bluuebunny/crossref_metadata_2025_split huggingface dataset:
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.
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.
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.
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.
Validation of Turbulent Natural Convection in a Square Cavity for Application of CFD Modeling to Heat Transfer and Fluid Flow in a Data Center
Authors: Durand-Estebe B. , Lebot C. , Arquis E. , Mancos Jn. 
Published: December 2013

Air flow management in a Data-center is a critical problem when designing HVAC (Heating, Ventilation and Air-Conditioning) system. Providing a sufficient cooling air volume at a designed temperature to all the informatics equipments, avoiding recirculation phenomenon, optimizing the installations in order to minimize the temperature difference between air exiting the CRAC (Computer Room Air Conditioning) and the air at the intake of the servers are parts of the multiples target that have to be reached in order to have the most efficient ventilation system.
In most of today’s data center, the IT (Information Technology) equipment dissipates between 12kW of heat for regular material, to up to 32kW for the recent high density server’s rack. Such a power release has to be cooled by efficient cooling system.
During this process the airflow temperature can increase by over 10K, and the air velocity can vary from 0.09m/s to more than 5m/s. Considering these large gradient of temperature and air speed several phenomenon must be taken into account, including turbulent natural convection.
To achieve these goals, we will use a CFD software to predict the airflow behaviour inside the Data-center. Therefore, the code must be able to accurately model turbulent airflow and heat transfers. We used the software (http/www.thetis.enscbp.fr) to simulate a 2D turbulent natural convection in a square cavity. The k-ε equations were solved to predict turbulent effects. The obtained results were compared to an experimental benchmark and are presented in the document.
In the last part of the paper we present the results of a 2D simulation representing a working server in a computer room cooled by a CRAC (Computer Room Air Conditioning) unit.
The airflow characteristics in the whole domain were determined using various dimensionless numbers in order to select the right physical and mathematical objects. Finally the results of a 3D simulation are presented and the cooling system performances are estimated.
Stability Analysis of 2D Flows by Numerical Tools Based on the Asymptotic Numerical Method: Application to the One and Two Sides Lid Driven Cavity
Authors: Cadou Jean-Marc , Guevel Yann , Girault Gregory 
Published: December 2013

This work deals with the complete stability analysis in the case of two dimensional fluid flows searching for steady and Hopf bifurcations.
The stability analysis starts with the computation of steady bifurcations. It is realized by first considering the monitoring of an indicator which is a scalar function. The indicator is computed via a perturbation method: the Asymptotic Numerical Method. Steady bifurcation point corresponds to the zero of this indicator. From this singular point, all the steady bifurcated branches are computed by using the perturbation method.
Then the stability analysis is pursued with the computation of Hopf bifurcations by a hybrid method. This latter consists in coupling a continuation method with a direct Newton solver.
The continuation method allows the bifurcation indicator to be determined using alternating reduced order and full size steps resolution. The quantities coming from the bifurcation indicator are used as initial approximations for the direct method iterations.
Then an augmented system whose solutions are Hopf bifurcation is solved by a direct method of Newton kind.
The examples of the one side and two sides lid driven cavities show the reliability and the efficiency of the proposed numerical tools.
Robust Analysis of a Wireless Bistable Micro-Actuator
Authors: Zaidi Syed Sajid Hussain , Cherfi-Boulanger Zohra , Boudaoud Nassim , Pouille Philippe , Lamarque Frédéric 
Published: December 2013

Nowadays, the integration of micro-actuators in the micro-systems poses a significant problem due to the complex designs as well as due to the contact power supply systems (e.g., via micro-batteries or via wires). A way to overcome this problem is to provide remote power supply and control to the bistable micro-actuators. It is mainly done by RF (radio-frequency) or optical means. As a consequence, the stability of the two positions of this kind of micro-actuators and the switching time evolution between them have to be studied to determine the robustness of the contactless bistable micro-actuators.
In this work, these system parameters were analysed by the ANOVA (Analysis Of Variance) method during a longlife test for 8 different configurations (Design of Experiments) of bistable micro-actuators controlled by laser. Transient and permanent regimes were observed for the stability of the positions, for the standard deviation around the positions and for the switching time as well. In each case, the transient regime represented only 3% of the total duration of the longlife test. A very good stabilisation was observed in the permanent regime whereas a decrease of the stroke was observed in the transient regime. As a consequence, during this regime, the switching time was reduced compared with the regular values (few seconds, optical power dependent). In the permanent regime, a progressive increase of this factor was noted that indicated the progressive fatigue of the bistable micro-actuator. A second indicator of the micro-actuator fatigue was given by the increase of the standard deviation of the stable position after cycle number 9000. Above this point, the micro-actuator was vibrating during the functioning even if the stability remained acceptable.
Numerical Study of Fluid-Structure Interactions in Tube Bundles With Multiphase-POD Reduced-Order Approach
Authors: Pomadere Marie , Liberge Erwan , Hamdouni Aziz , Longatte Elisabeth , Sigrist Jean-François 
Published: December 2013

