bluuebunny/crossref_metadata_2025 huggingface dataset:
Stochastic Finite-Time Stabilization for a Class of Nonlinear Markovian Jump Stochastic Systems With Impulsive Effects
Authors: Chen Wu-Hua , Wei Chenghai , Lu Xiaomei
Published: October 2014

This paper is dedicated to the study of stochastic finite-time stability (SFTS) and control synthesis for a class of nonlinear Markovian jump stochastic systems with impulsive effects. By introducing a time-varying stochastic Lyapunov function with discontinuities at impulse times, an improved criterion for SFTS is derived in terms of linear matrix inequalities (LMIs). Based on the new SFTS criterion, four kinds of finite-time hybrid/continuous-time state feedback controllers are constructed by using the solutions to certain sets of LMIs. The effectiveness of the proposed method is validated through one numerical example.
Microelectromechanical Systems Cantilever Resonators Under Soft Alternating Current Voltage of Frequency Near Natural Frequency
Authors: Caruntu Dumitru I. , Knecht Martin W.
Published: October 2014

This paper deals with nonlinear-parametric frequency response of alternating current (AC) near natural frequency electrostatically actuated microelectromechanical systems (MEMS) cantilever resonators. The model includes fringe and Casimir effects, and damping. Method of multiple scales (MMS) and reduced order model (ROM) method are used to investigate the case of weak nonlinearities. It is reported for uniform resonators: (1) an excellent agreement between the two methods for amplitudes less than half of the gap, (2) a significant influence of fringe effect and damping on bifurcation frequencies and phase–frequency response, respectively, (3) an increase of nonzero amplitudes' frequency range with voltage increase and damping decrease, and (4) a negligible Casimir effect at microscale.
Study the Impact Behavior of the Prosthetic Lower Limb Lamination Materials due to Low Velocity Impactor
Authors: Chiad Jumaa S.
Published: October 2014

This work involved three parts, the first one is manufacturing different types of laminated below knee prosthetic socket materials with different classical laminated materials used in Baghdad center for prosthetic and orthotic (4perlon layers+2carbon fiber layer+4 perlon layers), and suggested two laminated materials (3perlon layers+2carbon fiber layer+3 perlon layers) and (3perlon layers+1carbon fiber layer+3 perlon layers)) in order to choose the perfect laminated socket. While the second part is tested (Impact test) the laminated materials specimens used in socket manufacturing in order to get the impact properties for each socket materials groups using an experimental rig designed especially for this purpose. Also the interface pressure between the residual leg and prosthetic socket is measured covering all the surface area of the B-K prosthetic socket by using piezoelectric sensor in order to estimation the resulting stress according to loading conditions. A male with age, length, mass, and stump length of 42 years, 164 cm, 67 Kg and 13 cm respectively with a right transtibial amputation was chosen to achieve the above mentioned testing procedures. Finally the last part suggested a theoretical and analytical model for each group of specimens to find out the absorbed energy behavior and subjected maximum stress for each laminated B-K prosthetic socket materials.
Residual Vibration Reduction With Commanded Motion Optimization
Authors: Borboni Alberto , Lancini Matteo , Faglia Rodolfo
Published: October 2014

Residual vibrations affect machines at the end of commanded motion and represent an amplification factor for the work cycle. Furthermore, in repetitive cyclic movements, residual vibrations can lead to an important degeneration of the executed motion, due to a summation effect of undesired dynamic phenomena. For these reasons, the problem of residual vibrations is widely studied in literature and it is faced with different techniques. A first type of approach consists in the production of a structural device realized with proper mechanical solutions devoted to avoid the sources of vibrations. The second approach consists in introducing passive/active physical elements able to attenuate vibrations, by passively consuming their mechanical power or by actively counteracting them with external mechanical power. A third approach is the smart definition of the motion profile of each machine movable part to minimize the vibrational effects. The proposed work is addressed in this direction, with an optimization approach based on the Fourier transformation of the motion profile. More precisely, the natural frequencies of the system are evaluated through experimental tests, the designed motion profile is transformed with a Fourier analysis, a band around the natural frequencies of the system is suppressed from the motion profile spectrum, an antitransformation is implemented to obtain a temporal function, and, finally, a proper optimization is implemented to respect desired kinematical constraints. Experimental results confirmed a significant improvement, in terms of residual vibrations, with respect to the state of the art of motion profiles specifically designed for residual vibrations reduction.
Innovative Force Gauge
Authors: Liu Chien-Sheng , Li Hong-Fei , Yau Hong-Tzong
Published: October 2014

In the present study, we propose an innovative force gauge to replace the traditional spring sensors. The proposed force gauge is characterized numerically using commercial software Infolytica MagNet simulation analysis and then verified experimentally using a laboratory-built prototype. The results presented in this study show compared to traditional force gauge, the proposed force gauge has good measuring accuracy to replace the traditional spring sensors. As a result, the proposed method provides a promising solution for industrial applications of force measurement.
A Combined Experimental and Computational Study for the Design of a Low Water Consumption Cooling Tower
Authors: Dogan Burak , Yilmaz Ibrahim , Polat Ozgur , Karabulut Oytun , Ural Ahmet , Uludag Yusuf , Aradag Selin
Published: October 2014

In this study, a combined experimental and computational study for the design of a low water consumption cooling tower is performed. The purpose of the study is to reduce the water consumption without decreasing the efficiency of a typical cooling tower. To achieve this aim, it is necessary to enhance the homogeneity of mist/air mixture. For this purpose, firstly, an experimental set-up including a small scale wind tunnel is installed which provides opportunity to examine different inlet and outlet configurations easily.

