bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of Defects for Effective Gettering in Silicon Wafer and Polysilicon Thin Films
Authors: Macodiyo Dan O. , Soyama Hitoshi , Hayashi Kazuo
Published: September 2008

The scaling down of commercial products has fueled the rapid development of micro- and nano-electromechanical systems (MEMS/NEMS). The enabling technologies of surface micromachining for silicon has made it compatible with industry strategies towards integrated circuits used in actuation and controls of systems. During the silicon processing, microdefects do occur. If properly controlled, they act as gettering sites for metallic species and hence remove unwanted impurities in the active device regions of semiconductor devices. On the other hand, microdefects can be responsible for plastic deformation of silicon wafer. The occurrence of dislocations in the active device regions causes current leakage and even failure of devices. Determination of the optimum point at which bulk microdefects can be considered to have beneficial gettering effect in silicon wafer and the exact mechanisms by which mobile dislocations are generated in the bulk of an initially dislocation free silicon wafer are not well understood. The purpose of this study is to analyze types of dislocation misfits and the corresponding defect size that is responsible for effective gettering due to cavitation impacts. The authors have already studied electrical characteristics of backside damage gettering by cavitation impact [1–3]. Polysilicon has been grown on thin silicon suboxide layer by a gas-source molecular beam epitaxy (MBE). MBE was done by placing the silicon substrate in an ultra-high vacuum chamber and heating it to 800 °C for 10 min and then at 700 °C for 3 hours at a flow rate of 2.5 sccm. The atomic force microscopy (AFM), micro Raman spectroscopy and transmission electron microscopy (TEM) were used to characterize the Czochralski silicon (CZ–Si) in the plane (100) and poly-Si/SiO2 in the atomic scale before and after gettering the specimen. AFM results showed that the surface roughness and threshold deformation were 2.3 nm and 4.4 nm, respectively. Plan-view TEM analysis of silicon showed the coexistence of single dislocation and narrow dipoles. It can be concluded that cavitation impacts causes dislocation dipoles on CZ-Si(100) which are associated with dislocation loops. The initiation point takes the form of a micro Frank-Read dislocation source, less than 50 nm, that cause dislocation dipoles which are associated with dislocation loops. Plan view TEM observations reveal that the size of the dislocation misfits was approximately 100 nm. The polysilicon surface had a higher residual stresses when it was subjected to cavitation impacts. The cross-sectional TEM observation on poly-Si revealed random crystals on the noncavitated specimens while a mixer of columnar-textured grains on the specimen treated by cavitation. The textured grains have rough edges and the intra-grain size is about 40 nm. Deformation twins and set of streaks from an array of dislocations were observed in the cavitated poly-Si/SiO2 specimens. The spacing between the large grains was 8 nm.
Anamnesis for Improving Thermoeconomic Diagnosis: The Case of a 3×350 MW Coal-Fired Power Plant
Authors: Uso´n Sergio , Correas Luis , Valero Antonio
Published: September 2008

The aim of thermoeconomic diagnosis is to identify malfunctioning components in energy systems and to quantify the increment of fuel consumption due to each anomaly. Anamnesis, or the repetition of diagnosis along the time, allows to overcome error induced by measurement uncertainty. In this paper, a diagnosis system based on the diagnosis algorithm proposed by Correas [1] and implemented at Teruel 3×350 MW coal-fired power plant is presented and applied to the anamnesis for a period of several years. First, the plant and the diagnosis system structure are briefly described. Then, the diagnosis model is presented, including the definition of the free diagnosis variables, (independent causes of additional fuel consumption) and the system efficiency indicators (dependent variables). In the free diagnosis variables not only indicators of component efficiency are included but also set-points, ambient conditions and fuel quality. The system has been used by the power plant O&M staff for more than a year, and this experience has yielded important conclusions on how to design and implement such diagnosis systems. Afterwards, some results of the anamnesis performed by using this system are presented. It can be seen how the measurement uncertainty induces dispersion, so that the direct comparison of only two situations could lead to inexact conclusions.
Computer Simulation of Turbocharged Aftercooled Gasoline Engine
Authors: Kharazmi Shahabaddin , Hajilouy-Benisi Ali , Mozafari Ali Asghar
Published: September 2008

Turbocharging of gasoline engines has been improved less than diesel engines due to some difficulties, especially knock phenomena. They require wider air flow range and faster response too. A computer code is developed to simulate turbocharged gasoline engine behavior. A three zone combustion model is employed. Different performance curves at speed and equivalence ratio ranges are prepared. By this code naturally aspirated and turbocharged behavior are compared. A turbocharged aftercooled engine has been studied in various cases to complete the investigation. Some aftercooler effects are described experimentally. Modeling and experimental results are compared providing valuable achievements.
A New Mechanism for Wall Climbing Operation Based on 4-Bar Linkage
Authors: Sharif Shourijeh Mohammad , Sayyaadi Hassan
Published: September 2008

