bluuebunny/crossref_metadata_2025 huggingface dataset:
Control Strategies for a Linear MR-Brake With Serpentine Flux Path for Haptics
Authors: Alkan Mustafa Sait , Gurocak Hakan
Published: December 2013

In haptics applications actuators with compact volume and high force output are desired for stable and stiff interfaces. Magnetorheological (MR) brakes are viable options since they have large force-to-volume ratios. However, linear MR-brakes available on the market have limited stroke due to the piston-cylinder design and show viscous damping behavior where the force output highly depends on the velocity of the actuator resulting in a high off-state friction force. Another problem is the inherent magnetic hysteresis, which requires complex control systems.

In this research, we focused on the development and control of a linear MR-brake with infinite stroke and minimal off-state friction. The common piston-cylinder arrangement was removed from the design to address the limited stroke and high off-state-friction issues. The serpentine flux path methodology was followed to achieve compact geometry. Three control strategies namely, open-loop control, force feedback control, and current feedback with Preisach model, were implemented on the developed prototype. The results using Preisach model showed that the hysteresis could be reduced significantly without the need for an expensive force sensor in the control loop.

Our new device has a 3% ratio of the off-state friction force to the maximum force output in comparison to more than 10% for most MR-damper devices in the literature. At the same time, our prototype is about half the size of a commercially available product.
Modeling and Simulation of an Electro-Hydraulic Servovalve in an Intelligent Programming Environment
Authors: Harf Mait , Grossschmidt Gunnar
Published: December 2013

Composing of models and simulation of statics, steady state conditions and dynamic responses of an electro-hydraulic servovalve is considered in the paper. The observed servovalve contains an electro-mechanical transducer (as a torque motor), a nozzle-and-flapper valve and a sliding spool in sleeve with elastic position feedback from spool to flapper. For composing mathematical models of the servovalve multi-pole models of functional elements are used. For representing relations between inner variables oriented graphs are used.

Results of the current work will be used in modeling and simulation of electro-hydraulic servo-systems.
A Stability Analysis of the Wheel Shimmy
Authors: Di Massa Giandomenico , Pagano Stefano , Strano Salvatore , Terzo Mario
Published: December 2013

The wheel shimmy is a classical non-linear problem. The most frequently used approach to study this phenomena is based on linearized low degree of freedom models, that from one side, thanks the simplicity of the equations of the motion, allows to evaluate the stability with classical stability-analysis approach, but from the other side it limits the study about the equilibrium point. In this paper a stability-analysis, based on a three degree of freedom non-linear analytical model, is presented. Starting from the system numerical response, adopting a time-domain modal analysis method, the modal parameters were identified.

The proposed procedure, through a 3 degree of freedom nonlinear representation of the castor, highlights the three main castor oscillation modes whose characteristics can then be identified with a method applicable even for experimental investigations.
Path Following Performance of Narrow Tilting Vehicles Equipped With Active Steering
Authors: Robertson James W. , Darling Jos , Plummer Andrew R.
Published: December 2013

Narrow Tilting Vehicles offer an opportunity to reduce both traffic congestion and carbon emissions by having a small road footprint, low weight, and a small frontal area. Their narrow width requires that they tilt into corners to maintain stability; this may be achieved by means of an automated tilting system. Automated tilt control systems can be classed as Steering Tilt Control (STC) in which active control of the front wheel steer angle is used to maintain stability, Direct Tilt Control (DTC) in which some form of actuator is used to exert a moment between the tilting part(s) of the vehicle and a non-tilting base, or a combination of the two (SDTC). Combined SDTC systems have the potential to offer improved performance as, unlike STC systems, they are effective at low speeds whilst offering superior transient roll stability to DTC systems. However, alterations to the front wheel steer angle made by STC and SDTC systems may result in unwanted deviations from the driver’s intended path.

This paper uses multi-body simulations of a three-wheeled Narrow Tilting Vehicle performing an emergency lane change manoeuvre to show that the path followed by a SDTC equipped vehicle in response to a given series of steer inputs differs significantly from that followed by a DTC equipped vehicle. It is also shown that by using a revised series of steer inputs, a vehicle equipped with SDTC is able to successfully follow a similar path to one equipped with DTC, and that the roll stability of the vehicle is not unduly compromised. Finally, the influence of higher DTC system gains on the SDTC system is considered. It is shown that the result is a small improvement in the vehicle’s path following response at the expense of a small reduction in vehicle roll stability.
Real-Time Roll Angle Estimation for Two-Wheeled Vehicles
Authors: Lot Roberto , Cossalter Vittore , Massaro Matteo
Published: December 2013

