bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonlinear Normal Modes of Real-World Structures: Application to a Full-Scale Aircraft
Authors: Peeters M. , Kerschen G. , Golinval J. C. , Stephan C.
Published: June 2012

The objective of this paper is to demonstrate that the numerical computation of the nonlinear normal modes (NNMs) of complex real-world structures is now within reach. The application considered in this study is the airframe of the Morane-Saulnier Paris aircraft, whose ground vibration tests have exhibited some nonlinear structural behaviors. The finite element model of this aircraft, elaborated from drawings, has more than 80000 degrees of freedom, and softening nonlinearities exist in the connection between the external fuel tanks and the wing tips. From this model, a reduced-order model, which is accurate in the [0–100Hz] range, is constructed using the Craig-Bampton technique. The NNMs of the reduced model are then computed using a numerical algorithm combining shooting and pseudo-arclength continuation. The results show that the NNMs of this full-scale structure can be computed accurately even in strongly nonlinear regimes and with a reasonable computational burden. Nonlinear modal interactions are also highlighted by the algorithm and are discussed.
Planetary Gear Modal Properties and Dynamic Response: Experiments and Analytical Simulation
Authors: Ericson Tristan M. , Parker Robert G.
Published: June 2012

Planetary gear vibration is a major source of noise and may lead to fatigue-induced failures in bearings or other drivetrain components. Gear designers use mathematical models to analyze potential designs, but these models remain unverified by experimental data. This paper presents experiments that completely characterize the dynamic behavior of a spur planetary gear by modal testing and spinning tests under representative operating conditions, focusing on the independent motion of planetary components. Accelerometers are mounted directly to individual gear bodies. Rotational and translational accelerations obtained from the experiments are compared to the predictions of a lumped parameter model. Natural frequencies, modes, and forced response agree well between experiments and the model. Rotational, translational, and planet mode types presented in published analytical research are observed experimentally.
Model Reduction of Contact Dynamics Simulation Using Modified Lyapunov Balancing Method
Authors: Liang Jianxun , Ma Ou
Published: June 2012

Finite element models can accurately simulate impact-contact dynamics response of a multibody dynamical system. However, such a simulation remains very inefficient because very small integration time step must be used when solving the involved differential equations. Although many model reduction techniques can be used to improve the efficiency of finite element based simulations, most of these techniques cannot be readily applied to contact dynamics simulations due to the high nonlinearity of the contact dynamics model. This paper presents a model reduction approach for finite-element based multibody contact dynamics simulation, based on a modified Lyapunov balanced truncation method. An example is presented to demonstrate that, by applying the model reduction the simulation process is significantly speeded up and the resulting error is bounded within an acceptable level. The performance of the method with respect to some influential factors such as element size, shape and contact stiffness is also investigated.
Vibrational Analysis of Wavy Carbon Nanotube-Reinforced Composites
Authors: Motahar Mohamad Shafiee , Ahmadian Mohammad Taghi
Published: June 2012

Characterization and simulation of carbon nanotube-reinforced composites at large scale have been a concern of researchers in the past decade. This is due to the computational complication of considering many embedded carbon nanotubes (CNTs). However a simple meshing of organized CNT distribution in the matrix can ease this obstacle. In this study, a finite element approach is employed to investigate the elastodynamic behavior of a wavy CNT-reinforced composite structure. A three dimensional structure with up to 6400 uniformly distributed wavy CNTs is embedded in a polymer matrix. Each wavy nanotube is represented by a set of beam elements. The effect of nanotube waviness and volume fraction on the effective modulus of nanocomposite is evaluated and verified by previous studies. The results demonstrate that waviness tends to decrease the effective modulus of the structure. Furthermore, the natural frequencies of a nano structure at different boundary conditions are examined. The results reveal that the natural frequencies increase with volume fraction of CNT, while a nominal increase of CNT waviness decreases the natural frequencies sharply.
Designing and Manufacturing Spiral Bevel Gears Using 5-Axis CNC Milling Machines
Authors: Teixeira Alves Joe¨l , Guingand Miche`le , de Vaujany Jean-Pierre
Published: June 2012