Computational Fluid Dynamics (CFD) is used extensively to examine the effects of different configurations before experimental studies. Simulations of different inlet and outlet configurations are performed using only air. Several turbulators are designed and simulated to increase the turbulence levels. A three dimensional multi-phase CFD model is utilized to design a nozzle-turbulator system for the cooling tower. As results of the computational and experimental studies, the most efficient inlet and outlet configurations are specified and turbulators are selected from the alternative designs.
Shall We Continue Keeping High School Courses in Mechanical Engineering Curriculum?
Authors: Sönmez Murat
Published: October 2014

Since the entrance of the graduates of technical high schools to engineering programs is hindered, in application, the graduates of general or science high schools only are accepted to engineering education. For these students, four years are not sufficient to teach the basic and the related application courses of the profession. Looking at the existing curriculum of mechanical engineering, it can be seen that in the 1st Year, the physics and chemistry courses repeat the content of the ones given in high school education. The current approach considers the students as they come to university with inadequate and incomplete knowledge and therefore not ready to follow the engineering science courses. This approach underestimates and denies the high school education contrary to the main objective of its curriculum. The main objective of high schools (secondary schools) is expressed in the Laws and Regulations with such a statement: “General high schools do not prepare students for a specific profession but rather for higher education”. Today, the existing curriculum of Mechanical Engineering is to be renewed by some new science and application courses to satisfy the demands of labor market. However, the total course credit limit prevents such a renewal. In the face of this dilemma, the answer to this question becomes important: Should the university really repeat high school physics and chemistry? In science high schools and in science branch of general high schools the science and mathematics courses have the major importance. The students are well educated on physics, chemistry, biology and mathematics. They are provided with the necessary science and mathematics background that is required in engineering education. Although only the well-educated graduates of science and general high schools are admitted to engineering programs and the students are already ready to follow the engineering science courses thanks to their high school background, unfortunately in some universities (in Turkey in all) science courses part of engineering curricula is filled by physics and chemistry courses with the same content of the ones taught in high school.
Experimental Kinematics of a Special Shape Actuator
Authors: Borboni Alberto , Pandini Stefano , Cambiaghi Danilo , Lancini Matteo , Adamini Riccardo , Faglia Rodolfo , Bodini Ileana , Vetturi David , Dassa Luca , Riccò Theonis , Degli Espositi Micaela , Paderni Katia , Messori Massimo , Pilati Francesco , Toselli Maurizio
Published: October 2014

This paper investigates the kinematical behavior of a polymer based star-shaped actuator, able to produce mechanical work through the shape memory effect, that allows a significant shape variations on the application of an external stimulus. The adopted material is a semicrystalline network based on poly(ε-caprolactone) crosslinked by thermal curing; the material was adopted due to its fast recovery process when heated close to the melting temperature and the high recovery degree, and, due to its good biocompatibility, it may suitable for biomedical application. The original, or “permanent”, material shape is that of a cylindrical annulus, which is set in a “temporary” configuration as a six spikes star. The temporary shape is fixed through a thermo-mechanical program, involving deformation above melting temperature and cooling under fixed strain and carried out by means of an ad-hoc designed fixture. By heating the deformed specimen above the melting temperature, the system is able to recover the original cylindrical shape realizing a motion and a mechanical power. This peculiar response, consisting in a progressive radial expansion activated by temperature, may be considered for application as self-expanding stenting device triggered by the human body temperature.

The shape of the system, that changes during the transformation, can be described as a two dimensional temporal function that represents the mean line of the section of the cylindrical annulus (perpendicular to the height of the annulus). This temporal function is a combination of a circular function and of a modified rhodoneal function and, after a proper calibration through experimental tests, is used to evaluate the kinematics of the system. The function is able to describe adequately the shape evolution experimentally displayed by the samples, with a very good agreement at the starting and final instants of the transformation, while the accuracy during the transformation is acceptable for the proposed application.
First Steps in the Design and Construction of the Ocean Grazer
Authors: Vakis Antonis I. , Meijer Harmen , Prins Wout A.
Published: October 2014

A novel wave energy converter, termed the Ocean Grazer, designed to extract energy from waves of varying profiles and energy contents has recently been proposed by the University of Groningen. The authors have performed preliminary modeling work to predict the behavior of the converter’s power take-off system, and constructed a proof-of-concept prototype to validate basic model predictions.
Experimental Study of Solar Still With Energy Storage Materials
Authors: Reddy K. Vijaya Kumar , Somanchi Naga Sarada , Banoth Hima Bindu , Gugulothu Ravi
Published: October 2014

In recent years with the exacerbation of energy shortage around the world and the continuous increase in the level of greenhouse gas emissions, the use of various sources of renewable energy is increasingly becoming important for sustainable development.

