bluuebunny/crossref_metadata_2025 huggingface dataset:
A Comparison of Carbon Footprint Calculations for End of Life Product Recovery Methods Using PAS 2050
Authors: Appleby Michaela R. , Buckley Adam B. , Lambert Chris G. , Rennie Allan E. W.
Published: January 2011

This paper demonstrates a comparison of product recovery methods, by carbon footprint calculation, for repaired products with remanufactured products and the environmental impact that they have when they reach their end-of-life (EOL). Growing concerns of climate change and government legislation have changed the way in which consumers can dispose of used or broken products. Items can no longer be sent to landfill and it is now the responsibility of the producers to dispose of products in a more sustainable manner and take into consideration all stages of the products life cycle. A standardised method for calculating carbon footprints has been used and a carbon footprint carried out for each product recovery method. Specific data was collected, from a manufacturing company in England’s North West region, about the processes involved during each recovery method and have identified that repairing has a lower carbon footprint than remanufacturing. However, repairing only extends the existing life cycle of a product, whereas remanufacturing can be carried out up to three times, and provides the product with a new life cycle. Therefore, remanufacturing is seen as the most preferable method of product recovery in terms of carbon emissions and sustainable waste disposal.
A 3D Numerical Study to Investigate the Effects of Temperature Variation and Residual Stresses in Representative Volume MEMS Elements
Authors: Maligno A. R. , Whalley D. C. , Silberschmidt V. V.
Published: January 2011

The reliability of MEMS, and in particular of RF MEMES switches, might be increased by the use of a Physics of Failure (PoF) methodology. A numerical study, based on the finite element method (FEM), has been carried out to investigate the effects of temperature variations on failure (e.g. yielding of metals) onset within multilayered MEMS structures. Furthermore, the manufacturing processes of MEMS are the main sources of residual stresses development and they represent one of the most profound factors reducing the functionality and reliability of MEMS packages. Therefore, the effect of residual stresses on failure onset has been considered in these studies to examine their effects on MEMS reliability. Numerical results have shown that failure initiation is strongly influenced by the loading conditions (i.e. different range of temperatures), boundary conditions and finally by the presence of residual stresses.
A CFD Study on Heavy Duty DI Diesel Engine to Achieve Ultra-Low Emissions
Authors: Yilmaz M. , Koten H. , Gul M. Zafer
Published: January 2011

Nowadays, automotive industries focused on clean diesel combustion in their combustion processes are investigated for their potential to achieve near zero particulate and NOx (Nitrogen oxides) emissions. Their main disadvantages are increased level of unburned hydrocarbons (HC) and carbon monoxide (CO) emissions, combustion control at high load, power output and limited operating range. The simulation of the air flow, spray and combustion in an internal combustion engine were prepared for a single cylinder of a nine-liter, six cylinder diesel engine. Many times the geometry is complex because moving pistons and valves are involved, which makes it difficult to generate structured mesh. In-cylinder spray-air motion interaction, a Lagrangian multiphase model has been applied in a heavy-duty CI engine under direct injection conditions. A comprehensive model for atomization of liquid sprays under high injection pressures has been employed. Three dimensional CFD calculations of the intake, compression and power strokes have been carried out with different spray angle, spray profile and start of injection. A new combustion model ECFM-3Z (Extended Coherent Flame Model) developed at IFP is used for combustion modeling. Finally, a calculation on an engine configuration with compression, spray injection and combustion in a direct injection Diesel engine is presented. In this study, exhaust emissions, and particularly the emission of NOx, CO and soot derived from premixed combustion are investigated, and the relationship between combustion and emission characteristics are showed. The calculated CFD simulation in different combustion cases was compared. The cases were prepared by changing the parameters: start of injection, spray angle and spray profile. Modeling of combustion proposed in the present study can be outlined as follows. NOx concentration is decreased by combustion of a over lean-mixture modeled by the pre-injection. Most of pre-mixture is combusted by main-injection, and therefore the amount of pre-injection and main-injection come into prominence. The results are greatly in agreement qualitatively with the previous experimental and computational studies in the literature.
A Novel Kinematics Modeling Method for Snake Robot in Travelling Locomotion
Authors: Safehian Javad , Kalani Hadi , Akbarzadeh Alireza
Published: January 2011

Snake robots moving in traveling wave locomotion are able to move forward and backward in narrow passages and partial unstructured environment. In this paper, a novel kinematics modeling method for travelling wave gait is presented. This method can be implemented on different snake body curves. In the present work, snake body can assume any shape that can cause propulsive motion. Unlike previous studies, relative joint angles are more simply obtained using numerical methods. Furthermore, angles of the two links making contact with ground can have different values. To develop the kinematics model, dynamics model is necessary and is therefore developed. Finally, the kinematics model is simulated in Webots software. Results confirm that the established kinematics modeling generates traveling wave locomotion. Effects of asymmetrical absolute angels of contact points on progression speed using Webots software is also investigated and reported.
Analytical Investigation of Chatter and Its Effective Parameters in Milling, Using Modal Experiment
Authors: Abootorabi Zarchi Mohammad Mahdi , Zoghi Hamed , Razfar Mohammad Reza
Published: January 2011