Fluid-Structure Interactions are present in a large number of systems of nuclear power plants and nuclear on-board stoke-holds. Particularly in steam generators, where tube bundles are submitted to cross-flow which can lead to structure vibrations. We know that numerical studies of such a complex mechanism is very costly, that is why we propose the use of reduced-order methods in order to reduce calculation times and to make easier parametric studies for such problems.
We use the multiphase-POD approach, initially proposed by Liberge (E. Liberge; POD-Galerkin Reduction Models for Fluid-Structure Interaction Problems, PhD Thesis, Universite de La Rochelle, 2008). This method is an adaptation of the classical POD approach to the case of a moving structure in a flow, considering the whole system (fluid and structure) as a multiphase domain. We are interested in the case of large displacements of a structure moving in a fluid, in order to observe the ability of the multiphase-POD technique to give a satisfying solution reconstruction. We obtain very interesting results for the case of a single circular cylinder in cross-flow (lock-in phenomenon). Then we present the application of the method to a case of confined cylinders in large displacements too. Here again, results are encouraging.
Finally, we propose to go further presenting a first step in parametric studies with POD-Galerkin approach. We only consider a flowing-fluid around a fixed structure and the Burgers’ equation. A future work will consist in applications to fluid-structure interactions.
Comparisons Between Dynamic Characteristics of Pneumatic, Magnetorheological, and Hydraulic Shock Absorbers
Authors: Salem A. M. , Oyadiji S. Olutunde 
Published: December 2013

The dynamic performance of automotive vehicles is influenced by the suspension system design. Suspensions owing damping elements with a wide range of non-linear behaviour can provide higher mobility and better ride comfort performances. Pneumatic suspensions due to their inherent nonlinear behaviour can provide high mobility performance while suspensions with MR dampers can provide this nonlinearity through the controllable damping force produced by the control of the MR fluid. The pneumatic and MR suspension models are usually developed from experimental force-displacement and force-velocity characteristics.
The purpose of this paper is to measure and compare the dynamic characteristics of pneumatic, magnetorheological, and hydraulic shock absorbers. The study is carried out through measuring the characteristics of the different types of dampers at different frequencies and amplitudes using an Electro-Servo Hydraulic (ESH) testing machine. The shock absorber is subjected to sinusoidal excitation of frequency varying from 0 to 10 Hz, and amplitude varying from 0 to 10 mm. In the case of the MR damper, the tests are also done at different current levels of between 0 and 2 amp. The input displacement and acceleration to the shock absorber were measured using an LVDT (Linear Voltage Displacement Transducer) and an accelerometer, respectively while the input velocity was derived from the measured displacement and acceleration. This dual identification of the input velocity was done in order to ensure accurate representation of the velocity. The output force response of the shock absorber was measured by means of a force transducer. The force-displacement and force-velocity characteristics of each shock absorber were subsequently derived from the measured data. The results show the tunability of the MR damper characteristics in comparison to those of the pneumatic and hydraulic dampers.
Static and Dynamic Analysis of Electrostatically Actuated Microcantilevers Using the Spectral Element Method
Authors: Dileesh P. V. , Kulkarni S. S. , Pawaskar D. N. 
Published: December 2013

The objective of this paper is to present the Spectral Element Method (SEM) as an accurate and efficient design tool for static and dynamic simulations of cantilever based MEMS devices. The microcantilever under consideration is modeled as a Timoshenko beam and discretized using the spectral element formulation that accounts for fringing field and the nonlinearity arising from the electrostatic driving force. The static analysis has been carried out using Picard’s iteration method and the static pull-in displacement and voltage have been calculated. An eigenvalue analysis of this beam is also carried out to determine its natural frequencies. In addition, the dynamics of this cantilever is studied using the explicit Newmark predictor-corrector method to generate the time history. In all cases, the results have been compared to the one-dimensional Finite Element Method and three-dimensional finite element method (implemented through the commercial package COMSOL Multiphysics) to examine the accuracy and computational speed of the proposed SEM. The results of the simulations were also compared to those obtained by experiments in the existing scientific literature.
These comparisons lead to the inference that the SEM is able to reproduce the static and dynamic response of the beam to a high degree of accuracy. It was also found that several numerical features inherent in the SEM lead to a significantly faster computation than the corresponding finite element method for equivalent degrees of freedom. This advantage was verified by using the SEM to carry out static and dynamic simulations of variable width microcantilevers.
We therefore propose that the SEM is a viable tool for the MEMS community to accurately and quickly determine the static and dynamic pull-in parameters, frequency eigenvalues, and static and dynamic behavior at the design stage.
Improving Trajectory Tracking Performance of a 2 DOF Parallel Kinematic Manipulator With Flexible Links
Authors: Giberti Hermes , Cinquemani Simone , Ambrosetti Stefano 
Published: December 2013

