bluuebunny/crossref_metadata_2025 huggingface dataset:
Electromagnetic Shock Absorbers for Automotive Suspensions: Electromechanical Design
Authors: Amati Nicola , Canova Aldo , Cavalli Fabio , Carabelli Stefano , Festini Andrea , Tonoli Andrea , Caviasso Guglielmo
Published: September 2008

This article illustrates the modeling and design of electromechanical shock absorbers for automotive applications. Relative to the commonly used hydraulic shock absorbers, electromechanical ones are based on the use of linear or rotative electric motors. If electric motor is of the DC-brushless type, the shock absorber can be devised by shunting its electric terminals with a resistive load. The damping force can be modified by acting on the added resistance. An integrated design procedure of the electrical and mechanical parameters is presented in the article. The dynamic performance that can be obtained by a vehicle with electromechanical dampers is verified on a quarter car model.
Effects of Mechanical and Pneumatic Return Springs on Valve Train Dynamics
Authors: Pastorelli Stefano , Almondo Andrea , Sorli Massimo
Published: September 2008

The dynamic analysis of a cam transmission derived from an engine valve train is performed in frequency and time domain, by means of a combined lumped-distributed parameters models, capable of predicting the effects of the higher harmonics of the cam lift profile on system performances, in particular as concerning the return spring device. Dynamic stiffness of the transmission in frequency domain and time history of contact force between cam and follower are evaluated, highlighting the limits of the transmission at high-speed camshaft operations caused by the spring behavior. The aim of the study is to developed a comparison on the performances of the cam mechanism working with the original mechanical spring from design or with a pneumatic return device based on a pneumatic spring and a pressure control circuit.
Wave-Based Control of a Nonlinear Flexible System
Authors: O’Connor William J. , Ramos Francisco , Feliu Vicente
Published: September 2008

The motivation for this work is the control of flexible mechanical systems, such as long, light robot arms, gantry cranes, and large space structures, with an actuator at one end and a free boundary at the other. Very effective control strategies have recently been developed which are based on interpreting the actuator motion as launching mechanical “waves” (propagating motion) into the flexible system while absorbing returning “waves”. These control systems are robust to system changes and to actuator limitations. They are generic, require very little system modeling, need only local sensing, and are computationally light and easy to implement. In a flexible arm, when elastic deflections are large, frequently there is strongly nonlinear behavior. This paper investigates how such nonlinearities affect the wave-based control strategy. In summary, the news is good. It is found that errors arise only when trajectories are very demanding, and even then the errors are small. Some strategies for correcting these errors are explained: addition of a linear element at the actuator-system interface, error correction by second manoeuver, and redefinition of the waves in a less-than-optimal way. The paper presents these ideas and illustrates them with numerical simulations.
Experimental and Numerical Study for Determining the Mechanical Properties of Automobile Weatherstrip Seals
Authors: Dikmen Emre , Basdogan Ipek
Published: September 2008

Structural parts made of hyperelastic materials such as rubber mounts in automotive powertrains and weatherstrip seals are widely used in automotive and other engineering applications. In this study, compression load deflection (CLD) behavior of a highly non-linear type of joint, automotive weatherstrip seal made of Ethylene Propylene Diene Monomer (EPDM) sponge rubber is examined using finite element modeling techniques. The finite element modeling (FEM) results are then compared with the compression load deflection data obtained experimentally. The compression load deflection data for various punch velocities can be used to model the weatherstrip seal as a nonlinear spring-dashpot system with varying stiffness and damping coefficient proportional to the amount of compression. The weatherstrip seals should be modeled accurately in order to predict the dynamic performance of the automobiles under various load conditions. First part of the study includes modeling of the seal using various hyperelastic material models which are available in ANSYS. The strain energy functions’ coefficients required for the various material models are calculated using both linear and nonlinear least square fit procedures implemented in ANSYS for fitting the tension, shear and compression test data. After the coefficients are calculated, the compression test is performed in ANSYS using various hyperelastic material models. Second part of the study includes the compression experiment of weatherstrip seal with a robotic indenter specifically designed for measuring hyperelastic materials. The measured CLD data is then compared with the FEM results. The accuracy of using only simple tension test data to acquire the coefficients for strain energy functions is investigated and suitable strain energy functions to model compression of weatherstrip seal are determined. Additionally, Mullins Effect (stress softening) for this application is investigated using the compression experiments data.
Mathematical and Finite Element Modelling of Spine to Investigate the Effects of Intra-Abdominal Pressure and Activation of Muscles Around Abdomen on the Spinal Stability
Authors: Mokhtarzadeh Hossein , Farahmand Farzam , Parninapour Mohammad , Malekipour Fatemeh , Shirazi-Adl Abolfazl , Arjmand Navid
Published: September 2008