Chatter is modeled in milling using the planar vibratory equations of the tool. To solve these equations, dynamic parameters of the tool, e.g. natural frequency, damping ratio and stiffness must be known. To obtain these parameters modal experiment is carried out and the results are analyzed. The results show that, increasing the cutting speed, the system changes its behavior from stable to unstable and vice versa frequently, which is shown in a diagram known as stability lobes. The increase in stiffness of the tool and reduction in radial engagement of the tool and the workpiece, increase the stability of the process.
A Robust Design Optimization Methodology for External Gear Pumps
Authors: Mucchi Emiliano , Tosi Gabriele , d’Ippolito Roberto , Dalpiaz Giorgio
Published: January 2011

This work addresses the topic of external gear pumps for automotive applications, which operate at high speed and low pressure. In previous works of the authors, a hybrid lumped-parameter/finite-element model has been developed, in order to foresee the pump dynamic behaviour in terms of gear and casing acceleration. The model includes the main important phenomena involved in the pump operation and it has been validated on the basis of experimental data. In this research, an original optimization process has been applied to such a hybrid model in order to reduce the pump vibration level, i.e. the acceleration of the external casing. The set up of the optimization process comprises a single objective (case accelerations) and some operational and geometrical input variables (oil viscosity, oil Bulk modulus, relief groove dimension and radial clearance in the journal bearings). This paper compares three optimization methodologies for the optimization of the pump vibration level. In particular common optimization processes based on simulations are compared with a combined analysis based, firstly, on Design Of Experiments (DOE) and Response Surface Modelling (RSM) and, secondly, on the application of evolutionary algorithms to reach the optimal variable combination. The different methodologies are compared in terms of time efficiency and accuracy in the solution. Finally, a robust design process has been carried out in order to consider the manufacturing tolerances of the real pump and assess their effect on the performance of the component. The results offer important information and design insights that would be very difficult to obtain without such procedures.
Experimental Study of Corrugated Tubes Under Lateral Loading
Authors: Eyvazian A. , Shakeri M. , Zarei Mahmoudabadi M.
Published: January 2011

The protection of structures under impact loading often necessitates the need for energy absorbers; devices designed to absorb the impact energy in a controlled manner and hence, protect the structure under consideration. Thin-walled tubes are widely used as energy absorbers in various vehicles and moving parts. The objective of the present study is to investigate the energy absorption characteristic of tubes with corrugations in different geometries, in lateral direction. In order to produce corrugations, an innovative solution is introduced. Corrugations can be very easily generated on the surface of cylindrical aluminum tubes by stamping method. Corrugations with different wavelengths and amplitudes can be produced by this method. Experimental tests are conducted to study the effect of changing corrugation geometry (type and amplitude). Quasi-static tests are carried out whose results for lateral compression show that tubes with corrugation have a higher mean crushing force and this force is directly proportional to number of corrugations and their amplitude. Moreover, it is observed that corrugated tubes can absorb approximately four times more energy than tubes without corrugations, in the same size and weight. Finally, considering the experimental tests, corrugated tubes are shown to be more effective in lateral direction as an energy absorber, and they also exhibit desirable force-deflection responses which are important in the design of energy absorbing devices.
Manufacturing Signature: An Aeronautical Case Study
Authors: Ascione R. , Polini W. , Moroni G. , Petro` S.
Published: January 2011

Generally manufacturing processes are subjected to unpredictable variations, affecting process conditions, that yields manufactured parts characterized by geometric errors. This is due to the variability of the manufacturing conditions and to the behavior of the tools used in the manufacturing process (wear, thermal expansion or elastic deformation). Therefore, even if two part produced by the same manufacturing process have different local deviation, these are similar; this subject in literature is addressed as “Manufacturing Signature” (MS). In this work an approach to evaluate the form error of a free-form surface with profile tolerances by modeling the manufacturing signature is proposed. An industrial case study is discussed: an aeronautical component with free-form surfaces. Based on discrete data acquired by a Coordinate Measuring Machine (CMM), the manufacturing signature model is created, discussed and used to analyze the Manufacturing process.
Buckling Delamination of a Rectangular Sandwich Thick Plate With Band Cracks
Authors: Akbarov Surkay , Yahnioglu Nazmiye , Tekin Ayfer
Published: January 2011