Wall walking robots are designed for different purposes, rescue operations, wall inspections and jobs such as painting and cleaning and fire fighting for tall buildings. These are some cases that these types of robots are extensively used. This paper describes a design of a new serial mechanism for wall climbing job. In deed we are seeking to define a minimum degree of freedom mechanism to be applied in a robot moving vertically on a surface. This mechanism has 5 links, but at any point it works with its 4 links, actually in each cycle of motion the linkage will be interchanged.
Kinematical and Dynamic Analysis of Biped Robots’ Locomotion Using Dynamic Object Manipulation Approach
Authors: Beigzadeh Borhan , Nili Ahmadabadi Majid , Meghdari Ali
Published: September 2008

In this paper, we try to interpret “Duality of Dynamic Locomotion and Dynamic Object Manipulation”. Since our main goal in this paper is to offer the duality concept and to validate it with a case study, we deal with the problem in a simple and abstract system. As a case study, we describe the duality between the problem of 2D dynamic object manipulation of a sphere using two planar manipulators and 2D dynamic locomotion of lower part of a biped robot. Having obtained the equations of dynamic object manipulation, we change the boundary conditions of the problem in such a way that both radius and mass of sphere object tend to infinity. Simultaneously, both of size and mass of manipulators’ base, i.e. the planet earth, tend to some values in the order of human body’s mass and dimension. Regarding these changes, we can change the dynamic object manipulation problem to a dynamic locomotion one. A simple control strategy is introduced to handle the impact problem between the manipulators (legs) and the object (the earth). In addition, a motion planning system is devised in such a way that the manipulators (legs) catch and throw the manipulated object (the earth) in appropriate configurations. Simulation results are given to support the developed idea.
Redesign of a Centrifugal Compressor’s Vaned Diffuser to Improve Core Engine Performances
Authors: Mileshin Victor I. , Startsev Andrew N. , Brailko Igor A. , Orekhov Igor K.
Published: September 2008

Present paper is devoted to numerical optimization of a 8:1 total pressure ratio centrifugal compressor to improve performances of core engine belonging to a turbo-shaft engine. Main subject of optimization is vaned diffuser with following impeller’s pressure ratio increase. This compressor designed by CIAM [7] and tested as a part of core engine gave satisfactory performances even under the first test run. Further development requires new concepts one of which is reduction of core engine’s turbine inlet temperature. Redesign of vaned diffuser through elimination of reverse flow zone gives 5% increase of mass flow-rate and 0.7% increase of efficiency. Further 6% increase of impeller’s total pressure ratio (at the same rpm) modifies Brayton cycle of core engine reducing turbine inlet temperature by 32° and turbine exhaust temperature by 43°. To maintain the same power output, this drop of turbine exhaust temperature is compensated by 4% increase of the operational flow-rate.
Estimation of the Comfort Indexes of a Rail Vehicle at Design Stage
Authors: Corradi Roberto , Melzi Stefano , Ripamonti Francesco , Romani Mario
Published: September 2008

This work describes a numerical method allowing to estimate the comfort indexes of a rail vehicle at the very beginning design stage. Thanks to a flexible multi-body code developed by Politecnico di Milano a series of simulations relevant to an AnsaldoBreda high speed train vehicle has been performed. The accelerations on the carbody floor were processed in accordance with the EN 12299 normative and the NMV comfort indexes were calculated. Furthermore a deeper investigation about some aspects that significantly affect the comfort indexes has been carried out.
Compact Basis Free Relations for Stress Tensors Conjugate to Hill’s Strain Measures
Authors: Naghdabadi Reza , Asghari Mohsen , Ghavam Kamyar
Published: September 2008

If the double contraction of a stress tensor such as T and rate of a Lagrangean strain tensor such as E, i.e. T : E˙, produces the stress power then these stress and strain tensors are called a conjugate pair. The applications of the conjugate stress and strain measures are in the development of the basic relations in nonlinear continuum mechanics analysis such as modeling of constitutive equations of elastic-plastic materials. In this paper relations for stress tensors conjugate to an arbitrary Lagrangean strain measure of Hill’s class are obtained. The results of this paper are more compact and simpler in compare with those available in the literature. The results are valid for the three dimensional Euclidean inner product space and the case of distinct eigenvalues of the right stretch tensor U.
Computer-Aided Design and Numerical Flow Analysis of Axial-Flow Pump With Inducer
Authors: Li Yaojun , Wang Fujun
Published: September 2008

