bluuebunny/crossref_metadata_2025 huggingface dataset:
A Numerical Study of a Molten Aluminum for Investment Casting of 3D Cellular Metals
Authors: Mun Jiwon , Ju Jaehyung , Yun Byoung-Gwan , Chang Byung-Moon , Kim Doo-Man
Published: April 2014

Investment casting processes are influenced by a variety of parameters. Many researches considering viscosity as a constant have been conducted up to this point. In particular, however, viscosity with temperature change has not been much accounted for solidification and heat transfer simulation of molten metal in the investment casting process. In addition, analysis of behavior of metal flow as well as air gap problems for complex network structures have not been investigated much. The aim of this study is to build transient metal flow and velocity profile models considering temperature dependent viscosity in investment casting processes of cellular structures. In this study, a Computational Fluid Dynamics (CFD) modeling tool was used for metal flow and velocity profile in investment casting processing using User Defined Function (UDF) for temperature dependent viscosity. The results of the metal flow and velocity profile inside of the simple cylindrical geometry are represented. It is shown that for the validation of the numerical simulation, the velocity profile between analytical and numerical approaches showed very good agreement. Analytical approaches showed that velocity was reduced with the increase in viscosity, which is applied as a function of temperature. In particular, rapid decreasing in velocity was shown from under the melting temperature of the molten metal. There was no movement on metal flow at the room temperature. Numerical approaches showed that the liquid metal began to be solidified from the wall surface inside of the mold. For the same simulation time, it was shown that the metal flow in a cylinder that has 1mm diameter showed better fluidity rather than that of the cylinder that has 2mm diameter due to the increase in adhesion between liquid metal and the surface of the mold and surface tension between molten metal and air. The effective diameter by solidification is decreased with the time change.
Quality Aspects of Electrochemical Micro Drilling With Insulated Tool and Masked Workpiece
Authors: Singh Shweta , Jain V. K. , Choudhury S. K.
Published: April 2014

Electrochemical micro drilling (ECMD) is one of the sub-divisions of the electrochemical micro machining (ECMM) process. In the present work, a comparative study of ECMD with bare tool, insulated tool, and insulated tool with masked workpiece has been presented. Drilling of micro holes is done using copper wires of 500 μm tip diameter. These copper wires coated with varnish are easily available in the market. In ECMD, taper and undercut are produced in the hole. The effects of input parameters such as voltage, duty cycle, electrolyte concentration, feed rate and inter-electrode gap on the output parameters namely, taper angle and undercut have been studied. Empirical models have been developed. In the present paper, a new idea of insulated tool and masked workpiece has been presented. The present idea came out as the most effective method of minimizing both the taper angle as well as undercut. Photographic analysis of micro drilled hole in the workpiece has been carried out using Dino-Lite Digital Microscope.
Experimental Investigation on Electro-Discharge Deposition Process
Authors: Muralidharan B. , Chelladurai H. , Ramkumar J.
Published: April 2014

The demand for multifunctional micro parts is an ever increasing need for product miniaturization. Amongst the spectrum of micro manufacturing processes, Electro-Discharge Deposition (EDD) is a newly developing additive process to produce parts in micro scale. In EDD the tool and workpiece electrodes are connected to reverse polarity in order to remove material from anode which deposits on cathode surface. The advantage of EDD is, any conducting tool material can be deposited irrespective of its hardness on the specified conducting substrate. So far, limited work has been carried out to develop micro parts like micro cylinders, micro spiral structures, etc., by EDD. In this work an attempt has been made to study the effect of various process parameters like current, duty cycle, pulse on time, voltage and table feed rate in EDD using central composite rotatable design (CCRD). It is found from the experimental results that, current plays a significant role in deposition of tool material.
Vibration Effects on Surface Coke Deposition of Hydrocarbon Fuel at Supercritical Pressure Condition in Micro-Tubes
Authors: Fu Yanchen , Tao Zhi , Xu Guoqiang , Deng Hongwu
Published: April 2014

Experiments are performed to study vibration effects on surface coke deposition of aviation hydrocarbon RP-3 under supercritical pressure. The flowing RP-3 kerosene is stressed to 5MPa, and heated up from 127°C to 450°C in a stainless tube (1.8mm I.D., 2.2mm O.D., 1Cr18Ni9Ti) with a constant heat flux, and the mass flow rate is 3g/s. The working fluids flow downward through an 1800mm long tube. The vibration frequency is set from 100Hz to 600Hz, covering the main frequencies of the combustion chamber vibration when it works. Compared with stable condition, vibration effects have a distinct impact on the flow resistance and heat transfer.