The buckling delamination around the band cracks contained with the simply supported all edge-surface rectangular sandwich thick plate is investigated. It is assumed that the sandwich plate is composed of two face layers and a core layer. Face and core layers are made of different materials and it is assumed that there are two same cracks at the interfaces between the layers. Material of each layer is isotropic and homogeneous. For the solution procedure it is supposed that the surfaces of the cracks have insignificant initial imperfections. The development of this initial imperfection with an external compressive loading acting along the cracks is studied in the framework of the three dimensional geometrically nonlinear field equations of the elasticity theory and the piece-wise homogeneous body model. For the determination of the values of the critical force the initial imperfection criterion i.e. the case where the imperfection starts to increase and grows indefinitely, is used. The corresponding boundary value problems are solved by employing the boundary form perturbation techniques and the three dimensional FEM. The numerical results on the critical force are presented and analyzed. The influences of the material and geometrical parameters on these critical values are discussed.
Gas Turbine With Constant Volume Heat Addition
Authors: Gu¨len S. Can
Published: January 2011

Increasing the thermal efficiency of fossil fuel fired power plants in general and the gas turbine power plant in particular is of extreme importance. In the face of diminishing natural resources and increasing carbon emissions that lead to a heightened greenhouse effect and greater concerns over global warming, thermal efficiency is more critical today than ever before. In the science of thermodynamics, the best yardstick for a power generation system’s performance is the Carnot efficiency — the ultimate efficiency limit, set by the second law, which can be achieved only by a perfect heat engine operating in a cycle. As a fact of nature this upper theoretical limit is out of reach, thus engineers usually set their eyes on more realistic goals. For the longest time, the key performance benchmark of a combined cycle (CC) power plant has been the 60% net electric efficiency. Land-based gas turbines based on the classic Brayton cycle with constant pressure heat addition represent the pinnacle of fossil fuel burning power generation engineering. Advances in the last few decades, mainly driven by the increase in cycle maximum temperatures, which in turn are made possible by technology breakthroughs in hot gas path materials, coating and cooling technologies, pushed the power plant efficiencies to nearly 40% in simple cycle and nearly 60% in combined cycle configurations. To surpass the limitations imposed by available materials and other design considerations and to facilitate a significant improvement in the thermal efficiency of advanced Brayton cycle gas turbine power plants necessitate a rethinking of the basic thermodynamic cycle. The current paper highlights the key thermodynamic considerations that make the constant volume heat addition a viable candidate in this respect. First using fundamental air-standard cycle formulas and then more realistic but simple models, potential efficiency improvement in simple and combined cycle configurations is investigated. Existing and past research activities are summarized to illustrate the technologies that can transform the basic thermodynamics into a reality via mechanically and economically feasible products.
Parametric Study of an Innovative Counter-Flow Heat Exchanger
Authors: Catalano Luciano Andrea , De Bellis Fabio , Amirante Riccardo
Published: January 2011

An innovative Counter-Flow Sand Heat Exchanger (CFS-HX) is proposed, which makes use of very small solid particles as intermediate medium to perform heat transfer between two gas flows at different temperature. The potential of the CFS-HX was already demonstrated by the authors, both theoretically and experimentally. In this work, a parametric study has been employed in order to explore the capabilities of the proposed heat exchanger. A 1D model (validated by experiments) has been extensively used to perform sensitivity analyses with respect to the major design parameters, i.e.: specific heats, gas and sand densities, particle diameter, prescribed efficiency. Pipe length to obtain a prescribed heat exchanger efficiency has been calculated for a large number of configurations and results have been compared with a baseline case. The proposed computations show that a high efficient heat exchange can be obtained with relatively short pipes and with negligible pressure drop.
Modeling of Tarbela Reservoir and Water Flow Simulation Through Its Spillways
Authors: Abid Muhammad , Siddiqi Muftooh Ur Rehman
Published: January 2011

This numerical study is performed to predict the flow patterns and characteristics in Tarbela dam which is a multipurpose dam during the summer season the flow of the dam reaches to its design capacity or near flooding due to weather changes resulting from the global warming trend. A 3D model was made in Pro-Engineer® and meshed in ICEM CFD®. Commercially known software, ANSYS CFX®, was applied to numerically solve the Navier-Stokes equations for solution domain. The calculated results such as pressure, velocities, flow rate, surface height, and water buoyant force were compared with the actual data where available. The numerical calculations show uneven discharge through each gate due to the complex flow pattern just upstream of the weir. Maximum velocity was observed along the spillways outlet. In conclusion, the results from numerical simulation are generally well agreed with the existing data, the flow information such as flow field patterns at increased flow, local flow disturbances, discharge rate and surface height distribution obtained used for the behavior of existing dam and can be used for engineering design purpose of future dams.
Optimization of a Beam-Type IPMC Actuator Using Insects Swarm Intelligence Methods
Authors: Abachizadeh Mahdi , Yousefi-Koma Aghil , Shariatpanahi Masoud
Published: January 2011