Axial-flow pump equipped with inducer are widely used in marine propulsion systems. The interaction of inducer and impeller has significant effect on the performance of pump. In this study, a special axial-flow pump is designed and analysed by CAD-CFD approaches to study the interaction of inducer and impeller. The pump includes two main elements, an inducer with 3 blades mounted on a conical hub and a 6-blade impeller. The blade angle of impeller is adjustable to generate different relative circumferential angles between the inducer blade trailing edge and the impeller blade leading edge. The 3D pump solid model is generated by taking the data file as interface between hydraulic-design and 3D modelling. A computational fluid dynamics code is used to investigate the flow characteristics and performance of the axial-flow pump. Numerical simulation is performed by adopting 3D RANS equations with RNG k-epsilon turbulence model. An unstructured grid system and the finite-volume method are used for the solution procedure of the discretized governing equations for this problem. The rotator-stator interaction is treated with a multiple reference frame (MRF) strategy. Computations are performed in different cases: 7 different relative circumferential angles (Δθ) between the inducer blade trailing edge and the impeller blade leading edge, 3 different axial gaps (G) between the inducer and the impeller. Variation of the hydraulic loss in the rotator is obtained with the change of delta theta. The numerical results show that the pressure generated is minimum in case of (G = 3%D). This indicates that the interference between inducer and impeller is strong if the axial gap is small. The pump performances are predicted and compared to the experimental measurements. The current investigation leads to a thorough enough understanding of the flow characteristics in axial-flow pumps with complex configurations. Recommendations for future modifications and improvements to the pump design are also given.
Development of Measurement Equipment for Measuring Tire Rolling Resistance on Road
Authors: Leinonen Antti , Juhala Matti
Published: September 2008

In the Laboratory of Automotive Engineering at Helsinki University of Technology measurement equipment for rolling resistance measurements on road was developed. A whole new trailer was not constructed, but the equipment was placed in the noise measurement trailer HUT NOTRA. The measurement device is based on a load cell. The axle of the measurement tire is fastened with a rigid rod and two bearings to an auxiliary axle below it. Bearings allow the axle of the measurement tire to rotate around the auxiliary axle and this one degree of freedom is bound with the load cell that measures the rolling resistance force. Because the force reading is dependent on the alignment of the measurement device and that varies due to the suspension of the trailer, the alignment is monitored using an LVDT. The equipment was tested on different road surfaces. Several unexpected problems were encountered and therefore absolute values of rolling resistance force could not be determined. However, the project provided valuable information on different aspects related to development of a rolling resistance measurement device and that information can be used in forthcoming research projects.
Incremental Forming of Friction Stir Welded Taylored Sheets
Authors: Ambrogio G. , Fratini L. , Micari F.
Published: September 2008

In the last decade sheet metal forming market has undergone substantial mutations since the development of more efficient strategies in terms of flexibility and cost reduction is strictly due. Such requirements are not consistent with traditional metal stamping processes which are characterized by complex equipment, capital and tooling costs; thus the industrial application of such processes is economically convenient just for large scale productions. For this reason most of the research work developed in the last years has been focused on the development of new sheet forming processes able to achieve the above discussed goals. Contemporary, with particular reference to the automotive industries the requirement of light components and the engineering of the outer skin parts of the vehicles have determined the growing utilization of tailored blanks characterized by either different material or different sheet thickness. In the paper SPIF processes of FS welded aluminium blanks are investigated in order to analyse the product properties in terms of strength and formability. A proper experimental investigation has been carried out and interesting guidelines have been highlighted in the next paragraphs.
Friction Stir Welding of 3D Industrial Parts: Joint Strength Analysis
Authors: Fratini Livan , Piacentini Mario
Published: September 2008

In the recent years Friction Stir Welding (FSW) has become an important joining technique since it allows to weld light weight alloys rather difficult to be welded or even “un-weldable” with the classic fusion welding operations. In the paper the authors present the application of the FSW process to the joining of 3D complex shapes typical of the industrial environment. In particular the research was aimed to highlight the joint mechanical strength at the varying of the 3D geometry of the welding line.
Effect of Dual Beam on Reduction of Porosity in CO2 Laser Welding
Authors: Capello Edoardo , Previtali Barbara
Published: September 2008

In the recent past great study has been dedicated to porosity formation in laser welding. Using impressive apparatus for the experimentation Japanese authors have pointed out the main phenomenological causes of porosity produced by laser keyhole welding. Moreover, they have evidenced the effect of process parameters and bead configuration on porosity formation. Keyhole oscillation and consequently local vaporisation of the molten pool have been found to be present in all metals (stainless steel, carbon steel, aluminium and magnesium alloys) and in all process conditions (CO2 or Nd:YAG systems, continuous wave or pulsed lasers). Since keyhole porosity can not be totally avoided, the laser welding process should be accurately selected and process parameters designed in such a way as to minimise pore formation. The paper is aimed at studying the effect of laser configuration, single beam or dual beam, on the keyhole porosity. A dual beam system, allowing the laser beam to be divided in two beams, both of them working in keyhole mode, has been studied and compared to the traditional single beam welding process. In order to compare the two laser configurations, quantitative features of pores have to be individuated. Since the pores in the bead are supposed to have a negative effect on fatigue strength of the welded component, the main characteristics of investigated porosity were the porosity percentage and the pore diameter. The experimental results show that the dual beam configuration is effective in pore area reduction, if the related process parameters (inter-beam distance and feed rate) are accurately selected.
Mobile Robots for Airports Surveillance: A Modular Solution
Authors: Acaccia Gabriella M. , Bruzzone Luca E. , Razzoli Roberto P.
Published: September 2008