In spite of the several experimental and modeling studies on the biomechanical characteristics of the human spine, the role and significance of the intra-abdominal pressure (IAP) in spine mechanics has remained controversial. This study represents a simple analytical and a 3-D finite element model of spine and its surrounding structures to investigate the contribution of IAP to spinal stability. The mathematical model included the lumbar spine column, the abdominal cavity and a muscular layer around it, the rib cage and the pelvic ring. The lumbar spine column was modeled as a beam and the rib cage and pelvis as rigid bodies. The intra-abdominal cavity and the surrounding muscular layer were represented by a thin-wall cylindrical vessel with deformable shell wall. The free body diagram and equilibrium equations of each body of the model were derived while an external load to the rib cage was applied. The equations were then combined with the force-deflection relationships for the beam bending, the IAP fluid volume variation, and the muscle shell traction. Muscle activation levels were simulated by changing the Young’s modulus of the shell in the direction of fibers, up to an upper-limit value which was obtained based on the Valsalva maneuver. In the Finite Element (FE) model, the abdominal cavity was assumed to be cylindrical and filled by fluid with a bulk modulus of IMPa. The surrounding muscular layer was modeled as membrane with transverse isotropic material properties considering their fibers orientation. The spine, rib cage and pelvic ring were modeled by beam elements. The top plate simulated the active and/or passive role of diaphragm through its vertical displacement. The bottom membrane and distal spine were fully constrained. Good agreement between the analytical and FE model results was obtained. A larger external force and/or higher level of muscle activation caused a higher IAP, improving spinal unloading and stability. This effect was more significant for muscles with more horizontally directed fibers, e.g., Transverse Abdominis (TA).
Optimal Adjustment Procedure of the External Fixators to Minimize the Soft Tissue Injury
Authors: Rajabi Shadi , Farahmand Farzam
Published: September 2008

A typical fixator of tibia consists of an axial rotary joint, 4 revolute joints and 2 prismatic joints in the ends providing a total of 7 degrees of freedom for its maneuverability to reduce the bone fracture in the 3-D space. The purpose of the present study was to calculate the final configuration of the fixator joints to treat a general fracture and to optimize the path to this configuration. To obtain the final configuration, the known space orientation 4×4 matrix of the assumed healed bone was set equal to the orientation matrix of the fixator and the values for the seven joints were calculated assuming a seventh equation stating the final values of the two prismatic joints to be equal. In the second part of the study, the optimal path of the adjustment procedure to the final configuration of fixator was investigated. The optimization criterion was defined as the length of the path of the bone tips throughout the procedure, so that the connective soft tissues are minimally injured. The integral of path length with respect to time was calculated, then the Lagrange equations specifying equalities between joint values and their first and second derivatives were derived. The resulting set of 2nd- order differential equations were transformed into a set of 14 1st- order differential equations, and solved using MATLAB. The significance of this approach was examined considering a simple 2 link planar mechanism, going from a specified starting position to a final configuration. It was found that implication of the optimization procedure reduces the path length by 14.3% in comparison with when the joint angles are change linearly.
Robust Piecewise-Linear State Observers for Flexible Link Mechanisms
Authors: Caracciolo Roberto , Richiedei Dario , Trevisani Alberto
Published: September 2008

This paper tackles the problem of designing state observers for flexible link mechanisms: an investigation is made on the possibility of employing observers making use of suitable piecewise-linear truncated dynamics models. A general approach is proposed, which provides an objective way of synthesizing observers preventing the instability that may arise from using reduced-order linearized models. The approach leads to the identification of the regions of the domain of the state variables where the linear approximations of the nonlinear model can be considered acceptable. To this purpose, first of all, the stability of the equilibrium points of the closed-loop system is assessed by applying the eigenvalue analysis to appropriate piecewise-linear models. Admittedly, the dynamics of such a closed-loop system is affected by the pole perturbation caused by spillover, and by the discrepancies between the linearized models of the plant and the one of the observer. Additionally, when nodal elastic displacements and velocities are not bounded in the infinitesimal neighborhoods of the equilibrium points, the difference between the nonlinear model and the locally-linearized one is expressed in terms of unstructured uncertainty and stability is assessed by H∞ robust analysis. The method is demonstrated by applying it to a closed-chain flexible link mechanism.
Miniaturised Cutting Tool With Triaxial Force Sensing Capabilities for Minimally Invasive Surgery
Authors: Valdastri Pietro , Houston Keith , Menciassi Arianna , Dario Paolo , Sieber Arne , Yanagihara Masaru , Fujie Masakatsu
Published: September 2008

