bluuebunny/crossref_metadata_2025 huggingface dataset:
Experimental Study on Flow-Front Fingering Instabilities in Injection Molding of Polymer Solutions and Melts
Authors: Kabanemi Kalonji K. , He´tu Jean-Franc¸ois , Sammoun Samira H.
Published: April 2008

An experimental investigation of the flow behavior of dilute, semi-dilute and concentrated polymer solutions has been carried out to gain a better understanding of the underlying mechanisms leading to the occurrence of instabilities at the advancing flow front during the filling of a mold cavity. Experiments were performed using various mass concentrations of low and high molecular weight polyacrylamide polymers in corn syrup and water. This paper reports a new type of elastic fingering instabilities at the advancing flow front that has been observed only in semi-dilute polymer solutions of high molecular weight polymers. These flow front elastic instabilities seem to arise as a result of a mixture of widely separated high molecular weight polymer molecules and low molecular weight solvent molecules, which gives rise to a largely non-uniform polydisperse solution, with respect to all the kinds of molecules in the resulting mixture (solvent molecules and polymer molecules). The occurrence of these instabilities appears to be independent of the injection flow rate and the cavity thickness. Moreover, these instabilities do not manifest themselves in dilute or concentrated regimes, where respectively, polymer molecules and solvent molecules are minor perturbation of the resulting solution. In those regimes, smooth flow fronts are confirmed from our experiments. Based on these findings, the experimental investigations have been extended to polymer melts. Different mixtures of polycarbonate melts of widely separated molecular weights (low and high molecular weights) were first prepared. The effect of the large polydispersity of the resulting mixtures on the flow front behavior was subsequently studied. The same instabilities at the flow front were observed only in the experiments where a very small amount of high molecular weight polycarbonate polymer has been mixed to a low molecular weight polycarbonate melt (oligomers).
Experimental Validation of a Recurrent Neural Network for Air-Fuel Ratio Dynamic Simulation in S.I. I.C. Engines
Authors: Arsie Ivan , Marotta Michele M. , Pianese Cesare , Sorrentino Marco
Published: April 2008

The paper deals with the simulation of the wall wetting dynamics in SI engines, making use of Recurrent Neural Networks (RNN). RNN are derived from the Multi Layer Feedforward Neural Networks, largely adopted for static mapping, by considering feedback connections between output and input layers. A Multi Input-Single Output structure has been adopted, assuming injected fuel, manifold pressure and engine speed as external input variables; the Air-Fuel Ratio at the exhaust gas oxygen sensor location has been considered as system output. The RNN has been trained (i.e. identified) and tested vs. a set of transient data measured on a commercial 4 cylinders SI engine at the test bench. The results show a good level of accuracy confirming the suitability of RNN for both HIL simulation or off-line identification of classical Mean Value Models with a drastic reduction of the calibration effort.
A New Trajectory-Generation Scheme for Overhead Cranes With High-Speed Load Hoisting
Authors: Lee Ho-Hoon , Segura Del , Liang Yi
Published: April 2008

This paper proposes a new trajectory-generation scheme for a high-performance anti-swing control of overhead cranes, where the trajectory-generation problem is solved as a kinematic problem. First, a new anti-swing control law is designed based on the load-swing dynamics, for which the Lyapunov stability theorem is used as a mathematical tool. Then a new trajectory-generation scheme is proposed based on the anti-swing control law and typical crane operation in practice. For g iven hoisting motions, trolley-traveling trajectory references are computed based on the concept of minimum-time control, and then anti-swing trajectories are generated based on the trajectory references through the anti-swing control law. The new trajectory-generation scheme generates a typical anti-swing trajectory in industry with high-speed load hoisting. The effectiveness of the proposed trajectory-generation scheme is shown by generating high-performance anti-swing trajectories with high hoisting speed and hoisting ratio.
Effect of Pressure Oscillations on Neonatal Breathing
Authors: Manilal P. I. , Al-Jumaily A. M. , Prime N.
Published: April 2008

Various methods of ventilation and continuous positive airway pressure (CPAP) devices have emerged to treat neonates suffering from respiratory distress syndrome (RDS). Among them is the Bubble CPAP device whose key distinguishing feature is the production of pressure oscillations, the presence of which has been suggested to offer added benefits to neonatal breathing. The mechanisms that cause these benefits, however, are not fully understood and many theories exist as to why pressure oscillations enhance the ventilation process. Using Simulink within Matlab environment, a mathematical model is developed to simulate the generation of pressure oscillations in the Bubble CPAP system and to investigate the mechanical response of the lung due to the pressure oscillations. Although the lung model incorporated in this investigation is simple, it gives a good trend of the lung behaviours under various pressure frequencies and amplitudes.
Three Non-Destructive Methods for the Modulus of Elasticity of the Trachea
Authors: Hermawan V. , Al-Jumaily A. M. , Fatemi M.
Published: April 2008