The pursued goal of the present paper is to foresee modular solutions which are suitable for scale production of mobile robots for surveillance in airport indoor and outdoor areas. To this aim, a possible mechatronic modular architecture is proposed, giving details about the mechanical layout, the actuation characteristics, the power supply figures and the command-control organization. The application of quite consolidated modularity methodologies, already successfully exploited in the industrial field, offers the possibility of creating different mobile robots by the proper combinations of basic frame modules and traction/steering modules; this allows to match different requirements in terms of vehicle mobility (average speed, number of traction/steering wheels, maximum slope, etc.) and operability (payload, autonomy, type of onboard equipment, size/arrangements, etc.). Modularity, other than in the production phase, gives significant advantages during service and maintenance, reducing the MTTR and improving the overall availability. It is worthwhile noting how the outlined approach to mobile robotic systems may be effectively extended to the monitoring of similar sites, such as large squares, stock-park spots, containers districts, cars storing places, and the likes.
Flow Induced Vibrations of Pressure Let-Down Station in QATARGAS
Authors: Qaradawi Mohammed Y. , Moshaweh Abdulaziz R.
Published: September 2008

The use of the pipes to transfer oil and gases from production to export places is a common application in oil and gas industries. The safety and stability of the pipelines are crucial to prevent human and equipment losses. One of the criteria that jeopardize safety and stability of the pipelines is the vibration, and especially flow-induced vibration. Flow induced vibration in pipes is affected by many factors such as fluid type, flow velocity, fluid and pipes densities and fluid pressure. This study considers the analysis and modification of an upstream gas pipeline in QATARGAS Company. The study proposes some solutions to the problem of flow-induced vibration in pipes and the platform supporting them.
Development of the Control Strategy for an Innovative 4WD Device
Authors: Cheli Federico , Dellacha` Paolo , Zorzutti Andrea
Published: September 2008

The potentialities shown by controlled differentials are making the automotive industry to explore this field. While VDC systems can only guarantee a safe behaviour at limit, a controlled differential can also increase the handling performance. The system derives from a rear wheel drive architecture with a semi-active differential, to which has been added a controlled wet clutch that directly connects the front axle and the engine crankshaft. This device allows distributing the drive torque between the two axles, according to the constraints due to kinematics and thermal problems. It can be easily understood that in this device the torque distribution doesn’t depend only from the central clutch action, but also from the engaged gear. Because of that the central clutch controller has to consider the gear position too. The control algorithms development was carried on using a vehicle model which can precisely simulate the handling response, the powertrain dynamic and the actuation system behaviour. A right powertrain response required the development of a customize library in Simulink. The approach chosen to carry on this research was the one used in automotive industry nowadays: an intensive simulation campaign was executed to realize an initial controller design and tuning.
Positioning Accuracy Investigations in Face Spiroid Gears
Authors: Staniek Roman
Published: September 2008

There are two basic methods of forming the face spiroid gears. The first one, well known, is based on cutting the gear with multi-point cutting tool on the gear hobbing machine. The second method is based on machining with single-point cutting tool applying continuous indexing on universal NC machine tool and with application of NC rotary table. The second method is recommended for piece production because of the simple, cheap and universal cutting tool. There is also known the method of forming the face gears with involute tooth line obtained by machining with the inclined tool axis in relation to the face surface of the gear. The methods of forming face toothing in spiroid gear with the tool axis parallel to gear surface (according to author’s proposal) has been presented in the article. In this method the tool axis is located against the machined wheel at the same position as the worm is located in the gear and this is the greatest advantage of this method. For both methods there have been elaborated special machining programs for four axis NC milling machine of FYN 50ND type, together with NC rotary table of FNd-400 type. Then the obtained gears have been tested and investigated. Three types of such gears have been investigated, all of them with ratio 1:90. Two versions of the face spiroid gears have been assembled in the rotary table and then positioning accuracy has been measured. Additionally, for comparison reasons, the double pitch worm gear has been investigated using the same measuring instruments. There have been presented the chosen accuracy investigation of the gears in the range of one full rotation of the spiroid wheel that is connected with table disc (measurement by 4°) and in the range of two worm rotations (measurement by 0,1°) General evaluation of the chosen methods concerning the manufacturing of the face wheels in spiroid gears has been presented too. The data have been obtained from literature and from author’s own researches.
Experimental Study of Thermal Cavitation in an Orifice
Authors: De Giorgi Maria Grazia , Chiara Fabio , Ficarella Antonio
Published: September 2008