This paper reports a miniaturised triaxial force sensorized cutting tool for minimally invasive robotic surgery. This device exploits a silicon based MEMS triaxial force sensor that acts as the core component of the system. The outer diameter of the proposed device is less than 3 mm, thus enabling the insertion through a 9 French catheter guide. Characterization tests are performed for both normal and tangential loadings. A linear transformation relating the sensor output to the external applied force is introduced in order to have a triaxial force output in real time. Normal force resolution is 8.2 bits over a force range between 0 N and 30 N, while tangential resolution is 8.1 over a range of 6 N. Force signals with frequencies up to 250 Hz can successfully be detected, enabling haptic feedback and tissue mechanical properties investigation. Preliminary ex vivo muscular tissue cutting experiments are introduced and discussed in order to evaluate the device overall performances.
CFD Integration Into Design Process of Motorcycles
Authors: Conti Paolo , Argento Marco
Published: September 2008

This work displays an integrated approach — based on both experimental and numerical analyses (CFD) — to scooter design. In the last decade the market of maxi scooters is continually increasing. Any constructor must develop new models, new design, new concepts. Due to this fast evolution, the possibility to cope aesthetics and functionality, at each step design process, may be a crucial aspects. The purpose of this work is the development of a method to take into account aerodynamic behaviour of a scooter depending on its external geometry. The analysis is mainly directed to investigate stability, safety and comfort aspects rather than aerodynamic fairness. The paper presents a methodology to integrate in the conceptual design process many aerodynamic aspects. First a parametric simplified model was created and investigated. This model is composed of few plane panels which outline a commercial scooter. The scope was the validation of the analysis method through an experimental campaign in a wind tunnel. Then, the methodology was applied to a real scooter. As a conclusion the paper points out the importance of embedding aerodynamic skills into the very initial conceptual design of a scooter, and the method proposed tries to answer to this need.
Simulation of Cylinder Valves for Reciprocating Compressors
Authors: Giacomelli Enzo , Falciani Fabio , Volterrani Guido , Fani Riccardo , Galli Leonardo
Published: September 2008

Advanced mathematical models are now used to simulate reciprocating compressors and particularly the cylinder valves. The valves represent the most critical component of these machines and need particular attention from the technology point of view. In addition, the potential variable operating conditions must be properly addressed and investigated. The pulsations generated by the compressor and piping system can have a critical impact on valve behavior. Therefore for complex situations a simulation of the complete system including pressure vessels and piping can be performed. The results of the programs include displacement, pressure drop, compression cycle, and pressure pulsations based on coefficients obtained experimentally and through advanced CFD models. Through simulation an optimum compromise between mechanical valve behavior and minimum energy consumption can be found.
A Soil-Fluiddynamics Analysis of a Swelling-Shrinking Process in a Clayey Soil
Authors: Guarnieri Adriano , Lorenzini Giulio
Published: September 2008

Most soils show a swelling behaviour depending on their water content: this property can strongly affect the effectiveness of agriculture. Because of the importance of the topic, this paper is aimed at investigating a given vertisol in terms of swelling and shrinkage with variations in its humidity. For this, a suitable experimental setup was realised, tested and used allowing the study of the effect that the soil-fluiddynamics parameters have on the process. The results showed that swelling is more evident at lower water content values. Also relevant the initial compaction of the soil, that proved to increase the percentage swelling especially at low humidities. A hypothesis concerning the effect on swelling of the solid apparent volumic mass associated to the initial humidity is also formulated, even if more related research on this issue is necessary.
Simulation and Experimental Study in Position Control of Servo Hydraulic System With Flexible Load Using Adaptive Neural Network and Differential Evolution Strategy
Authors: Yousefi Hassan , Handroos Heikki
Published: September 2008

Hydraulic position servos with an asymmetrical cylinder are commonly used in industry. These kinds of systems are nonlinear in nature and generally difficult to control. Because of parameters changing during extending and retracting, using constant gain will cause overshoot, poor performance or even loss of system stability. The highly nonlinear behaviour of these devices makes them ideal subjects for applying different types of sophisticated controllers. This paper is concerned with a second order adaptive model reference and an artificial neural network controller to position tracking of a servo hydraulic with a flexible load. In present study, a neural network with two outputs is presented. One of the outputs of neural network is used for system’s dynamic compensator and another one for gain scheduling controller. To avoid the local minimum problem, Differential Evolution Algorithm (DEA) is used to find the weights and biases of neural network. The proposed controller is verified with a common used p-controller. The simulation and experimental results suggest that if the neural network is chosen and trained well, it improves all performance evaluation criteria such as stability, fast response, and accurate reference model tracking in servo hydraulic systems.
DNC Method for Flatness Reduction by Machine Tool Error Compensation in Planning Processes
Authors: Franco P. , Estrems M. , Faura F.
Published: September 2008