An original method for the real-time estimation of the roll angle using low-cost sensors in two-wheeled vehicles is proposed. The roll angle greatly affects the dynamics of single-track vehicles and its estimation is essential in control systems such as ABS, Traction Control, as well as Curve and Collision Warning, or even active suspensions. The proposed method uses a non-linear Kalman filter, its performances are assessed by using both a set of simulated data from a multibody model and a set of real data collected on an instrumented test vehicle.
Output-Only Modal Analysis of an Internal Unreachable Module Embedded in a Space Electronic Equipment
Authors: Ben Fekih Lassaad , Kouroussis Georges , Wattiaux David , Verlinden Olivier , De Fruytier Christophe
Published: December 2013

An approach is proposed to identify the modal properties of a subsystem made up of an arbitrary chosen inner module of embedded space equipment. An experimental modal analysis was carried out along the equipment transverse direction with references taken onto its outer housing. In parallel, a numerical model using the finite element (FE) method was developed to correlate with the measured results. A static Guyan reduction has led to a set of master degrees of freedom in which the experimental mode shapes were expanded. An updating technique consisting in minimizing the dynamic residual induced by the FE model and the measurements has been investigated. A last verification has consisted in solving the numeric model composed of the new mass and stiffness matrices obtained by means of a minimization of the error in the constitutive equation method.
Integrating Vehicle Body Concept Modelling and Flexible Multi-Body Techniques for Ride and Handling Simulations
Authors: Carpinelli M. , Mundo D. , Tamarozzi T. , Gubitosa M. , Donders S. , Desmet W.
Published: December 2013

This paper deals with the integration of a vehicle body concept modeling methodology, based on reduced models of beams, joints and panels, with flexible Multi-body (MB) representation of the chassis of a passenger car. The aim is to enable ride and handling simulations in the initial phases of the vehicle design process, where the availability of predictive Computer Aided Engineering (CAE) tools is a key factor to steer design choices such that a faster convergence of the vehicle development cycle towards improved products is achieved.

The proposed approach is demonstrated on an industrial case study, involving a commercial passenger car, for which a detailed chassis and suspension model for MB simulations is developed in LMS Virtual.Lab Motion. A flexible concept model of the vehicle’s Body In White (BIW) is created as well and included in the MB model to enable fast investigations on how ride and handling performance of the full vehicle are affected by body modifications.

To demonstrate the validity of the resulting concept model, a number of standard handling manoeuvres and ride excitations are simulated by using both the flexible MB model described above and a rigid MB model of the vehicle, which is derived from the same FE model. The numerical results are compared to allow assessing the influence of body flexibility on the predicted handling and ride behaviour of the vehicle.
Developing a Parallel Kinematic Solar Tracker for HCPV
Authors: Battezzato Alessandro , Mauro Stefano , Scarzella Cristina
Published: December 2013

The paper describes a new kind of solar tracker intended to satisfy the precision requirements of high concentration photovoltaic systems. The tracker is designed according to a Delta type parallel kinematic schematics. The paper describes the kinematic schematics, the sensor chain and the control algorithm. Finally results obtained in functional tests are shown.
Methodology for the Design of Cooling Channels in Thermoplastic Injection Moulding Process
Authors: Agazzi Alban , Sobotka Vincent , Le Goff Ronan , Jarny Yvon
Published: December 2013

Injection is one of the most used processes to manufacture thermoplastic parts. The design of the cooling channels in this process is of great importance during the mould design. Indeed, an inappropriate cooling will lead to defects in the part and a low production rate. In this paper, a new approach for the design of the cooling channels is assessed. Based on morphological concepts, the idea of regulation by cooling surface is introduced. The thermal behaviour of the mould can be restricted on the spatial domain delimited by the cooling surface on which a spatial temperature distribution is imposed. The first step of the methodology leads to the optimal determination of the fluid temperature distribution along the cooling surface in order to minimize a cost function composed of two terms linked to the quality of the part and the productivity of the process. The conjugate gradient algorithm coupled with a Lagrangian technique is implemented for the determination of fluid temperature parameters. However, the obtained solution is not workable in practice. The second step consists then in building real channels from this optimal distribution. The shape, location and fluid temperature level of these channels are determined a posteriori from the thermal analysis of the temperature field in the mould domain located between the plastic part and the cooling surface. Channels are builded by using the contours of isotherms in the thermal steady-state area of the mould. It becomes then possible to design the cooling channels with no a priori on the numbers, the location of these channels and on the temperature of the coolant fluid. The methodology is first illustrated with a 2D part. Results are compared with literature.
A Neural Network Approach to Analyse Cavitating Flow Regime in an Internal Orifice
Authors: De Giorgi M. G. , Bello D. , Ficarella A.
Published: December 2013