The amount of coke deposition reduced under all different frequencies with the maximize decline of 40.46%. Moreover, restraining efficiency is proportional to the vibration energy. Besides, vibration enhanced the heat transfer, the coefficient of which comes to a wave crest at the zone of second-order modes of response to the peak area with the biggest vibration energy.
Modeling Thermal Radiation With Focus on Particle Radiation in Grate Fired Furnaces Combusting MSW or Biomass: A Parametric Study
Authors: Hofgren Henrik , Sundén Bengt
Published: April 2014

This parametric study shows that thermal radiation from particles, fly ash and char, can be highly relevant for estimating the radiative heat flux to surfaces in grate fired furnaces, especially to the hot bed. The large effects of particle radiative heat transfer come from cases with municipal solid waste (MSW) as fuel whereas biomass cases have moderate effect on the overall radiative heat transfer. The parameters investigated in the study were the fuel parameters, representing a variety of particle loads and size distributions, emissivities of walls and bed, and the size of furnace. The investigations were conducted in a 3-D rectangular environment with a fixed temperature field, and homogeneous distribution of gases and particles. The choice of boundary emissivity was found to be much more or equally important as the particle radiation effects, dependent if biomass or MSW, respectively, was used as the fuel. The effect of particle radiation increased with increasing furnace size, mostly evident in the change of the radiative source term and the heat flux to the bed. Compared to previous studies of particle radiation in grate fired combustion, this study used realistic particle mass size distributions for fly ash. Estimates of char mass size distributions inside the furnace were conducted and used.
Acoustic Wave Propagation in Saturated Porous Media
Authors: Pazdniakou Aliaksei , Adler Pierre M.
Published: April 2014

Numerical tools were developed which are able to address acoustic wave propagation in dry and saturated porous media. Lattice methods, namely the lattice Boltzmann method (LBM) and the lattice spring model (LSM), can be successfully used for this purpose. The media are discretized by elementary cubes which can be obtained by computed micro-tomography [1]. Numerical results with a good precision can be obtained even for coarse geometry discretizations. Reasonable computational resources are necessary to obtain the results. The program codes can be parallelized in order to work with large samples.
Research of Whirlpool Sound Radiation in Turbulence Coherent Structures
Authors: Li Xiaosa , Qian Zegang , Yang Qichao
Published: April 2014

The compressor aerodynamic noise consists of suction, exhausting noise, gas power noise and so on, and the exhausting noise is dominating. Gas which is compressed released instantaneously to form vortex injection noise and exhausting pulsation noise, yet will cause pipe vibration. Large Eddy Simulation model in fluid software FLUENT have been adopted to analyze unsteady flow field and the acoustic field and research unsteady vortex shedding and its noise radiation characteristics in compressor pipes. The results show that: the trailing edge vortex shedding phenomenon, interaction between separation vortex and the trailing vortex of downstream lead to a large gas pulsation which makes noise radiation enhanced in the compressor pipe flow field in screw compressor exhausting orifice. Combination turbulence and vortex-pair phenomena in coherent structures, based on the vortex sound equation, a mathematical model of vortex-pair acoustic radiation is established. Finally unit length sound power of the whirlpool is draw to lρ0U3M4.
Dynamic Analysis of a Dual-Mode CO2 Heat Pump With Both Hot and Cold Thermal Storage
Authors: Houbak-Jensen Lars , Holten Anders , Blarke Morten Boje , Groll Eckhard A. , Shakouri Ali , Yazawa Kazuaki
Published: April 2014

We investigated the dynamics of a transcritical CO2 heat pump system including hot and cold thermal storages, which makes up the concept “thermal battery”. The analytical model is used for the study of the dynamics of the system involving simultaneous supply of heating and cooling for buildings. The model includes the dynamics of the gas cooler, evaporator and the thermal storages, while the compressor and the expansion valve are considered quasi-static. The heat transfer in the dynamically modeled components is described by partial differential equations (PDEs) consisting of heat conduction, convection, and source terms. Each component is divided into a number of volumes adjusted according to the required precision and reasonable computational time. We applied two discretization schemes in order to find a numerical solution to the PDEs. The spatial discretization for the heat exchangers is performed by using the upwind scheme, where the fluid properties are individually calculated within each volume. Due to the discrete events in form of tapping and loading (or charging and discharging) of the heat storages, the discretization approach takes into account the sharp spatial transitions within the thermal storages. Therefore, the method of lines in combination with the Superbee slope-limiter was applied for the spatial discretization for high resolution calculation. The modeling approach results in a set of algebraic and ordinary differential equations (ODEs), hence the model becomes an algebraic differential equation problem, which we solved by using MATLAB solver ODE15s.

This extended model was used to simulate a dynamic response of the case with varying heating and cooling consumption over a period of 24 hours in a building. The heating and cooling energy consumption follow a sinusoidal and continuous pattern. The results include the effect on both the outlet temperatures and the system coefficient-of-performance (COP). The outlet energy from the hot storage and the cold storage is used for heating tap water and a chilled water space cooling application subject to temperature requirements. Dimensioning of both storages is crucial for obtaining the required temperatures. The model identifies the critical storage levels required to satisfy the periodic but out-of-phase combination of heating and cooling demands. The volume of the cold storage will have to be considerably larger than the hot storage due to the lower temperature difference.
Computational Study of Fuel Dilution Effect on the Soot Formation in Methane-Air Laminar Confined Diffusion Flame
Authors: Chowdhuri Achin Kumar , Mitra Arindam , Chakraborti Somnath , Mandal Bijan Kumar
Published: April 2014