The design of spiral bevel gears still remains complex since tooth geometry and the resulting kinematics performance stem directly from the manufacturing process. Spiral bevel gear manufacture owes most to the works of Gleason and Klingelnberg. However, recent advances in milling machine technology and CAM (Computer Aided Manufacturing) make it possible to manufacture good quality spiral bevel gears on a standard 5-axis milling machine. This paper describes the CAD definition and manufacturing of spiral bevel gear tooth surfaces. Process performance is assessed by comparing the resulting surfaces after machining with the pre-defined CAD surfaces. Using this manufacturing process allows to propose new type of geometry. This one is more theoretical and, in some respects, easier to design than the standard spiral bevel gear as it enables simpler mesh optimization. The latter can be achieved by using the model of meshing under load recalled in this paper.
Limitations of B-Spline Geometry in the Finite Element/Multibody System Analysis
Authors: Shabana Ahmed A. , Hamed Ashraf M. , Mohamed Abdel-Nasser A. , Jayakumar Paramsothy , Letherwood Michael D.
Published: June 2012

This paper examines the limitations of using B-spline representation as an analysis tool by comparing its geometry with the nonlinear finite element absolute nodal coordinate formulation (ANCF) geometry. It is shown that while both B-spline and ANCF geometries can be used to model non-structural discontinuities using linear connectivity conditions, there are fundamental differences between B-spline and ANCF geometries. First, while B-spline geometry can always be converted to ANCF geometry, the converse is not true; that is, ANCF geometry cannot always be converted to B-spline geometry. Second, because of the rigid structure of the B-spline recurrence formula, there are restrictions on the order of the parameters and basis functions used in the polynomial interpolation; this in turn can lead to models that have significantly larger number of degrees of freedom as compared to those obtained using ANCF geometry. Third, in addition to the known fact that B-spline does not allow for straight forward modeling of T-junctions, B-spline representation cannot be used in a straight forward manner to model structural discontinuities. It is shown in this investigation that ANCF geometric description can be used to develop new spatial chain models governed by linear connectivity conditions which can be applied at a preprocessing stage allowing for an efficient elimination of the dependent variables. The modes of the deformations at the definition points of the joints that allow for rigid body rotations between ANCF finite elements are discussed. The use of the linear connectivity conditions with ANCF spatial finite elements leads to a constant inertia matrix and zero Coriolis and centrifugal forces. The fully parameterized structural ANCF finite elements used in this study allow for the deformation of the cross section and capture the coupling between this deformation and the stretch and bending. A new chain model that employs different degrees of continuity for different coordinates at the joint definition points is developed in this investigation. In the case of cubic polynomial approximation, C1 continuity conditions are used for the coordinate line along the joint axis; while C0 continuity conditions are used for the other coordinate lines. This allows for having arbitrary large rigid body rotation about the axis of the joint that connects two flexible links. Numerical examples are presented in order to demonstrate the use of the formulations developed in this paper.
Herbie: Demonstration of Gyroscopic Effects by Means of a RC Vehicle
Authors: Huber Robert , Clauberg Jan , Ulbrich Heinz
Published: June 2012

Classical mechanics is mainly based on two mechanical principles, the principle of linear momentum (Isaac Newton) and the principle of angular momentum (Leonhard Euler). The principle of angular momentum implies that the time derivative of the angular momentum equals the sum of all torques, acting on the body. Concerning all types of education it is particularly important that theoretical basic principles are profoundly understood. This often enables to understand difficult mechanical systems by drawing parallels between complex mechanical systems and simple basic principles. One way to generate profound understanding of theoretical correlations is to use interesting experimental examples. In this paper, a teaching model is presented, which has the ability both to demonstrate the effects of the principle of angular momentum and to catch the attention of students. For this purpose, a remote-controlled model car was built carrying a high-speed gyroscope on its top. The gyroscope can cause that the car turns over to the inside of a turn against the centrifugal force. Even more, it is possible to drive in a circle on the inner tires of the RC vehicle.
A New Method to Measure Planet Load Sharing and Sun Gear Radial Orbit of Planetary Gear Sets
Authors: Boguski B. , Kahraman A. , Nishino T.
Published: June 2012

A new method of measuring planet load sharing of planetary gear sets is proposed in this paper. The method uses strain gauges mounted directly on the planet pins to measure continuously the loads carried by the planets assembled in a fixed carrier. Example 4-planet gear sets of different planet phasing conditions are procured and tested with a family of planet carriers having various levels and combinations of planet pinhole position errors to demonstrate the measurement method. As the radial floating capability of the central members is critical to planet-to-planet load sharing, a companion proximity-based measurement system is also implemented to measure the radial motions of the floating sun gear under various planet phasing and carrier pinhole error conditions. It is shown that both measurement methods are effective in characterizing the loads carried by planets.
Engineering System Design Using Firefly Algorithm and Multi-Objective Optimization
Authors: Lobato Fran Se´rgio , Arruda Edu Barbosa , Cavalini Aldemir Ap. , Steffen Valder
Published: June 2012