In this paper, employing developed models of Ionic polymer metal composites, a cantilever beam made of Nafion is optimized for maximum tip deflection as well as maximum blocking (tip) force using the Min-Max method in a multi-objective discipline. Regarding the optimization procedure, saturation level of hydration, length and thickness of the beam, and applied voltage are considered as design variables. The robust and novel methods of continuous ant colony optimization (ACOR) and artificial bee colony (ABC), both inspired from collective behavior of ant and bee swarms, are here employed to guarantee finding near-optimal solutions in a continuous nonlinear constrained optimization schedule. Results obtained from several independent runs clearly demonstrate fast convergence with nearly identical results for both methods, conservatively claimed as global optima. In addition, it is shown that the multi-objective approach has ended in a reasonable reduction of tip deflection for a remarkable increase in blocking force.
Analysis of Free and Forced Ship Vibrations Using Finite Element Method
Authors: Yucel Adil , Arpaci Alaeddin
Published: January 2011

With the increase of ship size and speed, shipboard vibration becomes a great concern in the design and construction of the vessels. Excessive ship vibration is to be avoided for passenger comfort and crew habitability. In addition to undesired effects on humans, excessive ship vibration may result in the fatigue failure of local structural members or malfunction of machinery and equipment. The propeller induces fluctuating pressures on the surface of the hull, which induce vibration in the hull structure. These pressure pulses acting on the ship hull surface above the propeller as the predominant factor for vibrations of ship structures are taken as excitation forces for forced vibration analysis. Ship structures are complex and may be analyzed after idealization of the structure. Several simplifying assumptions are made in the finite element idealization of the hull structure. In this study, a three-dimensional finite element model representing the entire ship hull, including the deckhouse and machinery propulsion system, has been developed using a solid modeling software for local and global vibration analyses. Vibration analysis has been studied under two conditions which are free-free (dry) and in-water (wet). Wet analysis has been implemented using acoustic elements. The total damping associated with overall ship hull structure vibration has been considered as a combination of the several damping components. As the result of global ship free vibration analysis, global natural frequencies and mode shapes have been determined. Besides, responses of local ship structures have been determined as the result of propeller induced forced vibration analysis.
Coupled Axial-Flexural-Torsional Vibration of Internally Damped Timoshenko Frames
Authors: Yucel Adil , Arpaci Alaeddin , Tufekci Ekrem
Published: January 2011

In this study, free in-plane and out-of-plane bending vibrations of frame structures have been analyzed together with torsional vibration. Axial extension, rotational inertia and shear effects have also been considered. The frame structure has been constructed as having two beams with doubly symmetric cross-sections and connected at any angle to each other. These types of frames frequently appear on ships as bridge wings which are probably the most problematic members experiencing severe vibration. Internal damping has been incorporated into the analyses by using a complex modulus of elasticity. Natural frequencies have been obtained analytically by solving simultaneous linear equations of complex coefficients. A finite element analysis has also been conducted to verify the analytical results. Furthermore, an experimental modal analysis has been carried out and the results have been compared with theoretical ones in tables for various connection angles and damping factors. The agreement among results has been found to be good.
Effect of Thermal Growth on Vibration Behavior of Flexible Rotor System Mounted on MR Squeeze Film Damper
Authors: Ghaednia Hamed , Ohadi Abdolreza
Published: January 2011

In this paper a Magnetorheological squeeze film damper (MR-SFD) has been modeled using two governing equations. Firstly, considering Bingham model for MR fluid (MRF), a hydrodynamic model has been presented. Secondly, a thermal model for the system has been modeled and used to calculate the temperature rise in the squeeze film and different damper’s components. Time and frequency domain analysis has been performed over a system consists of an unbalanced flexible rotor (FE model) mounted on a pair of MR-SFDs. Results show that the amplitude of rotor’s vibration is not a simple function of electrical current such that, increase in the current cannot guaranty decrease in the value of amplitude. The steady state response of rotor versus rotation velocity is presented for different values of electrical current, which show the effects of temperature and current on the steady state response of rotor.
Slab Method of Analysis for Three Dimensional Forward Extrusion of Squared End Section
Authors: Samadi Ghoshchi Amin , Ghoshchi Aydin Smadi , Bazargani Sajad Mohammadi , Emami Sajjad
Published: January 2011