Although diffusion flame is free from many problems associated with premixed flame, soot formation is a major problem in diffusion flame. The techniques of dilution of fuel or air with inert gases such as nitrogen and argon are used to decrease soot level in the flame. In this work, a CFD code has been developed to predict the flame height, soot volume fraction and soot number density in an axisymmetric laminar confined methane-air diffusion flame after diluting the fuel with nitrogen. The temperatures of the air and fuel at inlet are taken as 300K. Mass flow rate of the fuel stream is considered as 3.71×10−6 kg/s and mass flow rate of the air is taken as 2.2104×10−6 kg/s. The total mass flow rate through the central jet (fuel jet) is, however, kept constant. The radiation effect is also included through an optically thin radiation model. An explicit finite difference technique has been adopted for the numerical solution of reacting flow and two equations soot model with variable thermodynamic and transport properties. The prediction shows that flame height decreases with the addition of nitrogen to the fuel. Temperature of the flame is considerably reduced in the given computational domain. Both soot volume fraction and soot number density decrease with dilution by adding nitrogen in the fuel jet. The soot formation at different nitrogen dilution level of 0%, 10%, 20%, 30%, 40% and 50% are plotted and the soot get considerably reduced as the concentration of nitrogen is increased in the fuel stream.
Scaling Effect on Dynamic Impact Response of Structures in Fluid Fields
Authors: Guo Zhongheng , Sun Lingyu , Wang Taikun , Du Junmin , Li Han , Cheng Yi
Published: April 2014

At the conceptual design phase of a large-scale underwater structure, a small-scale model in a water tank is often used for the experimental verification of kinematic principles and structural safety. However, a general scaling law for structure-fluid interaction (FSI) problems has not been established. In the present paper, the scaling laws for three typical FSI problems under the water, rigid body moves at a given kinematic equation or is driven by time-dependent fluids with given initial condition, as well as elastic-plastic body moves and then deforms subject to underwater impact loads, are investigated, respectively. First, the power laws for these three types of FSI problems were derived by dimensional analysis method. Then, the laws for the first two types were verified by numerical simulation. In addition, a multipurpose small-scale water sink test device was developed for numerical model updating. For the third type of problem, the dimensional analysis is no longer suitable due to its limitation on identifying the fluid pressure and structural stress, a simulation-based procedure for dynamics evaluation of large-scale structure was provided. The results show that, for some complex FSI problems, if small-scale prototype is tested safely, it doesn’t mean the full-scale product is also safe if both their pressure and stress are the main concerns, it needs further demonstration, at least by numerical simulation.
Surface Tension Driven Kinetics of the Triple Line of a Liquid Metal Free Surface
Authors: Fu H. , Dong F. , Sekulic D. P. , Mesarovic S. Dj. , Krivilyov M.
Published: April 2014

Spreading kinetics of molten Al-Si alloy on both alumina and aluminum surfaces, driven by surface tension and retarded by viscosity, with or without significant impact of gravity, has been studied experimentally. Spreading takes place during a transient formation of the free liquid metal surface in a wedge-tee configuration corner between horizontal and vertical metal mating surfaces with a small Bo number. A high temperature optical dynamic contact angle measuring system has been used to monitor in real time in situ the free surface formation. Tests were performed under different oxygen concentration levels and at atmospheric pressure conditions, with a benchmark case involving ultra-high purity Nitrogen. An auxiliary study of the surface tension of the particular molten alloy considered has been performed under conditions of a large Bo number as well. These tests were performed over a flat non-wetting ceramic substrate of pure alumina (96%) using an optical sessile drop method. The former experiments resulted in capturing a 2-D configuration of the observed alloy liquid formation at elevated temperatures during a time evolution of the molten metal free surface spreading. The kinetics of the triple line movement at the vertical mating surface constitutes the main objective of the study. It is established that the triple line kinetics features a sequence of multiple, well defined spreading phases. These phases of the joint formation were identified, and the influential parameters were assessed. The power law spreading kinetics has been established. The experimental results show a good agreement with the hypothesized theoretical model.
Production, Characterization and Application of Meso-, Micro- and Nano-Scaled Surface Structured Devices for Boilers and Heat Exchangers
Authors: Beyer M. , Kölling A. , Kohn S. , Nowitzki M. , Sagasser H. , Hellwig U. , Sachno N.
Published: April 2014

In this paper we report on the investigations of 48 tubular and 3 planar meso-, micro- and nano-scaled surface structured devices for boilers and heat exchangers made of steel, copper and brass.

The tubular structured components are object of protective right in terms of industrial power tube (ip tube). Hexagonal types with sinusoidal structures and roughness values in the order of bts/dHyd = 0.3 used for heating of a fluid by a fluid proved to have a heat transmittance of k = 1737 W · m−2 · K−1 and to be increased by 47 % compared to the corresponding value of a smooth tube k = 1182 W · m−2 · K−1.