Three non-destructive testing techniques are developed and investigated to determine the Young’s modulus of elasticity of the trachea and the results are compared with the standard uniaxial state of stress method. These techniques are based on: (1) simulating the trachea as a pressurized vessel and deducing a special relationship between the pressure and the radial strain; (2) using two hydrophones and determining the variation in acoustic transmittance caused by the presence of the trachea in a propagation path within a water-bath; (3) considering the trachea as a thin cylindrical shell and determining the resonance radial vibration response. Discussion is presented to identify the “pros” and “cons” of each technique and final practical recommendations are made.
Tracheal Smooth Muscle Response to Vibrations
Authors: Du Y. , Al-Jumaily A. M.
Published: April 2008

An experimental and theoretical investigation is conducted to study the dynamic response of a tracheal smooth muscle under isometric conditions. The stiffness variation due to external vibration is investigated experimentally using trachea smooth muscles from excised pigs. The finite element method is used to model the muscle as a 2-D strip with variable stiffness and subjected to an external excitation. The Cauchy’s first law is invoked to describe the motion and Galerkin’s method is used to develop the finite element formulation. Different boundary conditions are considered to simulate the vibration characteristics and to get realistic compatibility with actual muscle conditions. The model predicts the stiffness variation due to vibration that is observed experimentally. The main outcome from this investigation is the fact that smooth muscle contractions could be relaxed by tuning the excitation within predetermined frequencies.
A Model for the Dynamic Simulation of Hybrid Vehicles With PEM Fuel Cell
Authors: Arsie Ivan , Domenico Alfonso Di , Pianese Cesare , Sorrentino Marco
Published: April 2008

The paper focuses on the development of a dynamic model for a hybrid vehicle equipped with a PEM fuel cell and a battery pack. An integrated structure of mathematical models has been implemented, whose development is based on previous studies carried out by the research group on the modeling of energy conversion systems for conventional and hybrid vehicles. The whole model simulates real driving cycles aiming at providing the data needed for selecting the best control strategies in terms of performance and fuel economy. A comparison with thermal-hybrid vehicles and conventional systems performance is presented together with an energy analysis carried out for both the single stack and its auxiliaries and the overall system (vehicle).
An Integrated Performance Modeling System
Authors: Kazmer David , Zhu Liang
Published: April 2008

An integrated performance modeling system is presented for use in general decision making problems including engineering design, manufacturing process and quality control, and other applications. The system relies on a function matrix that relates decision variables to performance variables. The system utilizes both global and local linearization of non-linear functions, after which the Extensive Simplex Method is used to derive the set of all feasible decisions based upon the specification limits for the performance variables and the control limits on the decision variables. Beyond current Six Sigma best practices, the described system explicitly considers both modeling uncertainty and uncontrolled variation. The specification limits may be automatically tightened by the confidence intervals and variation limits to ensure feasibility to a desired level of confidence and robustness. Three sets of feasible decisions are established including 1) the global feasible set that establishes the extreme limits of feasibility by allowing all the decision variables to vary simultaneously within their range of the control limits, 2) the local feasibility, which shows the immediate feasibility for each decision variable holding other decision variables at their current value, and 3) the controllable feasibility for each performance variable holding other performance variables at their current value. The system provides a perspective view of 1) the function matrix, 2) a historical view of the decision variables which may be used in a manner similar to statistical process control X-Bar charts, 3) a historical view of the performance variables which may be used in a manner similar to statistical quality control charts, 4) a set of decision windows showing the joint feasibility of all pairs of decision variables, which may be used in a manner similar to process windows, and 5) a set of performance windows showing the joint feasibility of all pairs of performance variables, which may be used in a manner similar to Pareto Optimal graphs. An example is provided for a beam design model with four decision variables and three performance variables.
Applied Heat Transfer in the Development of the New Wind Chill Temperature Chart
Authors: Bluestein Maurice
Published: April 2008

In November, 2001, the national weather services of the United States and Canada, recognizing inaccuracies in the original, adopted a revised Wind Chill Temperature (WCT) chart. This revision was developed by the authors under a mandate from a joint action group for temperature indicies (JAG/TI) formed by the U.S. Office of the Federal Coordinator for Meteorology. This new chart provides, for a given air temperature and recorded wind speed, that air temperature, the WCT, which would result in the same rate of heat loss from exposed human skin in still air. Values of the WCT are given for a range of air temperatures from −45°F to 40°F and a range of wind speeds from 5 mph to 60 mph. For Canada, the ranges are from −50°C to 10°C and 10 km/hr to 80 km/hr. The new chart was developed using principles of heat transfer, including conduction, forced convection and radiation. Skin tissue resistance was obtained from human studies. This paper describes the application of these principles and will show how these same principles have been used to demonstrate the errors in the original chart developed over 60 years ago by our military in Antarctica and adopted by the U.S. Weather Service in 1973. As was the case for the original chart, a clear night sky has been assumed, thus ignoring any direct solar radiation that would otherwise tend to elevate the WCT. The new chart is unlikely to be the final version long term and this paper will also discuss possible future modifications.
Transonic Passage Turbine Blade Tip Clearance With Scalloped Shroud: Part III — Heat Transfer in Engine Configuration
Authors: Wilkins F. Casey , Feldman Gregory M. , Strasser Wayne S. , Leylek James H.
Published: April 2008