Solar energy is considered to be one of the most promising sources of energy, owing to its clean and renewable characteristics. Thermal energy storage (TES) is used to assist in the effective utilization of thermal energy in wide number of industrial and domestic applications. Thermal energy is stored as sensible heat (SHS) or latent heat (LHS). Sensible heat storage (SHS) materials are combination of materials (both solids and liquids) which undergo no phase change in the defined temperature range of the storage process. Example concrete, cast steel, cast iron etc.

The use of a latent heat storage system (LHS) using phase change materials (PCMs) is an effective way of storing thermal energy and has the advantages of high energy storage density, narrow operating temperature range and the isothermal nature of the storage process. The phase change materials are more energy dense than sensible energy storage when the temperature difference between heat source and sink are low. Phase change material can store or release energy through its morphology change mechanism. These advantages lead to small volume and less heat loss, which attract attention of researchers in different fields. Ex: Sodium acetate trihydrate, NaNO3.

There are large numbers of PCMs that melt and solidify at a wide range of temperatures, making them attractive in a number of applications. PCMs have been widely used in latent heat thermal storage systems for heat pumps, solar engineering and spacecraft thermal control applications. The uses of PCMs for heating and cooling applications for buildings have been investigated within the past decade.

The experimental results computed in the field of water distillation process using solar energy in the presence of energy storage materials are discussed in this paper.
Forces in Liquid Metal Contacts
Authors: Duggen Lars , Mátéfi-Tempfli Stefan
Published: October 2014

Using rather well known theory about capillary bridges between two electrodes we calculate the tensile force that can be applied to liquid metal contacts in the micrometer regime. Assuming circular symmetry, full wetting of the electrodes, and neglecting gravity, we present a brief review of the necessary theory and find numerically the forces to be in the 100μN range for liquid metals as mercury and liquid Gallium suspended between electrodes of 20μm radius.
A Comparison of Two Different Approaches to Camera Calibration in LSDM Photogrammetric Systems
Authors: Bai Ou , Franceschini Fiorenzo , Galetto Maurizio , Mastrogiacomo Luca , Maisano Domenico A.
Published: October 2014

Large Scale Dimensional Metrology (LSDM) is a branch of metrology that deals with the measurement of objects with dimensions in the order of several meters. Optical systems, relying on the use of multiple cameras and photogrammetric techniques, are among the most used instruments in this field. These systems require a preliminary calibration procedure to determine some essential parameters, such as camera positions and orientations, focal length, distortion parameters, etc. A structured comparison between two different approaches to camera calibration is herein discussed.
A Study on a Grade-One Type of Hypo-Elastic Models
Authors: Momeni S. Alireza , Asghari Mohsen
Published: October 2014

In Hypo-elastic constitutive models an objective rate of the Cauchy stress tensor is expressed in terms of the current state of the stress and the deformation rate tensor D in a way that the dependency on the latter is a homogeneously linear one. In this work, a type of grade-one hypo-elastic models (i.e. models with linear dependency of the hypo-elasticity tensor on the stress) is considered for isotropic materials based on the objective corotational rates of stress. A positive real parameter denoted by n is involved in the considered type. Different values can be selected for this parameter, each selection leads to a specific model within the class of grade-one hypo-elasticity. The spin of the associated corotational rate is also dependent on the parameter n. In the special case of n=0, the corresponding hypo-elastic model reduces to a grade-zero one with the logarithmic rate of stress; noting that this rate is a corotational rate associated with the logarithmic spin tensor. Moreover, by choosing n=2, the model reduces to a grade-one hypo-elastic model with the Jaumann rate, i.e. the corotational rate associated with the vorticity spin tensor. As case studies, the simple shear problem is investigated with utilizing the considered type of hypo-elastic models with various values for parameter n, and the curves for the stress-shear response are depicted.
Performing Difficult Teleoperation Tasks Using Dominant Metaphors of Interaction
Authors: Frank Jared A. , Kapila Vikram
Published: October 2014