Flexible-link robots are an important class of manipulators which uses lightweight arms for assembly, civil infrastructure, bridge/vehicle systems and large-scale space structures. The wide spread of these systems in various application areas has ensured that the modeling of flexible elements and the control of vibration have received a great deal of attention in recent years.
In this work it is analyzed a two DOF parallel robot with two flexible links used for pick and place operations, developing a control strategy based on piezoelectric actuators and strain gauges or accelerometers embedded in the links.
The analysis of the robot behaviour and the development of the controller, have been carried out on an electromechanical model built in Matlab® and co-simulated with the multibody flexible model built in Adams®.
Results show positive confirmation of the study and encourage future tests on the real manipulator to validate the multibody model and the control strategy.
The Specific Accelerating Factor to Compare Brushless Motors
Authors: Giberti Hermes , Cinquemani Simone 
Published: December 2013

This work is focused on the analysis of the parameter named “accelerating factor” and on its use in choosing the correct electric brushless motor and gearbox in automation field. The “accelerating factor” is analyzed from a phenomenological point of view, analyzing data available on catalogs of motor manufacturers, and from the point of view of the design of such devices, trying to find a relationship between the accelerating factor and the construction parameters of a brushless motor.
The result achieved in this paper is the definition of a specific value of the accelerating factor allowing a better comparison between different motors and helping the designer in the choice of the best motor for a given application.
Workpiece Placement Optimization of Six-Revolute Industrial Serial Robots for Machining Operations
Authors: Dumas Claire , Caro Stéphane , Garnier Sébastien , Furet Benoît 
Published: December 2013

Roboticists are faced with new challenges in robotic-based manufacturing. Up to now manufacturing operations that require both high stiffness and accuracy have been mainly realized by using computer numerical control machine tools. This paper aims to show that manufacturing finishing tasks can be performed with robotic cells knowing the process cutting phenomena and the robot stiffness throughout its Cartesian workspace.
It makes sense that the finishing task of large parts would be cheaper with robots. However, machining robots have not been adapted for such operations yet. As a consequence, this paper introduces a methodology that aims to determine the best placement of the workpiece to be machined knowing the cutting forces exerted on the tool and the elastostatic model of the robot. In this vein, a machining quality criterion is proposed and an optimization problem is formulated. The KUKA KR270-2 robot is used as an illustrative example throughout the paper.
Transfer Matrix Computation for Wave Action Simulation in an Internal Combustion Engine
Authors: Mezher Haitham , Chalet David , Chessé Pascal , Migaud Jérôme , Raimbault Vincent 
Published: December 2013

A new technique for simulating engine pressure waves consisting of linking pressure response and mass flow rate excitation in the frequency domain has been presented. This is achieved on the so-called “dynamic flow bench”. With this new approach, precise, fast and robust results can be obtained while taking into account all the phenomena inherent to compressible unsteady flows. The method exhibited promising results when it was incorporated in a GT-Power/Simulink coupled simulation of a naturally aspirated engine.
However, today’s downsized turbocharged engines come with more stringent simulation necessities, where discontinuities such as the charge air cooler (CAC) must be correctly modeled. Simulating such engines with the transfer function methodology is quite difficult because it requires mounting the entire intake line on the bench. Modeling wave action for these engines requires an understanding in the frequency domain of the flow’s characteristics through the different elements that make up the intake line. This leads us to study the acoustic transfer matrices.
In order to split the intake line into separate elements, a straight duct of 185mm length is chosen as a first reference. It is mounted on the dynamic flow bench and pressure response is measured after an impulse mass flow excitation. Transfer functions of relative pressure and mass flow rate are then identified at given points upstream and downstream of this reference tube. These functions produce the desired transfer matrix poles.
The resulting matrix is validated by inserting the tube in the intake lines of two four-cylinder engines which are modeled in GT-Power. Pressure and mass flow are registered at the measurement points of the tube from the simulation. The time series data upstream of the tube is treated in the frequency domain and the transfer matrix is used to calculate the corresponding downstream values. Measured values from the native simulation and those calculated using the transfer matrix propagation are then compared.
Finally, the experimental technique for identifying transfer matrices of more complex elements using two versions of the previous tube is presented.