Slab method of analysis has been used for solving metal forming problems for a long time. However it has been restricted to plane strain and axisymmetric problems due to limitations in its formulations. In this paper a new formulation has been proposed so that it could be applied to three dimensional problems in metal forming. A parametric slab has been considered in this analysis and the force balance on the slab was carried out to obtain equilibrium equations in terms of these parameters. The parameters in fact are related to the geometry of the final extruded shape, the die and the material flow regime assumed in the formulation. In this way most of the limitations encountered in previous formulations were surpassed. In fact the parametric slab considered in this formulation is a very general element that could be adjusted to any changes made in the process. As an example the forward extrusion of a square cross section was analyzed using the new formulation. The effect of reduction of area, frictional conditions and other process parameters on the extrusion pressure was investigated. The theoretical results obtained in this paper were compared with similar results of previous work from other methods and good agreement was observed. Dies were designed and manufactured based on this analysis for several reductions of area. Tests were done using above dies and the experimental data were found to verify the theoretical results. It was concluded that the new slab method of analysis gave reasonable results for the problem analyzed and that it could be applied to other bulk metal forming processes such as rolling, wire drawing and forging.
Power Harvesting Through Magnetostrictive Devices: A Linear Model
Authors: Braghin Francesco , Cinquemani Simone , Resta Ferruccio
Published: January 2011

Energy harvesting, sometimes referred to as “power scavenging” or “energy extraction”, can be defined as “converting ambient energies such as vibration, temperature, light, RF energy, etc. to usable electrical energy by using energy conversion materials or structures, and subsequent storage of the electrical energy for powering electric devices”. There has been a significant increase in the research on vibration-based energy harvesting in recent years. In this contest magnetostrictive devices are considered a promising technology. The Villari effect, also known as the inverse magnetomechanical effect, is the change in magnetization that a magnetostrictive material undergoes when subjected to an applied uniaxial stress. This effect pertains to the transduction of energy from the elastic to the magnetic state and is inverse of Joule magnetostriction. Furthermore, the Villari effect exhibits many of the attributes of the direct magnetostrictive effect since its physical origin lies in magnetoelastic coupling. Transducers utilizing the Villari effect consist of a coil wound on a core of magnetostrictive material. In this paper, a linear magnetomechanical coupling model is developed to analytically calculate the potential electrical power such transducers can generate when subjected to applied harmonic mechanical vibration. Theoretical results are confirmed by experimental tests on two different magnetostrictive devices.
On the Use of POD-Models for Convective Flow in a Grooved Channel
Authors: Cadirci Sertac , Gunes Hasan
Published: January 2011

In this study we develop Proper Orthogonal Decomposition (POD) models for combined steady and transitional (quasi-periodic) convective air flows in a grooved channel with periodic boundary conditions. The grooved channel is appropriately mounted with constant heat flux sources. The constructed POD models for the flow and temperature fields are used in order to predict the off-design flow conditions. Considering the grooved channel geometry (with the height of the heat source H = 2.3 cm and the distance between the heat sources L = 3.0 cm), we form a database using a combination of three distinct databases. Thus we could compare the ability of a POD model applied to the combined database consisting of various flow regimes. The first database consists of steady flow fields with varying Reynolds number up to Re = 230. The second and third databases include instantaneous snapshots of a periodic flow field at Re = 300 and snapshots of a quasi-periodic (chaotic) flow field at Re = 1000 respectively. Then, the combined database is used to perform the POD analysis and extract the POD modes. The modes of the flow and temperature fields are used for off-design reconstructions. The performance of POD model for off-design conditions is evaluated. The mode coefficients are interpolated by kriging to predict off-design conditions. We show that POD model can be used as a useful tool to predict the flow and heat transfer at off-design conditions and to solve inverse design problems in thermo-fluids.
Experimental and Analytical Investigation on a Liquid Balance Ring for Automatic Washing Machines
Authors: Urbiola-Soto Leonardo , Lopez-Parra Marcelo
Published: January 2011

A high-speed camera and a Particle Image Velocimetry (PIV) technique are used on a transparent liquid balancing device typical of modern washing machines. Experimental results indicate that the baffles placed inside the ring cavity interact with the fluid for it to develop modes of vibration of circumferential and axial type, thus rendering a complex swirl flow inside the annular cavity comprised of two inertial waves. One of such waves travels backwards relative to the rigid body motion. As as a result, a damping effect is induced and a phase lag with respect to the exciting unbalance occurs. An analytical dynamic model of the unbalanced response is derived and correlated with fluid flow visualization experiments and vibration measurements.
Variational Geometry With Algebraic Level Set Model
Authors: Zhang Jiwei , Wang Michael Y. , Wu Xiaojun
Published: January 2011

Variational Geometry technique, also known as Constraints Satisfaction Problem technique (CSP), is one of the core components in modern CAD systems. One of the known problems of the existing technique is its inability of solving topological changes. In this paper, we propose a new Varaitional Geometry technique with Algebraic Level Set (ALS) geometric model. Based on half-space model theory and classic Level Set formulation, Algebraic Level Set concept is first described, its merits are also addressed within this context. Using this geometry representation, the topological changing problem caused by constraint variations could be solved in a natural way. This proposed method is capable of performing shape deformation capability that can be provided by conventional Variational Geometry technique, meanwhile, keeps the implicit topological definition of Algebraic Level Set functions which accounts for the topological changes in our proposed framework. Several numerical results demonstrate the preliminary capacity of our proposed approach.
Application of Appropriate Coatings on Extrusion Dies and Evaluation of Their Performance During Hot Extrusion of Aluminum
Authors: Lontos Antonios , Demosthenous George , Soukatzidis Filippos
Published: January 2011