User interfaces that incorporate intuitive interaction metaphors have the potential to make remote control of physical systems feel more natural than ever before. The spread of smart mobile devices, such as smartphones and tablets, provides opportunities to develop and examine examples of such interfaces due to the devices’ portability and the intuitiveness and reprogrammability of mobile applications. However, the design of metaphors for interacting with a particular system poses an open-ended, creative design challenge that lacks a single-point solution. This paper explores what we refer to as a dominant metaphor for performing a teleoperation task via interaction with a mobile user interface. These dominant metaphors may be inspired from the physical nature of the system to give the user the most natural experience when using a mobile interface. Our approach for choosing an appropriate metaphor of interaction is demonstrated with an experiment wherein participants are asked to use different interaction metaphors to control a ball and beam testbed. Experimental data shows that the preferred metaphor of the participants is the dominant metaphor of interaction, the one which yields significantly better task performance.
Development of Impedance Control Based Strategies for Light-Weight Manipulator Applications Involving Compliant Interacting Environments and Compliant Bases
Authors: Roveda Loris , Vicentini Federico , Pedrocchi Nicola , Tosatti Lorenzo Molinari , Braghin Francesco
Published: October 2014

The paper defines impedance control based control laws for interaction tasks with environments of unknown geometrical and mechanical properties, both considering manipulators mounted on A) rigid and B) compliant bases. In A) a deformation-tracking strategy allows the control of a desired deformation of the target environment. In B) a force-tracking strategy allows the control of a desired interaction force. In both A) and B) the on-line estimation of the environment stiffness is required. Therefore, an Extended Kalman Filter is defined. In B) the on-line estimation of the robot base position is used as a feedback in the control loop. The compliant base is modelled as a second-order physical system with known parameters (offline identification) and the base position is estimated from the measure of interaction forces. The Extended Kalman Filter, the grounding position estimation and the defined control laws are validated in simulation and with experiments, especially dedicated to an insertion-assembly task with A) time-varing stiffness environment and B) constant stiffness environment.
Application of Differential Quadrature Method and Evolutionary Algorithm to MHD Fully Developed Flow of a Couple-Stress Fluid in a Vertical Channel With Viscous Dissipation and Oscillating Wall Temperature
Authors: Fidanoglu Melih , Baskaya Elgiz , Komurgoz Guven , Ozkol Ibrahim
Published: October 2014

In this paper, fully developed flow of a couple-stress fluid between two long vertical walls in presence of viscous dissipation and radiative heat flux with heat and mass transfer is considered. Temperature and concentration fields at one of the walls are oscillating around a non-zero value. The coupled equations governing the problem are discretized using Differential Quadrature Method, and solved using Newton-Raphson Method and Evolutionary Algorithm hybrid scheme. The expressions for velocity, temperature, and concentration fields for fully developed unsteady flow are obtained.
Modelling and Simulation of Regenerators With Complex Flow Arrangements for Active Magnetocaloric Refrigeration
Authors: Lei Tian , Nielsen Kaspar K. , Engelbrecht Kurt
Published: October 2014

Compared to a conventional vapor compression refrigeration system, a magnetocaloric refrigerator has many advantages, such as potentially high efficiency, low vibration and avoidance of refrigerants that deplete the ozone layer and cause the greenhouse effect. As a main component of the active magnetic regenerative refrigerator, the regenerator plays an important role in the cooling performance and efficiency of the whole system. However, the regenerator design is constrained by several external factors, such as the geometry of the magnetic field source and flow resistance.

In this work, novel regenerators with complex flow arrangements, providing high performance at lower pressure drop, are investigated. Correspondingly a one dimensional model is presented and comparative studies between novel and conventional regenerators are carried out by simulation. The effect of regenerator geometries and different flow arrangements on the cooling performance, pressure drop and efficiency are investigated. In particular, the effect of so-called dead volume on the performance of a regenerator is researched.
Simulation of Fluid Sloshing for Decreasing the Response of Structural Systems
Authors: Vuruşkan İlker , Sert Cüneyt , Özer Mehmet Bülent
Published: October 2014

In the last decade, there is a renewed interest in the integration of a sloshing tank into structural systems to decrease the vibrations of the structure. The purpose of this study is to try different numerical simulation programs for further use in studies in evaluation of the effectiveness of the sloshing tank absorbers for structural systems. The programs chosen for sloshing simulations are COMSOL Multiphysics®, ANSYS CFX and ANSYS-FLUENT. In the numerical simulations, the free surface shape during sloshing will be simulated under small and large amplitude sinusoidal displacements. The results obtained using different software will be compared with the results of the experiments reported in literature. Since the purpose is to use the sloshing forces on the container to decrease the structural response, the total force on the container walls is calculated and compared with the reported experimental results. The dynamics of a container coupled with the a structural model is simulated and forces applied on the container walls are analyzed in the frequency domain which is important in understanding the tuning of the vibration absorber. To the best of authors’ knowledge, in a fluid-structure coupled system the frequency domain analysis of the container wall forces at varying amplitudes of sinusoidal excitation is not presented in literature. The results showed even though higher harmonic forcing magnitudes increase with increasing base motion, the fundamental harmonic component does not change significantly.
Injury Criteria Based Optimisation of Automobile Passive Safety Systems to Mitigate the Effects of Full-Frontal Automobile Collisions
Authors: Esat Volkan
Published: October 2014