Some experimental tests were performed studying the flow of water thought an orifice, in order to investigate the onset of the various cavitation structures and the effects of cavitation at different cavitation numbers and temperature. Different flow rates have been tested for different values of temperature. The results show that the cavitation originates at the inlet of the flow constriction area. It grows intensively and transforms into a cavitating cloud. As flow rate was increased, it was observed that the cavitating cloud travels downstream of the hole oscillating around the exit position and it is connected to the hole inlet through a sheet having a complex turbulent structures. The decrease in the cavitation number causes a corresponding increase of the width of the cavitating area especially in proximity of the critical cavitation number. In particular, it was observed that the critical cavitation number increases as the temperature increase. The behavior of the cavitation phenomenon can be related to the pressure fluctuations measured downstream of the orifice; a Fourier Transform of the downstream pressure signal was performed. The development of the cavitation phenomenon for lower cavitation numbers affects the pressure frequency components, related to the impacts due to vapor bubbles implosions. Finally, soma numerical simulations have been performed; the simulation results were compared with the experimental ones.
Mathematical Modelling of Particle Formation in Combustion Processes
Authors: Zucca Alessandro , Marchisio Daniele L. , Barresi Antonello A. , Baldi Giancarlo
Published: September 2008

In recent years the problem of studying particle formation and evolution in turbulent flames has become increasingly important, for both environmental and technological reasons. Information on particle size and morphology is often required, since these characteristics largely influence the effects of particulate matter on human health and global climate in the case of soot. A mathematical model able to describe the evolution of these particulate systems must solve the population balance equation within a Computational Fluid Dynamics (CFD) code that predicts the temperature, composition and velocity fields of the flame. In this work, the recently proposed Direct Quadrature Method of Moments (DQMOM) is applied to the study of soot formation in turbulent non-premixed flames. The model takes into account nucleation, molecular growth, oxidation and aggregation of soot particles; simplified kinetic rates are employed, while velocity and scalar fields are computed by simulations based on the solution of the Reynolds Averaged Navier Stokes (RANS) equations. Different population balance formulations are implemented and compared and results show that DQMOM is a suitable modelling tool; comparison of predictions with experimental data shows that the model accurately describes the morphological properties of soot aggregates.
Transfer Function Modeling of a Flexible Gear Train
Authors: Peled Irit , Halevi Yoram
Published: September 2008

The problem of dynamic, infinite dimension, modeling of a gear train is considered. It includes derivation of the accurate, Laplace transfer function matrix of the system that consists of flexible shafts, individually governed by the wave equation, connected by gears that are either rigid or flexible. The first step is deriving a set of single input, infinite dimension, transfer functions for a single uniform link. The building blocks of those transfer functions are time delays, representing the wave motion, and low order rational expressions, representing the boundary phenomena. The next step is constructing a model for the multi-link gear train system, by using the natural feedback within the system to arrive at a generalized dynamic model. This explicit and highly structured form of transfer functions, allows physical insight into the system, which is lacking in finite dimension approximations. It was used for the analysis of the dynamical behavior of the gear train and may also be used for the design of dedicated control laws.
Thermo-Elasto-Hydrodynamic Analysis of a Crankshaft Journal Bearing
Authors: Lachina Filippo M. , Cappello Francesco , Pisano` Emanuele , Durando Mario V. , Rivara Roberto
Published: September 2008

This paper summarizes the essential parts of a numerical analysis activity in which the application of the Thermo-Elasto-Hydro-Dynamic (TEHD) lubrication theory to a crankshaft journal bearing is examined. The study is carried out through numerical computations performed by a commercial flexible-multibody code which simulates the lubricated contact between elastic bodies in large displacement motion. A multibody model has been created and its thermal behaviour has been validated by comparison with experimental temperatures. The validated model is used to perform two comparative analyses between the TEHD modelling and the Elasto-Hydro-Dynamic (EHD) modelling for max torque and max power conditions. A parametric analysis is also performed in which some functional parameters of the bearing (such as journal speed and bearing clearance) are varied and the influence of these variations on reliability (damage parameters) and performances (lost power) of the bearing is monitored.
Localization of a Mobile Robot With Omnidirectional Wheels Using Angular Kalman Filtering and Triangulation
Authors: Font Josep M. , Batlle Joaquim A.
Published: September 2008

Localization is one of the fundamental problems in mobile robot navigation. Several approaches to cope with the dynamic positioning problem have been made. Most of them use an extended Kalman filter (EKF) to estimate the robot pose — position and orientation — fusing both the robot odometry and external measurements. In this paper, an EKF is used to estimate the angles, relative to the robot frame, of the straight lines from a rotating laser scanner to a set of landmarks. By using this method angles are predicted, between actual laser measurements, by means of the time integration of its time derivative, which depends upon the robot kinematics. Once these angles are estimated, triangulation can be consistently applied at any time to determine the robot pose. In this work, a mobile robot with three omnidirectional wheels — that consist of two spherical rollers — is considered. Computer simulations showing the accuracy of this method are presented.
Structural Optimization of Elastic Articulation Rotor System for Dynamic Stability
Authors: Ku Jieun , Schrage Daniel P.
Published: September 2008