The identification of the water cavitation regime is an important issue in a wide range of machines, as hydraulic machines and internal combustion engine. In the present work several experiments on a water cavitating flow were conducted in order to investigate the influence of pressures and temperature on flow regime transition. In some cases, as the injection of hot fluid or the cryogenic cavitation, the thermal effects could be important. The cavitating flow pattern was analyzed by the images acquired by the high-speed camera and by the pressure signals. Four water cavitation regimes were individuated by the visualizations: no-cavitation, developing, super and jet cavitation. As by image analysis, also by the frequency analysis of the pressure signals, different flow behaviours were identified at the different operating conditions. A useful approach to predict and on-line monitoring the cavitating flow and to investigate the influence of the different parameters on the phenomenon is the application of Artificial Neural Network (ANN). In the present study a three-layer Elman neural network was designed, using as inputs the power spectral density distributions of dynamic differential pressure fluctuations, recorded downstream and upstream the restricted area of the orifice. Results show that the designed neural networks predict the cavitation patterns successfully comparing with the cavitation pattern by visual observation. The Artificial Neural Network underlines also the impact that each input has in the training process, so it is possible to identify the frequency ranges that more influence the different cavitation regimes and the impact of the temperature. A theoretical analysis has been also performed to justify the results of the experimental observations. In this approach the nonlinear dynamics of the bubbles growth have been used on an homogenous vapor-liquid mixture model, so to couple the effects of the internal dynamic bubble with the other flow parameters.
Computer-Aided Design of Mechatronic Systems Using Multiobjective Optimization and Object-Oriented Languages
Authors: Casner Didier , Renaud Jean , Knittel Dominique
Published: December 2013

This paper deals with the fast modeling and fast multiobjective optimal design of mechatronic systems. To solve this problem, the object-oriented modeling language Modelica and object-oriented programming language Java have been used to build an innovate software platform. This platform has been designed to allow multidisciplinary design optimization of complex systems using a free platform. This platform only contains open-source tools and frameworks and was validated on an optimization application: the stabilization of a quarter-car system.
Needs for Tracing the Consequences of Decisions in Mechatronics Design
Authors: Lo Mambaye , Couturier Pierre
Published: December 2013

As the design of mechatronic systems relies on different technical and scientific disciplines, it is often difficult to anticipate, at the earliest, the consequences of design choices on the final product. The role of the evaluation process is to support designers each time engineering choices must be made or justified. Being able to estimate the impact of design decisions on key technical performance indicators is one objective of our research. After having presented the activities of the evaluation process, we propose a meta-model of the data required by evaluation in the context of the Systems Engineering framework. Then we investigate how the top down and bottom up tracing of technical requirements through Block Systems and between systems engineering layers of the ‘onion model’ may help designers analyze the consequences of design decisions on the final product. The research is illustrated through the development of a wheelchair with electrical assistance so as to allow reduced mobility people to move and work outside with less tiredness.
Performance Assessment of Hexahedral Meshing Methods for Design and Mechanical Analysis of Composite Materials
Authors: Podshivalov Lev , Fischer Anath , Bar-Yoseph Pinhas Z.
Published: December 2013

Composite materials can be designed and modeled as material volumes with inclusions of several materials. These multiple inclusions are randomly distributed in a unit cube volume according to the material parameters (density, dimensions, orientation etc.). Then, the finite element (FE) analysis method is applied on the resulting structure to estimate the equivalent material properties. Therefore, these models should to be meshed prior to mechanical FE analysis.

Automatic high quality hexahedral meshing is considered a very complex task. Hence, despite extensive research, currently there are no robust methods that can handle grain-based geometry. Meshing a composite material modeled by multiple inclusions presents a number of challenges: (a) the meshing needs to be robust to dimensions, position and orientation of the inclusions; (b) mesh continuity must be achieved on the boundaries between the volume (also known as the matrix) and the inclusions; (c) the mesh needs to approximate the original geometric model with high accuracy; and (d) high quality mesh elements are required for mechanical analysis.

Structured and unstructured meshing methods can be used for handling this task. In this research two meshing methods were developed to generate high quality meshes: (a) structured meshing created by warping the grid according to the model’s geometry, and (b) unstructured meshing created by projecting the nodes onto the boundaries of the inclusions to achieve exact geometric representation.

The performance of these methods was then evaluated and compared on composite materials with ellipsoidal inclusions. Among the performance criteria for these methods are mesh element quality, geometry approximation error, stress concentrations near the boundaries, and computational complexity.