Passive safety systems such as airbags, seat belts, and interior structural design of the automobile play a significant role in injury prevention of the occupant during collisions. Important design and operation parameters of the passive safety systems such as airbag firing times and steering wheel position as an interior design attribute potentially affect the dynamics of the occupant during impact and determine the amount of mitigation of a possible injury. This research aims to contribute towards improving passive safety systems in automobile design for mitigation of injuries by optimising the features and parameters of various subsystems such as driver’s airbag and steering wheel. Two separate computational models, a 5th percentile female and a 50th percentile male, comprising of a typical automobile interior with passive safety systems are constructed in the specialised impact simulation software MADYMO. Two different crash pulses of 30 kph and 48 kph are applied to the computational human body models in full-frontal crashes. Passive safety system parameters; in particular, airbag firing times and steering wheel column angles, are varied to investigate their effects on the head, neck and upper torso through injury criteria. Injury criteria predictions are employed in optimisation algorithms to figure out the best combinations for passive safety system parameters in order to mitigate possible injuries for all drivers.
On the Attainment of Optimum Injection Timing of Pilot Fuel in a Dual Fuel Diesel Engine Run on Biogas
Authors: Bora Bhaskor J. , Saha Ujjwal K.
Published: October 2014

The race among the different nations to attain supremacy has given rise to twin crisis: depletion of fossil fuel reserves and degradation of environment. Every nation wants to increase the per capita income by producing more power. In order to achieve this feat, each nation has to burn huge amounts of fossil fuels causing an increase in the emission of greenhouse gases. In this regard, renewable energy can be a panacea to the above mentioned problems. Biogas, one form of biomass energy, has an immense potential as a renewable fuel. This biogas can be used successfully in diesel engines for the generation of power. However, in order to achieve an optimum efficiency, the operating parameters of the biogas run dual fuel engine have to be standardized. In such an engine, injection timing of the pilot fuel is one of the important operational parameters that greatly affects the engine performance. In view of this, in the present paper, an attempt has been made to standardize the injection timing of pilot fuel a biogas run dual fuel diesel engine on the basis of its performance and emission characteristics of. Experimental investigation demonstrates an improvement in efficiency and a reduction in emissions at the injection timing of 29° before top dead centre.
Optimizing Computer Controlled-Polishing of Flat Surfaces
Authors: Mosaddegh Peiman , Koosha Rasool , Tehrani Alireza Fadaei
Published: October 2014

The aim of this study is to optimize the Computer Controlled Polishing (CCP) of flat surfaces based on discretization of tool path. First, a new method has been developed to simulate the polishing Process. This method capable of expanding any tool path such as spiral, raster or even random over the surface, meaning that it has the capacity of simulating polishing process under different tool path strategies. Second, a numerical optimization method is applied to optimize the dwell time distribution over the defined tool path. The new method developed in this study was conducted to operate polishing process of a flat lens with 128 mm in diameter and initial surface roughness of 3.975 μm for PV and 987 nm for rms using a 3-axis CNC machine. After two passes of polishing, the final surface roughness reduced to 784 nm for PV and 190 nm for rms which shows around 80 percent reduction in surface roughness for PV and rms.
Modal Analysis of Automotive Clutch Using Finite Element Method
Authors: Aktir Yasser , Brunel Jean-François , Dufrenoy Philippe , Mahe Hervé
Published: October 2014

Clutch system is an important element in the vehicle powertrain. It transmits the rotation from the crankshaft to the gearbox input shaft and filters axial and torsional vibrations providing from engine or induced by friction. This paper discusses axial dynamic behavior of automotive clutch for manual transmission. For this study, a tridimensional finite element model of clutch system is developed to simulate a clutch shaker test. First, an impact hammer test is performed to identify vibration properties of each clutch component. A pre-stressed modal analysis is then carried out to determine mode shapes and its associated natural frequencies of the clutch assembly. Shaker and simulation results are eventually compared to validate the clutch model. This latter offers for the design phase, a tool to avoid natural vibrations or to vibrate at specified frequencies.
Aerodynamic Performance Prediction of a Profile in Ground Effect
Authors: Cravero Carlo
Published: October 2014

A very detailed experimental case of a reversed profile in ground effect has been selected in the open literature and the available experimental data have been used as reference data for CFD analysis. The CFD approach has been used to predict the aerodynamic performance of the profile at different heights with respect to the ground: from the freestream case (no ground effect) to a low height where the stall on the suction surface limits the profile operation. Different CFD codes have been used starting with a well-known commercial code to different open source codes. The set of analysis with the commercial code has allowed the setup of the mesh to have the best accuracy from the simulations. The same grids have been used for the other codes in order to directly compare the solver properties without mesh influence. The results obtained by the codes are compared and discussed.
Drive System Sizing of a 6-DOF Parallel Robotic Platform
Authors: Giberti Hermes , Ferrari Davide
Published: October 2014

In this work, it is considered a 6-DoF robotic device intended to be applied for hardware-in-the-loop (HIL) motion simulation with wind tunnel models. The requirements have led to a 6-PUS parallel robot whose linkages consist of six closed-loop kinematic chains, connecting the fixed base to the mobile platform with the same sequence of joints: actuated Prism (P), Universal (U), and Spherical (S).

