bluuebunny/crossref_metadata_2025 huggingface dataset:
Linear Finite Element Analysis of a 3-Dimensional Tooth and Its Prototype Model
Authors: Padole Pramod , Uddanwadiker Rashmi , Arya Harshwardhan
Published: September 2008

Dentist, follow root canal therapy to treat teeth with pulpal involvement due to dental caries or as a result of trauma. In order to restore fractured and broken down teeth internal reinforcement is required in the form of a post-core restoration. The post extends into the root canal space and provides retention for the core, which subsequently helps to provide a foundation for the crown restoration. For the treatment procedure, post, core and crown are casted by an indirect procedure by taking the measurements from patient’s tooth in the form of impressions. These impressions are then converted into solid gypsum casts and then wax patterns are developed in order to facilitate casting by the lost wax technique. The final shape of the core and crown and success of the treatment entirely depends upon the skill of the dental technician and involves a number of variables in impressioning, cast poring and wax pattern fabrication. The treatment can be further simplified by making a prototype model of the post, core and the crown by taking the dimensions from the patient’s tooth. This paper presents four prototype models prepared from the solid model of the original tooth and three restored tooth.
Experimental Investigation of Free Convection Heat Transfer With Entrance Restriction Placed at Top of a Vertical Circular Tube
Authors: Mohammed H. , Yusaf T. , Salman Y.
Published: September 2008

A free convection from the inside surface of vertical circular tube with a uniformly heated surface (constant wall heat flux) was investigated experimentally for laminar air flow in the ranges of RaL from 6.9 × 108 to 5 × 109. The effect of restriction lengths placed at top position of the heated tube on the surface temperature distribution and the local and average heat transfer coefficient were studied. The experimental apparatus consists of aluminum tube with 900mm length and 30mm inside diameter. The entry restrictions were included a circular tube of same diameter as the heated tube but with different lengths of 60cm, 90cm, 120cm, 150cm, and 180cm. It was found that the surface temperature along the tube surface higher values for restriction with length of 180cm and smaller values for the restriction with length of 120cm. The results showed that the local Nux and average Nusselt number Nu were higher values for the restriction with length of 120cm and smaller values for the restriction with length of 180cm. The results obtained are correlated by dimensionless groups as Log NuL against Log RaL for each case and proposed a general correlation for all cases.
A Comparison Between the Local Free Convection Heat Transfer Coefficients of Horizontal Cylinders in Vertical and Inclined Arrays
Authors: Ashjaee Mehdi , Yousefi Tooraj
Published: September 2008

Laminar free convection heat transfer from vertical and inclined arrays of horizontal isothermal cylinders in air was investigated experimentally and numerically. Experiments were carried out using Mach-Zehnder interferometer and the FLUENT code was used for numerical study. Investigation was performed for vertical and horizontal cylinder spacing from 2 to 5 and to 2 cylinder diameter respectively. The Rayleigh number based on the cylinder diameter varied between 103 and 3×103. The effect of vertical and horizontal cylinder spacing and Rayleigh number on the local heat transfer from each individual cylinder was investigated. It was seen that the local heat transfer coefficient of each cylinder strongly depends on its position relative to the others. This variation of the local heat transfer coefficient was explained by the interaction of plume’s temperature and velocity profiles.
Formation of Protective Films of Octadecylamine on the Surface of Construction Materials in the Water-Steam Cycle at Fossil Power Plants
Authors: Petrova Tamara I. , Kashinsky Valery I. , Verkhovsky Andrei Ye. , Chernyshev Yevgeny V. , Trofimov Igor N.
Published: September 2008

One of the reasons of the degradation of operational efficiency of fossil power plants is corrosion that takes place in the water-steam cycle during operation or downtime. Filming amine octadecylamine (ODA) is one of the chemicals used for reduction of corrosion rate of construction materials during downtime. This chemical not only reduces corrosion rate, but also helps to remove deposits. The data on the ODA effect on the efficiency of removal of deposits from heat exchange surfaces during equipment layup are presented. After ODA application a change in distribution of impurities along the height of deposits was found. In particular, chlorides move from the metal surface to the upper deposit layer, resulting in decrease of the corrosion rate. Results of field tests at co-generation fossil power plant indicate that the use of ODA for the equipment layup reduced tube failures and deposition rate in district water heaters and hot water boilers.
Neural Network Analysis of Free Convection Around Isothermal Elliptic Tube
Authors: Ashjaee Mehdi , Afzali Reza , Niknami Mohammad , Amiri Mehdi , Yousefi Tooraj
Published: September 2008