The results indicate that the proposed methods can be used for design and mechanical analysis of composite materials. Moreover, in homogenization applications the structured warped mesh is compatible in terms of performance and element quality to the unstructured mesh.
Vibration Identification of Gasoline Engine Part
Authors: Chang Jiuk , Lee Sangkwon , Park Jongho , Kim Byunghyun , Park Hongseok
Published: December 2013

This paper presents the method estimating the contribution of vibration sources in gasoline engine with a multiple input system. Multi Dimensional Spectral Analysis (MDSA) has used to identify the cause of a linear dependence indicated by an ordinary coherence function. In order to apply the MDSA to the vibration source identification in gasoline engine, the virtual model of two inputs and single output system is simulated. For the validation of this model, the vibration of alternator was measured by using tri-axial accelerometers attached on the selected vibration source. After calculating the coherence analysis between each source based on the virtual model, the vibration contribution of alternator is calculated.
A Study on the Dynamic Load Simulation for a Crawler Excavator Considering Ground Effect
Authors: Yang Seongpil , Kim Mooseung , Hwang Donghyeon , Kim Panyoung
Published: December 2013

A fatigue life is one of the key design factors for crawler excavators because they are usually operated in a very harsh working condition. In order to evaluate the fatigue life, the fatigue loads in various working conditions should be decided in advance. In case of the attachments such as boom and arm, the forces at the bucket tip due to digging and lifting are primary fatigue loads, which can be calculated relatively easily using design specifications. However, the forces at the track need to be considered additionally for the upper and lower frames. And it is almost impossible to measure the forces at track in a field test. In this study, a dynamic model of excavator including track system is implemented and dynamic load simulations are carried out to investigate the distribution of the reaction forces at each roller for the typical working scenarios. The model and the simulation technique are verified by comparison with the results of measurement in view of weight balance, cylinder forces, accelerations of counter weight and stresses at concerned points. The normalized distribution of the reaction forces at each roller in digging and lifting working mode are presented and the distribution is expected to be used as the baseline of fatigue load estimation for the upper and lower frames of various class crawler excavators. To get the multibody dynamic simulation results by the excavator motion, we used the commercial software such as Recurdyn for kinematic and dynamic modeling. Especially the track modeling of the excavator is composed using Track_LM module of the Recurdyn. And stress analysis of the frame is carried out using the NX-Nastran program.
Identification of Pick Up Noise for Laser Printers Based on Psychoacoustic Parameters
Authors: Lee Young-Jun , Lee Sang-Kwon , Shin Tae-Jin , You Jin , Seo Sang-Hyun
Published: December 2013

This paper illustrates that a method for identification of pick up noise and an analysis the cause of pick up noise by substituting components of a laser printer. The operating sound radiated from a laser printer includes the tonal noise components caused by the rotating mechanical components such as gear, shaft, motor, fan, etc. A sound operated by laser printers has become important competitiveness in printer industries as the demand of laser printers increases. Especially, a noise between a friction pad and a paper in the process of printing has become an essential issue in an aspect of quality evaluation. However the existing criteria for determining the above noise have solely relied on human’s subjective judgments; which highlights the requirement to objectify these criteria.

In this paper, the standard of existing pick up noise is established by finding the tonality, which is a psychoacoustic parameter, of noticeable limit sound level. Based on the findings of the method, the study has found factors which cause pick-up noise and suggests the substitution of following components of printers such as: spring constants, spring force, and the quality of friction pads.

As a result, it is confirmed that the proposed pick up noise index has usefulness to classify whether existence of pick up noise with an objective evaluation and not to occur the noise based on design optimized combination of laser printer components.
Assessment of Modal Strain Energy Method: Advantages and Limitations
Authors: Koruk Hasan , Sanliturk Kenan Y.
Published: December 2013

The Modal Strain Energy Method (MSEM) is widely used in practice for the prediction of damping levels in structures. MSEM is based on a fundamental assumption that the damped and the undamped mode shapes of a structure are identical. Therefore, when MSEM is to be used, it is essential to ensure that this assumption is an acceptable assumption. However, detailed information on the accuracy of the method as a function of the system parameters including modal (or mode shape) complexity is quite limited. In this paper, the performance of MSEM is assessed in terms of the damping levels of the structure, proportionality of damping distribution and/or the modal complexity. To do so, an effective finite element based MSE approach is proposed first. Then, a proportionally damped structure with different damping levels is modeled and the performance of MSEM is assessed as a function of the structural damping level. After that, a non-proportionally damped structure is studied in order to examine the performance of the method with respect to mode shape complexity. In all cases, a more accurate reference method, based on complex eigenvalue approach, is used for comparison purposes. Furthermore, a few definitions of mode shape complexity are utilized in order to quantify the mode shape complexity. The results show that as long as the mode shapes are real or close to being real, MSEM can predict the damping levels as well as the natural frequencies of a damped structure with good accuracy. However, the accuracy that can be achieved with MSEM decreases as mode shape complexity increases.
Wheel Shimmy Experimental Investigation
Authors: de Falco Domenico , Di Massa Giandomenico , Pagano Stefano
Published: December 2013

This paper presents a test rig adopted for a basic investigation on the shimmy phenomenon that, even if with some differences, characterizes the dynamic behavior of many mechanical systems such as aircraft landing gear, motorcycles, towed vehicles, etc..