Dodecahedronal closed structured tubes with smaller roughness of bts/dHyd = 0.1 used for falling film evaporation showed a heat transmittance of k = 5130 W · m−2 · K−1 corresponding to an increase by 19 % depending on the Reynolds number Re between 7100 and 17600.

Types of micro-structured tubes with 1000000 straight pins per square centimeter investigated in boiling experiments with Solkatherm SDS 36 at 0.7 bar appeared to have a decreased temperature excursion by 21 %, while there is a 25 % greater boiling resistance at low heat fluxes of about 25 W.

Steam condensation experiments were performed using copper tubes fabricated both with meso-scaled structures and 1000 straight pins per square centimeter. At a subcooling temperature of ΔT = 60 K at 1.1 bar the heat flux density proved to be increased by 340 % to a value of k = 420 kW · m−2 · K−1 compared to the conventional component. In addition the formation of droplets with a diameter of 0.003 m was observed. The numerical calculation of the local heat transfer coefficient at the interior wall resulted in a value of αi = 11.4 kW · m−2 · K−1. Micro-scaled tubular devices with 3.3 million crossed pins per square centimeter made of copper were investigated with respect to heterogeneous catalysis of carbon monoxide under oxidizing conditions at 478 K and 1 bar. The achieved yield measured by CO conversion rate was equal to the unit value with a delay time of 17000 s due to an initial oxygen layer at the surface.

Prototypic air cooled hot gas coolers were developed, constructed and evaluated, configurated with steel tubes and a small number of conical structures with a roughness of bts/dHyd = 0.01–0.03. By experiments using a biomass gasification test facility the heat transmittance of one cooler model proved to be increased by 22 % to a value of k = 11 W · m−2 · K−1. The corresponding pressure loss was so small that the effectivity of the applied measures to enhance heat transfer had a value of about 10 %. Moreover the formation of deposits on the side of the raw gas was found to be suppressed by 40 % to a fouling rate of 1.1 Mas.-% of the initial freight.
Rapid Capture of Rare Cancer Cells Using a High-Performance Microfluidic Chip
Authors: Sheng Weian , Chen Tao , Tan Weihong , Fan Hugh
Published: April 2014

Rare circulating tumor cells (CTCs) are cancer cells that detached from either a primary tumor or metastatic sites. CTCs circulate into bloodstream and become the origin of metastasis, the spread of cancer to distant organs, which is the primary cause of cancer-induced death. This paper describes our development of a microfluidic chip with unique micropillar geometry for rapid capture of CTCs from whole blood. The microscope-slide-sized microchip contains tens of thousands of isotropically-etched elliptical micropillars, which enhanced the interactions between cells and chip surfaces. The microchip was coated with DNA aptamer, an antibody-like molecule which can specifically bind with their target cells. With optimized channel geometry and flow rate, the microchip yielded a capture efficiency of >95% and a purity of >81% when capturing leukemia cells from a cell mixture. Then, the device was applied to capture colorectal tumor cells from whole blood; as few as 10 tumor cells can be efficiently isolated from 1 mL blood in 28 min. We envision that this high-performance microchip is promising for the detection, enrichment and isolation of rare CTCs, and will open up new opportunities for cancer diagnosis and monitoring cancer treatment.
The Role of Epistemic Uncertainty of Contact Models in the Design of Mechanical Systems
Authors: Brake M. R.
Published: April 2014

Impact is a wide-spread phenomenon in mechanical systems that can have a significant effect on the systems dynamics, stability, wear, and damage. The simulation of impact in complex, mechanical systems, however, is often too computationally intensive for high fidelity finite element analyses to be useful as design tools. As a result, rigid body dynamics and reduced order model simulations are often used, with the impact events modeled by ad hoc methods such as a constant coefficient of restitution or penalty stiffness. The effect of epistemic uncertainty in the choice of contact model is investigated in this paper for a representative multiple-degree of freedom mechanical system. Five contact models are considered in the analysis: a constant coefficient of restitution model, a piecewise-linear stiffness and damping (i.e. Kelvin-Voight) model, two similar elastic-plastic constitutive models, and one dissimilar elastic-plastic constitutive model. The predictions of wear and mechanical failure are assessed for each of the contact models. The ramifications of the choice of the contact model for an optimization study of the system’s geometric design are also presented. These results emphasize the importance of choosing an accurate contact model when simulations are being used to drive the design of a system.
Establishment of a Wave Energy and Technology Lab to Promote the Experimental Study of Ocean and Wave Energy
Authors: Liu Yucheng , Pastor Jeremiah , Viera Raul J.
Published: April 2014

A wave generation system was built and equipped in the wave energy and technology lab at the University of Louisiana at Lafayette (UL Lafayette). The system can generate dynamic waves to simulate the ocean conditions in the Gulf of Mexico. This paper explains the design, construction, and validation of such system. With the installation of the designed wave generation system, the ocean and wave model produced in the Gulf of Mexico can be reproduced and simulated in the lab, which allows us to explore the ocean and wave energy in that gulf through experimental and computational approaches. A workshop of wave energy technology was organized in the lab to reach a broad audience and look for potential partnerships with industry and research community.
Validating the Critical Areal Density for a New Ballistic Armor Exhibiting Blunt Trauma Reduction
Authors: Bhat Advait , Jayakumar Balaji , Hanan Jay C.
Published: April 2014