An artificial neural network (ANN) was applied successfully to predict laminar free convection heat transfer coefficient from an isothermal horizontal cylinder of elliptical cross section confined between two adiabatic walls. Neural networks were used since they constitute a general, powerful function-approximator tool proving able to represent a convectional heat transfer coefficient precisely in the present case. The input database for the network includes 171 experimental data points. The experiment is carried out using Mach-Zehnder Interferometry. Tube axis ratio, wall spacing to miner axis ratio of tube and Rayleigh number are variable parameters or the experimental study. The values of the average Nusselt numbers predicted by the network are in very good agreement with the available experimental data. Therefore the network is used to predict the unavailable data points within the range of our experimental results.
Cyclic Loading of Beams Based on Kinematics Hardening Behavior Coupled With Isotropic Damage
Authors: Nayebi Ali , Shirazi Kourosh H.
Published: September 2008

The kinematic hardening theory of plasticity based on the Prager model and incremental isotropic damage is used to evaluate the cyclic loading behavior of a beam under the axial, bending, and thermal loads. This allows damage to be path-dependent. The damage and inelastic deformation are incorporated and they are used for the analysis of the beam. The beam material is assumed to follow linear strain hardening property coupled with isotropic damage. The material strain hardening curves in tension and compression are assumed to be both identical for the isotropic material. Computational aspects of rate independent model is discussed and the constitutive equation of the rate independent plasticity coupled with the damage model are decomposed into the elastic, plastic and damage parts. Return Mapping Algorithm method is used for the correction of the elastoplastic state and for the damage model the algorithm is used according to the governed damage constitutive relation. The effect of the damage phenomenon coupled with the elastoplastic kinematic hardening is studied for deformation and load control loadings.
Reliability-Based Multi-Objective Optimization Methodology for Engineering Systems
Authors: Sinha Kaushik
Published: September 2008

This paper presents a methodology for reliability-based multi-objective design optimization (RBMODO) of automotive body components under impact scenario. Conflicting design requirements arise as one tries, for example, to minimize structural mass while maximizing energy absorption of an automotive rail section under structural and occupant safety related performance measure constraints. Because deterministic optimum designs obtained without taking uncertainty into account could lead to unreliable designs, a reliability-based approach to design optimization is preferable using a Reliability-based design optimization method. Uncertainty quantification is performed using two methods: reliability based approach and robustness based approach. The technique employed here treats multiple objective functions separately without combining them in any form. A decision-making criterion is subsequently invoked to select the “best” subset of solutions from the obtained non-dominated Pareto optimal solutions. The pareto optimal set obtained in case are compared and contrasted and observations made comparing reliability based approach vis-a`-vis robustness based approach. Deterministic, reliability-based and robustness based multi-objective optimization solutions are compared.
Bowl-Type Diffusers for Low Specific-Speed Pumps: An Industrial Application
Authors: Boncinelli Paolo , Biagi Roberto , Focacci Antonio , Corradini Umberto , Arnone Andrea , Bernacca Marco , Borghetti Massimiliano
Published: September 2008

In this paper, the aerodynamic design of a bowl–type diffuser for a low specific–speed pump is presented and described in detail. The main goal was to achieve an optimal configuration in terms of diffuser recovery capacity and stage aerodynamic efficiency, while satisfying severe constraints concerning stage size and multistage feasibility. Both geometrical parametrization tools and a fully–viscous three–dimensional numerical solver were exploited in the design process. The geometrical parameterization allowed one to control and modify the geometry of the component by changing a limited number of parameters. CFD analysis was exploited to assess the effectiveness of the geometrical modifications on the performance, and to identify critical problems. A number of aerodynamic ID coefficients with simple physical meanings were also introduced and used as a support to the design to synthesize the main feature of the strongly three–dimensional flow evolving in the component. As a result, a new stage configuration was developed according to the imposed constraints, whose performance is at the same level as standard pumps of the same class.
A New Method to Simulate Rotor-Stator Interactions in a Centrifugal Pump Stage
Authors: Feng Jianjun , Benra Friedrich-Karl , Dohmen Hans Josef
Published: September 2008

A new method is put forward to model rotor-stator interactions in the first stage of a multistage centrifugal pump consisting of an impeller, a vaned diffuser and a vaned return channel. A directional loss model is utilized to model the function of a water tank behind the return channel. A periodic boundary condition between the inlet and the outlet is applied to model a closed loop. Thus no flow specification either in the inlet or outlet is required, neither is the turbulence level. Consequently it can avoid specifying unphysical stationary boundary conditions at the inlet and the outlet for transient simulations. Transient numerical results are compared with those by the conventional simulation with stationary boundary conditions (constant total pressure at the inlet and fixed mass flow at the outlet) in detail. The new model can predict the mass flow fluctuation in the pump, which reaches 0.5% of mean flow rate during one period. The mass flow fluctuation does not have a significant influence on the velocity field; however it does have some important effects on the pressure and turbulent kinetic energy fields.
An Analytical Solution for Nonlinear Cylindrical Bending of Functionally Graded Plates
Authors: Navazi H. M. , Haddadpour H. , Rasekh M.
Published: September 2008