Milling is a widely used manufacturing process with the main purpose of generating high precision mechanical components of shapes and sizes given by the numerical control programmed cutting tool trajectory. These mechanical components frequently needs the application of milling operations in order to satisfy the technical specifications that corresponds to their dimensional, geometrical and surface quality requirements. For that reason, the effects of different factors such as cutting tool dynamics, fixturing system design, workpiece material behaviour and applied cutting forces on the desired dimensional precision must be studied, as well as cutting tool and machine tool performance. In this work, the relation between machine tool inaccuracies and geometrical tolerances is analyzed, and a methodology is proposed for improving flatness in planing operations by the correction of imperfections detected in cutting tool displacement according to machine tool axis. These machine tool error correction methodology could be implemented in the current CAD/CAM/CAPP techniques as a means of increasing the milling process performance by identification and correction of CNC milling machine imperfections. The deviations in machine tool displacement during cutting process are identified by metrological analysis, and a modified trajectory for cutting tool is defined by direct numerical control (DNC) from systematic error compensation in machine tool.
Numerical Investigation on Load Transfer Effects in Bogies of Urban Rail Vehicles
Authors: Corradi Roberto , Facchinetti Alan , Sempio Giovanni
Published: September 2008

Urban rail vehicles can present many types of architecture, definitely different from those of traditional rail vehicles. When dealing with long articulated tramcars, complex coupling effects between the vertical and lateral dynamics may arise. Making reference to a modern tramcar, the coupling phenomena are investigated in detail by means of numerical simulation, considering the dynamic behaviour during the negotiation of curves with or without superelevation.
Ion Current Based Spark Advance Management for Maximum Torque Production and Knock Control
Authors: Cavina Nicolo` , Po Giacomo , Poggio Luca
Published: September 2008

The objective of the present work is the development of a closed-loop individual cylinder spark advance control strategy that allows maximizing torque production while keeping the knocking phenomenon at levels considered safe for the engine components. The research activity has consisted of several phases: the first one was focused on the analysis of the relationship between knocking level and indicated mean effective pressure. The main result of this preliminary phase is a methodology for identifying target values of the chosen in-cylinder pressure based knocking index. A subsequent phase of the work has been devoted to a correlation analysis between pressure-based knocking indexes and knocking indexes obtained by processing other combustion-related signals (engine block vibration and ion current), showing that the ion current based system that has been developed allows reaching high correlation levels. Finally, in order to achieve the target knocking levels, the spark advance control strategy proposed here consists of two parallel contributions: a slower, adaptive and statistically-based contribution, and a fast but range-limited term. The process of designing the controller has been particularly fast and cost-effective, due to the development of a specific software environment that allows verifying the performance the controller would achieve when applied to the actual engine. Such structure may be described as a software rapid control prototyping environment, since an experimental database has been used to reproduce in a simulation environment the response of the controlled system (the engine) coupled to the spark advance control system. The proposed control strategy has been successfully implemented on a V12 6.0 liter high performance engine, allowing to maximize output torque while protecting engine components from knock-related damage.
Theoretical Model for the Dynamics of an Unconstrained Cutting Brush of a Street Sweeper
Authors: Vanegas Useche Libardo V. , Abdel Wahab Magd M. , Parker Graham A.
Published: September 2008

A theoretical model for the free-flight behaviour of an oscillatory cutting brush of a street sweeper is developed. The bristles are modelled as cantilever beams, and the equation of motion for the transverse vibrations is derived based on the theory of vibrations and small deflection beam theory. Two angular velocity functions are studied: a sinusoidal function and a function that provides small shaft accelerations and whose exact shape depends on a parameter b. The model is applied for a range of frequencies of oscillation that contains the first and second natural frequency of the bristle. The effects of the alternating component of the rotational speed, the type of function, and the value of b are also studied. The results are compared with those obtained in a previous work for a flicking brush. The findings suggest that the bending moment and bristle deflection tend to depend fairly linearly on the alternating velocity. In contrast to the bristles of a flicking brush, in the cutting brush resonance tends to occur only near the natural frequencies of the bristle. Additionally, the behaviour of the cutting brush is similar for both functions and for different values of b.
A 4WS Control Strategy for Improving Race Car Performances
Authors: Braghin Francesco , Sabbioni Edoardo
Published: September 2008

Design and implementation of an active control system to enhance the vehicle’s performances is of great interest for any vehicle type, but for race cars, if allowed by the rules, is of fundamental importance since the vehicle is working most of the time in limit conditions. This paper presents a control strategy for rear wheels steering with the aim of increasing the reactivity of the vehicle while entering the curve and of stabilizing the vehicle in full curve, thus allowing higher vehicle speeds.
Experimental Investigation of Charpy Impact Resistance in Rail Vehicle Steel Wheels
Authors: Asadi Lari A. , Hashemi S. H.
Published: September 2008