Modern engineering problems, such as aircraft or automobile design, are often composed by a large number of variables that must be chosen simultaneously for better design performance. Normally, most of these parameters are conflicting, i.e., an improvement in one of them does not lead, necessarily, to better results for the other ones. Thus, many methods to solve multi-objective optimization problems (MOP) have been proposed. The MOP solution, unlike the single objective problems, is a set of non-dominated solutions that form the Pareto Curve, also known as Pareto Optimal. Among the MOP algorithms, we can cite the Firefly Algorithm (FA). FA is a bio-inspired method that mimics the patterns of short and rhythmic flashes emitted by fireflies in order to attract other individuals to their vicinities. For illustration purposes, in the present contribution the FA, associated with the Pareto dominance criterion, is applied to three different design cases. The first one is related to the geometric design of a clamped-free beam. The second one deals with the project of a welded beam and the last one focuses on estimating the characteristic parameters of a rotary dryer pilot plant. The proposed methodology is compared with other evolutionary strategies. The results indicate that the proposed approach characterizes an interesting alternative for multi-objective optimization problems.
Equivalent Same-Order System for Multi-Rational-Order Fractional Differential System With Caputo Derivative
Authors: Li Changpin , Zhang Fengrong
Published: June 2012

The equivalent same-order system for multi-rational-order fractional differential system with Caputo derivative is studied. With the relationship between Caputo derivative and generalized fractional derivative, we can change the multi-order fractional differential system whose fractional order is rational into a much higher-dimensional fractional differential system with the same order lying in (0,1). Based on the equivalent results, the stability analysis of any multi-rational-order fractional differential system is given. Finally, several examples are provided to illustrate the results in this paper.
The Study of PHEV Shift Strategy Based on AMT Without Synchronizer
Authors: Dong Xiangyu , Xi Junqiang , Chen Huiyan
Published: June 2012

The research is based on single-axis parallel hybrid electric vehicle (PHEV) equipped with AMT (Automatic mechanical transmission). Dynamics model of shift process is established based on the shift control strategy without disengaging the clutch. This paper analyses the active synchronization and shift process. On this basis, the control strategy model of shifting without synchronizer and vehicle model are established respectively by using MATLAB and Cruise. Through the union simulation and analysis of the simulation data, it validates that the control strategy of shifting without synchronizer is feasible.
A Computer Aided Approach for Reformulating “Ill-Defined” Problems
Authors: Russo Davide , Birolini Valentino
Published: June 2012

It is proven that a low accuracy in setup or an insufficient attention during the problem structuring [1] may affect the accuracy of the final solution [2], while a problem that is properly defined is virtually solved [3], especially for “ill-defined” problems. Many efforts have been made since the 1970s for improving problem assessment, managing problem information (their functioning, constraints and requirements) and avoiding psychological barriers and memory loads [4]. Other studies have been focused on overcoming trivial points of view, such as lateral thinking [5] and to systematize an abstraction path for the initial situation by using theoretical models as functional models [6], cause effect analysis, and contradictions [7]. This work takes into account this background in problem solving methods, especially root cause analysis [8] and TRIZ [7], the theory of inventive problem solving. In this paper, a set of steps, called BOB-UP® have been conceived in order to support designers during the correct reformulation of the initial problem. This procedure has the aim to reformulate every technical problems, turning an ill-defined initial problem into a well-defined final problem. In this paper the framework of the procedure based upon an inedited cause-effect analysis is widely shown. For completing each design step, ontologies, linguistic rules, modeling tools and sketches are carefully integrated. Novel and key points are extensively presented in this paper, together with an exemplary case about a toaster implementation. The overall procedure was translated into software to ease the completion. The output of such computer aided reformulation consists of a “well defined” problem reformulation. Unlike the most famous and traditional cause-effect approaches, in the BOB-UP® environment the user is guided step by step to identify the best level of detail, focusing on the undesired effect(s), and finally identify the crucial element on which intervention is needed. A preliminary validation, conducted with 9 industrial cases by 30 users selected from the teaching staff of the University, research assistants and PhD and Master Degree students in Mechanical Engineering, has demonstrated the effectiveness of the method.
An Experimentally Validated Model of a Motorcycle Shock Absorber for Studying Suspension Dynamics
Authors: Doria Alberto , Lucchini Marco
Published: June 2012