In this paper, the nonlinear cylindrical bending of a functionally graded plate is studied. The material properties of the plate are assumed to be graded continuously in the direction of thickness. The variation of the material properties follows a simple power-law distribution in terms of the volume fractions of constituents. The von Karman strains are used to construct the nonlinear equilibrium equations of the plates subjected to in-plane and transverse loadings. The governing equations are reduced to linear differential equation with nonlinear boundary conditions yielding a simple solution procedure. The results show that the functionally graded plates exhibit different behavior from plates made of pure materials in cylindrical bending. Also, it is shown that the linear plate theory is inadequate for analysis of FG plate even in the small deflection range.
Constitutive Formulation for Numerical Analysis of Visco-Hyperelastic Damage Phenomena in Soft Biological Tissues
Authors: Natali Arturo N. , Carniel Emanuele L. , Pavan Piero G. , Gasparetto Alessio , Sander Franz G. , Dorow Christina , Geiger Martin
Published: September 2008

Soft biological tissues show a strongly non linear and time-dependent mechanical response and undergo large strains under physiological loads. The microstructural arrangement determines specific anisotropic macroscopic properties that must be considered within a constitutive formulation. The characterization of the mechanical behaviour of soft tissues entails the definition of constitutive models capable of accounting for geometric and material non linearity. In the model presented here a hyperelastic anisotropic formulation is adopted as the basis for the development of constitutive models for soft tissues and can be properly arranged for the investigation of viscous and damage phenomena as well to interpret significant aspects pertaining to ordinary and degenerative conditions. Visco-hyperelastic models are used to analyze the time-dependent mechanical response, while elasto-damage models account for the stiffness and strength decrease that can develop under significant loading or degenerative conditions. Experimental testing points out that damage response is affected by the strain rate associated with loading, showing a decrease in the damage limits as the strain rate increases. This phenomena can be investigated by means of a model capable of accounting for damage phenomena in relation to viscous effects. The visco-hyperelastic damage model developed is defined on the basis of a Helmholtz free energy function depending on the strain-damage history. In particular, a specific damage criterion is formulated in order to evaluate the influence of the strain rate on damage. The model can be implemented in a general purpose finite element code. This makes it possible to perform numerical analyses of the mechanical response considering time-dependent effects and damage phenomena. The experimental tests develop investigated tissue response for different strain rate conditions, accounting for stretch situations capable of inducing damage phenomena. The reliability of the formulation is evaluated by a comparison with the results of experimental tests performed on pig periodontal ligament.
A System Design Approach for Thermal Insulation of Subsea Equipment Using CFD
Authors: Sorbye Stein , Moe Randi
Published: September 2008

Subsea oil and gas production systems are becoming more complex and more automated. At ocean depths down to 2300m reliability and dependability are of utmost importance. During a production shut-down the production fluid in the subsea equipment will be cooled off by the surrounding ocean water. Simultaneous presence of light hydrocarbons and water in a cold environment with relatively high pressure can create hydrates that are ice like substances capable of blocking the production piping and prevent fluid flow. The equipment is therefore thermally insulated to slow down the cooling process. Field operators are challenging subsea equipment makers to break new boundaries with respect to passive thermal insulation and to increase reliability of the thermal performance. This paper will present the methodology and results of a thermal insulation design project conducted for Total E&P Angola. The project aimed to meet cool down times in excess of 20 hours in areas where 8 hours were previously the norm. In order to meet such a stringent requirement, a system approach to thermal design had to be adopted and reliance on computational analyses tools had to be strengthened. Following a design phase in which the computational analyses tools CFD and FE were used to design the thermal insulation, a full scale cool down test was performed with a subsea Manifold. The simulated cool down results generated by CFD and FE compared well to the results of a full scale cool down test.
Analysis of a Virtual Prototype First-Stage Rotor Blade Using Integrated Computer-Based Design Tools
Authors: Arnal Michel , Precht Christian , Sprunk Thomas , Danninger Tobias , Stokes John
Published: September 2008

The present paper outlines a practical methodology for improved virtual prototyping, using as an example, the recently re-engineered, internally-cooled 1st stage blade of a 40 MW industrial gas turbine. Using the full 3-D CAD model of the blade, a CFD simulation that includes the hot gas flow around the blade, conjugate heat transfer from the fluid to the solid at the blade surface, heat conduction through the solid, and the coolant flow in the plenum is performed. The pressure losses through and heat transfer to the cooling channels inside the airfoil are captured with a 1-D code and the 1-D results are linked to the three-dimensional CFD analysis. The resultant three-dimensional temperature distribution through the blade provides the required thermal loading for the subsequent structural finite element analysis. The results of this analysis include the thermo-mechanical stress distribution, which is the basis for blade life assessment.
Dynamic Simulation Technique for Prediction of Stress on Element of Metal Pushing V-Belt Under CVT Operation
Authors: Saito Toshihiro
Published: September 2008