This work presents a numerical study that was done to investigate the heat transfer characteristics of a transonic turbine blade with a scalloped shroud operating at realistic engine conditions typical of those found in a large scale, land-based gas turbine. The geometry under investigation was an infinite, linear cascade composed of the same blade and shroud design used in an experimental test rig by the research sponsor. This simulation was run for varying nominal tip clearances of 20, 80, and 5.08 mm. For each of these clearances, the simulation was run with and without the scrubbing effects of the outer casing, resulting in a total of six cases that could be used to determine the influence of tip clearance and relative casing motion on heat transfer. A high quality grid (ranging from approximately 10–12 million finite volumes depending on tip clearance) with y+ for first layer cells at or below 1.0 everywhere was used to resolve the flow down to the viscous sublayer. The “realizable” k-ε turbulence model was used for all cases. A constant wall heat flux was imposed on all the surrounding surfaces to obtain heat transfer data. Results produced include a full map of heat transfer coefficients for the suction and pressure surfaces of the blade as well as the tip, shroud, and outer casing for every case. Physical mechanisms responsible for the final heat transfer outcome for all six cases are documented.
Transonic Passage Turbine Blade Tip Clearance With Scalloped Shroud: Part I — Aerodynamic Losses in a Dual-Passage Cascade
Authors: Feldman Gregory M. , Strasser Wayne S. , Wilkins F. Casey , Leylek James H.
Published: April 2008

State-of-the-art experimental and computational techniques are used to study a unique class of problems involving the investigation of the flow field surrounding shrouded-airfoils with tip gap leakage in a dual passage cascade. A complex hybrid grid generation methodology was established, and used to model the complete experimental setup. This complex gridding methodology allowed the physics of the experiment to be modeled completely, while at the same time keeping the overall cell count of the grid within reasonable limits. The final mesh consisted of a fine, high quality grid comprised of over 31,000,000 finite volumes. The gridding methodology allowed for the use of a high-quality, super-block, multi-topology (including triangular prisms, hexahedra, pyramids, and tetrahedra), unstructured/adaptive, non-conformal mesh to accurately resolve both the near wall, and the mean flow features. The experimental setup that was simulated was run under realistic engine conditions with inlet Reynolds number based on chord length of approximately 650,000 and maximum Mach number of 1.1. The realizable k-ε turbulence model was used, with the viscous sub-layer resolved on all surfaces down to y+ equal to one or less everywhere. A comprehensive solution management technique was established to obtain a fully converged solution in a robust and economical manner. The simulation was run using a Sun Ultra Enterprise 15000 server with 72 cpus in parallel. Using this optimal solution technique the simulation ran for over 6000 iterations, while taking only about 150 hours to run such a massive simulation to convergence. Both experimental and computational results are used in Part I of a three part series of papers to show good agreement between the cases for purposes of validation. The computational results are then used to document physics mechanisms responsible for total pressure loss, loss location, and relative magnitude of losses that were not identifiable through the experimental techniques used. Parts II by Strasser et al. [1] and III by Wilkins et al. [2] go on to document the physics of similar flow through realistic engine conditions and to document the heat transfer also involved.
Turbine Nozzle Endwall Inlet Film Cooling: The Effect of a Back-Facing Step and Velocity Ratio
Authors: Zhang Luzeng , Moon Hee Koo
Published: April 2008

Endwall inlet film cooling serves two purposes: to suppress the secondary flows and to provide effective cooling. To optimize endwall inlet film cooling, the combined effects of a back facing step and jet velocity ratio were studied in a warm cascade simulating realistic engine conditions. Film effectiveness distribution was measured on a nozzle endwall surface using the pressure sensitive paint (PSP) technique. A double staggered row of holes was used to supply cooling air in front of the nozzle leading edges. Changing the diameter of the film injection hole varied the velocity ratio and the back-facing step was designed to simulate the discontinuity of the nozzle inlet to the combustor exit cone. Nitrogen gas was used to simulate cooling flow as well as a tracer gas to indicate oxygen concentration such that film effectiveness by the mass transfer analogy could be obtained. Cooling mass flow was controlled to be from 0.5% to 3.0% of the mainstream mass flow. The film effectiveness distribution was locally measured for each of the cooling mass flows. It was demonstrated that by optimizing the jet velocity ratio the adverse effect of the back-facing step could be reduced, particularly for the range of mass flow practical in design. The pattern of the film effectiveness distribution suggested the opposite effect of the film injection and the back-facing step on the secondary flows, while one suppresses and the other enhances it.
Atomization Characteristics of Effervescent Atomizer With Two-Aerator Tube
Authors: Kim Hyung Gon , Torii Shuichi , Yano Toshiaki , Song Kyu Keun
Published: April 2008