Nowadays advanced shock absorbers are equipped with hydraulic valves that offer many possibilities of adjustment of orifices and shims. The theoretical force-velocity curve can be accurately designed and modified by means of these adjustments, in order to achieve the desired performance. Actually, compressibility of gas in compensation chamber, compressibility of oil, cavitation and compliance of seals and cylinders can significantly alter the force-velocity diagram. In some working conditions the behavior of the shock absorber may differ from the optimized one, with important consequences on the performance of the vehicle. Therefore there is the need of mathematical models able to predict the behavior of shock absorbers in the presence of large hysteresis phenomena, these models cannot be too complex and cumbersome, because they have to be implemented in multibody models of vehicles. The paper starts showing some experimental data collected by testing in laboratory a motorcycle shock absorber and aims to quantify the effect of hysteresis on performance and tuning. Then a mathematical model of a shock absorber is developed and presented. Valves are modeled with detail taking into account flow through bleed orifices and shim stacks and the effect of adjustments can be predicted. Compressibility of oil and compliances are taken into account by means of an equivalent compressibility coefficient. The model has a little number of parameters and a method is presented for identifying these parameters from laboratory tests. Some simulations show that the model is able to predict the behavior of the shock absorber over a wide range of frequencies. After validation, the shock absorber model is implemented into a two degree of freedom model of a rear suspension of a motorcycle. A MATLAB code is developed to solve the system of differential equations that describe the dynamic response of the suspension and the fluid motion inside the shock absorber. The response of the vehicle to a road bump is simulated. Acceleration of the suspended mass and tire load fluctuations show the effect of hysteresis and of adjustments of shock absorber on the performance of the vehicle.
Robust Optimization and Analysis of NURBs-Based Metamodels Using Graph Theory
Authors: Steuben John , Turner Cameron J.
Published: June 2012

NURBs-based metamodels have been shown to accurately reproduce the behavior of computationally expensive models. These models in turn represent engineering problems of great complexity and importance. While the structure of NURBs-based metamodels has facilitated the development of discrete optimization algorithms, other analysis areas such as robust and multiobjective optimization have proven to be more difficult. We present here a new method for the analysis and optimization of these metamodels which is based on graph theory principles. The adoption of these principles allows the use of powerful existing algorithms for graph analysis. We have focused on the problem of robust optimization in this work, as the robust optimization of NURBs-based metamodels has been previously examined using more conventional techniques. We demonstrate that the graph-based analysis technique provides the design engineer a more comprehensive understanding of design problems and their behavior. We also demonstrate the new technique on a range of test functions in order to establish its validity and usefulness in the context of product and process optimization. We conclude with a discussion of the use of this new approach in addressing other analysis challenges such as multiobjective or mixed-integer optimization.
Some Simulations of Gear–Journal Bearing Interactions
Authors: Farge`re Romain , Velex Philippe
Published: June 2012

This article deals with the static and dynamic interactions between journal bearings and gears in mechanical transmissions. The proposed approach combines classic lumped parameter and shaft elements, a specific wide-faced spur or helical gear model and external bearing forces. Bearing reactions are determined based on the linearized and non-linear solution to the Reynolds equation for short bearings. The corresponding parametrically excited non-linear state equations are solved by inserting a Newton-Raphson’s method and a unilateral normal contact algorithm into a Newmark’s time-step integration schema. Finally, the influence of bearing non-linearity, external and internal forcing terms is analyzed on several single stage reduction units with spur and helical gears.
Dynamic Modeling, Stability and Energy Consumption Analysis of Turning Motion of Realistic Hexapod Walking Robots
Authors: Roy Shibendu Shekhar , Pratihar Dilip Kumar
Published: June 2012

This paper presents a detailed dynamic modeling of a realistic hexapod walking robot during its turning motion over flat terrain. An energy consumption model is derived for generating statically stable wave-turning gaits by minimizing dissipated energy for the optimal feet forces distributions. Two approaches, such as minimization of norm of feet forces and minimization of norm of joint torques have been developed using least squared method. The performances of these approaches have been compared with one other for different values of duty factor. The effects of walking parameters, namely angular velocity, angular stroke and duty factors are studied on energy consumption and stability during turning motion. In order to minimize total energy consumption, the angular velocity should be as high as possible for a particular duty factor. A stability analysis based on normalized energy stability margin is performed for the turning motion of robot with four duty factors for different angular strokes.
Uncertainty Quantification of Pull-In Phenomenon in Capacitive RF-MEMS
Authors: Mathur Sanjay , Sun Lin , Das Shankhadeep , Peroulis Dimitrios , Kovacs Andrew , Zeng Juan , Murthy Jayathi Y.
Published: June 2012