In this research the Charpy impact properties of the two steel wheels of grade B2N and R7 were investigated. The dynamic toughness levels of test materials were measured experimentally according to the general recommendations of International Union of Railways (UIC) test standards. To do this, two sets of standard Charpy U-notch impact specimens were taken from the original rail vehicle steel wheels (made from B2N and R7) in their circumferential direction. As the conventional Charpy impact machine gives only one output (i.e., total fracture energy), an instrumented Charpy rig was used for conducting the impact experiments. This provided novel impact test data as well as full failure information (appeared for the first time in the literature for rail vehicle steel wheels). The obtained data included elastic strain energy, fracture initiation, and fracture propagation energy. All these parameters were calculated by double integration of load history captured by a high frequency digital oscilloscope during impact tests. The results showed that the impact toughness of both steel wheels was above the minimum toughness specified by the UIC leaflet. Detailed analysis of instrumented fracture test data showed that a significant portion of total measured Charpy energy (more than 75%) was consumed in fracture initiation and non-related fracture processes in each test material. This is a direct result of high strain-hardening capacity of B2N and R7 steel wheels and their characteristics, which allows the material to absorb high amounts of energy and to deform plastically before any fracture initiation. The total fracture energy of the R7 wheel steel was 160% higher than the B2N (21J against 13J), which was indicative of better dynamic crack resistance of R7 wheel material.
Generalized Coupled Thermoelasticity of Functionally Graded Layers
Authors: Bagri A. , Eslami M. R. , Samsam-Shariat B. A.
Published: September 2008

This Paper illustrates the behaviour of a functionally graded layer under thermal shock load based on the Lord-Shulman theory. The coupled form of the equations are considered and the material properties of the layer are assumed to vary in a power law form function through the thickness of the layer. The Galerkin finite element method via the Laplace transformation is employed to solve the system of equations in the space domain. Finally, the temperature, displacement and stress fields are inverted to the physical time domain using a numerical inversion of the Laplace transform. The temperature and stress waves propagation through the thickness of the layer are investigated and the effects of material composition and the relaxation time on thermal and elastic waves propagation are studied.
Mechanical Characterization of Myosin II, Actin and Their Complexes by Molecular Mechanics Approach
Authors: Aprodu Iuliana , Redaelli Alberto , Montevecchi Franco Maria , Soncini Monica
Published: September 2008

The knowledge of the mechanical properties of myosin and actin is of a crucial importance in order to better understand the molecular mechanism of sliding force generation in muscle contraction. The aim of our work was to realize a mechanical characterization of myosin II and actin monomer using the molecular mechanics approach, by assessing the elastic properties of the two proteins, and by establishing the interaction forces between the two monomers of the actomyosin complex, and between myosin’s scissure and adenine nucleotides (ATP and ADP). A restraining method was used in order to modify the axial length of the proteins or the intermolecular distances. The interaction force and the stiffness were calculated as first and second order derivative of the potential energy with respect to the applied elongation and intermolecular distance respectively. According to our results, the values of elastic modulus of myosin motor domain and actin are 0.48 GPa, and 0.13 GPa respectively, and myosin-ATP complex is characterized by an attraction force of 130 pN which is twofold greater than the interaction force between myosin and ADP. As for the actomyosin complex, the interaction force has a maximum value of 180 pN. The results of our simulations comply with theoretical and experimental remarks about mechanical properties of myosin II, actin, and their complex.
Improving the Ethanol Production From Sugar Cane Biomass
Authors: Modesto Marcelo , Nebra Silvia A. , Zemp Roger J.
Published: September 2008

The sugar and ethanol production is one of the most important economical activities in Brazil, mainly due to its efficiency and competitively. The alcohol production is made through the following steps: juice extraction, purification, fermentation and distillation. The process begins with the sugar cane juice extraction, usually made in mills, where the juice is extracted by compression of the sugar cane between great pronged cylinders. The extracted juice goes to purification and fermentation operations where it is converted in an ethanol/water mixture called wine, after, it is heated in a heat exchanger and through a distillation operation, as a sub product in the process, hydrated ethanol is finally obtained. Each step of this process consumes electric and thermal energy that coming from a cogeneration system whose fuel is the own sugar cane bagasse, obtained as a sub product, in the extraction operation., Energy and exergy balances along the process were performed, the exergy of water/sucrose and water/ethanol solutions were carefully calculated considering that them are non ideal solutions. The exergetic cost methodology was applied as a tool to suggest modifications to improving the use of energy in ethanol, electrical energy and bagasse production.
Structural Damage Identification Based on Model Updating
Authors: Yin T. , Yu L. , Zhu H. P.
Published: September 2008

This paper presents a new method for structural damage identification based on the finite element (FE) model updating techniques. First, an objective function is defined as minimizing the sum of differences between the experimental and analytical modal data (natural frequencies and mode shapes), which is set as a nonlinear least-squares problem with bound-constrains. The trust-region approach is then used to solve the minimization problem in order to make this optimization process more robust and reliable. In addition, the expansion and weighting of the original objective function are investigated so that the presented method can be well applied into the damage identification of more real structures. Finally, a numerical simulation model of two-story portal frame structure is adopted to evaluate the efficiency of the proposed technique when both the single and multiple damage cases are set up in the model. Some important issues are also discussed in this paper. The illustrated results show that the single and multiple damages on the two-story portal frame structure can be well identified by the proposed method.
An Oil-Hydraulic Workbench for Advanced Dynamic Testing
Authors: Ravina Enrico
Published: September 2008