An experimental study was conducted to investigate the atomization characteristics of spray from the effervescent atomizer, which has two-aerator tube. The atomization characteristics were examined through the influence of ALR (Air-to-Liquid Ratio) and the changes of atomizer geometry (nozzle orifice diameter, diffusion angle, mixing chamber volume). PDPA (Phase Doppler Particle Analyzer) was used to evaluate the SMD (Sauter Mean Diameter) and droplet velocity. During the experiments, the mass flow rate of liquid was kept constant at 2.8g/s and the mass flow rate of atomizing air was changed from 0.2 to 0.6g/s. Experimental results showed that SMD is not a linear function of ALR. While SMD is very sensitive to the changes of ALR, the changes of atomizer geometry have little effect on droplet mean diameter. As the effervescent atomizer with two-aerator tube is insensitive to the changes of atomizer geometry, it is expected that the effervescent atomizer with two-aerator tube is capable of requirements of many applications, without the drawbacks of atomization characteristics.
Energy-Based Crashworthiness Optimization for Multiple Vehicle Impacts
Authors: Fang H. , Solanki K. , Horstemeyer M. F.
Published: April 2008

In this paper, we use a full-scale finite element vehicle model of a 1996 Dodge Neon in simulating two types of vehicle crashes, offset-frontal and side impacts. Based on an analysis of the vehicle’s histories of internal energy absorption under both impacts, we select twenty components as design variables in the optimization of the vehicle’s weight without decreasing the vehicle’s energy absorption capacity and energy absorption rate. We use the second-order polynomials in creating the metamodels for the response functions of energy absorption under both impacts. The optimization result shows a significant reduction on the total weight of the selected components. The LS-DYNA MPP v970 and a full-scale finite element vehicle model of 320,872 nodes and 577,524 elements are used in the simulations. A simulation of 100 ms offset-frontal impact takes approximately 17 hours with 36 processors on the IBM Linux SuperCluster, which has a total of 1038 Intel Pentium III 1.266 GHz processors and 607.5 GB RAM. A simulation of 100 ms side impact takes approximately 29 hours with the same condition as the offset-frontal simulation.
Parametric Geometry Definition and Analysis of the Human Carotid Artery Bifurcation
Authors: Bressloff N. W. , Banks J. , Bhaskar K. V.
Published: April 2008

Three-dimensional parametric computer aided design (CAD) geometry definitions of the human carotid artery bifurcation are presented for both Y-shaped and tuning-fork models. Drawing on methods largely developed in aerodynamic design, these parametric CAD geometries are deployed within a response surface methodology to systematically map the variation of spatially integrated mean shear stress with the angles of the internal carotid artery (ICA) and the external carotid artery (ECA). Although the absolute values of this shear stress metric agree in some regions of the design space, significant differences exist in the shapes of the response surfaces for the alternative CAD models. The tuning-fork data reveals unexpected results in the location of the lowest value of the metric (at large ICA angles and small ECA angles) and also in the presence of two regions of high metric values — one, unsurprisingly, at large ICA and ECA angles but another exists close to the baseline geometry at the centre of the design space. In contrast, the Y-shaped data is such that a very spiky response surface is produced dominated by changes in the ICA angle. Also, the minimum is located at small ICA and large ECA angles. Finally, evidence is presented for strong recirculation at the outflow of the sinus bulb for small ICA angles that is nonexistent for large ICA angles.
Finite-Element Simulation of Thin-Shell Fracture and Fragmentation
Authors: Cirak Fehmi , Ortiz Michael , Pandolfi Anna
Published: April 2008

We develop a finite-element method for the simulation of dynamic fracture and fragmentation of thin-shells. The shell is spatially discretized with subdivision shell elements and the fracture along the element edges is modeled with a cohesive law. In order to follow the propagation and branching of cracks, subdivision shell elements are pre-fractured ab initio and the crack opening is constrained prior to crack nucleation. This approach allows for shell fracture in an in-plane tearing mode, a shearing mode, or a bending of hinge mode. The good performance of the method is demonstrated through the simulation of petalling failure experiments in aluminum plates.
Nanoscale Inking, Melting, and Soldering With a Heated Atomic Force Microscope Cantilever Tip
Authors: King William P. , Nelson Brent A. , Wright Tanya L. , Sheehan Paul A. , Whitman Lloyd J.
Published: April 2008

Thermal dip pen nanolithography (tDPN) is a nanolithography technique that leverages previous advances in dip pen nanolithography and the design and fabrication of heated atomic force microscope cantilevers. In tDPN a heated atomic force microscope cantilever tip deposits high-melting temperature materials from the tip onto a surface. This technique is distinct from conventional DPN in that the ink molecules are not mobile at room temperature, allowing local control of deposition allowing the tip to be used for metrology of written features without contamination. tDPN represents an advancement in nanometer-scale lithography and manufacturing, which could enable the rapid prototyping and economical manufacture of nanodevices.
Dependence of Impact Performance on Process Parameters and Weld Attributes for Spot Welded Advanced High Strength Steels
Authors: Karve Girish S. , Zhang Hongyan
Published: April 2008