The goal of this paper is to elucidate the effects of device geometry and fabrication process variations on the statistical pull-in performance of an electrostatically-actuated capacitive radio frequency micro electro-mechanical system (RF-MEMS) switch through the use of uncertainty quantification. The prediction of switch dynamics and pull-in voltage involves the coupled interaction of elastodynamics, fluid dynamics, and electrostatics. A comprehensive computational framework based on the finite volume method (FVM) is developed to account for these effects. The immersed boundary method (IBM) is employed to couple the fluid, structure and electrostatics. A population of switches is fabricated, and geometry and material properties measured; these measurements provide the probabilistic input information needed for uncertainty quantification. Deterministic simulations are first made for a specific device, and the gap-versus-voltage and pull-in voltage predicted compare favorably with measurements and theoretical estimation. Uncertainty quantification of dynamic pull-in is performed next, using the stochastic collocation method for uncertainty propagation. Probability density functions (PDFs) of pull-in voltage and gap-versus-time are computed. The primary determinants of uncertainty in pull-in voltage are found to be the membrane thickness and gap size, with uncertainty in residual stress having a relatively small effect.
A Micro-Scale Swimmer Propelled by Traveling Surface Waves
Authors: Bucher Izhak , Setter Eyal
Published: June 2012

Micro-scale slender swimmers are frequently encountered in nature and recently in micro-robotic applications. The swimming mechanism examined in this article is based on small transverse axi-symmetrical travelling wave deformations of a cylindrical long shell. In very small scale, inertia forces become negligible and viscous forces dominate most propulsion mechanisms being used by micro-organisms and robotic devices. The present paper proposes a compact design principle that provides efficient power to propel and maneuver a micro-scale device. Shown in this paper is a numerical analysis which couples the MEMS structure to the surrounding fluid. Analytical results compare the proposed mechanism to commonly found tail (flagella) driven devices, and a parametric comparison is shown suggesting it has superior performance. Numerical studies are preformed to verify the analytical model. Finally, a macro-scale demonstrator swimming in an environment with similar Reynolds numbers to the ones found in small scale is shown and its behavior in the laboratory is compared to the theory.
Consideration of Uncertainty in Virtual Product Design
Authors: Mosch Lucia , Sprenger Andre´ , Anderl Reiner
Published: June 2012

In design, manufacturing and usage of technical products uncertainty arises according to process properties and results in influence of products properties. In current CAD-systems, where products and product properties are presented, uncertainty is not considered yet. In this paper, we propose a new enhanced concept for the visualization of information about uncertainty in CAD-systems. The presentation of uncertainty is realized on basis of three-dimensional parametric models in a CAD-system and an implemented uncertainty-browser. The uncertainty-browser acts as a graphical user interface to categorize information about uncertainty, the processes and product properties. Beyond that, information about uncertainty will be visualized as annotations referring to chosen properties. Being aware of information about uncertainty during product design, the engineer is able to improve his product. The representation of uncertainty is based on an ontology based information system for supporting the collection and categorization of information about processes, products and uncertainty.
Visualizing Non-Linear Control System Performance by Means of Multidimensional Scaling
Authors: Machado J. A. Tenreiro
Published: June 2012

This paper addresses the use of multidimensional scaling in the evaluation of control system performance. Both linear and non-linear systems are analysed based on the closed loop time response under the action of a reference step input signal. Two alternative performance indices, based on the time and frequency domains, are tested. The numerical experiments demonstrate the feasibility of the proposed methodology and motivate its extension for other performance measures and a broader classes of non-linearities.
CRONE Control-System Design Toolbox for the Control Engineering Community
Authors: Lanusse Patrick , Malti Rachid , Melchior Pierre
Published: June 2012

The CRONE CSD methodology proposes to design robust controllers by using fractional order operators. A Matlab toolbox has been developed based on this methodology and is freely available for the international scientific and industrial communities. This paper presents both the methodology and the toolbox. The design of two robust controllers for irrigation canals show how the toolbox can be used.
A Review and Evaluation of Existing Adaptive Sampling Criteria and Methods for the Creation of NURBs-Based Metamodels
Authors: Pickett Bethany , Turner Cameron J.
Published: June 2012

Metamodels are widely used during the design process in place of expensive simulation models when computationally efficiency is imperative. Non-Uniform Rational B-Splines (NURBs) based metamodels have proven to be an effective modeling technique. Although metamodels can reduce the computation expense of design analysis and optimization, the sampling methods used to create the metamodels also play an imperative role in the computational efficiency and overall model quality. The research presented in this paper reviews various adaptive sampling criteria and methods and evaluates the different methods to determine the best sampling technique for the development of NURBs-based metamodels.
A Study on Tooth Modification for Spur Gear for Articulated Hauler
Authors: Zhang Qi , Xu Zhezhu , Lyu Sungki
Published: June 2012