A simulation method enabling simultaneous prediction of dynamic behavior and stress distribution on an individual element has been developed for durability evaluation of dynamic strength of metal pushing V-belts. The finite-element-method that enables contact analyses in time history with large-scale model was adopted to reproduce the dynamic behavior of the V-belt in high rotational speed range of CVT. This paper focuses on the element strength in actual CVT operation, and also discusses modifications made to the previously reported simulation method to enable the prediction of detailed stress. A new technique named inertia-relief is introduced, which does not require the application of constraint conditions when calculating the detailed stress on element in respectively. This results in allowing the stress distribution on any element to be found at any position on the trajectory of the V-belt and the elastic deformation of the element to be identified. Using this technique, it has been found that the stress on the necks of elements at the entrance and exit of the pulleys affects the dynamic strength of the V-belt. Furthermore, a method of evaluating this stress was also determined. In addition, consideration was given to the effect of the elements tail side concave shape on the dynamic strength of the V-belt.
Manufacture of Propulsion Systems for Micro Underwater Vehicles
Authors: Cheng Yih-Lin , Shen Yu-Shen , Lin Jiang-Hong
Published: September 2008

Underwater vehicles have been used in many ocean exploration and rescue applications. Recent researches are trending toward the vehicle’s application in smaller regions. As size of the parts decreases, challenges exist in the manufacturing of critical components which are hard to obtain commercially. This paper focuses on developing the propulsion systems of the micro underwater vehicle, and exploring the feasibility of the manufacturing. The target hull size of the micro underwater vehicle that the propulsion systems use is less than 50×30×30mm. In this research, two types of propulsion systems, propeller-type and jet-type, were investigated. In the propeller-type propulsion system, a propeller with the selected electric motor was designed to generate sufficient thrust, and the blade section was based on NACA four-digit airfoils. The outer diameter of the propeller is 25 mm with a minimum blade thickness of 0.9 mm. The thin 3D blade geometry is hard to achieve by traditional manufacturing approaches. As a result, Shape Deposition Manufacturing (SDM) process, a layered manufacturing technique, was used to generate the complex 3D propeller. The thrust performance of the fabricated propeller was also compared with the theoretical thrust. The jet-type propulsion system utilized the concept of piezoelectric-actuated valveless micro-pump, and a special design with 3 inlets from the side and one outlet in the back was implemented in order to satisfy the micro underwater vehicle application. The 3D geometry of the channel with minimum width of 80 μm creates great challenges in fabrication and poses difficulty when done by traditional micro fabrication techniques. SDM process is also applied to manufacture the chamber and channels of the micropump. The piezoelectric buzzer was attached to the fabricated valveless micropump chamber for testing back pressure and flow rate. This research provides solutions to manufacture propeller-type and jet-type propulsion systems for micro underwater vehicle applications. SDM process was proved to be the suitable approach to generate small complex 3D propellers and a pre-assembled valveless micropump structure with micro channels.
Extending Lagrange Interpolation to Develop a 4-Node Quadrilateral Element
Authors: Pradeep Kumar A. S. , Udipi Shrinivasa
Published: September 2008

Today finite element method is a well established tool in engineering analysis and design. Though there are many two and three dimensional finite elements available, it is rare that a single element performs satisfactorily in majority of practical problems. The present work deals with the development of 4-node quadrilateral element using extended Lagrange interpolation functions. The classical univariate Lagrange interpolation is well developed for 1-D and is used for obtaining shape functions. We propose a new approach to extend the Lagrange interpolation to several variables. When variables are more than one the method also gives the set of feasible bubble functions. We use the two to generate shape function for the 4-node arbitrary quadrilateral. It will require the incorporation of the condition of rigid body motion, constant strain and Navier equation by imposing necessary constraints. The procedure obviates the need for isoparametric transformation since interpolation functions are generated for arbitrary quadrilateral shapes. While generating the element stiffness matrix, integration can be carried out to the accuracy desired by dividing the quadrilateral into triangles. To validate the performance of the element which we call EXLQUAD4, we conduct several pathological tests available in the literature. EXLQUAD4 predicts both stresses and displacements accurately at every point in the element in all the constant stress fields. In tests involving higher order stress fields the element is assured to converge in the limit of discretisation. A method thus becomes available to generate shape functions directly for arbitrary quadrilateral. The method is applicable also for hexahedra. The approach should find use for development of finite elements for use with other field equations also.
Fracture Mechanics Study of Cracked Pipe Bends Under Internal Pressure and Bending Moments
Authors: Joglekar Manish M. , Joshi S. G. , Dutta B. K.
Published: September 2008