In order to improve fuel economy and safety of vehicles, many advanced materials such as aluminum alloys and advanced high strength steels have been introduced in automobile body construction in recent years. A key to the adoption of such materials is their manufacturability, such as forming and welding. Resistance welding, as the major enabling technique, has been widely applied in joining these materials. Although there has been a large amount of research in characterizing static and fatigue strengths of Al or AHSS welds, their impact performance is largely unknown, even though it is extremely important for safety. In this paper, the impact strength of AHSS spot welded specimens is analyzed, as a function of welding process parameters and weldment geometry. Both energy and peak load during impacting, as well as failure mode were recorded. The geometric attributes of spot welds, such as indentation width, nugget width, indentation depth, etc. were measured before the specimens were destructively tested. Then these quantities were linked to the impact strength of the welds. Besides several advanced high strength steels, high strength, low alloy (HSLA) steels were also tested in the study for comparison. Models were developed to correlate impact strength with individual factors, both welding parameters and spot weld geometry variables. The effects of interactions between the factors were also investigated. The results showed that these parameters should be examined together in determining a weld’s impact performance.
Analysis to Reduce Thermal Stress in Oxide Single Crystal During Czochralski Growth
Authors: Hirasawa Shigeki , Ishibashi Hiroyuki , Kurashige Kazuhisa , Gunji Akihiro
Published: April 2008

Temperature distributions and thermal stress distributions in a semi-transparent GSO crystal during Czochralski (CZ) single crystal growth were numerically investigated by thermal radiation heat transfer analysis and anisotropy stress analysis. As GSO has special optical properties, such as semi-transparency at a wavelength shorter than 4.5 μm, thermal radiation heat transfer was calculated by the Monte Carlo method. These calculations showed that thermal stress is caused by the radial temperature distribution on the outside of the upper part of the crystal. To reduce this temperature distribution, the following three manufacturing conditions were found to be effective: use a sharp taper angle of the crystal, install a lid to the top of the insulator, and install a ring around the tapered part of the crystal.
Modeling and Analysis of Human Task-Performing Process in Manufacturing Systems With Human Task and Error Classifications
Authors: Shin Dongmin , Wysk Richard A. , Rothrock Ling
Published: April 2008

Development of a formal model for control and analysis of manufacturing systems in which a human operator is incorporated is difficult, nevertheless the human is a key component. It requires building a model of human functional specifications for executing various tasks. In this paper, a human parts handler is considered and the human task performing process is described in terms of human tasks and errors. For this purpose, human tasks and errors are classified into two sets, respectively. Based on the number of locations where an operator is required to move to complete a task, tasks are divided into an on-the-spot task set and an around-the-system task set. For human errors associated with each of task set, a location error set and an orientation error set are defined, respectively. As the initial step toward building a controller for Human-involved Computer Integrated Manufacturing Systems (HiCIM), assessment of the impact of human involvement on the control of a system, much of which is controlled by a computerized execution system, is presented. The complexity of systems from the control perspective is modeled and analyzed with human tasks and errors. The human task performing process is described using a flow chart format and a colored Petri net model is presented, and the complexity of process is analyzed in terms of human errors. A shop floor control example where the human operator performs material handling tasks is provided to illustrate the proposed methodology.
Tumor Detection With a New Boundary Integral Equation Formulation
Authors: Han F. , Pan E. , Jiang X. , Qiao Y.
Published: April 2008

During pathological evolution, tissues mechanical properties, such as elastic moduli, will be changed. This feature has already been used in theory and application of elastography for detecting and characterizing tumors. In this paper, a tumor mass embedded in a breast tissue is modeled as an Eshelby inhomogeneity problem. Using a new anisotropic boundary element method (BEM) developed recently by the authors, the stress and strain fields due to an external load are solved efficiently and accurately. Furthermore, an inverse algorithm is also proposed for the detection and characterization of the embedded tumor mass. Numerical examples are presented to show that the BEM algorithm based on the Eshelby inclusion concept provides a useful method to solve certain biomedical problems.
Development of Nano-Scale Reusable Quartz Master for the Fabrication of Nickel Stampers
Authors: Seo Young Ho , Choi Doo-Sun , Yoo Yeong-Eun , Je Tae-Jin , Whang Kyung-Hyun
Published: April 2008

In this paper, we present reusable quartz master fabricated by electron-beam lithography and dry etching process of quartz, and results of injection molding based on the reusable quartz master for the manufacturing of nano-scale information media. Since patterned structures of photoresist can be easily damaged by separation (demolding) process of nickel stamper and master, a master with photoresist cannot be reused in stamper fabrication process. In this work, we have made it possible of the repeated use of master by directly patterning on quartz in nickel stamper fabrication process. We have designed and fabricated four different specimens including 100nm, 140nm, 200nm and 400nm pit patterns. In addition, both intaglio and embossed carving patterns are fabricated for each specimen. In the preliminary test of injection molding, we have fabricated polycarbonate patterns with varying mold temperature. We have experimentally verified the fabrication process of the reusable quartz master and possibility of quartz master as direct stamper.
On the Possibility of Destabilising Convection in a Gravity Modulated Porous Layer Heated From Above
Authors: Govender S.
Published: April 2008