Construction equipment is heavily loaded during normal operation. In recent years, there is a trend that lower gear noise levels are demanded for driver to avoid annoyance and fatigue of operation. For articulated haulers, meshing transmission error (T.E.) is the excitation that leads the tonal noise known as gear whine, and radiated gear whine is also the dominant source of noise in gearbox. This paper presents a method for the analysis of the tooth modification, and the prediction of transmission error under the loaded torque for the spur gear pair of the articulated hauler’s final drive. And the transmission error, contact stress, root stress and load distribution are also calculated and compared before and after tooth modification under one torque. The simulation result shows that the transmission error and stress under the load can be minimized by the appropriate tooth modification. It is a good approach where the simulated result is used to improve the design before the prototype is available for the test.
Geometric Calculations of the Chamfered Tip and the Protuberance Undercut of a Tooth Profile
Authors: Nemcek Milos , Dejl Zdenek
Published: June 2012

Nowadays special modified tools are mostly used for rough or semi-finishing milling in the mass production of ground or shaved gears today. These modifications ensure the desired chamfer at the head or the undercut at the bottom of the gear tooth. Diameters of the beginning and the end of the operational involute (exact knowledge of them is necessary for the calculation of important meshing parameters) are found by using several techniques. The first one is the simulation of the generating action of a hob tooth using suitable graphic software with the subsequent measuring of these diameters from the envelope of hob tooth positions which was created. The second one is measuring directly on the gear manufactured using a measuring device. These simulations or measuring are often not performed and the tool with recommended parameters of the protuberance or the ramp is simply chosen by an educated guess [1]. But it is not an acceptable technique in a mass production (car industry). Standard DIN 3960 [2] gives a certain manual for the determination of these diameters. It suggests the iterative method for the calculation of the chamfer beginning circle diameter but without a reliable guideline. And as regards the protuberance, it refers to the correct calculation only in theory. This paper deals with the computing method to determine diameters of the beginning and the end of the function part of a tooth flank involute. It is designed for a specified tool with modifications for creating the chamfer or the protuberance undercut. The paper also takes into account the necessary shaving (grinding) stock or the backlash. Furthermore it refers to possible problems when the basic profile of the generating tool with the protuberance is designed from the basic rack tooth profile.
Efficient Multirate Simulation of Complex Multibody Systems Based on Free Software
Authors: Solcia Tommaso , Masarati Pierangelo
Published: June 2012

Complex aeroservoelastic and mechatronic systems imply interaction between multidisciplinary or multifield subcomponents, whose dynamics are characterized by problem- and field-specific time scales and frequency ranges. As opposed to what is usually termed monolithic approach to the simulation of coupled problems, where a single formulation (and software solver) directly models the entire problems, the co-simulation approach allows to exploit state-of-art formulations for specific fields by coupling them as appropriate to establish the required interaction between the subcomponents. The interaction problem between the different and even incompatible interfaces of subcomponent domains can be split in spatial and temporal. This work focuses on the latter aspect. In fact, when subdomains require different time scales to achieve the desired trade-off between accuracy and computational cost, multirate methods can be used to avoid the need of a subdomain solver to comply with excessively stringent requirements resulting from another one. Many multirate methods are designed for monoblock systems and used in single-disciplinary simulations (e.g. electric networks). Their application to co-simulation setups may be not straightforward. A key problem in co-simulation, especially when stability and free response of a system are addressed, as in aeroservoelasticity, is related to the numerical stability of the coupled solution process. This work investigates the linear stability properties of a multirate formulation called ‘Double Extrapolation’ (DE) consisting in integrating each subproblem using second-order accurate, L-stable Backward Difference Formulas (BDF) while each subdomain extrapolates the behavior of the other one. It has been chosen because it allows to eliminate most of the idle time of each subdomain solver. The resulting performance gains are illustrated by applying the proposed method to the simulation of a complex aeroservoelastic system consisting in the aeroelastic model of a Horizontal Axis Wind Turbine (HAWT), developed using the general-purpose multibody formulation implemented in the free solver MBDyn, and a dynamic model of the electric generator, modeled in the free general-purpose block-diagram simulation environment ScicosLab. Both modeling environments are real-time capable; thus the proposed system represents an affordable and versatile solution for the hardware-in-the-loop analysis and design of complex multidisciplinary systems.
Characteristics Analysis of Wind Turbine Gearbox Considering Fatigue Loads Caused by Wind Fluctuation
Authors: Park Youngjun , Lee Geunho , Song Jinseop , Nam Yongyun
Published: June 2012