Today there are several armor technologies for reducing penetration injuries. Some of the best technologies are light weight, but alone the trauma to the wearer remains significant. The areal density of a new Hybrid Composite Armor (HCA) maintaining compliance with level III NIJ 0101.06 standards was evaluated using ballistic testing and FEM. This new HCA has a multilayered composite design tailored for Behind Armor Blunt Trauma (BABT) reduction. Three areal densities of HCA were ballistic tested using 7.62 FMJ Lead Core projectiles and measurements of Back Face Signature (BFS) and V50 velocities were collected. For comparison, baseline monolith inserts of similar areal densities were also tested. A critical areal density was found to qualify for the standard while demonstrating a 29.4% reduction in BFS (and hence BABT) in comparison to its baseline. This armor design showed the greatest known propensity to reduce injury both due to the light weight and improved trauma performance compared to existing commercial designs. Numerical simulations in finite element code were carried out to validate with the experimental results. A method for evaluating change-in-velocity and volumetric stress distribution plots was presented using a mock HCA-P2 model. In the future, a similar FEA scheme can be used for predicting the ballistic limit and estimating improvements possible in BABT reduction for HCA concepts with relative design changes.
Dynamic Analysis of a Jack-Up Rig, SDOF Approach: Design Consideration — I
Authors: Godoy Francisco J. , Lorenzo Fernando
Published: April 2014

A jack up rig, such as those used for oil drilling in the Gulf of Mexico, is a dynamic sensitive system subjected to random and periodic environmental loads (wave, wind, current, etc.), in which the inertia forces cannot be ignored. However, a static load analysis approach can be justified only if an extra inertial load set, due to the dynamic effect response, is included in the analysis. The Society of Naval Architects and Marine Engineers, SNAME T&R 5-5A, “Guidelines for Site Specific Assessment of Mobile Jack-Up Units”[1], addresses the calculation of the inertial load set by using the classical Single Degree of Freedom (SDOF) analogy to calculate such dynamic effect.

This study evaluates how far apart crucial structural members’ stresses/loads obtained by using the SDOF analogy method are from those values obtained from a more realistic modal dynamic analysis. The analysis is performed for wave loads at different heights and frequencies such as those existing on extreme or severe design conditions as a storm. Although a jack up rig structure presents some non-linearities, especially in the legs-hull contact areas and the spud-cans interaction with the soil; a modal superposition analysis can be used if proper linearization is considered.

The results of this study for a jack show that the SDOF analogy method tends to underestimate the base shear loads for high wave periods and conversely overestimate some stresses on crucial members, such as the legs’ chords close to the hull for all the wave periods.

This study shows that the stresses on one of the legs’ chord of the most loaded leg, due to the dynamic effect produced by the harmonic loads calculated with the SDOF analogy developed in this study tend to be overestimated as the wave period decreases. Conversely, the calculation of the base shear of the structure employing a quasi-static analysis with inertial load set (ILS) as calculated in this study shows that the base shear forces difference between the modal dynamic analysis and the quasi static analysis tends to decrease as the periods of the wave decreases.
Virtual Tools for Safety and Ergonomic Evaluations of Electric Vehicle Architecture
Authors: Kulkarni Ambarish , Kapoor Ajay
Published: April 2014

Electric vehicles (EV’s) are alternative fuel technology in auto industry with wide acceptance across globe. This paper elaborates virtual methods used to as tool for safety and ergonomic evaluations of in wheel design using Switch Reluctance Motor (SRM). In our recent research, a unique design of in wheel design using SRM has been developed. Special advantages of this design include modularity, scalability, cost effectiveness, and easy installation. Easy installation of in wheel design architecture is one of the prime criteria, since it relates to changing of tyres in long runs. In the proposed passenger car, if work is carried out for maintenance issues, generally single operator (mechanic) dose tyre changing or wheel/brake servicing. Two validations are important, mainly safety of the operator; secondly design for assembly of motor, and tyre rims. As a part of this research, Virtual Reality (VR) based safety and ergonomic evaluation studies have been conducted for the in wheel design adaptations. The computational models and virtual modelling simulations using motion capture, Arena and EON reality mimicked live system environments, so as to validate effectiveness motor assembly and disassembly functionality using human as an interface.