The linear stability theory is used to investigate analytically the possibility of destabilising convection in a porous layer heated from above and subjected to vibration. The linear stability theory shows that there exists a bandwidth of frequencies for which convection in a porous layer, with a stable density gradient, can be destabilized.
Computer Aided Dynamic Analysis of the Drive of a Chain Conveyor
Authors: Modak Jayant P. , Mehta Girish D. , Belkhode Pramod N.
Published: April 2008

Literature indicates availability of dynamic analysis of a drive shaft of a chain conveyor in a limited way. Relations for estimation of a conveyor chain pull to overcome, (i) Rolling resistance of the track, (ii) Tail sprocket and drive sprocket shaft bearing friction resistances, (iii) Drive and tail sprocket chain binding resistances and (iv) Impact loading on the chain have been only derived [1,2]. However, further extension to deduce the load torque demand on drive sprocket during one articulation of the chain is not seen derived in the literature. This paper details this, followed by digital computer simulation including illustration of application of this new procedure to a representative case study. Work on the same lines is not much seen in the literature. However, similar work by Harrison [4] is done for the belt conveyor.
Thermal Analysis of a Micro-Polymerase Chain Reaction Device
Authors: Punch Jeff , Rodgers Bryan , Newport David , Davies Mark
Published: April 2008

Micro-scale polymerase chain reaction (micro-PCR) systems offer substantial advantages over macro-scale systems. Smaller sample volumes are required, and faster process times are feasible. Thermal control of micro-PCR systems is a substantial technical challenge, however. The PCR process requires the fluid sample to be cycled through three temperature ranges — typically 90–95°C, 50–65°C and 72–77°C for denaturation, hybridisation and replication respectively. Durations of the three steps are required to be in the ratio of 4:4:9. In this paper, the thermal analysis of a continuous flow micro-PCR device is reported. The objective of the analysis is to optimize the thermal performance of the device for fast amplification cycles with high efficiency - an efficient PCR features rapid heating and cooling between steps, and good temperature uniformity within each step. The device comprises an array of parallel microchannels formed within a polypropylene substrate to carry fluid, with the base of the substrate mounted on an aluminium carrier. Substrate depth is 500 micron, and each channel is 60 micron wide by 40 micron deep. Thermoelectric cells (TECs) are bonded to the carrier, and powered by a thermoelectric controller with feedback from sensors embedded in the carrier. A Pyrex Glass slide is bonded to the substrate to form closed channels. Arrays of film heaters mounted on the slide adjacent to the channel are used to establish the required temperature regions along the channel. By pumping the fluid at a fixed flow rate, temperature cycling of specific period is achieved. Thermal analysis of the substrate is performed using an approximate closed-form solution, in conjunction with Finite Element (FE) and Computational Fluid Dynamics (CFD) simulations. The analysis is used to conduct a parametric study in order to determine the optimum configurations of substrate materials, cooling conditions, heaters and flow rates required to impose specific temperature cycles. The use of thermoelectric cells is shown to increase the rate of change of temperature between the various regions, improving the efficiency and decreasing the cycle time of the PCR process. Cycle times of 6s or less are shown to be feasible, yielding benefits in time saved for multiple amplifications. Finally, the analysis is also used to identify the dimensionless parameters which govern the thermal characteristics of the device, illustrating the importance of the Biot number.
Crashworthiness of Aluminum Extrusion Under Simulated Service Life Heat Exposure
Authors: Baccouche Ridha , Sherman Andy , Ward Susan , Wagner David , Miller Craig , Mahmood Hikmat
Published: April 2008

An investigation of the service life aging and heat exposure effects on extruded aluminum alloy properties and structural crashworthiness has been conducted. This research, part of a broader program, consists of investigating five aluminum alloy extrusions each of which is subjected to two heat treatments. The aluminum extrusion investigated are 6063T6, 6061T6, 6260T6, 6014T6, and 7129T6. The two heat treatments are 177°C for 30 minutes and 200°C for 24 hours. The 200°C/24 hours treatment represents an upper limit thermal exposure i.e. components adjacent to exhaust pipes and manifolds. The 200°C heat treatment was applied in addition to the 177°C for 30 minutes. All specimens were subjected to the reference 177°C for 30 minutes treatment. These ten crash members were subjected to dynamic axial crashing at a target speed of 40 kph (25 mph). Force-time data was collected and responses were plotted for all tests. Force-displacement responses were then integrated for the crash energy management and mean axial crash load for each of the aluminum extruded crash members. Bar charts were then generated to describe the crash loads and energy management behaviors of the various aluminum alloys and associated heat treatments. Service life simulated heat exposure was found to effect the mean crash load and crash energy management of the aluminum structural crash members. The heat exposure effects on the crashworthiness of the extruded aluminum members ranged from a reduction of 10% to over 20% in the mean crash load and crash energy management with highest variation observed with the 6260T6 aluminum extrusion.
Response of a Tethered Aerostat to Simulated Turbulence
Authors: Stanney Keith A. , Rahn Christopher D.
Published: April 2008