The present work attempts to investigate some aspects of the fracture behavior of cracked pipe bends under the action of in-plane bending moments, with and without internal pressure. The results of the elastic-plastic FE analysis of the defect free elbow under the action of in-plane opening and closing bending moments are presented with the emphasis on the hoop and axial stress distribution at various salient locations in the elbow. A severity matrix is outlined subsequently, correlating the various possible cracked configurations and the loading patterns. Parametric studies on the cracked elbows are carried out, in which the parameters, such as ratio of crack depth to elbow thickness (a/t), angle of the part-through wall crack, bend factor ‘h’ and the internal pressure ‘P’ are varied. The variations of the J-integral versus load and load versus load line displacement are presented. The crack initiation load is determined from the material specific critical value of the J-integral. A non-dimensional parameter is suggested as ratio of plastic collapse load to the crack initiation load, which increases with the increase in the internal pressure both in case of the throughwall flawed elbow as well as in the part-throughwall flawed elbow.
On the Resolution of Existing Discontinuities in the Dynamic Responses of an Euler-Bernoulli Beam Subjected to the Moving Mass
Authors: Kargarnovin M. H. , Saeedi K.
Published: September 2008

The dynamic response of a one-dimensional distributed parameter system subjected to a moving mass with constant speed is investigated. An Euler-Bernoulli beam with the uniform cross-section and finite length with specified boundary support conditions is assumed. In this paper, rather a new method based on the time dependent series expansion for calculating the bending moment and the shear force due to motion of the mass is suggested. Governing differential equations of the motion are derived and solved. The accuracy of the numerical results primarily is verified and further the rapid convergence of this new technique was illustrated over other existing methods. Finally, it is shown that a considerable improvement is obtained in capturing the incurred discontinuities at the contact point of traveling concentrated mass.
Extending Design Structure Matrices and Domain Mapping Matrices by Multiple Design Structure Matrices
Authors: Eichinger Markus , Maurer Maik , Pulm Udo , Lindemann Udo
Published: September 2008

Design Structure Matrices (DSMs) and Domain Mapping Matrices (DMMs) are generally used by designers for dynamic optimization of engineering design processes and products. Both methodologies help producing valuable results; however, they are lacking a holistic view onto the processes and products. Dependencies that span multiple product development domains can therefore not be recognized with isolated DSM or DMM analysis. In this paper, we present an integrative approach that combines DSMs and DMMs to obtain the Multiple Design Structure Matrix (MDSM). This methodology offers the possibility to analyze multiple product development domains using one coherent matrix representation form. A holistic perspective helps the designer to identify domain-spanning structures that would not have been recognized with single-domain optimization approaches or isolated analysis of the DSMs and DMMs. Domain-spanning structures are important to identify, as they may cause unpredictable product or process behavior. Our research showed that a holistic perspective can help designers to identify important elements more easily and therefore save time and enhance quality in analysis of engineering systems design. The framework we present consists of a proposal for the selection of appropriate product development domains, their integration, and the derivation of analysis results.
Robust Biaxial Contouring Controller Design Incorporating Frictional Dynamics
Authors: Lin Kuan-Chen , Chen Chieh-Li
Published: September 2008

The performance of a contouring action is evaluated by the geometric deviation called contour error. By analysis, this error is significantly affected by coordination of axes, frictional effects and load variations. To improve the contouring performance, both the coordination control and the friction compensation should be incorporated into controller synthesis. Besides, friction forces are also found tending to vary quantitatively with position and time, which can be termed as parametric uncertainties in the friction modeling. Therefore, this paper provides an integrated structure such that all the factors can be combined into a single formulation, and a robust chattering-free output feedback sliding mode contouring controller design is proposed based on this formulation such that the coordination control, friction compensation, load variation and parametric uncertainties can be together solved by a systematic procedure. Numerical results with 20% system parametric uncertainties are shown consistent to the theoretical analysis, and reveal the effectiveness and the robustness of the proposed method.
A Thermally-Driven Micromixer Based on Fluid Volume Variation
Authors: Franc¸ais Olivier , Jullien Marie Caroline , Rousseau Lionel , Poulichet Patrick , Desportes Serge , Lefevre Jean Pierre , Chouai Assia , Delaire Jacques
Published: September 2008

In microfluidics, flows are laminar due to low Reynolds number (<1). Consequently, mixing between two liquids is mainly obtained by natural diffusion which may take a long time or equivalently requires centimetre length channels. However, it is possible to generate chaotic-like flows either by modifying the channel geometry or by creating an external perturbation of the flow. In this paper, an active micromixer is presented consisting on thermal actuation with heating resistors. In order to disturb the liquid flow, an oscillating transverse flow is generated by heating the liquid. Depending on the value of boiling point, either bubble expansion or volumetric dilatation controlled the transverse flow amplitude. The configuration is identical to the one of Dodge et al. [7], but the transversal oscillating flow is created by thermal actuation instead of pneumatic ones. A chaotic like mixing is then induced under particular conditions depending on volume expansion, liquid velocity, frequency of actuation… This solution presents the advantage to achieve mixing in a very short time (1 s) and along a short channel distance (channel width). It can also be integrated in a more complex device due to actuator integration with microfluidics.
Motion Transmissibility Characteristics of Some Linear and Nonlinear Passive Suspension Systems With Elastically Supported Damper
Authors: Garule Milind B. , Joshi S. G.
Published: September 2008