Initial phase consists of schematic representations of models to evaluate conceptualisation for different designs. Based on schematics, SR motor and rim tyre models were developed and interfaced in VR environment. In second phase, vehicle topology was reverse engineered using hand held 3D scanner and converted to metafile for full scale model development. In third phase, motion capture was used with 20 camera systems to video record the existing human movements and rigid body such as tyre to develop live environment. Finally all three phases were interfaced together in VR environment to evaluate assembly and disassembly functions. Based on the validation of these, designs were fine tuned for effective assembly functionality. The VR based safety and ergonomic evaluation procedures were used for demonstration of wheel assembly disassembly functions by single operator. Similar context can be extended to other automotive design evaluations, without substantial prototype costs for safety and ergonomic evaluations.
Modelling and Analysis of the Effect of Angular Velocity and Acceleration on Brain Strain Field in Traumatic Brain Injury
Authors: Hoursan Hesam , Ahmadian Mohammad Taghi , Barari Ahmad , Beidokhti Hamid Naghibi
Published: April 2014

Traumatic brain injury (TBI) has long been known as one of the most anonymous reasons for death around the world. A presentation of a model of what happens in the process has been under study for many years; and yet it remains a question due to physiological, geometrical and computational complications. Although the facilities for soft tissue modeling have improved and the precise CT-imaging of human head has revealed novel details of brain, skull and the interface (the meninges), a comprehensive FEM model of TBI is still being studied. This study aims to present an optimized model of human head including the brain, skull, and the meninges after a comprehensive study of the previous models. The model is then used to investigate the effects of various sudden velocity-acceleration impulses on the strain field of the brain by using FE method. Next, the results are summed up and compared with an existing criterion on damage threshold in the brain during trauma. To reach this aim, a full geometrical model of a 30-year-old patient’s head has been generated from CT-scan and MR data. The model has been exposed to 20 angular velocity-acceleration pulses. Subsequently, the changes in the strain field have been compared with the results obtained in the previous studies yielding acceptable accordance with a major previous criterion. The results also show that certain criteria can be generated on the threshold of damage in the brain.
Damage and Failures of CGA/BGA Assemblies Under Thermal Cycling and Dynamic Loadings
Authors: Ghaffarian Reza
Published: April 2014

Commercial-off-the-shelf column/ball grid array packaging (COTS CGA/BGA) technologies in high-reliability versions are now being considered for use in high-reliability electronic systems. For space applications, these packages are prone to early failure due to the severe thermal cycling in ground testing and during flight, mechanical shock and vibration of launch, as well as other less severe conditions, such as mechanical loading during descent, rough terrain mobility, handling, and ground tests. As the density of these packages increases and the size of solder interconnections decreases, susceptibility to thermal, mechanical loading and cycling fatigue grows even more.

This paper reviews technology as well as thermo-mechanical reliability of field programmable gate array (FPGA) IC packaging developed to meet demands of high processing powers. The FPGAs that generally come in CGA/PBGA packages now have more than thousands of solder balls/columns under the package area. These packages need not only to be correctly joined onto printed circuit board (PCB) for interfacing; they also should show adequate system reliability for meeting thermo-mechanical requirements of the electronics hardware application. Such reliability test data are rare or none for harsher environmental applications, especially for CGAs having more than a thousand of columns.

The paper also presents significant test data gathered under thermal cycling and drop testing for high I/O PBGA/CGA packages assembled onto PCBs. Damage and failures of these assemblies after environmental exposures are presented in detail. Understanding the key design parameters and failure mechanisms under thermal and mechanical conditions is critical to developing an approach that will minimize future failures and will enable low-risk insertion of these advanced electronic packages with high processing power and in-field re-programming capability.
Waste Heat Recovery From the Exhaust of a Diesel Generator Using Shell and Tube Heat Exchanger
Authors: Hossain Shekh N. , Bari Saiful
Published: April 2014

The heat from exhaust gas of diesel engines can be an important heat source to provide additional power and improve overall engine efficiency. Bottoming Rankine Cycle (RC) is one of the promising techniques to recover heat from the exhaust. One derivative of RC known as Organic Rankine Cycle (ORC) is also suitable for heat recovery for moderate and small size engines as the exhaust heat content and temperature of these engines are low. To recover heat from the exhaust of the engine, an efficient heat exchanger is necessary. In this current research, a shell and tube heat exchanger is optimized by computer simulation for two working fluids, water and HFC-134a. Two shell and tube heat exchangers were purchased and installed into a 40 kW diesel generator. The performance of the heat exchangers using water as the working fluid was then conducted. With the available data, computer simulation was carried out using CFD software ANSYS CFX14.0 to improve the design of the heat exchanger for both fluids. Geometric variables including length, number of tubes, and baffle design are all tested separately. Using the optimized heat exchangers simulation was conducted to estimate the possible additional power generation considering 80% isentropic turbine efficiency. The proposed heat exchanger was able to produce 11% and 9.4 % additional power using water and HFC-134a as the working fluid at maximum working pressure of 15 and 40 bar respectively. This additional power results into 12% and 11% improvement in brake-specific fuel consumption (bsfc) by using water and HFC-134a respectively. This indicates that besides water, organic fluids can also be a suitable option to recover heat from the exhaust of diesel engine.
A Technique for the Measurement of Wall Shear Stress Based on Micro Fabricated Hot-Film Sensor
Authors: Sawada Takuya , Terashima Osamu , Sakai Yasuhiko , Nagata Kouji , Shikida Mitsuhiro , Hida Hirotaka , Onishi Kazuhiro , Ito Yasumasa
Published: April 2014

The objective of this study is to establish a technique for accurately measuring the wall shear stress in turbulent flows using a micro-fabricated hot-film sensor.