The test rig is constituted of a castor derived from a scooter front assembly, joined to a rigid steel frame so that it can vertically translate and rotate around the steering axis; the castor wheel rolls on a flat track belt driven by an electric motor. The rake angle, the steer damping, the vertical load, the inertia proprieties and the wheel/tire characteristics can be adjusted to experimentally investigate their influence on the castor dynamic behavior.

The paper deals with the dynamic behavior of a castor characterized by a low lateral stiffness and a simple procedure to identify its vibrating modes is presented. It is also shown a numerical model adopted to test the sensitivity of the system to the parameters changes.
Hysteresis Switching Design for Stabilization of Switched Neutral Systems Using Multiple Lyapunov Functionals
Authors: Li Tai-Fang , Dimirovski Georgi M. , Zhao Jun
Published: December 2013

The stabilization problem for a class of switched neutral systems with a discrete time-varying delay is studied in this paper. The upper bound of derivative of the discrete time-varying delay can be an arbitrary given constant which is not necessary to be less than one. Each subsystem is not assumed to be stable. A hysteresis switching law is designed based on multiple Lyapunov functionals to avoid sliding modes and chattering phenomena. The obtained delay-dependent stabilization criterion is given in terms of linear matrix inequalities (LMIs). The result is illustrated by an example.
Synthesis and Optimization of Transient Performances for Underdamped Second-Order Linear System Based on the Switching Control Strategy
Authors: Su Qingyu , Dimirovski Georgi M. , Zhao Jun
Published: December 2013

In this paper, the synthesis and optimization problems of the transient performances, such as overshoot and setting time, of the output response with respect to a step signal for an under-damped second-order linear system are studied. The traditional control strategy and the switching control strategy are used, respectively. Our control objective is twofold: Objective 1 is to ensure that the overshoot of the system output does not violate the given safety bound and objective 2 is to ensure that the settling time is smaller than the given allowable time. The obtained results indicate that the switching control strategy has main two evident advantages: firstly, the switching proportional controllers can take advantages of both the quick response and the small overshoot of the output response. Secondly, the switching controller is always available, while the single proportional controller is available in some special cases. Finally, an example of servomotor is given to demonstrate the effectiveness of the proposed method.
Analysis of a Reciprocate Engine–Based Cogeneration Plant With High Temperature Heat Recovery for Industrial Uses
Authors: Cardona Fabio , Panno Domenico , Piacentino Antonio
Published: December 2013

In consequence of the increasing awareness on the future scarcity of fossil energy sources and the global warming impact of energy conversion processes, the European Union has been planning several actions to enhance the efficiency of energy use and reduce the environmental impact. The declared goals of EU actions are synthetized in the 20-20-20 formula, consisting of an expected 20% increase of energy efficiency, a 20% contribution to the total energy supply by renewable sources and a 20% abatement of pollutant emissions. Applications of cogeneration in process industry can significantly contribute to achieve these targets. In this paper a reciprocate engine-based Combined Heat and Power (CHP) plant is presented, serving a pasta factory located in Sicily and installed by an Energy Service COmpany (ESCO) within the context of a national implementation scheme of Energy Saving Certificates (or “white certificates”). The CHP plant, with a 650 kWe capacity, currently covers a relevant fraction of the electric and high-temperature heat loads during peak hours, while it is switched off during off-peak hours because of the much lower electricity price. Heat content of flue gases is recovered by two cascaded gas-diathermic oil and diathermic oil-water heat exchangers; the superheated water obtained is then supplied to the pasta dryers. The first part of the paper provides a detailed plant description and an energetic analysis of historical performance data collected along the last two years of operation. Both the critical analysis of the lay-out and the evaluation of energy saving indicators reveal the current scheme to represent a sub-optimal solution for the particular application. In the second part of the paper a modified solution is simulated, consisting of the same CHP unit equipped with additional heat exchangers for heat recovery from the cooling water jacket circuit. The marginal energetic and economic benefits compared to the current plant setup are calculated; the results are presented in analytic and graphical form, coherently with the provisions of Directive 2004/8/EC and accounting separately for the different cost and revenues (fuel for the CHP unit and the supplementary boilers, electricity purchased from or supplied to the grid, taxes, etc.). The improved solution, designed to increase the thermal efficiency of the CHP unit by allowing a full exploitation of heat cascades, resulted to provide evident benefits and to make the CHP unit to comply with all the current legislative provisions for the assessment of highly efficient CHP plants. Margins for further improvements are also briefly discussed.
Characterization of a Four Discrete Positions Electromagnetic Actuator
Authors: Petit Laurent , Huyan Pengfei , Prelle Christine , Dore Emmanuel , Lamarque Frédéric
Published: December 2013