The aim of this paper is to study the effect of extrusion parameters (extrusion speed and temperature), die geometry, and the application of appropriate coating materials on the extrusion dies in order to extend their working life. To achieve the above goal FEM techniques and experimental tests adopted and simulating and experimental results evaluated. In this way, special FEM software was used to set up the finite element model of the aluminum extrusion. As a billet material the 6061 aluminum was used, with a specific diameter and length. The extrusion process was modeled as isothermal, which means that the billet material preheated at the specific temperature and then it was pressured into the two different dies, with a specific extrusion ratio. The extrusion speed was varied between 0.5 to 1 mm/sec and the extrusion temperature varied between 400 °C to 500 °C. The extrusion angle of the two different dies was 9° degrees. The fillet radius at the top surfaces was selected to be 1 mm. The friction between aluminum material (billet) and the extrusion equipment was i) aluminum material and die 0.3, ii) aluminum material and ram 0.9 and iii) aluminum material and container equal to 0.96. Optimized algorithms of extrusion parameters were proposed regarding to the concluded simulating results. The results obtain from the simulation procedure help to the better understanding of the specific extrusion process, leading to better modification of the experimental procedure. In this way, experimental tests were conducted on special laboratory extrusion press using the two different die geometries coated with three different PVD coatings. By means of these experimental tests the additional working life of the coated dies, during hot extrusion process, was able to be evaluated. In addition, the three different coatings where tested by established quality procedures in order to determine their behavior on the material of the extrusion die.
Microcutting of NiTiCu Alloy With Pulsed Fiber Laser
Authors: Arnaboldi Sergio , Bassani Paola , Biffi Carlo Alberto , Carnevale Marco , Lecis Nora , Lo Conte Antonietta , Previtali Barbara , Tuissi Ausonio
Published: January 2011

Laser microcutting of thin sheets made of innovative and hard to machine materials, such as shape memory alloys (SMAs), is a very interesting topic. Innovative laser sources, such as pulsed fiber lasers, are becoming promising tools to be used in precise and fast operations in industrial applications. The positive features of this type of laser sources are high beam quality, strong focusability, high pulse energy and consequently high productivity. On the contrary the most important drawback is the pulse width in nanosecond regime, which means thermal effects in the workpiece. The investigated material is a nickel-titanium-copper (Ni40Ti50Cu10) alloy, a ternary SMA derived from NiTi binary alloy. In this work the effect of laser process parameters, such as number of laser passes, type of shielding gas, gas pressure and process speed on the cutting edge quality features, such as the amount of spatter and the kerf width, was studied. Finally functional characterization, i.e. differential scanning calorimetry (DSC) and mechanical measurements (nanoindentations), of the laser cutting edge was performed.
Potentialities of Active Suspensions for the Improvement of Handling Performances
Authors: Braghin Francesco , Prada Alessandro , Sabbioni Edoardo
Published: January 2011

Active and semi-active suspension systems are widely diffused into the automotive industry and several control strategies have been proposed in the literature both concerning ride comfort and handling. The capability of several suspension active control systems in enhancing the vehicle handling performances are compared in this paper. In particular, a low-bandwidth active suspension (actuator in series with the suspension spring), an active antiroll bar, an active camber suspension and a semi-active high-bandwidth suspension (closed loop damper control) are considered. The benchmark is represented by an ideal vehicle which does not present any load transfer and has no yaw moment of inertia. The possibility of combining more than one active/semi-active suspension system is also discussed.
A Low Cost Pneumatronic Unit for Pipes Inspections
Authors: Ravina Enrico
Published: January 2011

The paper shows the results of a theoretical and experimental research activity oriented to the design and the realization of a of a low cost pneumatronic prototype, proposed for tasks of pipes and ducts inspection. Geometries and sizes of ducts are significantly different and for their inspection very flexible units are needed. Different researchers propose several solutions: the present proposal is specifically oriented to an automated pneumatic low cost unit. The prototype is conceived to emulate the grub’s motion: variable geometry components are deformed under the action of pneumatic power supply, following a programmable logic actuation. A fluidic muscle is used to generate the motion and two deformable air chambers are arranged at the ends of the muscle in order to assure the anchorage to the internal pipe wall. The automatic phases of the motion are managed by an external micro-PLC, allowing flexible and bi-directional motions. The unit is equipped with a micro-camera and can be also equipped with micro grippers and micro mechanical tools. The design and the optimization of the prototype’s mechanical structure is discussed and related to the mechatronic approach applied to perform the cyclical movement.
Coatings Obtained by the Metal Directional Explosion Spraying Technique
Authors: Vilys Jonas Steponas
Published: January 2011