The influences of external loads caused by wind fluctuation on the load distribution on the gear tooth flank and the planet load sharing are investigated. A whole system model is developed to analyze the wind turbine gearbox (WTG) consists of planetary gear sets. The model includes non-linear mesh stiffness of gears, non-linear stiffness of bearings and the flexibilities of housing, planet carriers and ring gears. Two models for different design loads are employed to quantify the effect of external loads acting on input shaft of the WTG on the load distribution of gears and the load sharing amongst the planets under the quasi-static conditions. The results of gear mesh misalignment, contact pattern, load distribution and load sharing are all different for comparing two models, and this leads the gear safety factor to be not same each other. In other words, the gear safety factor can be varied due to the difference of the design load. Therefore, the results state that it is appropriate to utilize 5 DOF fatigue load caused by wind fluctuation as well as the torque as the design load for designing the WTG.
On a Unified Fractional Derivative
Authors: Ortigueira Manuel D. , Trujillo Juan J.
Published: June 2012

A new fractional derivative of complex Gru¨wald-Letnikov type is proposed and some properties are studied. The new definition incorporates both the forward and backward Gru¨wald-Letnikov and other fractional derivatives well known. Several properties of such generalized operator are presented.
Simulation and Analysis for Sustainability in Manufacturing Processes
Authors: Muroyama Alexander , Mani Mahesh , Lyons Kevin , Johansson Bjorn
Published: June 2012

“Sustainability” has become a ubiquitous term in almost every field, especially in engineering design and manufacturing. Recently, an increased awareness of environmental problems and resource depletion has led to an emphasis on environmentally friendly practices. This is especially true in the manufacturing industry where energy consumption and the amount of waste generated can be high. This requires proactive tools to be developed to carefully analyze the cause-effect of current manufacturing practices and to investigate alternative practices. One such approach to sustainable manufacturing is the combined use of Discrete Event Simulation (DES) and Life Cycle Assessment (LCA) to analyze the utilization and processing of manufacturing resources in a factory setting. On an economic aspect such method can significantly reduce the financial and environmental costs by evaluating the system performance before its construction or use. This project considers what-if scenarios in a simplified golf ball factory, using as close to real-world data as possible, to demonstrate DES and LCA’s ability to facilitate decision-making and optimize the manufacturing process. Plastic injection molding, an energy-intensive step in the golf ball manufacturing process, is the focus of the DES model. AutoMod, a 3-D modeling software, was used to build the DES model and AutoStat was used to run the trials and analyze the data. By varying the input parameters such as type and number of injection molding machines and material used, the simulation model can output data indicating the most productive and energy efficient methods. On a more detailed level, the simulations can provide valuable information on bottlenecks or imbalances in the system. Correcting these can allow the factory to be both “greener” and more cost-effective.
Improving the Condition Number of Finite Element Stiffness Matrices via Inverted Elements
Authors: Danczyk Josh , Suresh Krishnan
Published: June 2012

In the finite element method, poor quality elements typically increase the condition number of the underlying stiffness matrix, thereby potentially: (1) degrading the computed solution, and (2) slowing the convergence of iterative solvers. Current mesh improvement strategies rely on node movement and edge-flipping to alleviate these problems. However, these methods cannot guarantee a lower-bound on mesh quality, especially in 3-D. In this paper we propose the concept, and use, of inverted elements to improve mesh quality and condition number. Inverted elements are standard finite elements, but with negative Jacobian. After establishing the mathematical properties of these elements we show how they can be used to dramatically improve the quality of a mesh through the use of an ‘element cover’. Further, we show that a lower-bound on the mesh quality can be easily achieved, as supported by numerical experiments and case-studies.
Model Predictive Control of Gear Shift Process in AMT Trucks
Authors: Gao Bingzhao , Lu Xiaohui , Li Jun , Chen Hong
Published: June 2012

In order to improve shift quality, a model predictive controller is proposed for gear shifting control of vehicles with automated manual transmissions (AMTs). During the clutch engagement process, the contradictive requirements of short engagement time and small shift shock are taken into consideration in the optimal objective function. Through simulation test on a complete powertrain simulation model, it is verified that the shift shock is reduced significantly while at the same time the shift time is kept small enough.
A Method for Estimating Parameters of P-S-N Curves Based on Weibull Distribution
Authors: Ling Dan , Zhu Shun-Peng , Huang Hong-Zhong , He Li-Ping , Wang Zhong-Lai
Published: June 2012