Multilevel optimization methodology is implied on Elastic Articulation (EA) rotor system to find the global and local configuration to ensure the dynamic stability with Autorotation Index (AI) consideration. EA rotor is the rotor system of generic Georgia Tech Helicopter (GTH) and it is soft-in-plane with 10% effective flapping hinge offset and forward sweep angle. Also, EA rotor has the beneficial features such as flexure beams and torque tube that eliminate dampers and hinges that lead to the its simplicity, structural safety, and reduced weight. To ensure the dynamic stability of such superior system, the methodology utilizes the high-fidelity structural beam analysis tools, DYMORE and VABS that reduce the computation time by allowing a hierarchical decomposition of the problem that separates the local (cross-sectional) sub-problem from the global optimization. The procedure is implemented using MATLAB as the overall optimizer. The results showed that the system achieved optimum values through iteration, however, sensitivity analysis is needed.
Optimal Design of a Hip Joint Implant With Hollow Stem Using Finite Element Method
Authors: Zakeri Nasser , Farahmand Farzam , Katoozian Hamid
Published: September 2008

Complication of artificial joint replacement is often attributed to the distribution of mechanical stresses over the bone-cement, and cement-implant interfaces. This study represents the analysis and optimization of a hollow-stem hip prosthesis to reduce the micro-motion and maintain uniformity of stress distribution over the interface regions. A three-dimensional finite element model of the proximal femur was constructed in ANSYS, including the cortical bone, the cancellous bone, the bone cement and the femoral component of hip joint implant. Three design parameters were considered for the implant stem, including the length of the stem and the length and radius of the distal cylindrical cavity. The optimization criterion was defined as a linear combination of the standard deviations of the equivalent Von-Mises stresses and the total displacements at the cement-implant interface nodes. The Response Surface Method and sensitivity analysis indicated that the length of the stem has a major impact on the optimization criterion and the length and the radius of the cavity stand as the minor factors. The optimal design was obtained to have a 10.5 cm length stem with a cylindrical cavity of 23.4 mm length and 1.3 mm radius. The assumed optimization criterion reduced substantially from 3.1 in the initial design to 2.52 in the optimal deign.
Reducing RMS on Wheel Load in ABS-Braking Situations by Control of Semi-Active Suspension
Authors: Niemz Tobias , Winner Hermann
Published: September 2008

In the presented research project the authors’ goal is to determine the potential of reduction of braking distance by automatic control of active dampers in passenger cars. Control strategies are being developed and tested in simulation models to be validated afterwards in test stand trials and test drives. In the presented paper the model assumptions regarding the vibration behavior of the vertical dynamics of the testing vehicle were checked. The assumptions regarding the influence on the wheel load of adaptive dampers could be verified and information about the time behavior and about the strength of the damper change effect could be gained. A control algorithm for the active dampers was developed and implemented in a testing vehicle. The control algorithm, which is called MiniMax control, makes it possible to reduce the RMS on dynamic wheel load in non-braking situations significantly. This could be shown in test rig trials as well as in test drives with defined obstacles. In full braking test drives the chosen controller is able to reduce the RMS on wheel load at initial velocities up to 70 km/h.
Washers to Reduce Vibration and Noise From the Injection Molding Process
Authors: Tsuei Kuang-Yih , Kuo Shu-Fen
Published: September 2008

The noise and vibration problems created by injection molding machines can be moderated by the installation of absorbers. The pull rods of the machine, which are guided to the molding movements, might be a better location for mounting a spring, rubber or hybrid elastomer for energy absorption and reduction of noise and vibration. In this paper, some special washers are designed to fit the guide rods and performance tests are carried out. The results show that noise and vibration decreased over 10 dB and 2 times, respectively.
Synergy-Based Approach to Bad Engineering
Authors: Martin Andres , Kaljas Frid , Reedik Vello
Published: September 2008

In the present paper unique data about initial shortcomings in the design and application of different industrial and consumer products are presented. The research area covers all of the products’ development stages beginning with factory automation and equipment control systems, and continuing with the design and realization of light fittings up to follow-up on the product development of office machines. The statistical results of this research are presented. Further the essence of the synergy-based approach to the design process, focussing on the most common human faults/mistakes, is clarified. Evidence is presented to show that the reason for human shortcomings is either the lack of synergy in teamworking or problems in inner personal communication. A detailed definition of the concepts of positive and negative synergy, with examples from both categories is given. Guidelines are given to reduce human risks at the conception of interdisciplinary systems design to avoid bad engineering. A framework for the synergy-based design of interdisciplinary systems is presented capable of adapting to the competences of the design team.
Traction of Synthetic Traction Fluids and Its Related Rheological Properties
Authors: Muraki Masayoshi , Kawabata Ryuta
Published: September 2008