The rapid progress of high technology, especially in industrial machinery and electronic applications, requires the development of advanced coatings having many properties such as high hardness, wear resistance, anticorrosion, thermal barrier, and of good quality. For this purpose are used metal coatings by the electro-thermal explosion spraying technique. A huge drawback of this method is that only internal cylindrical surfaces of components may be metallized up to 120 mm diameter. The study was aimed at extending the electro-thermal explosion spraying technique to external profile and plane surfaces, at the examination of the properties of the coatings.
A New Sheet Die Design Methodology to Eliminate Scrap Shedding Problems During Mass Production
Authors: Gu¨mu¨s¸ Beril , Ekici Bu¨lent
Published: January 2011

Manufacturing companies need to improve their production technology with improved dimensional accuracy at lower cost in order to manufacture sheet metal based products. Scrap shedding is an issue that should be examined at the cutting and sheet metal forming operations. In order to extend the life cycle of the cutting moulds, scrap shedding should be identified. When scrap shedding has not been taken into consideration, scraps have accumulated in the moulds reducing the production quality and causing deformation of the mould, increasing the production cost by obligating to perform extra transactions. This study becomes more focused upon the analysis of scrap shedding. In order to simulate the scrap shedding LS-Dyna and Pam Stamp software have been used. For examining of the scrap shedding an automotive part was chosen. In order to realize scrap shedding having any problems, new improvements have been suggested. Design of Experiments techniques which provide important advantages to engineering studies have been examined. By means of experimental design techniques the scrap shedding design process was also added to the classical mold design approach via a less quantities of simulations.
A Novel Method for Robust Control Using Taguchi Method and Genetic Algorithm in QFT Controller
Authors: Akbari Ali Akbar , Samiee Amir homayun , Naeemi Amini Pouria , Fallah Danial
Published: January 2011

This paper proposes a novel method to design and optimize a robust controller for a SCARA robot using quantitative feedback theory (QFT). In every physical system, there are number of factors that cause uncertainty in the performance. A robot arm is an example of such systems. Although QFT design technique has been successfully used for plants having structured parameter uncertainty, there are some difficulties that a designer encounters. In this paper we investigated the effects of parameter uncertainties of a SCARA robot on frequency response of open loop system. Taguchi’s experimental design technique is used for determination of the uncertain parameters, which have the greatest influence on the outcome through a very limited number of experiments. With consideration of important parameters, the next step in QFT design procedure is loop-shaping. In the presented method the controller is designed directly by choosing and optimization of coefficients of transfer function by using genetic algorithm. In optimization procedure, stability and bounds of the system were considered as the constraints of the problem. Non-linear simulations on the tracking problem are performed and the results highlight the success of the designed controllers. The results indicate that applying the proposed technique successfully overcomes the obstacles to robust control of non-linear SCARA robots.
The Effects of Dimension Ratio on the Micropolar Peridynamic Model
Authors: Ferhat Y. , Ozkol I.
Published: January 2011

The aim of this study is to investigate the capability of the micropolar peridynamic theory to analyze elastic behavior of plates with various length and width. Since the quantities such as stress and strain are related to displacement field, only the displacement fields of these structures are computed using the micropolar peridynamic model while Poisson’s ratios are kept constant. The results are compared both to the analytical solution of the classical elasticity theory and to the solution of displacement based finite element methods. The software package ANSYS is used for FEM results. To compute the displacement field, a programming code is developed using MATHEMATICA. In the peridynamic theory the constitutive model contains only central forces and can be applied only to the materials having 1/4 Poisson’s ratio. It is the biggest shortcoming of the peridynamic theory. To overcome strict Poisson’s ratio limitation of the peridynamic theory, the micropolar peridynamic theory is proposed. The micropolar peridynamic model allows peridynamic moments, in addition to peridynamic central forces, to interact with the particles inside the material horizon. The introduction of the moments to the theory allows us to deal with the materials having Poisson’s ratio different from 1/4. This modification can be seen as the generalization of the peridynamic theory. Furthermore, the micropolar peridynamic theory can be easily implemented using the finite element methods. This provides easy application of the boundary conditions to the physical model in hand. In this work, by applying the micropolar peridynamic theory, we observed that the displacement fields of the plates are strongly affected by dimensional ratio of the plates. However, it is naturally expected that the micropolar and classical theories should give the same results, at least to a certain extend. This strong dependability on the dimensions of the structure can be a significant shortcoming of the micropolar peridynamic theory.
Fatigue Life Prediction of a Drag Link by Using Finite Element Method
Authors: Koca Barıs¸ , Ekici Bu¨lent
Published: January 2011