The paper refers on a polyvalent oil-hydraulic testbench, designed and realized in order to develop a wide and diversified range of static and dynamic tests on mechanical components and structural elements. The testbench is an experimental mechatronic unit, integrating mechanical equipment, electronic devices and elaboration and control systems, aided by virtual instrumentation. In order to describe the main features and potentialities of the proposed testbench, the paper refers on tests of specific mechanical devices (shock absorbers) and of samples of structural elements (glued junctions). The possible and potential applications of the proposed workbench are very wide and oriented to validation, experimental identification, advanced testing and diagnostics in mechanical field.
Shear Strength Tests of Joined Advanced Ceramics
Authors: Avalle Massimiliano , Ventrella Andrea , Ferraris Monica , Salvo Milena
Published: September 2008

Advanced ceramics appear to be a very important resource for the development of many new technologies (fuel cells, nuclear fusion…) and in many manufacturing processes. An important issue in the construction of ceramic components is related to their joining methods. When size and complexity of the components grow, it is impossible to sintherize them in a single monolithic piece. It is necessary to join several parts: apart from mechanical joining systems, the primary solution is to use a material — that acts as adhesive — able to intimately join the two materials. The joining material needs to give sufficient mechanical strength, and to maintain resistance to external actions at high temperatures, as the adherend material is able to. In this paper, some results obtained in the Innovative Materials Laboratory (La.M.In.) of the II Faculty of Engineering of the Politecnico di Torino, will be shown. Since there is no unique method to measure the shear strength of the ceramics joints (the most important is ASTM C1469-00) and lack of agreement on a common test still exists, different testing methods were considered. One of the main difficulties is still to correlate the results from different tests: in fact, in each testing method the sample is subjected to different states of stress, and failure is induced differently. A thorough stress analysis has to be carried, by means of detailed finite elements models.
Tribomaterial Evaluation and Ranking Using Fuzzy Multicriteria Decision Making
Authors: Wani M. F.
Published: September 2008

A procedure based on fuzzy multicriteria decision making is developed for evaluation and ranking of tribomaterials. Tribomaterial properties which influence performance of triboelements at operational stage are considered as criteria for evaluation of tribomaterial. Tribomaterial properties, weighting factors and desired values are converted into fuzzy membership functions called trapezoidal fuzzy numbers. Tribomaterial ranking index is evaluated from weighted fuzzy tribomaterial suitability value for various degrees of optimism through a series of fuzzy arithmetic operations. Higher the value of index better is ranking of tribomaterial. A step by step procedure for evaluation and ranking of tribomaterial is suggested. An example of plain bearing has been presented for illustration of the procedure.
Higher Order Global-Local Theory Coupled Bending and Extension for Laminated Composite Plates and Refined Element Methods
Authors: Chen Wanji , Wu Zhen
Published: September 2008

In this paper an augmented higher order global-local theories are presented to analyze the laminated plate problems coupled bending and extension. The in-plane displacement field is composed of a mth-order (9 > m > 3) polynomial of global coordinate z in the thickness direction and 1,2-3 order power series of local coordinate ζk in the thickness direction of each layer and a nth-order (5 > n >= 0) polynomial of global coordinate z in the thickness direction of transverse deflection. The transverse shear stresses can satisfy continuity at interfaces, and the number of unknowns is independent of the layer numbers of the laminate. Based on this theory, a refined three-node triangular element satisfying the requirement of C1 weak-continuity is presented. Numerical results show that present theory can be used to predict accurately in-plane stresses and transverse shear stresses from direct use of the relations of stresses and strains without any postprocessing method. However, to accurately obtain transverse normal stresses, the local equilibrium equation approach in one element is employed herein. It is effective when the number of layers of laminated plates is more than five and up to fourteen, and it can solve the problems for coupling bending and extension. It is also shown that the present refined triangular element possesses higher accuracy.
Hierarchical Finite Element Analysis of Multilayered Plates Subjected to Mechanical, Thermal and Electrical Loadings
Authors: Carrera Erasmo , Fagiano Christian
Published: September 2008

This paper addresses to static and dynamic problems of multilayered plate and also embedded piezoelectric layers by means of finite element methods (FEM). Formulation on the basis of Principle of Virtual Displacements (PVD) and Reissner Mixed Variational Theorem (RMVT) are considered. A series of hierarchic, two-dimensional plate elements are presented within the “Unified Formulation” recently introduced by the first author. Finite element matrices are derived for static and dynamic problems of piezoelectric laminates. Numerical solutions are compared to available ones to assess mixed and classical finite elements in both case of Layer-Wise (LW) and Equivalent-Single-Layer (ESL) variable description. The superiority of RMVT applications with respect to classical ones based on Principle of Virtual Displacements (PVD) has been confirmed by the conducted numerical investigation.
The Design of Advanced Composite Structures Using Evolutionary Design Methods
Authors: van Wyk David , Jonson David
Published: September 2008

