive Manufacturing File Format for Printed Electronics
Authors: Panhalkar Neeraj , Paul Ratnadeep , Anand Sam
Published: April 2014

Additive Manufacturing (AM) based Printed Electronics (PE) is an emerging technique where electronic components and interconnects are printed directly on substrates using a layered technique. The direct printing of the electronic components allows large scale and ultra-thin components to be printed on a wide variety of substrates including glass, silicon and plastic. These attributes make AM based Printed Electronics an invaluable manufacturing technique in the area of electronic sensors and sensor networks where thin, flexible and rugged form factors are very important. However, currently this technology is a labor intensive and manual process with the machine operator using his experience and judgment to slice the CAD file of the part to create 2D layers at different levels. This manual process increases the overall production time as well as the cost of the product and also results in inconsistent quality of parts.

A major challenge faced by existing AM based Printed Electronics users for automating this process is the lack of a standard input file format that can be used by different PE machines for producing the components in layers. To leverage the capabilities of both AM and PE processes, a new file format based on the Constructive Solid Geometry (CSG) technique is proposed in this research paper. This file format data will not only include CAD data in the form of CSG primitives and Boolean representation but will also include manufacturing information related to the AM based PE process. The manufacturing information embedded within this new format will include data about the location of the different electronic components such as interconnects, resistors, capacitors, inductors, transistors, memory and substrate, and the materials required for the different components part. Different circuit board components will be represented as primitives or a combination of primitives obtained using CSG technique. In addition to the new file format, a slicing algorithm will also be developed which can be used to create the layers automatically using user inputs. The proposed file format and the slicing algorithm will be explained with the help of a case study.
Effect of Including a Fetus in the Uterus of Pregnant Occupant Model in Crash Test Simulations
Authors: Acar B. Serpil , Moustafa M. , Acar Memis
Published: April 2014

Motor vehicle accidents are the largest single cause of accidental death and the leading cause of traumatic injuries for the pregnant occupant and her fetus. Computational pregnant occupant modeling has a role to play in the investigation of the risk of fetal injuries and mortality in crash test simulations. Effective investigation depends on realistic representation of pregnant occupant and her fetus in a virtual environment. However, known pregnant occupant models normally do not include a fetus in the uterus. ‘Expecting’, the first computational model of a pregnant occupant with a fetus, is used in the current research. The model has a detailed multi-body representation of the fetus as well as finite element uterus and placenta.

In this paper, the effect of including the fetus in the uterus of the pregnant occupant model is investigated using ‘Expecting’ in crash test simulations. Previously, drop test simulations with and without a fetus showed that, the presence of fetus in the uterus suggests higher risks to the fetus. Using the pregnant occupant model, ‘Expecting’, with and without a fetus, provides more realistic simulations to explore the role of inclusion of fetus in the uterus. Five frontal impact speeds, 15, 20, 25 30 and 35 kph with varying levels of restraint system including ‘seatbelt and airbag’ (ie fully restrained), ‘seatbelt only’, ‘airbag only’ and ‘no restraint’ are used in the simulations. Maximum strains developed in the uteroplacental interface with and without a fetus are compared. The effect of including a fetus in the pregnant occupant model is discussed.
Hysteresis Strain Energy Behavior of Al6061-T6 With Multi-Fatigue Load Levels as Applied to an Energy-Based Fatigue Life Prediction Method
Authors: Letcher Todd , Nesaei Sepehr , Auen Cody , Nielsen Matt , Delfanian Fereidoon
Published: April 2014

Fatigue testing is a time and resource-consuming task. Historically, SN testing was conducted at many stress levels on simple representative specimen in order to determine an SN curve, which could then be used to design a component from the same type of material. Recently, an energy-based fatigue life prediction method has been in development. The goal of this method is to quickly determine a material’s fatigue characteristics using simple test procedures. The main theory behind the energy-based fatigue life prediction method is that the strain energy in a monotonic tensile test is equal to the cumulative hysteresis energy of a cyclic test. This theory has always been tested using a single stress level on each specimen. The hysteresis loop information was then used to make fatigue life predictions at other stress levels. Further testing has been done to learn more about the hysteresis energy behavior throughout the lifetime of a specimen, but only for a single stress value. In this study, several stress levels were tested on a single specimen. This new information will help make fatigue life predictions by completely removing the difficult and inconsistent process of determining experimental curve fit coefficients traditionally used in the energy-based fatigue life prediction method.
Heat Transfer Characteristics of Three-Dimensional Surface Roughness in Nuclear Fuel Rod Bundles
Authors: Najeeb Umair , Carrilho Leo A. , Khan Jamil A.
Published: April 2014