The traction μsp in the transverse direction due to spin was experimentally determined for commercially available traction oils. An increase in contact pressure increased μsp because of an increase in elastic strain, while a decrease in the radius of the roller in the transverse direction increased μsp owing to an increase in the effective shear modulus. Then, the effect of contact pressure on the maximum traction coefficient μmax in the rolling direction was studied. Under a constant temperature, μmax increased with increasing contact pressure, and then it decreased after reaching a peak value. The calculated results by the thermal solution based on an elastic-plastic model, using the limiting shear stress as a quadratic equation of pressure, agreed well with the experimental traction curves. This suggested that a peak value of μmax was brought about by less than a proportional increase in the limiting shear stress with pressure.
An Investigation on Energy Transfer Mechanism Caused in Rotating Flow Passage of Turbomachinery and Practical Performance Characteristic Curve
Authors: Tanaka Takaharu
Published: September 2008

Hydraulic energy is constructed from two different kinds hydraulic energies. One is the singled irreversible kinetic hydraulic energy that acts horizontal direction. It produces mass weight flow rate. The other is the un-kinetic reversible potential energy. Potential energy is stored on the fluid particle in the form of coupled (or twined) real and imaginary energies. Typical of real energy is potential energy, which is equivalent to pump and water turbine heads. It is caused by the real gravitational acceleration and directs vertical downward. Real potential head is balanced with the imaginary force, which is caused by the imaginary acceleration whose magnitude is equivalent to real gravitational acceleration but its acting direction is opposed to that, therefore, vertical upward. Therefore, to produce the higher real potential pump head that directs vertical downward, the imaginary centrifugal force, whose acting direction is opposed to real potential head, has to be produced and act on the fluid particle vertical upward as much by the impelling action in the rotating flow passage of centrifugal pump.
The Effect of Ultrasonic-Vibration on Upsetting
Authors: Hung Jung-Chung , Tsai Yu-Chung , Hung Chinghua
Published: September 2008

Ultrasonic-vibration upsetting is a process in which a cylindrical specimen is compressed by an axial force while the ultrasonic vibration is simultaneously applied to the die. Homogenous deformation is difficult to achieve during this process because of the friction at the interface between the specimen and the die. An extrapolated compression test was performed in this study on aluminum alloy specimens to explore the effect of superimposing ultrasonic-vibration during upsetting. Experimental results indicate that ultrasonic-vibration reduced the compressive force when the friction was eliminated by the extrapolated compression test. The specimen size also influences the force-reducing effects of ultrasonic-vibration. The decrease in the compressive force is smaller for a larger specimen. The barreling profile of the specimen after test indicates that the interface friction will increase during ultrasonic-vibration compression. Additionally, the raised material temperatures are caused by ultrasonic-vibration. Experimental results of the hot extrapolated compression test and the hot ring compression test indicate that the drop in the flow stress and the increase in the interface friction are caused by the increase in the temperature of the material under ultrasonic vibration.
The Effect of the Exhaust Pipe Arrangement on Motorcycle Engine Acoustics
Authors: Lin Frank K. T.
Published: September 2008

This paper uses a commercial CAE software GT-POWER to simulate the V-twin cylinder motorcycle engine exhaust acoustics. Ten different engine exhaust pipes with equal and unequal length and with or without arc connecting tube are designed. The engine performance and tailpipe exhaust noise on nineteen different engine speeds from 1000rpm to 10000rpm in wide-open throttle are studied. It is found that the effect of exhaust pipe configuration on the engine performance appears to be negligible. The tailpipe exhaust flow rate will be reduced and the overall sound level will bring down as the arc tube is connected to the exhaust front pipes. Also, the equal pipe length adapted with arc tube design gives a major function on pressure attenuation which may reduce the noise level significantly. The results may be useful for exhaust pipe design.
A Novel Method on Singularity Analysis in Parallel Manipulators
Authors: Pendar Hodjat , Mahnama Maryam , Zohoor Hassan
Published: September 2008

A parallel manipulator is a closed loop mechanism in which a moving platform is connected to the base by at least two serial kinematic chains. The main problem engaged in these mechanisms, is their restricted working space as a result of singularities. In order to tackle these problems, many methods have been introduced by scholars. However, most of the mentioned methods are too much time consuming and need a great amount of computations. They also in most cases do not provide a good insight to the existence of singularity for the designer. In this paper a novel approach is introduced and utilized to identify singularities in parallel manipulators. By applying the new method, one could get a better understanding of geometrical interpretation of singularities in parallel mechanisms. Here we have introduced the Constraint Plane Method (CPM) and some of its applications in parallel mechanisms. The main technique used here, is based on Ceva Theorem.
A Novel Injection System for Hypovolemic Patients
Authors: Ercolani Simone P. , Conti Paolo , Banetta Lucio
Published: September 2008