As is common for parallel kinematic manipulators (PKMs), the actual performances of the robot depend greatly on its dimensions. Therefore, a kinematic synthesis has been performed and several Pareto-optimal solutions have been obtained through a multi-objective optimization of the machine geometric parameters, using a genetic algorithm.

In this paper, the inverse dynamic analysis of the robot is presented. Then, the results are used for the mechanical sizing of the drive system, comparing belt- to screw-driven units and selecting the motor-reducer groups. Finally, the best compromise Pareto-optimal solution is definitely chosen.
Optimizing 5-Axis Sculptured Surface Finish Machining Through Design of Experiments and Neural Networks
Authors: Fountas Nikolaos A. , Kechagias John , Benhadj-Djilali Redha , Stergiou Constantinos I. , Vaxevanidis Nikolaos M.
Published: October 2014

Five axis machining and CAM software play key role to new manufacturing trends. Towards this direction, a series of 5 axis machining experiments were conducted in CAM environment to simulate operations and collect results for quality objectives. The experiments were designed using an L27 orthogonal array addressing four machining parameters namely tool type, stepover, lead angle and tilt angle (tool inclination angles). Resulting outputs from the experiments were used for the training and testing of a feed-forward, back-propagation neural network (FFBP-NN) towards the effort of optimizing surface deviation and machining time as quality objectives. The selected ANN inputs were the aforementioned machining parameters. The outputs were the surface deviation (SD) and machining time (tm). Experimental results were utilized to train, validate and test the ANN. Major goal is to provide results robust enough to predict optimal values for quality objectives, thus; support decision making and accurate machining modelling.
Vibration Analysis of a Vertical Roller Mill: Modeling and Validation
Authors: Çopur Engin H. , Salamci Metin U. , Gülbeyaz Selahattin
Published: October 2014

In this paper, vibration characteristics of a Vertical Roller Mill (VRM) are studied by using physical parameters of an operating VRM. The mathematical model is derived and simulated for a set of working parameters. Mechanical properties of the grinding material and the physical properties of the mechanical construction are used in the vibration model in order to obtain more realistic results. Simulation results are presented which give critical frequencies of the VRM. The effects of the hydraulic compressive force to the vibration characteristics are investigated. The effects of the material feeding rate (which affects the mineral thickness to be grinded) to the vibration characteristics are also simulated.

In order to validate the mathematical model, a set of experimental vibration tests are performed on the VRM. Vibrations are measured during the run-down procedure of the VRM in order to determine natural frequencies of the mill as well as excitation frequencies of the system. The measurements showed the validity of the proposed mathematical model for the vibration analysis of the VRM.
An Arithmetic Correction for Avoiding Non-Uniform Heat Input Distribution Caused by Translational Motions Within Time-Discrete Thermal Analyses
Authors: Partzsch Marian , Beitelschmidt Michael
Published: October 2014

Using a coarse time discretisation for saving calculation effort will induce non-uniform heat input within thermal-transient analyses which include translational rigid body motions by the technique of discrete displacement adjustment. We are going to show, why these non-uniformities are generally unavoidable and how a suitable choice of time step size pre-minimizes their consequences. Afterwards, the amount and location of the remaining load-bumps are analytical deduced for an arbitrary motion. With this information, we develop a correction method based on arithmetic calculations to avoid these numerical caused errors. For practical use, the correction is applied as an algorithm to the solution process of analyses with spatial discretized motion partners. We finish by demonstrating the performance of the correction.
Numerical Simulation of Friction Stir Welding by an Efficient 3D Updated Lagrangian Technique
Authors: Canales D. , Ghnatios Ch. , Leygue A. , Chinesta F. , Alfaro I. , Cueto E. , Feulvarch E. , Bergheau J. M.
Published: October 2014

Friction Stir Welding (FSW) is a welding technique which since its invention in 1991 is of great interest to the industry for its many advantages. Despite being widely used, its physical foundations and its relation to the technological parameters of the process are not known in detail. Numerical simulations are a powerful tool to achieve a greater understanding of the physics of the problem. Although several approaches can be found in the literature for FSW, all of them present different limitations that restrict their applicability to the industry. This paper presents a new solution strategy that combines a meshless method, the Natural Element Method (NEM), with a solution separated representation making use of the Proper Generalized Decomposition (PGD), for creating a new powerful updated-Lagrangian method for addressing the 3D model while maintaining a 2D computational complexity.
Efficiency Enhancement of Bidirectional Impulse Turbine Using Artificial Neural Network
Authors: Badhurshah R. , Samad A.
Published: October 2014