The development of an evolutionary optimisation method and its application to the design of an advanced composite structure is discussed. Composite materials are increasingly being used in various fields, and so optimisation of such structures would be advantageous. From among the various methods available, one particular method, known as Evolutionary Structural Optimisation (ESO), is shown here. ESO is an empirical method, based on the concept of removing and adding material from a structure, in order to create an optimum shape. Much work has been done on ESO by various researchers. V. Young, G.P Steven, Y.M. Xie and O.M. Querin extended the basic ESO algorithm to the addition of elements and multiple load cases. S. Savas, M. Ulker, and M.P. Saka utilised ESO to create structures with a uniform stress distribution. Both ESO algorithms were applied to isotropic structures. The basic principle of ESO is to remove material from the model, based on certain criteria, stress being typical. The method can also add material back, where it may become necessary to reinforce the structure, which may happen when excessive material is removed. The model undergoes an iterative process of analysis and modification, the cycle continuing until certain conditions are met, ranging from weight reduction to stress limits. The objective of the current research is to create an ESO method, utilising MSC.Patran/Nastran, to optimise composite structures. The final algorithm created is simple, in order to improve efficiency and reduce total analysis runtimes. The algorithm modifies the properties of the element, rather than removing it from the structure completely. This ensures that the connectivity of the elements remains intact. Elements are selected for removal or addition based on a driving criterion. The composite structures are modelled as a core and shell. The core consists of 3D elements with orthotropic properties, and the skin is represented by non-removable 2D shell elements. These shell elements bear the loads and boundary conditions. They also keep the external shape of the model, which is important for aerodynamic structures. The models were run through the ESO algorithm until the final optimised structure remained. A tailfin of an aircraft was used as an application example. The aim was to reduce weight and create an optimised design for manufacture. The criterion for the analyses undertaken was stress based. The results of this research are presented in the paper.
Influence of Material System, Lay-Up and Thickness on the Energy Absorption Capability of Composite Laminates
Authors: Mian Stefano , Quaresimin Marino , Magistrali Stefano
Published: September 2008

The paper presents the results of an experimental campaign devoted to investigate energy absorption during impact and its dependence on some relevant design parameters, such as material system, laminate thickness and laminate lay-up. Three different material systems were investigated, carbon/epoxy, kevlar/epoxy and glass/epoxy, and four stacking sequences [0]8, [0/45]2s, [0]12 and [0/45]3s. A total of 11 different configurations were considered, including a hybrid glass-carbon-kevlar/epoxy laminate. Low velocity impact tests were carried out on flat samples at several energy levels from barely visible damage up to penetration, according to ASTM 5628 standard. The penetration energy is pointed out as a key-parameter in determining the absorption capability of a laminate.
Test Rig for Experimental Investigations on Motion Control Valves
Authors: Gilardino Luca
Published: September 2008

The paper addresses the analysis and design of a motion control valves test rig and reports its final layout. The equipment allows the investigation of steady state and transient performance of overcentre and counterbalance valves. Resistive, inertial and overrunning loads can be generated to reproduce typical conditions on winches, aerial platforms and earth moving machines. The interest in this experimental facility originates from the fact that an oscillatory behaviour is at times observed in systems embodying motion control valves. Beside system layout and applied loads the behaviour is also influenced by specific valves characteristics. It is therefore relevant to reproduce in a lab environment such critical and unwanted situations in order to deeply investigate causes and effects on system dynamics. The rig is complemented by an automatic data acquisition system developed in Lab VIEW, which is also briefly described. Experimental tests and results are finally presented and critically analysed.
On the History of ESDA: 1992 to Present
Authors: O¨zer Arnas A.
Published: September 2008

The Engineering Systems Design and Analysis (ESDA) conference was started by the then Petroleum Division of the American Society of Mechanical Engineers (ASME). Petroleum Division was, and still is under the umbrella organization International Petroleum Technology Institute of ASME International, one of the very active, forward looking, and entrepreneurial group of engineers whose sole purpose is to serve their membership through technical activities that will benefit society at large. Their leaders have always been very creative, open minded, and helpful to the engineers they served as well as all who needed their expertise. It was under this type of leadership that ESDA was born in 1992. In 2000, after the 5th Biennial Conference in Montreux, Switzerland, a meeting was held by the Petroleum Division Chairman, the General and Technical Program Chairmen of ESDA 2000, two staff members from the Petroleum Division, the Chair of the Swiss Section, and the ASME Region XIII Vice President where it was decided to turn over the responsibilities for future conferences of ESDA to the international region of ASME, Region XIII. Thus, this, the third conference since then, has become the premier conference for this region of ASME and is still thriving at this the 8th Biennial Conference in Torino.
A Multipurpose Device for Some Hydrostatics Questions
Authors: Ganci Salvatore
Published: September 2008