Ruzicka and Cavanaugh have presented a passive suspension system with an elastically supported damper with a view to improve its performance in the region of resonance as well as in high frequency region. In this paper, some linear and nonlinear modified forms of Ruzicka’s model of suspension system have been analysed for their motion transmissibility characteristics. The effect of variation of parameters such as, the support spring stiffness, the auxiliary spring stiffness, damping ratio and nonlinearity coefficient on motion transmissibility of the modified models is studied. From the results of analysis, it is observed that for a certain combination of the suspension parameters, the motion transmissibility of the system can be made almost independent of variation in the damping ratio of the system. The method of nonlinear analysis presented in this paper and the results obtained will provide alternative solutions for the design of passive suspension systems for improved ride comfort characteristics for a large class of road vehicles.
Design and Analysis of the Basic Components in a SOFC Anode Cycle
Authors: Bernardi Davide , Travis Rowland
Published: September 2008

Rolls-Royce Fuel Cell Systems Ltd (RRFCS) is developing a 1MW SOFC hybrid system for power generation with the University of Genoa contributing design of the anode and cathode flow systems. The fuel cell design contains two basic cycles: a cathode cycle to deliver air to the stack and an anode cycle to supply fuel. Both of these are based on a recycling technology where a proportion of the exhaust from each stream is recycled to the inlet of that stream. On the anode side this achieves heating of the fuel to the optimum temperature thereby avoiding undesired carbon deposition. An ejector has been designed to achieve a good mix of the exhaust fuel from the stack with fresh fuel from the pre-processor. Downstream from the ejector a reformer converts methane into hydrogen by steam reforming. The gas produced as a result has the composition and the temperature that generates the optimum condition for the operation of the fuel cell stack. The current paper highlights how the design process of the ejector and a reformer to achieve optimum operation conditions for the fuel cell stack.
Flow Visualization and Pattern Dynamics in Be´nard-Marangoni Convection
Authors: Rahal Samir , Azuma Hisao
Published: September 2008

The aim of this experimental work is to study the pattern dynamics in the Be´nard-Marangoni convection. The free surface deformation fields were visualized by interferometry and the temperature fields by infrared thermography. The influence of the aspect ratio, Rayleigh, Biot and Prandtl numbers, was considered. More dynamics are found to be induced by increasing the Biot number. Conversely, increasing the Prandtl number reduces the dynamics. The deformation magnitude and the wavenumber increase as functions of the gradient of temperature. Two behaviours of the deformation, as a function of Prandtl and Biot numbers, were observed, depending on the value of the gradient of temperature.
The Influence of Injection Pockets on the Performance of Tilting-Pad Thrust Bearings: Part II — Comparison Between Theory and Experiment
Authors: Heinrichson Niels , Fuerst Axel , Santos Ilmar Ferreira
Published: September 2008

This is Part II of a two-part series of papers describing the effects of high pressure injection pockets on the operating conditions of tilting-pad thrust bearings. Measurements of the distribution of pressure and oil film thickness are presented for tilting-pad thrust bearing pads of approximately 100 cm2 surface area. Two pads are measured in a laboratory test-rig at loads of approximately 0.5, 1.5 and 4.0 MPa and velocities of up to 33 m/s. One pad has a plain surface. The other pad has a conical injection pocket at the pivot point and a leading edge taper. The measurements are compared to theoretical values obtained using a three dimensional thermoelasto-hydrodynamic (TEHD) numerical model. At low and intermediate loads the theoretical pressure distribution corresponds well to the measured values for both pads although the influence of the pocket is slightly underestimated. At high loads large discrepancies exist for the pad with an injection pocket. It is argued that this is likely to be due to the unevenness of the collar surface. The measured and theoretical values of oil film thickness compare well at low loads. At high loads discrepancies grow to up to 25 %. It is argued that this is due to the accuracy of the measurements.
The Step Effect and Particle Removal From an Enclosure
Authors: Hendijanifard M. , Saidi M. H. , Taeibi-Rahni M.
Published: September 2008