The work represents a systematic numerical optimization methodology using artificial neural network and hybrid genetic algorithm for a bi-directional axial impulse turbine used in wave energy harvesting system. Reynolds-averaged Navier-Stokes equations with k-ε turbulence model were discretized and solved for unstructured tetrahedral grid elements for flow analyses. Efficiency enhancement of the turbine was chosen as an objective. The design variables chosen were numbers of stator and rotor blades. The responses obtained from CFD analysis were used to train the neural network. The optimal point search from the network by hybrid genetic algorithm produced 13% increase in turbine efficiency. Detailed description of the methodology and analysis of the results has been presented in this paper.
Thermo-Economic Analysis of a Solar Heating and Cooling System With Desiccant-Based Air Handling Unit by Means of Dynamic Simulations
Authors: Angrisani Giovanni , Roselli Carlo , Sasso Maurizio , Tariello Francesco
Published: October 2014

Solar Heating and Cooling systems are a virtuous alternative to conventional air conditioning plants, as a renewable energy source (solar energy) is exploited.

In this paper the coupling of low temperature solar devices with an innovative desiccant-based air handling unit, which meets the sensible and latent loads of a simulated lecture room, is analyzed through TRNSYS dynamic simulation software. The components have been characterized by means of experimental tests carried out at the test facility of Università degli Studi del Sannio. The desiccant-based air handling unit current set-up allows summer operation only. However, heating operation is also simulated, as comfort conditions can be maintained in the conditioned space exploiting solar thermal energy also in winter, with some modifications to the air handling unit. A parametric analysis is performed to compare different technical solutions (collector types, surface, tilt angle) and to identify the optimal one, taking into account energy, economic and environmental performance with respect to a reference system.

The best case in terms of energy and environmental performance is represented by evacuated collectors, achieving a primary energy saving of 64% and a CO2 emissions reduction of 61%; flat-plate collectors are instead the best solution in terms of pay-back period (6 years).
Configuration Design and Energy Balancing of Compact-Hybrid Powertrains
Authors: Walker Paul D. , Roser Holger M.
Published: October 2014

The development of compact and efficient hybrid electric vehicle powertrains for low initial and on-going costs requires consideration of numerous, often competing factors. Appropriately designing and sizing these powertrains requires the consideration of requirements for vehicle range and performance, considered directly through the sizing of motors and engines, and indirectly through minimization of vehicle mass whilst being constrained by total stored energy in the vehicle, against the impact on vehicle emissions and on purchase and ongoing operational costs. In addition to these considerations the actual driver use will strongly influence the energy consumed and vehicle emissions. It therefore becomes beneficial to provide flexibility in hybrid vehicle configuration design to enable the minimization of vehicle emissions and ongoing vehicle costs.

The purpose of this paper is to study the various alternative vehicle powertrain configurations for application to small scale hybridization demands, such as scooters or motorcycles. Powertrain configurations studied in this paper include plug-in hybrid electric (PHEV), battery hybrid electric (BHEV), and a pure electric vehicle (PEV). To design and size each of the configurations a statistical approach is taken, power and load demands are studied and utilized to size powertrain components. Results are extended to size vehicle energy storage for electric only range of 25, 50 and 100 km, and total vehicle range of 100 km for the BHEV and 200 km for the PHEV. Based on the results developed from the analysis mathematical models of each of the powertrain configurations are then developed in Matlab/Simulink and numerical studies of vehicle energy consumption in comparison to range are conducted. Outcomes of these simulations are compared to an operating cost based analysis of the suggested powertrains; the benefits and limitations of each design are considered in detail.
Product Design Knowledge Model in Distributed Resource Environment
Authors: Dai Xudong , Ma Xuefen
Published: October 2014

Product design is a process of knowledge flowing and integrating. From the perspective, product design in distributed resource environment could be defined as the constructing process of a product knowledge model to satisfy specific needs of customers. This paper studies and builds structured models of product design knowledge, i.e. a customer need knowledge model, a DE knowledge model and a RU knowledge model. A product design knowledge model is the structured specification of a desired artifact including customer Need, Function with Environment (constraints), Physical principle with its Structure and Implement method and Technology detail (FEPSAT). A customer need knowledge model is constructed by customer Group feature, need Content and product Meaning (GCM). The DE knowledge model is constructed by Value, Profession, Culture and Experience background (VPCE). The RU knowledge model is built by knowledge service Content, service Input and service Output (CIO). The evolution of the product design knowledge models and the interaction with each other were analyzed.
Influence of Explicit and Implicit Integration of Hyperelastic-Plastic Combined Hardening Models on the Springback in Sheet Forming
Authors: Pietryga Michael P. , Vladimirov Ivaylo N. , Reese Stefanie
Published: October 2014