A number of well-known hydrostatics problems dealing with Archimedes' principle concern a loaded boat floating in a pool.1–4 Examples of this sort of problem include: 1. (a) If a stone is thrown overboard from a boat floating in a pool, does the water level in the pool rise, fall, or remain unchanged? (b) If a hole is made in the bottom of the boat so that the boat sinks, does the water level in the pool change? If so, when does the change begin (when water first begins to enter the boat or later)? 2. A boat floating in a pool carries a mass M that can either be placed on the raft or hung below the raft. (a) How does the water level in the pool compare in the two cases? (b) In which case does the raft float higher in the water? This paper describes a simple low-cost experimental setup that can be used to demonstrate the solutions to such problems in a concrete and dramatic way.
Journal Writing in the Physics Classroom
Authors: Hopp J. Johanna
Published: September 2008

J. Johanna (Jo) Hopp is an assistant professor of physics at the University of Wisconsin-Stout, where she teaches both a one-semester calculus-based introductory course and a conceptual-based course. She received her doctorate from the University of Washington Department of Physiology and Biophysics.
An acoustic cue reliance pattern in second language speech perception
Authors: Ito Yasuko
Published: September 2008

The present study employed acoustic analysis to examine which acoustic cues, spectral (formant) or temporal (duration), native Japanese speakers rely on to identify four mid- and low back vowels in English as a second language. It is generally agreed that Japanese possesses five vowels, whereas English has 15 including diphthongs. This discrepancy is considered to cause confusion to the Japanese learners when they identify English vowels. Furthermore, Japanese possesses a long–short vowel contrast, which may help or cause confusion to the Japanese learners in the English vowel identification. In the present study, a perception test, which was a forced-choice identification task, was administered to Japanese learners of English, and the target back vowels used in the test were later examined acoustically. The results indicated that the learners confused the target back vowels that are temporally similar while they are spectrally different. The acoustic results, together with the patterns of confusion in identifying English back vowels, suggest that these Japanese learners of English are relying primarily on temporal cues rather than spectral cues.
Band gap engineering in three dimensional system of air bubbles in water
Authors: Kushwaha M. S. , Djafari-Rouhani B. , Dobrzynski L.
Published: September 2008

This work reports systematic and extensive evidence for the existence of complete, multiple, huge stop bands in the band structures for cubic arrays of air bubbles in water. All three important structures: face-centered cubic (fcc), body-centered cubic (bcc), and simple-cubic (sc) arrangements are investigated using the Fourier-series expansion (of position dependent density and elastic constant) method. It is noteworthy that this formulation does not require matching of the messy boundary conditions. The lowest stop bands are largest for a volume fraction f≤10%, with a gap/ midgap ratio of 1.8, for all three geometries. It is found that the low-frequency, flat passbands for the perfectly periodic systems correspond to the discrete modes of a single bubble. This is an artifact of the low filling fraction and huge density contrast in air and water. It is stressed that such a simple inhomogeneous system as made up of air bubbles in water gives rise to the largest stop bands ever reported for elastic/acoustic as well as dielectric composites—save the similar 2D composites discussed in the preceding work. [This work was partially supported by CONACyT grant No. 28110E.]
TMEM16A, A Membrane Protein Associated with Calcium-Dependent Chloride Channel Activity
Authors: Caputo Antonella , Caci Emanuela , Ferrera Loretta , Pedemonte Nicoletta , Barsanti Cristina , Sondo Elvira , Pfeffer Ulrich , Ravazzolo Roberto , Zegarra-Moran Olga , Galietta Luis J. V.
Published: September 2008

Calcium-dependent chloride channels are required for normal electrolyte and fluid secretion, olfactory perception, and neuronal and smooth muscle excitability. The molecular identity of these membrane proteins is still unclear. Treatment of bronchial epithelial cells with interleukin-4 (IL-4) causes increased calcium-dependent chloride channel activity, presumably by regulating expression of the corresponding genes. We performed a global gene expression analysis to identify membrane proteins that are regulated by IL-4. Transfection of epithelial cells with specific small interfering RNA against each of these proteins shows that TMEM16A, a member of a family of putative plasma membrane proteins with unknown function, is associated with calcium-dependent chloride current, as measured with halide-sensitive fluorescent proteins, short-circuit current, and patch-clamp techniques. Our results indicate that TMEM16A is an intrinsic constituent of the calcium-dependent chloride channel. Identification of a previously unknown family of membrane proteins associated with chloride channel function will improve our understanding of chloride transport physiopathology and allow for the development of pharmacological tools useful for basic research and drug development.