A digital electromagnetic actuator having two displacement directions and four discrete positions is presented. These discrete positions are located at each corner of a closed square bracket where a mobile magnet moves due to Lorentz force generated with a driving current through a wire. An optimized design of this actuator is presented, modeled and tested. At first, plane displacements are presented which proves the ability of the actuator to realize this type of displacement. Second, comparisons between the experimental and modeled displacements are carried out which show a good agreement from dynamic point of view and finally, the measured positioning repeatability errors in discrete position are given.
A Parallelized Node-Centered Finite Volume Method for Computing Radiative Heat Transfer on 3D Unstructured Hybrid Grids
Authors: Lygidakis Georgios N. , Nikolos Ioannis K.
Published: December 2013

An algorithm for the computation of radiative heat transfer for absorbing, emitting and either isotropically or anisotropically scattering gray medium in three dimensions is developed. Radiative transfer equation is solved using a node-centered finite volume method in combination with an edge-based data structure, while scattering phase function is defined by Legendre polynomial expansions. Hybrid unstructured grids are used, due to their good viscous layer resolving capability, considering that our final objective is the analysis of coupled heat transfer-fluid flow problems. In addition, domain decomposition approach with message passing interface model is utilized, in order the proposed algorithm to be implemented in a parallel computational system. Numerical results reveal that the present methodology has a good performance in terms of accuracy, geometric flexibility, and computational efficiency.
Experimental Study of Very Low Aspect Ratio Wings in Slender Bodies
Authors: Arevalo-Campillos M. A. , Tuling S. , Parras L. , del Pino C. , Dala L.
Published: December 2013

The dynamics of very low aspect ratio wings (or strakes) vortices in slender bodies are complex due to the interaction of the shed vortex sheet and the body vortex. For missiles at supersonic speeds these interactions are not easily predicted using engineering level tools. To shed some new light onto this problem, an experimental study in a water channel for moderate Reynolds number (Re = 1000) was performed for a 19D body and strake configuration with strakes having a span to body diameter ratio of 1.25. Comparisons to numerical simulations in supersonic flow are also performed. Flow visualisation has been carried out to characterize the vortex dynamics at different angles of attack; these being 11°, 16°, 22° and 27°. The comparison between a slender body without strakes and the body-strake configuration has given some key indicators in relation to the vortex position of the core. Furthermore, unsteady wing-body interference has been observed at angles of attack above 20° for both experimental and numerical simulations. Consequently, the average position of the vortex core is located at larger distances from the missile in comparison to the body without strakes. The numerical simulations show good correlation with the experimental tests even though the dynamic convective interactions between the body vortex and strake vortex sheet are not predicted.
Safety Protection Control for the Aeroengines via Switching Strategy
Authors: Chen Chao , Dimirovski Georgi M. , Zhao Jun
Published: December 2013

For the simplified linear hypersonic air-breathing propulsion model, aiming at the safety boundaries existing during the working progressing, this paper considers the output regulation/ safety protection switching control problem. Several comments are given to the minimum control switching strategy studied in our previous work, and to make the designing of the switching controller more systematic, a novel command switching strategy is proposed, where discontinuous controllers are adapted. The protected output will be forced to escape from the safety boundary once the danger comes. The asymptotic tracking problem is transformed into the asymptotic stability problem of the linear switched and impulsive systems or that of the switched systems whose subsystems have different equilibrium points. The design of the dynamical output feedback controllers and the switching laws can be finished separately, and the principles guaranteeing asymptotic tracking are given, the decline of the candidate Lyapunov function can be checked by solving an optimal problem. Finally, simulations verify the effectiveness of the given results, which also indicate that the commands switching control can improve both the safety margin of the protected output and the tracking performance of the regulated output, the ability of tracking commands safely and quickly is thus enhanced.
Use of Inverse Method for Bonding Quality Assessment Between Bitumen and Aggregates Under Asphalt Mixes Manufacturing Conditions
Authors: Somé Sâannibè-Ciryle , Gaudefroy Vincent , Delaunay Didier
Published: December 2013

In roads building, classical asphalt mix manufacturing commonly requires the heating (at 160°C) and the complete drying of aggregates. The induced energy cost has opened the way to develop alternatives processes and materials with low energy/carbon materials such as Warm Mix Asphalt (WMA). In warm mixes processes, aggregates manufacturing temperatures are different and lower than the Hot Mix ones. However, manufacturing temperature reduction can locally lead to poor bonding between bitumen and aggregate during the mixing step, due to the bitumen viscosity increasing, although bonding quality measurement remained a challenge. The aim of our study was to presents two thermal inverse methods for bonding quality assessment. These methods are based on Thermal Contact Resistance (TCR) assessment between bitumen and aggregate, during asphalt mix manufacturing. The experimental test principle consisted of heating both bitumen and cylindrical aggregate to their manufacturing temperatures (over 100°C) and to put them into contact thanks to a special experimental device. According to initial samples temperatures, heat transfer occurs from the bitumen to the aggregate. Two variants of the sequential Beck’s method were used to solve the inverse heat conduction problem. The first one consisted of determining the TCR from heat flux and temperatures and the second one consisted of identifying directly the TCR. The TCR values were interpreted as bonding quality criteria.