This paper reports the results of a study of the transient removal of contaminant particle from enclosures containing an obstacle. We study specially a phenomena occur sometimes called the step effect. This phenomenon may occur if the size of the obstacle is small enough in comparison with the length or height of the enclosure. These results are the basic instruments for finding a model for contaminant particle removal from an enclosure containing an obstacle. A numerical CFD code is developed and validated with different cases, and then proper two- and three-dimensional cases are modeled. The size of the obstacle affect the order of magnitude of the convection-diffusion terms in the Navier-Stokes equations, hence results in different phenomena while removing the particles. It may end to a simple removal of the particles from the enclosure or it may contain two or three steps in removal, which is due to increase in scale of magnitude of the convection terms in the Navier-Stokes equations. The results of this paper and Ref. [3] may be compacted into one whole theory, describing the particle removal efficiency from an enclosure as a function of obstacle position and size.
Dynamic Behaviour of Human Body During Operation of Mobile Machines
Authors: Launis Sirpa , Leino Simo-Pekka , Kortelainen Juha M.
Published: September 2008

The goal of our research work has been to build up an easy-to-use, computationally feasible virtual simulation model of the human body which could be applied to various studies of the vibration transmission and the human exposure to vibration during mobile machine operation. The proposed human model is a 46 degrees-of-freedom multibody model, in which PD-controllers are used to describe the muscular action in driving situations. In the presented case study, random, real driving situation based excitations are applied on the model. The results of the virtual simulation are compared with measurement data from physical test drive simulator. It is shown, that the conventional PD-controller can predict the human behavior in a reasonable accuracy with smaller amplitude excitation. When the human undergoes larger shock loads, there could be added a delay term in the control law.
Automatic Definition of the Sequence of Operations in Progressive Dies
Authors: Fado´n Salazar Fernando , Cero´n Hoyos Jose´ Enrique
Published: September 2008

We are working in the design process of progressive dies to make that process more structured and, by this way, to be able to automate the different design phases. The basic phases that it’s necessary to follow in the design of a progressive die could be divided into two groups: 1. The strip layout design. This phase involves several steps such as to obtain blank development, to find the best layout, to define the sequence of operations, to calculate the forces... 2. The die design according to the strip layout previously designed. The characteristics’ die depends on the tools are necessary to use (standard or specific for each die), maintenance... These two phases are not independent between them, and the final and optimal design is achieved improving iteratively these phases. In the first phase, the strip layout design, one of the more important steps is to define all the operations that it’s necessary to carry out and the sequence that these operations have to follow to get the part with the wanted characteristics. In the present paper it’s presented a methodology and the software with its application. This methodology consists of extracting all data are going to be use to manufacture the part from its solid modeling or 3D representation. These data are used to create a relational diagram (or relational tree) that shows the relationship among the different features that form the part. Once this tree is represented, it’s used to define the operations that are going to be made and to obtain a first approximation to the sequence of operations that the designers could change according their experience.
Strength of Adhesive Joints Under Impact Stress Conditions
Authors: Goglio Luca , Rossetto Massimo
Published: September 2008

The paper reports an experimental study on the bonded joints, carried out by means of an instrumented impact pendulum, equipped to load overlap specimens in tensile shear. Such testing configuration is the most adequate and natural to study the possible modifications of the behavior of the joint, changing from static to dynamic loading condition, keeping the same specimen type. The specimens were steel strips bonded by an epoxy adhesive (Hysol 3425). Several values of lap length, adhesive and adherends thickness were adopted, to achieve rupture under different stress combinations. The stress state at rupture has been calculated by means of a structural solution. The results show that it is possible to represent the failure condition on a chart having as axes the peel and shear structural stress, in a way similar to that found for static cases. Furthermore, in spite of the concerns associated with the impact condition, the strength of the adhesive does not decrease with respect to the case of static loading.
Numerical and Experimental Approaches to Investigate the Stability of a Motorcycle Vehicle
Authors: Cheli Federico , Bocciolone Marco , Pezzola Marco , Leo Elisabetta
Published: September 2008

The study of motorcycle’s stability is an important task for the passenger’s safety. The range of frequencies involved for the handling stability is lower than 10 Hz. A numerical model was developed to access the stability of a motorcycle vehicle in this frequency range. The stability is analysed using a linearized model around the straight steady state condition. In this condition, the vehicle’s vertical and longitudinal motion are decoupled, hence the model has only four degrees of freedom (steering angle, yaw angle, roll angle and lateral translation), while longitudinal motion is imposed. The stability was studied increasing the longitudinal speed. The input of the model can be either a driver input manoeuvre (roll angle) or a transversal component of road input able to excite the vibration modes. The driver is introduced in the model as a steering torque that allows the vehicle to follow a reference trajectory. To validate the model, experimental tests were done. To excite the vehicle modes, the driver input was not taken into account considering both the danger for the driver and the repeatability of the manoeuvre. Two different vehicle configurations were tested: vehicle 1 is a motorcycle [7] and vehicle 2 is a scooter. Through the use of the validated model, a sensitivity analysis was done changing structural (for example normal trail, steering angle, mass) and non structural parameters (for example longitudinal speed).
Pull-In Parameters of Cantilever Type Nanomechanical Switches in Presence of Casimir Force
Authors: Ramezani Asghar , Alasty Aria , Akbari Javad
Published: September 2008