Previously, we developed a hot-film sensor with a flexible polyimide-film substrate. This sensor can be attached to curved walls and be used in various situations. Furthermore, the sensor has a 20-μm-wide, heated thin metal film. However, the temporal resolution of this hot-film sensor is not very high owing to its substrate’s high heat capacity. Consequently, its performance is inadequate for measuring the wall shear stress “fluctuations” in turbulent flows.

Therefore, we have developed another type of hot-film sensor in which the substrate is replaced with silicon, and a cavity has been introduced under the hot-film for reducing heat loss from the sensor and achieving high temporal resolution. Furthermore, for improving the sensor’s spatial resolution, the width of the hot-film is decreased to 10 μm. The structure of the hot-film’s pattern and the flow-detection mechanism are similar to those of the previous sensor.

Experimental results show that new hot-film sensor works as expected and has better temporal resolution than the previous hot-film sensor. As future work, we will measure the wall shear stress for a turbulent wall-jet and discuss the relationship between a large-scale coherent vortex structure and wall shear stress based on data obtained using the new hot-film sensor.
Practical Identifiability of the Manipulator Link Stiffness Parameters
Authors: Klimchik Alexandr , Caro Stéphane , Pashkevich Anatol
Published: April 2014

The paper addresses a problem of the manipulator stiffness modeling, which is extremely important for the precise manufacturing of contemporary aeronautic materials where the machining force causes significant compliance errors in the robot end-effector position. The main contributions are in the area of the elastostatic parameters identification. Particular attention is paid to the practical identifiability of the model parameters, which completely differs from the theoretical one that relies on the rank of the observation matrix only, without taking into account essential differences in the model parameter magnitudes and the measurement noise impact. This problem is relatively new in robotics and essentially differs from that arising in geometrical calibration. To solve the problem, several physical and statistical model reduction methods are proposed. They are based on the stiffness matrix sparseness taking into account the physical properties of the manipulator elements and also on the heuristic selection of the practically non-identifiable parameters that employs numerical analyses of the parameter estimates. The advantages of the developed approach are illustrated by an application example that deals with the stiffness modeling of an industrial robot used in aerospace industry.
Mathematical Modeling and Experimental Study of Hydrogen Production by Catalytic Steam Reforming of Methane
Authors: Sadooghi Parham , Rauch Reinhard
Published: April 2014

Steam reforming of methane in a packed bed reactor filled with Nickel based catalyst supported on Alumina, (Al2O3) is theoretically and experimentally studied and analyzed. State of the art Finite Element Method software, COMSOL Multiphysics is used to simulate a steady state two dimensional heterogeneous model, coupled with detailed reaction mechanisms modeling surface and gas-phase kinetics that takes into account the diffusion reaction phenomena inside the particles. The simulation results are compared favorably with experimental data. It is shown that strong axial and radial temperature gradients exist near the reactor wall The obtained results are important in design and optimizing of commercial reactors.
Actuators Orientation Influence in the Energy Consumption of the 3-PRS Manipulator
Authors: Herrero Saioa , Pinto Charles , Corral Javier , Altuzarra Oscar
Published: April 2014

In this work, a comparative study of the energy needed to run a 3-degree of freedom (DOF) parallel manipulator (PKM) for two different configurations of the inputs and two different transformation matrices for a concrete trajectory is presented. The 3-PRS is a PKM of low mobility, i.e., it has less than 6-DOF and when the main motion takes place, unexpected motions in the constrained DOF appear. These are parasitic motions. As previous studies show, these parasitic motions lead to less accuracy and, therefore, they are not desired from the point of view of the kinematics. It would be of great interest to know if the parasitic motions affect the dynamics as well and, if so, in which way. Thus, with those parasitic motions in mind, the inverse kinematic problem of position, velocity and acceleration is solved. Once the accelerations of all the elements have been derived, the rigid solid dynamics and the results of force requirements and power consumption in inputs are analysed. The trajectory studied is a rotation about an axis in a plane Pu,v in a mobile reference frame and the parasitic expressions depend on the transformation matrix combination used. In this paper, the results for two of those transformation combinations are presented for two configurations of the inputs — in the first one, the inputs are in a horizontal plane, while in the second one they are vertical.
Free Vibration Analysis of Rotating Structures by One-Dimensional, Variable Kinematic Theories
Authors: Carrera Erasmo , Filippi Matteo , Zappino Enrico
Published: April 2014