This paper presents convective heat transfer results for enhanced surface rod bundles for a pressurized water nuclear reactor (PWR). The experiments, to determine the single-phase heat transfer characteristics, were performed in a Single Heater Element Loop Tester (SHELT). The heater element simulates a single fuel rod for PWR. In this experimental investigation, the effects of enhancing the outer surface roughness of a simulated nuclear fuel rod bundle were studied. The outer surface of the simulated fuel rod was created with a three-dimensional (Diamond-shaped blocks) surface roughness. The simulated rod was made of Inconel 615, and was supported by Nickel 200 rods. Joule heating was supplied to the rod by passing electric current through the rod. The rod had an outside diameter of 9.5 mm and wall thickness of 1.5 mm, placed in a test-section made of 38.1 mm inner diameter aluminum pipe with a wall thickness of 6.35 mm. Tests were conducted for Reynolds numbers ranging from 105 to 106. Enhancement in heat transfer coefficient at all Re was recorded. The maximum heat transfer coefficient enhancement recorded was 86% at Re = 4.18×105.
Definition of a Protocol for Implementing Lean Production Methodology in Textile and Clothing Case Studies
Authors: Costa Maia Laura , Carvalho Alves Anabela , Leão Celina P.
Published: April 2014

This paper presents a protocol used in case studies with the objective to validate a Lean Production methodology in Textile and Clothing Industry (TCI) in North of Portugal. The methodology was developed under a Doctoral Program on Industrial Engineering and Systems. During the development of the methodology, the TCI contextualization was studied in parallel with the development of a survey applied to the TCI companies. The development of the methodology (structured in three phases) was followed by its validation in case studies.

Thus, this paper objective is to describe and explain the case study designed and conducted to attain feedback from companies. These case studies demanded a protocol constituted by an overview of the project, the field procedures (meetings and visits, interviews, questionnaires and checklist form), the preliminary questions of the project and the guide for the reports from the case studies. From the field procedures, the interviews was the first instrument used and it allowed the identification of the needs of change, the workers and management role in this change, the expected and achieved results. These preliminary results are presented in this paper. The questionnaire, adapted from others studies, would be used for a better context in the national framework and it would be applied in a following phase as the checklist. It will enable the data and metrics collection related with several aspects, namely work ergonomic conditions. This protocol will allow the knowledge of the work environment for a good implementation of the Lean Production.
Design of Phononic Materials Using Multiresolution Topology Optimization
Authors: Vatanabe Sandro L. , Silva Emilio C. N.
Published: April 2014

In this work the Multiresolution Topology Optimization (MTOP) scheme is investigated to obtain high resolution designs of phononic (elastic) materials, focusing primarily on acoustic waveguides. We demonstrate via numerical examples that the resolution of the design can be significantly improved without refining the finite element mesh. The first one is the simplest case where one might be interested in maximizing the energy reaching certain parts of the domain. The second and more interesting example is the creation of different propagation patterns for different frequencies, thus creating smart filters. The results demonstrate the power and potential of our computational framework to design sophisticated acoustic wave devices.
Interfacial Shear Strength of Banana Fiber in Low-Density Polyethylene
Authors: Weed Joshua D. , Jordan William
Published: April 2014