Results showed low sensitivity to temperature measurement noise in the second variant of the inverse method. Moreover our study showed that bonding quality depends on bitumen and aggregate temperatures. The higher the component’s temperatures, the lower the TCR values and better is the bonding quality.
Numerical Modeling of the Dynamic Behavior of Shredder Hammers and Correlation With Material Damage
Authors: Brusa Eugenio G. M. , Bosso Nicola , Morsut Stefano
Published: December 2013

Pre-forming and fragmentation of the ferrous scrap used into the electric arc furnace for the melting process is a relevant activity for a steelmaking plant. Shredding machines are applied to suitably reduce the size of scrap. A set of hammers is connected to a main rotor. Rotation converts the high kinetic energy of each hammer into a strong impact against the scrap. Metallic parts are crushed and fed into the electric arc furnace. Damage of the hammer material is due to impact, vibration, wear and temperature. In addition fatigue affects its life. An effective prediction of the damage location as well as of its propagation in the hammer is rather difficult. A resident health monitoring system cannot be easily applied. Therefore a preliminary model was built to predict the dynamic behavior of each hammer in rotation and to compute the applied stress, while the impact is occurring. A rotor-dynamic analysis was performed by means of a Multi Body Dynamics and a Finite Element code, respectively. Magnitude, direction and frequency of the dynamic loads were first computed by the Multi Body Dynamics code. Stress exciting the hammer material was then computed by the Finite Element Method. Nonlinearities are crucial for the design operation. Friction among the materials, clearance between the pin and the hammer and the nonlinear behavior of materials are all relevant for the nonlinear dynamic response of the hammer. Numerical results were compared to some preliminary observations performed on an industrial plant. They allowed motivating the occurrence of cracks and wear effects in some critical points of the hammer. Some design criteria were defined and successfully tested to improve the performance of materials.
Numerical Investigation of Natural Convection in a Mono-Span Greenhouse
Authors: Kruger Sunita , Pretorius Leon
Published: December 2013

In this paper, the use of computational fluid dynamics is evaluated as a design tool to investigate the indoor climate of a confined greenhouse. The finite volume method using polyhedral cells is used to solve the governing mass, momentum and energy equations. Natural convection in a cavity corresponding to a mono-span venlo-type greenhouse is numerically investigated using Computational Fluid Dynamics. The CFD model is designed so as to simulate the climate above a plant canopy in an actual multi-span greenhouse heated by solar radiation. The aim of this paper is to investigate the influence of various design parameters such as pitch angle and roof asymmetry and on the velocity and temperature patterns inside a confined single span greenhouse heated from below. In the study reported in this paper a two-dimensional CFD model was generated for the mono-span venlo-type greenhouse, and a mesh sensitivity analysis was conducted to determine the mesh independence of the solution. Similar two-dimensional flow patterns were observed in the obtained CFD results as the experimental results reported by Lamrani et al [2]. The CFD model was then modified and used to explore the effect of roof pitch angle and roof asymmetry at floor level on the development of the flow and temperature patterns inside the cavity for various Rayleigh numbers. Results are presented in the form of vector and contour plots. It was found that considerable temperature and velocity gradients were observed in the centre of the greenhouse for each case in the first 40mm above the ground, as well as in the last 24mm close to the roof. Results also indicated that the Rayleigh number did not have a significant impact on the flow and temperature patterns inside the greenhouse, although roof angle and asymmetry did. The current results demonstrate the importance of CFD as a design tool in the case of greenhouse design.
Electromechanical Coupled Response of the AC Electric Arc Furnace Structures During the Scrap Melting Process
Authors: Brusa Eugenio G. M. , Bosso Nicola , Zampieri Nicolò , Morsut Stefano , Picciotto Maurizio
Published: December 2013