In this paper, Carrera’s Unified Formulation (CUF) is extended to perform free-vibrational analyses of rotating structures. CUF is a hierarchical formulation which offers a procedure to obtain refined structural theories that account for variable kinematic description. These theories are obtained by expanding the unknown displacement variables over the beam section axes by adopting Taylor’s polynomials of N-order, in which N is a free parameter. The linear case (N = 1) permits us to obtain classical beam theories while higher order expansions could lead to three-dimensional description of dynamic response of both rotors and centrifugally stiffened beams. The Finite Element method is used to derive the weak form of the three-dimensional differential equations of motion in term of fundamental nuclei, whose forms do not depend on the approximation used (N). The present formulations include gyroscopic effects and stiffening due to centrifugal stresses. In order to verify the accuracy of the new theories, several analyses are carried out and the results are compared with solutions presented in the literature in graphical and numerical form. The advantages of the variable kinematic models are evident especially when shafts with deformable discs and thin-walled rotating beams made up with composite materials are studied.
Numerical and Experimental Investigations of Non-Newtonian Polymer Heating in a Static Mixer
Authors: Chamoun George , Strasser Wayne , Herrera Renato Acosta , Casper Bob
Published: April 2014

A non-Newtonian polymer is heated by co-current hot water in an insulated jacketed pipe. Both the viscosity and density depend on the temperature and shear rate. The polymer passes through two static mixers which are manufactured by KOFLO and are intended to accelerate the heating process. Each static mixer’s length to diameter ratio is approximately 16. An experiment was carried out in which the temperature of the polymer was measured directly downstream of the first static mixer with a thermocouple. The results from a 3D computational model were compared with those from an experiment. It was found that the polymer’s temperature rise with the simulation was within 6.5% of the experiment. The heating performance and residence time were also compared with a regular pipe.
Analysis of Self-Pressurization Phenomenon in a Cryogenic Fluid Storage Tank With VOF Method
Authors: Fu Juan , Sunden Bengt , Chen Xiaoqian
Published: April 2014

The self-pressurization phenomenon is studied numerically with the Volume of Fluid (VOF) method in a cryogenic fluid tank. Heat and mass transfer modelling is used for the phase change calculation at the interface. Transient simulations of the vaporization and pressure rise in a cylindrical liquid hydrogen tank are performed. The computations are carried out by using the CFD software package, Ansys Fluent, and an in-house developed code to calculate the source term associated with the phase change. Effects of the heat flux, fill level and gravity acceleration are investigated. Numerical results indicate that the pressure starts to rise after a certain time of sidewall heating and pressure rises gradually once the vaporization occurs. The rise rate increases as time elapses and is larger at higher heat flux at the same time. Multiple loops are observed in the fluid flow and thermal stratification is developed. The stratification degree is nearly the same for different fill levels at the same heat flux while the pressure rise rate increases as the fill fraction becomes larger. High temperature area appears when the fluid mixing becomes weaker as gravity acceleration decreases. Heat transfer turns to nucleate boiling at the wall from convection as evaporation occurs at the interface.
Integrated Thermal Conduction and Hardenability Laboratory Activity
Authors: Smith Natasha L. , Field Brandon S.
Published: April 2014

This paper describes an integrated laboratory project between separate heat transfer and machine design courses. The project was structured around a Jominy end quench hardenability test. Most of the students participating were simultaneously enrolled in both classes. In the heat transfer class, students were required to model one-dimensional, transient thermal conduction for an end quench geometry of 4140 steel. In machine design, students applied their theoretical temperature profiles to a continuous cooling transformation curve (CCT) of 4140 steel to predict microstructure and matched the theoretical cooling rates with hardenability curves from literature to predict hardness. In laboratory, students then performed an end quench test in accordance with ASTM A255 on four steel rods. By combining activities across the two courses, students developed an appreciation for the interconnectivity of material within the engineering curriculum, and learned that practical applications typically require they employ knowledge from a variety of sources.
The Evaluation of Friction Behavior Between EG and EGA Coated Automotive Steels
Authors: Shih Hua-Chu , Vanfleteren Michele L.
Published: April 2014

Zinc-based Electrogalvanized (EG) and Electrogalvanized zinc-iron alloy (EGA) coatings have been widely used in automotive body-in-white components for corrosion protection. The formability of zinc coated sheet steels depends on the properties of the sheet and the interactions at the interface between the sheet and the tooling. The frictional behavior of zinc coated sheet steels is influenced by the interfacial conditions present during the forming operation. Previous studies showed that the EG coated steel tended to have a lower friction coefficient than the EGA coated steel in the laboratory tests. However, the opposite trend is sometimes seen in production. The objective of this study is to evaluate the friction differences of these two coated sheet metals using laboratory simulative tests similar to production conditions. Process variables such as forming speed, lubricant composition, temperature, interface pressure, and die material are evaluated using the Bending Under Tension (BUT) test, the Draw Bead Simulator test (DBS) and the Strip Draw (SD) test. The results revealed that the friction behavior of the EGA coated sheet steel tends to be less sensitive to the lubricant amount supplied in forming. The EG coated sheet steel usually delivers a lower friction coefficient than the EGA coated sheet steel. However, the trend reverses when the sheet metal is tested in the bending and unbending mode at a lower speed under a well lubricated condition.