The focus of this study is to find fatigue behavior and fatigue life of a drag link in the different road and loading conditions. Finite element method was used for fatigue analysis and fatigue life of the drag link was predicted. Firstly, the historical changes in the concept of the fatigue and fatigue life calculation methods were explained in the chapter one and two. Factor affecting the fatigue performance was explained. Stress and strain based fatigue analysis methods were described clearly. Finally, fatigue life analysis in the frequency domain which is a new method relative to the others was explained. Then, two different steering drag links of a midibus were examined and fatigue life calculations of these two drag links were made. The fatigue life analysis in the time domain of the drag links were made in the static steering conditions and the results were compared with the test results made by the vendor of the drag links. After that, the drag link which has a greater fatigue life than the other was selected, the road loads were taken from another test report which was made by using the same drag link and the fatigue life of the drag link was computed by using the finite element method in the time domain. Finally, the same road loads were converted in the frequency domain and the fatigue life analysis of the same drag link were made in the frequency domain. The results from the time domain and the frequency domain were compared and the advantages of the fatigue life analysis in the frequency domain were expressed.
Investigation of Heat Transfer Over a Rotating Disk in Case of Temperature and Velocity Jump Conditions by Using Differential Transform Method
Authors: Gunes A. Y. , Komurgoz G. , Arikoglu A. , Ozkol I.
Published: January 2011

The energy crisis in the last two decades has turned the attention of scientific and engineering communities to redesigned and developed heat-fluid interaction systems. All of the details in analyses are reconsidered to reduce energy consumption. The present work examines the effects of temperature and velocity jump conditions on heat transfer, fluid flow over a single rotating disk. The flow due to rotating disks is of great interest in thermal engineering as it appears in many industrial and engineering applications such as gas turbine engines and micropumps. The related equation of flow, which is nonlinear and coupled, and heat transfer governing equations are reduced to ordinary differential equations by applying the so-called classical approach which was first introduced by Von Karman. Instead of this approach, a pure numerical one, the recently developed popular semi numerical analytical technique differential transform method (DTM), with Benton transformation, is employed to solve the reduced governing equations under the assumptions of velocity-slip and temperature jump conditions on the disk surface. The solution is valid for continuum and slip-flow regime which has a Knudsen number smaller than 0.1. The results attained for various physical cases are interpreted by using non-dimensional parameters related to flow and temperature fields. Velocity and temperature profiles are presented graphically. The effect of various parameters such as the Knudsen Number (Kn), Reynolds Number (Re) and Nusselt Numbers (Nu) are examined. The observed physical consequences are the velocity slip and temperature jump at the wall becoming strongly dependant on the Knudsen number. It is also observed that the temperature jump and velocity jump conditions have nonlinear effects on slip; these effects are investigated with great details and presented graphically.
Analytical and Numerical Simulation of Ultrasonic Assisted Grinding
Authors: Farhadi Ahmad , Abdullah Amir , Zarkoob Javad , Pak Abbas
Published: January 2011

Ultrasonic assisted grinding of hard materials is a novel technique which is used in order to decrease grinding forces and energy. Grinding force is in direct connection with wheel wear, grinding accuracy, grinding temperature and surface integrity. In this paper the effects of ultrasonic vibration in creep feed grinding process which is superimposed to the workpiece in feed direction has been represented. The mechanism of grain-workpiece interaction in the presence of ultrasonic vibration has been investigated both analytically and numerically. The cutting path of a single grain in ultrasonic assisted grinding has been derived using equations of motion and has been compared to the grain cutting path in ordinary grinding. Using displacement equations of a single grain in ultrasonic assisted grinding and drawing the motion path, it has been shown that there exist a multiple-impact between grain and workpiece. By implementing a 2-D finite element modeling, the mechanism of chip formation in ultrasonic assisted grinding and ordinary grinding has been compared. Furthermore the effects of longitudinal workpiece vibration on the grinding forces have been investigated. FE analysis of grain-workpiece interaction in case of using ultrasonic vibration has shown a reduction of about 40% of grinding forces compared to ordinary grinding.
Effect of Processing Parameters on Thermo-Mechanically Affected Zone of Friction Stir Processed AZ91 Magnesium Alloy
Authors: Taherishargh M. , Parvin N. , Asadi P.
Published: January 2011

AZ91 Magnesium alloy was subjected to friction stir processing (FSP). The microstructural analyses of the friction stir processed (FSPed) specimens were carried out and the effects of pass number, rotational speed, and traverse speed upon thermo-mechanically affected zone (TMAZ) were investigated. The TMAZ is consisted of a region with highly elongated grains and a partially recrystalized zone. Decreasing the rotational speed and increasing the traverse speed increased the thickness of recrystallized zone; while, the thickness of the other zone decreased. On the other hand, it lessened the gradient of the grain size from the stir zone (SZ) to the base metal. Applying several FSP passes, lead to more homogeneous TMAZ structure with the finer grain size.