The increasing social pressure for biodegradable, sustainable, and environmentally-friendly products has launched the use of natural fibers in fiber reinforced polymer composites. Unfortunately, due to the integration of organic material in thermoplastic components, the fiber-matrix interfacial bonding is poor. While the organic material is hydrophilic, able to absorb water, the majority of polymer matrices are hydrophobic, unable to bond with water. The interfacial shear strength, a quantity to measure this bonding, has been shown to be improved through morphological and chemical treatment. In this context, the interfacial shear strength of banana fiber in low-density polyethylene has not been fully characterized. The aim of this study is to identify and optimize the interfacial shear strength of banana fiber in a polymer matrix through a polymer-compatibilization technique. For characterization of the fiber-matrix interfacial bonding, a commonly used micromechanical technique, the pull-out test, is used. While these initial results range from 0.4 MPa to 1.5 MPa, multiple samples exhibit greater than 30% improvement in interfacial bonding. The results reveal a need for a more exact measurement method; however, they also reveal the potential use of polymer-compatibilization as a replacement to fiber-modification treatments.
Vulnerability, Uncertainty and Probability (VUP) Quantification of a Network of Interacting Satellites Using Stochastic Petri Nets (SPN)
Authors: Einafshar Atefeh , Sassani Farrokh
Published: April 2014

A new approach to Vulnerability, Uncertainty and Probability (VUP) quantification procedure using Stochastic Petri Nets within a network of interacting satellites is presented. A Stochastic Petri Net based model is developed to quantify VUP in a network of interacting satellites. Three indicators are proposed to determine the VUP definitions in interacting network of satellites. The proposed VUP quantification scheme addresses a methodology which employs a Stochastic Petri Net for quantitative analysis of the behavior of the network. With the random variables associated with the Petri Net transitions, the dynamic behavior of the cooperating satellites in a SPN model can be mapped onto a time-continuous Markov chain with discrete state space. After generating a Markov Stochastic Petri Net model, the probability of a given condition in the network at a specified time can be computed and quantified as well as the vulnerability and uncertainty of the system using the identified indicators.
An Analysis of an Impact of the Background Atmosphere on the Aluminum Brazing Joint Formation
Authors: Yu Cheng-Nien , Hawksworth Doug K. , Sekulic Dusan P.
Published: April 2014

This paper summarizes mapping of an impact of the background atmosphere on a brazed joint formation. The broad range of background atmosphere conditions was considered. Two main parameters include: (i) the oxygen content in the range of 20 ppm to 200,000 ppm, and (ii) the dew point temperature in the range of 225 K to 266 K. The metrics used to evaluate that impact involve multiple joint fillet topographical features. The assessment was performed following detailed brazeability studies of the experimental specimens. The experimental program has involved Controlled Atmosphere Brazing of a wedge-tee brazing sheet mating surface with a variable gap clearance (over the length of 50 mm), to a non-clad AA3003 sheet. Brazing was performed (i) without or (ii) with a coating of the potassium-fluoro-aluminate flux. The tests were performed in a transparent hot zone brazing furnace. The peak brazing temperature in all tests was at the 873 K level, with the ramp-up heating of less than 100 K per minute and a rapid quench in industrial grade Nitrogen.
Significance of Kinetotherapy in Rehabilitation Treatment of Osteoporosis
Authors: Pop Petru A. , Lazar Liviu , Marcu Florin M.
Published: April 2014

Osteoporosis is a systemic skeleton disease, characterized by a low bone mass and micro-architectural deterioration of bone tissue with consecutive increasing of fragile bones and susceptibility of fractures. Risk facture, advanced ages, family history, rheumatoid arthritis, low calcium intake, physical inactivity, and low body weight can lead to this condition. The aim of treatment in osteoporosis is to grow-up the bone mineral density of the skeleton and to increase resorption of formed bone, used diverse methods as medications, conservative measures, weight reduction, physical and occupational therapy, mechanical support devices and surgery. This paper presents a balneal-conservative treatment applied to 82 patients diagnosed with osteoporosis from Rehabilitation Clinical Hospital of Felix Spa in 2011–2012, which has combined with a kinetotherapy and medication treatment. The complex rehabilitation treatment involves balneal-physical-kinetic recovery treatment that must be periodical repeated every six months, while the subjects themselves at home followed the kinetotherapy with drugs between balneal-treatments at hospital. The significance of rehabilitation treatment for the osteoporosis patients is to rise both functional and independence level, and improving their quality life. DEXA, Qualeffo-41 Test, fragility fractures, difference of height patients, using the statistical analysis have performed the evaluation of trial. These results emphasized the efficiency of balneal-rehabilitation treatment with main accent on respect the kinetotherapy applied the osteoporosis patients. The future research will be focused upon the implementation of vibration therapy with balneal-conservative treatment on patients with osteoporosis to reduce the therapy time and improving the quality patients life.