In this paper, we investigate the computational efficiency of explicit and implicit integration schemes for hyperelastic-plastic combined hardening plasticity and examine the influence on the simulated springback in sheet metal forming. Due to the deviatoric character of the evolution equations, the finite strain combined hardening model discussed here is integrated by means of the exponential map algorithm in order to fulfil plastic incompressibility. We focus here on different possibilities of evaluating the exponential tensor functions of the material model. One option is to use the spectral decomposition to evaluate the exponential tensor functions in closed form. Alternatively, the latter functions can be evaluated by Taylor series expansion. Furthermore, we examine the potential of an explicit formulation of elasto-plasticity with combined hardening regarding accuracy and efficiency. The material model equations have been implemented as user material subroutines UMAT and VUMAT for use in the commercial solvers ABAQUS/Standard and ABAQUS/Explicit, respectively. The numerical models are applied to the finite element simulation of draw bending, where the forming step is simulated both in implicit and explicit manner, whereas the ensuing springback step is carried out only implicitly.
Mechanical Property and Microstructural Characterization of AISI 304L: Application Spot Welding
Authors: Sidhoum Zehra , Ferhoum Rabah , Almansba Madjid
Published: October 2014

In recent years, the development of high-strength steels such as multi-phase TRIP (transformation-induced plasticity)-aided steels have shown great promise due to their excellent combination of high strength and ductility. In this paper, the effect of strain-induced martensitic transformation on mechanical properties is studied. Uniaxiale tension tests at different strain rate (10, 15 and 20 mm / min) are conducted at 25° C in order to characterize the mechanical behavior of AISI 304L. The microstructure, particularly retained austenite, is analyzed using optical microscopy, Vickers hardness measurements. The results showed that all properties measured are increased from (Re=390.96MPa to Re=425.96MPa and Hv=300.94Hv to 343.51HV).

Secondly, the influence of the annealing treatment on microstructure and mechanical properties of the joint formed by the spot welding are characterized using tensile test, metallographic analysis and Vickers hardness measurements.
Numerical Simulation of Convective-Radiative Heat Transfer in a Solar Chimney
Authors: Buonomo Bernardo , Manca Oronzio , Nardini Sergio , Tartaglione Gianluca
Published: October 2014

Solar chimney is a new method to produce electrical power. It employs solar radiation to raise the temperature of the air and the buoyancy of warm air to accelerate the air stream flowing through the system. By converting thermal energy into the kinetic energy of air movement, solar chimneys have a number of different applications such as ventilation, passive solar heating and cooling of buildings, solar-energy drying, and power generation. Moreover, it can be employed as an energy conversion system from solar to mechanical. A component, such as a turbine or piezoelectric component, set in the path of the air current, converts the kinetic energy of the flowing air into electricity.

In this paper, a numerical investigation on a prototypal solar chimney system integrated in a south facade of a building is presented. The chimney is 4.0 m high, 1.5 m wide whereas the thickness is 0.20 m for the vertical parallel walls configuration and at the inlet 0.34 m and at the outlet 0.20 m for convergent configuration. The chimney consists of a converging channel with one vertical wall and one inclined of 2°. The analysis is carried out on a three-dimensional model in airflow and the governing equations are given in terms of k-ε turbulence model. The problem is solved by means of the commercial code Ansys-Fluent. The numerical analysis was intended to examine the effect of the solar chimney’s height and spacing. Further, comparison between radiative and non-radiative model is examined and discussed. Results are given in terms of wall temperature distributions, air velocity and temperature fields and transversal profiles for a uniform wall heat flux on the vertical wall equal to 300 W/m2. Thermal and fluid dynamics behaviors are evaluated in order to have some indications to improve the energy efficiency of the system.
Assessment of Turbocharger Turbine Unsteady Flow Modelling Methodology on Engine Performance
Authors: Mustafa Ammar , Martinez-Botas Ricardo F. , Pesiridis Apostolos , Chiong Meng Soon , Rajoo Srithar
Published: October 2014

Although it is well known that the flow entering a turbine of a turbocharger engine is highly unsteady, engine manufacturers prefer to use turbine performance predictions that are based on steady-state performance maps, which inherently lead to inaccuracies in the turbine’s behavior and mismatches between turbocharger turbines and engines. The reason for this preference is due to the turbocharger turbine design software that are generally available to engine manufacturers being based on and compatible with steady-state performance maps and this fact led researchers to investigate how the inaccuracies of this steady-state treatment of the turbine can be alleviated.

To this effect, this paper investigates how modelling techniques on Ricardo Wave, a 1D gas dynamics engine simulation software, gives rise to more accurate turbine swallowing curve predictions using steady-state maps. In particular, the turbine being investigated is that of Szymko [1], which is a twin nozzleless mixed-flow turbine that is being powered by a 10 litre, 6 cylinder 4 stroke diesel engine with an operating range from 800–2000 RPM for which 800, 1200 and 1600 engine RPM relate to 40, 60 and 80Hz exhaust gas pulse frequencies at the turbine.

The main investigation in this paper is to demonstrate the capability of the engine simulation software to deal with unsteady flows and specifically to show the significant effect of accounting for the volute design in the single turbine wheel entry model. The data obtained in this investigation were compared with those of Szymko [1], which offered a validated set of data to compare against.