In this paper, the influence of the Casimir force on two main parameters describing an instability point of cantilever type nanomechanical switches, which are the pull-in voltage and deflection are investigated by using a distributed parameter beam model. The nonlinear differential equation of the model is transformed into the integral form by using the Green’s function of the cantilever beam. The integral equation is solved analytically by assuming an appropriate shape function for the beam deflection. The detachment length and the minimum initial gap of the cantilever type switches are given, which are the basic design parameters for NEMS switches. The pull-in parameters of micromechanical electrostatic actuators are also investigated as a special case of our study by neglecting the Casimir effect.
An Investigation on the Effect of Drivetrain Hybridization in a Transit Bus, Series Configuration
Authors: Khanipour Ahmad , Esfahanian Mohsen , Sangtarash Farhad , Amiri Meisam
Published: September 2008

To achieve higher fuel economy and lower emissions hybridization of conventional vehicles seems to be an effective solution and an important step. In this paper, after a short introduction about the hybrid electric vehicles a brief design of series electric vehicles is introduced. Then one of the Iran-Khodro city buses named O457 is chosen to change to a series hybrid electric bus. After choosing the proper hybrid components the bus performance is investigated to assure whether it can satisfy the required performance or not. Then the conventional O457 and its series configurations for two different control strategies are defined and evaluated using the ADvanced VehIcle SimulatOR, ADVISOR. Simulations are carried out in a combined urban drive cycle because of the lack of a real drive cycle for Tehran city. The fuel consumption and the amount of produced emissions are compared together for three mentioned cases. The validity of simulation has been proved by the close conformity between the value of fuel consumption of the conventional vehicle reported by the company to what has been achieved from the simulation. It is observed that compared to the conventional vehicle, a reduction in fuel consumption about 32% in the maximum SOC control strategy and about 27% in the thermostat control strategy are possible to achieve. In addition, simulation results indicate that air pollution caused by vehicle engine can be greatly reduced through hybridization using each of the mentioned control strategies.
Automotive Systems: End-of-Life Vehicles Dismantling Facilities
Authors: Acaccia Gabriella M. , Michelini Rinaldo C. , Penzo Luca , Qualich Nicola
Published: September 2008

The paper discusses characterising features of the end-of-life vehicles EU regulation, with account of the process transparency and knowledge build-up, to tailor economic instruments with reverse logistics profitability. In the short future, these issues will affect the automotive market, and the recovery (reuse/recycle) targets will become competition prerequisites for the carmakers survival. For explanatory purposes, the investigation is especially limited to consider the dismantling facility, with, in foreground, facts and technicalities arising at local and regional scales, and, in background, the whole forward and backward supply chain and related logistics problems. The basic technicalities, leading to the build-up of the reference knowledge for the most effective setting of car-dismantling facilities, are explored by means of simulation results. These lead to consider to develop automotive systems with recovery in mind, according to the carmakers responsibility for the free-take-back of the end-of-life vehicles.
Application of a Finite Element Quasi-3D Solution of the Energy Equation to the TEHD Analysis of Dynamically Loaded Journal Bearings
Authors: Stefani Fabrizio A.
Published: September 2008

Taking advantage of the quasi-three-dimensional (quasi-3D) solution of the energy equation in the lubricant film presented in a previous work, a new method for analyzing the lubrication of dynamically loaded bearings is proposed. Cavitation is taken into account with a mass-conserving formulation of the hydrodynamic problem, where viscosity variations through the oil thickness are considered. The heat exchanged by the lubricant film with the bearing and the shaft is computed. Hence the thermo-elastic expansion of both the journal and the sleeve can be considered, together with the mechanical deformations of the bearing.
Transformer Eddy Current Dampers for the Vibration Control of Rotating Machines
Authors: Amati Nicola , Carabelli Stefano , Macchi Pietro , Silvani Mario , Tonoli Andrea
Published: September 2008

Eddy current dampers are promising devices for the passive and semi-active vibration control of mechanical structures. Among them “motional” eddy current dampers are based on the Lorentz forces between a moving conductor and a stationary magnetic field. “Transformer” eddy current dampers are based on the forces that develop in a voltage driven electromagnet when part of the magnetic circuit is movable. Considering the simplicity of the layout, transformer configurations seem to be very promising as alternative to traditional rubber or squeeze film dampers to control the lateral vibration of rotating machines. The aim of the present paper is to investigate the dynamic behavior of “transformer” eddy current dampers integrated in a mechanical structure. To this end the bond graph formalism is adopted with the aim of evidencing the causality effects between the mechanical and electromagnetic parts. The modeling approach allows to propose a design procedure of the damper. The mathematical models have been validated experimentally using two test benches with different layouts and geometrical characteristics of the magnetic circuit.