The aim of this paper is to test a new infusion system prototype which is intended to recover the normal venous return and lost blood quantity in hypovolemic patients. For this purpose a bolus of fluid is injected at a high speed in the vena cava, accelerating and dragging the stagnating flow upstream the catheter. In order to improve the effects of the injection and to avoid damage to heart valves, the injection is synchronized with the heart cycle and should be controlled by the electrocardiogram track of the patient in such a way that the maximum flow rate injected occurs when the tricuspid valve is open. An in-vitro experimental apparatus — simulating the vena cava and its environment — has been built and used to measure velocity and pressure fields in the vena cava during the high velocity injection. In a first embodiment, the experimental apparatus consists of two reservoirs arranged, respectively, upstream and downstream a Starling Resistor, but at different heights. A constant flow rate inside the vena cava is maintained, thus simulating the diastolic phase of the heart. In a second embodiment of the experimental apparatus, two electrical valves, arranged downstream the Starling Resistor, generate an oscillating pressure wave along the vena cava, thus simulating the human central venous pressure. By varying the flow rate inside the vena cava and the opening rate of the valves, it has been possible to evaluate the dragging effect of the new injection system and the mechanical behavior of the vena cava during both continuous and pulsating infusion.
Numerical Model of a Tensioner for Undersea Pipes Laying
Authors: Mattiazzo Giuliana , Almondo Andrea , Mauro Stefano , Guinzio Paolo Serena , Sorli Massimo
Published: September 2008

The paper describes the activities carried out for the modeling and identification of the pipe tensioning system used in the lay of off-shore piping lines. First, the interactions between the components of the tensioning system are discussed. Then, a model of the pipe stiffness based on the catenary formulation is presented. It is valid for S or J-lay, depending on the pipe parameters and on the lay conditions. The tensioner model follows. It is composed by a torque controlled electric servomotor that powers a tracks tensioning system. Finally results obtained in the simulation for different work and disturbance conditions are shown.
Stochastic Reliability Based Design Criteria for Linear Structure Subject to Random Vibrations
Authors: Marano G. C. , Trentadue F. , Chiaia B.
Published: September 2008

Random vibration is a common state in many real structural problems concerning dynamic environment loads, as base excitation induced by rotating machinery or wind loads. In this work a full stochastic approach for optimal design of linear structures subject to random dynamic loads is presented. By adopting a covariance approach a reliability based optimum criterion is developed, where both objective function (OF) and constraints are defined in a stochastic way. This criterion can be applied both for stationary and for non stationary vibration conditions. Constraints impose a limit to failure probability, here associated with the first threshold crossing of a structural displacement, while the inertial acceleration variance or the elastic force variance are minimized in order to control vibration effects. Two applications are developed for simple structural vibration control problems to evaluate the efficiency of the proposed criterion. The first regards a vibration absorber modelled by a SDoF, while the second is a tuned mass damper represented by a TDoF. Both cases are subject to filtered white noise.
Surface Acoustic Love Waves Sensor for Chemical and Electrochemical Detection
Authors: Fourati Najla , Fougnion Jean-Marie , Rousseau Lionel , Lepeut Patrick , Franc¸ais Olivier , Boutin Patrick , Vedrine Christophe , Bonnet Jean-Jacques , Mercier Bruno , Pernelle Christine
Published: September 2008

The present work is an experimental study of shear horizontal surface acoustic wave (SH-SAW) miniaturized sensors which offer a high potential for electrochemical applications in liquid environments and in real-time. Our devices consist of a 42° rotYX lithium tantalate (LiTaO3) substrate coated with an SU8 photoresist polymer in order to produce acoustic waveguides supporting a Love–wave. The sensors architecture and fabrication techniques are presented. Standard techniques employing continuous wave system and pulse mode measurements have shown the propagation of both surface skimming bulk waves (SSBW) and leaky SH-SAW (LSAW) on 42°rot YXLiTaO3. A numerical calculation using a simple balanced summation waves model is presented. Taking into account waves reflections and our measured velocity values, the simulation is in accordance with measurement. A copper’s electrodeposition experiment was performed to estimate the sensitivity of SAW devices. The measured sensitivity of 0.38 cm2.g−1 is discussed in the framework of previously published works concerning Love wave devices.
Modeling Run in Process in External Gear Pumps
Authors: Dalpiaz G. , D’Elia G. , Mucchi E. , Ferna´ndez del Rinco´n A.
Published: September 2008

In this work, the authors have developed a mathematical model that simulates the run in of external gear pumps, as an useful tool in the optimization of this time-consuming process. The model calculates the wear profile of the case by enveloping the tip circle of the gears concerning all the run in steps. For each step, the positions of the gear centers are obtained by the equilibrium between pressure forces and torques due to the pressure distribution, meshing forces and hydrodynamic journal bearing reactions. The pressure distribution depends on the clearance between case and gears, so for each run in step, since the positions of the gear centers change, the pressure distribution is recalculated considering the wear profile obtained in the previous step. Besides, the model also estimates the quantity of material taken away in each step and it shows the effects of modifications in the run in parameters (time, pressure and speed). In particular, the simulation results indicate that a meaningful reduction of run in global time, can be obtained by increasing the duration of the steps that remove the greater part of material and by decreasing the duration of the other steps. This model is used by TRW Automotive Italia S.p.A. (section Automotive Pumps, Ostellato, Italy) to improve the run in process with good reduction in manufacturing-time.