Aerostats are lighter-than-air vehicles tethered to the ground by a cable and used for broadcasting, communications, surveillance, and drug interdiction. The dynamic response of tethered aerostats subject to extreme atmospheric turbulence often dictates survivability. This paper develops a theoretical model that predicts the planar response of a tethered aerostat subject to atmospheric turbulence and simulates the response to 1000 simulated hurricane scale turbulent time histories. The aerostat dynamic model assumes the aerostat hull to be a rigid body with nonlinear fluid loading, instantaneous weathervaning for planar response, and a continuous tether. Galerkin’s method discretizes the coupled aerostat and tether partial differential equations to produce a nonlinear initial value problem that is integrated numerically given initial conditions and wind inputs. The proper orthogonal decomposition theorem generates, based on Hurricane Georges wind data, turbulent time histories that possess the sequential behavior of actual turbulence, are spectrally accurate, and have non-Gaussian density functions. The generated turbulent time histories are simulated to predict the aerostat response to severe turbulence. The resulting probability distributions for the aerostat position, pitch angle, and confluence point tension predict the aerostat behavior in high gust environments. The results uncover a worst case wind input consisting of a two-pulse vertical gust.
Nonlinear Dynamic Simulation and Stress Prediction for a Tethered Aerostat
Authors: Docimo Anthony , Rahn Christopher D.
Published: April 2008

Aerostats are lighter-than-air vehicles tethered to the ground by a long cable. Their operational availability as a communications and surveillance platform, however, is limited by high winds during inclement weather. This paper develops aerostat dynamic models that predict the aerostat motion and tether and confluence line stresses in response to wind inputs. A nonlinear dynamic simulation is developed based on recent models for lighter-than-air vehicles that more accurately reflect aerodynamic loading in gust environments. Comparison of the dynamic response with previously published flight data for the TCOM 71M aerostat validates the model and demonstrates up to 44% higher accuracy results than previous techniques. A static truss finite element model predicts confluence line loads based on the dynamic response.
ABET EC-2000 Assessment Using Outcome Portfolios
Authors: Barbero Ever J. , Prucz Jacky C. , Banta Larry E. , Stanley Charles E. , Mukherjee Nilay
Published: April 2008

A comprehensive implementation of outcome portfolios is presented. Outcome portfolios are assessment tools used by the authors to accomplish triangulation in the Accreditation Board for Engineering and Technology (ABET) EC-2000 assessment process. Systematic and effective use of outcome portfolios has provided us with a convenient, reliable, and powerful tool for assessing the level of achievement of our graduates on all the program outcomes for the Aerospace Engineering and Mechanical Engineering programs at West Virginia University. The objective of this paper is to describe our approach to assembling, assessing, and improving outcome portfolios as an essential outcome assessment tool under ABET Criterion 3. The process is illustrated in detail using outcome “k” [1] as an example. Assessment data are presented to support the hypothesis that survey data alone are inconclusive and that outcome portfolios provide additional, valuable information for program enhancement. A comparison between the assessment data for the two programs, Aerospace Engineering and Mechanical Engineering, is used to support our conclusions.
Three-Dimensional Continuum Damage Model for Polymer Matrix Composites
Authors: Barbero Ever J. , Mayugo Joan A. , Lonetti Paolo
Published: April 2008

A constitutive model for fiber reinforced composite materials with damage and unrecoverable deformation, which for the first time accounts for thru-the-thickness damage, is presented. The formulation is based on Continuous Damage Mechanics coupled with Classical Plasticity Theory in a consistent thermodynamic framework using internal state variables. A novel formulation of the parameter identification is included in order to describe the main failure modes of polymer matrix composite laminae. The new parameter identification is simpler than those available in the literature. It is also more sensitive and allows for better control of material behavior to match experimental data. Furthermore, it uses material properties that are simpler to test than previous models. The model uses a small number of adjustable parameters, which are identified from available experimental data. Comparisons with experimental data for composite laminates under in plane and torsion loading are shown to validate the model. The new model, although simpler than previous ones, is able to model all experimentally observed behavior of laminates that were previously modeled with more complex models.
A Methodology to Determine Work Material Flow Stress and Tool-Chip Interfacial Friction Properties by Using Analysis of Machining
Authors: O¨zel Tug˘rul , Zeren Erol
Published: April 2008

In this paper, we develop a methodology to determine flow stress at the machining regimes and friction characteristics at the tool-chip interface from the results of orthogonal cutting tests. We utilize metal cutting analysis originally developed by late Oxley and present some improvements. We also evaluate several temperature models in calculating the average temperatures at primary and secondary deformation zones and present comparisons with the experimental data obtained for AISI 1045 steel through assessment of machining models (AMM) activity. The proposed methodology utilizes measured forces and chip thickness obtained through a basic orthogonal cutting test. We conveniently determine work material flow stress at the primary deformation zone and the interfacial friction characteristics along tool rake face. Calculated friction characteristics include parameters of the normal and frictional stress distributions on the rake face. Determined flow stress data from orthogonal cutting tests is combined with the flow stress measured through split-hopkinson pressure bar (SHPB) tests and the Johnson-Cook work material model is obtained. Therefore, with this methodology, we extend the applicability of Johnson-Cook work material model to machining regimes.
Effect of Bituminous Coal Properties on Heat Transfer Characteristic in the Boiler Furnaces
Authors: Chudnovsky B. , Talanker A.
Published: April 2008