Prediction of structural dynamics of the Electric Arc Furnace (EAF) is rather difficult, because of a number of phenomena occurring during the scrap melting process. Three large electrodes, corresponding to each phase of a AC circuit, are lowered by the main mast towards the scrap to activate the melting process, induced by the electric arc. Electric current fed to each electrode produces a strong magnetic field and applies an electromechanical force on the other electrodes. Arc voltage looks irregular upon time, even because of the scrap motion within the vessel and temperature growth. The vertical position of the mast is controlled by an hydraulic actuator. Nevertheless, a heavy vibration of the structures affects the regularity of the melting process. A fully coupled model of the whole system is herein proposed, through a multi-physics approach. A first analytical approach, describing the electric circuit of the whole system, is implemented into a Multi Body Dynamics (MBD) model of the EAF, while a reduced Finite Element Method (FEM) model of the flexible structures is used for a preliminary optimization of the design parameters. Electromechanical forces due to the mutual induction among the electrodes are computed and the dynamic response of the system is investigated. Proposed model allows a first refinement of the EAF design, although a complete experimental validation on the real machine has to be performed, in spite of problems due the extremely difficult accessibility of structures during the melting process.
An Unified Design Procedure for Flying Machining Operations
Authors: Strada Roberto , Zappa Bruno , Giberti Hermes
Published: December 2013

“Flying machining” represents synchronization of an axis (slave) with a master axis in motion. One of the most important aspects of the design of “flying machining” operation is the choice of the proper law of motion of the slave axis. In literature, technical reports and papers can be found concerning this subject, but they deal with specific problems and the solutions or suggestions proposed are specific as well, suitable for those cases. In order to try to overcome this limitation, in this paper we analyze the subject of the flying machining operations from a wider point of view. We propose a unified design procedure with general validity, suitable for the choice of the slave axis’ law of motion for whatever “flying machining” operation. Furthermore methodologies for the selection of the drive system will be proposed. The procedure is described applying it on a cross sealing operation, typical of wrapping machine.
Optimum Mandrel Configuration for Efficient Down-Hole Tube Expansion
Authors: Pervez Tasneem , Al-Abri Omar S. , Qamar Sayyad Z. , Al-Busaidi Asiya M.
Published: December 2013

In the last decade, traditional tube expansion process has found an innovative application in oil and gas well drilling and remediation. The ultimate goal is to replace the conventional telescopic wells to mono-diameter wells with minimum cost, which is still a distant reality. Further to this, large diameters are needed at terminal depths for enhanced production from a single well while keeping the power required for expansion and related costs to a minimum. Progress has been made to realize slim wells by driving a rigid mandrel of a suitable diameter through the tube either mechanically or hydraulically to attain a desirable expansion ratio. This paper presents a finite element model which predicts the drawing force for expansion, the stress field in expanded and pre/post expanded zones, and the energy required for expansion. Through minimization of energy required for expansion, an optimum mandrel configuration i.e. shape, size and angle was obtained which can be used to achieve larger in-situ expansion. It is found that mandrel with elliptical, hemispherical and curved conical shapes have minimum resistance during expansion as compared to the widely used circular cross section mandrel with a cone angle of 10°. However, further manipulation of shape parameters of the circular cross section mandrel revealed an improved efficiency. The drawing force required for expansion reduces by 7% to 10% having minimum dissipated energy during expansion. It is also found that these cones yield less reduction in tube thickness after expansion, which results in higher post-expansion collapse strength. In addition, rotating a mandrel further reduces the energy required for expansion by 7%.
PGD-BEM Applied to the Nonlinear Heat Equation
Authors: Joyot Pierre , Verdon Nicolas , Bonithon Gaël , Chinesta Francisco , Villon Pierre
Published: December 2013

The Boundary Element Method (BEM) allows efficient solution of partial differential equations whose kernel functions are known. The heat equation is one of these candidates when the thermal parameters are assumed constant (linear model). When the model involves large physical domains and time simulation intervals the amount of information that must be stored increases significantly. This drawback can be circumvented by using advanced strategies, as for example the multi-poles technique. We propose radically different approach that leads to a separated solution of the space and time problems within a non-incremental integration strategy. The technique is based on the use of a space-time separated representation of the unknown field that, introduced in the residual weighting formulation, allows to define a separated solution of the resulting weak form. The spatial step can be then treated by invoking the standard BEM for solving the resulting steady state problem defined in the physical space. Then, the time problem that results in an ordinary first order differential equation is solved using any standard appropriate integration technique (e.g. backward finite differences). When considering the nonlinear heat equation, the BEM cannot be easily applied because its Green’s kernel is generally not known but the use of the PGD presents the advantage of rewriting the problem in such a way that the kernel is now clearly known. Indeed, the system obtained by the PGD is composed of a Poisson equation in space coupled with an ODE in time so that the use of the BEM for solving the spatial part of the problem is efficient. During the solving, we must however separate the nonlinear term into a space-time representation that can limit the method in terms of CPU time and storage, that is why we introduce in the second part of the paper a new approach combining the PGD and the Asymptotic Numerical Method (ANM) in order to efficiently treat the nonlinearity.