Over the past years experience has been gained in employing changing types of imported coal. Apart from the proximate analysis this led to development of evaluation criteria regarding the operation of coals. These are criteria numbers obtained from operational experience and criteria numbers used for the characterization of specific operational properties on the basis of special laboratory analyses. The study evaluates the effect of the characteristics of pulverized coal on the furnace fouling and radiation heat transfer. The aim of the study was to access whether fouling and radiation heat transfer could be predicted from coal characteristics. The paper presents the experimental results on the fouling propensity of fifteen coals tested in a 575 MW combustion engineering tangential firing boiler. The results showed that no coals produced a strong molten deposit. In order to rank the fouling propensity and radiation heat transfer properties numerically, we measured the profile of incident heat fluxes, defined furnace exit flue gas temperature and absorbed heat fluxes. The basic molar ratio correlates the fouling propensity. Besides that increasing of SiO2 and Al2O3 content in the ash strongly reduces water wall absorptivity factor. The present work is also concerned with the effect of different bituminous coal on their flame emissivity. Using the radiation properties of flue gases derived from the full scale experiments, we run computational fluid dynamics (CFD) on the combustion process. The known fouling and radiation heat transfer properties enable the prediction of the effect of coal quality on the performance of a specific boiler.
Thermal Hysteresis Analysis of MEMS Pressure Sensors
Authors: Chiou J. Albert , Chen Steven
Published: April 2008

Thermal hysteresis reduction is usually a difficult task to tackle for micromachined pressure sensors especially when shrinking the piezoresistive transducer (PRT) sensing element. Since thermal hysteresis involves the entire thermal cycling history and complicated material properties varied with temperatures, viscoplastic deformation makes the problem very complicated when dealing with high-precision sensor signals. The approach to simplify and quickly resolve the thermal hysteresis problem is the key methodology proposed by this paper. The objective of this project is to optimize the metal layout design on the sensing element and lower down the thermal hysteresis. It is time consuming and cost ineffective to rely purely on the hardware tests to solve the thermal hysteresis problem. ANSYS is used to predict the shear stress at the transducer location and the phenomenological theory of silicon piezoresistance is used to calculate the output voltage and thermal hysteresis. The element-death-and-birth technique is used to simulate the bonding process at various temperature levels for the sensing element packaging. With the aid of the finite element analysis (FEA) tool, the PRT sensing element design was quickly optimized and product development cycle time was reduced.
Parameter Identification for a High Performance Hydrostatic Actuation System Using the Variable Structure Filter Concept
Authors: Habibi S. R. , Burton R.
Published: April 2008

Parameter estimation is an important concept that can be used for health and condition monitoring. Estimation or measurement of physically meaningful parameters and their evaluation against predetermined thresholds allows detection of gradual or abrupt deteriorations in the plant. This early detection of faults enables preventative unscheduled maintenance that is of benefit to industries concerned with reliability and safety. In this paper, a recently proposed state estimation strategy referred to as the Smooth Variable Structure Filter (SVSF) is reviewed and extended to parameter estimation. The SVSF is applied to a novel hydrostatic actuation system referred to as the ElectroHydraulic Actuator (EHA). Condition monitoring of the EHA for preventative unscheduled maintenance would increase its safety in applications pertaining to aerospace and would reduce its operational and maintenance costs.
Modeling the Evaporation of Multicomponent Diesel Droplets
Authors: Stegemann Danica , Rakowski Sebastian , Pagel Sven , Merker Guenter P.
Published: April 2008

A multicomponent fuel evaporation model was developed to describe diesel fuels. This model is based on the principles of continuous thermodynamics. In contrast to conventional. models, each component is not described by discrete relations for energy and mass, but the whole mixture is characterized by a distribution function. In most CFD (computational fluid dynamics)-applications the droplet interior is assumed to be well mixed, this means that composition and temperature are spatially constant inside the droplet. But this assumption is only correct in the case of turbulent mixture with high velocity gradients between spray and surrounding gas, e.g. the area near the nozzle. Due to areas with low relative velocities this formulation is inaccurate and demands a more detailed description of the processes inside the droplet. For these areas the use of a model based on a droplet consisting of several shells is advantageous, because composition and temperature are not spatially constant inside the droplet. The model divides the droplet into a finite number of layers that interchange energy and mass. The implementation of these two models into the CFD-code KIVA-3V implifies the effects of the multi-component character of the fuel by describing the different areas of the spray more correctly. Both models are compared in single droplet calculations and show a detailed description of evaporation.