An S-N curve is a traditional tool for design against fatigue. Because there is often a considerable amount of scatter in fatigue performance of specimens, The P-S-N curves capturing the probability of failure should be employed instead of S-N curves. In order to minimize the time and the number of specimens required for fatigue test, many researches had been done. Most studies were focused on a three-parameter S-N curve model; lognormal distribution and maximum likelihood estimation were employed to estimate unknown parameters. In this paper, a three-parameter Weibull distribution is used to describe the scatter of fatigue life. The relationship among survival probability, stress level and fatigue life is considered. A method for estimating parameters of P-S-N curves is proposed. According to this method, three groups of specimens are needed. Each group is submitted to a stress level. The parameters of P-S-N curves can be estimated by solving a set of nonlinear equations. And a numerical example shows that the method is effective.
Nonlinear Modes of a 2-DOF Inverted Pendulum
Authors: Gavassoni Elvidio , Gonc¸alves Paulo Batista , Roehl Deane M.
Published: June 2012

A number of practical structures such as compliant offshore towers can be physically modeled, as a first approximation, as an inverted pendulum. The nonlinear dynamics of such model can present some complex features due to the nonlinear coupling among its degrees-of-freedom. In this paper a model of a spatial inverted pendulum restrained by three inclined extensional springs is adopted. Geometric imperfections are considered, and the solutions for both perfect and imperfect systems are presented herein. Especial attention is given to the determination of the nonlinear vibration modes. Non-similar and similar NNMs are obtained analytically by direct application of asymptotic methods and the results show important NNM features such as instability and multiplicity of modes. Poincare´ maps of the conservative system are used to identify the existence of modes that do not have a linear counterpart. Analytical approximations are derived for these nonlinear modes by the use of a two-dimensional polynomial fitting procedure obtained by the application of the Levenberg-Marquardt method. The points coordinates used in the fitting procedure were obtained through numerical integration of the governing equations of motion. Such analytical expressions can then be used in modal reduction, parametric analysis and in the derivation of important features of the system such as its frequency-amplitude relations and resonance curves.
A Fuzzy Similarity-Based Approach to Reliability Allocation of Diesel Engine
Authors: Chen Zhong-Zhe , Liu Yu , Huang Hong-Zhong , Ling Dan , He Li-Ping
Published: June 2012

Most of new products evolve based upon existing products. The reliability indices and maintenance records of existing products are very important to provide useful information for the reliability allocation of the new evolutionary products. In this paper, a fuzzy similarity-based reliability allocation method which considers not only the similarity between the new product and old ones, but also the judgments from domain experts, is proposed to realize a reasonable reliability allocation at the initial design stage of diesel engines. The new method allows for using both the objective information from the old products and the subjective judgments from experts simultaneously, and it is more comprehensive and objective compared to the traditional reliability allocation method.
Property Analysis of an Electro-Mechanical Regenerative Damper Concept
Authors: Yu Changmiao , Wang Weihua , Wang Qingnian , Rakheja Subhash
Published: June 2012

This study proposes a concept of an electro-mechanical regenerative damper, composed of a gear mechanism and overrunning clutches to achieve uni-directional angular motion of the armature, and asymmetric damping in compression and rebound. An analytical model of the regenerative damper is formulated to derive its force-velocity properties, which revealed predominant inertia damping effect in addition to the electro-magnetic damping. The formulations further revealed that the damping properties of proposed concept could be easily varied through variation in both the electrical circuit and mechanical design parameters. The model is analyzed under harmonic excitations to determine its damping properties and the influences of various design parameters. The results suggest that the total force developed comprises two major components attributed to the generator and the effective inertia. The generator force resembles that of a bilinear asymmetric damper, while the variations in the inertia force exhibit a pattern similar to a ‘high-low’ damper. The proposed concept could thus yield ‘high-low’ damping variations in an entirely passive manner, while offering energy harvesting potential.
On the Dynamics Behavior and a Control Design to a Nonlinear 2-DOF Vibrating Gyroscopic-MEMS Model
Authors: Peruzzi Nelson Jose´ , Chavarette Fa´bio Roberto , Balthazar Jose´ Manoel
Published: June 2012

In this paper, we deal with the nonlinear dynamics, the transfer of energy and control of the vibrations of a Micro Electro-mechanical System (MEMS) gyroscope. The MEMS are micro-transducers whose operation is based on elastic and electrostatic forces that convert electrical energy into mechanical energy and vice-versa. These systems can be modeled by 2-DOF spring-mass-damper system and the coupling of the system equations is performed by Coriolis force. This coupling is responsible for the energy transfers of the two vibration modes (drive-mode and sense-mode) and for the resonance in MEMS gyroscope. The governing equations of motion have periodic coefficients and as the dimensions of the quantities involved in the system may be inconsistent it is not advisable the use of perturbation methods for the solution of the MEMS gyroscope. For this reason, in the dynamic analysis and control of the vibrations of the MEMS gyroscope, we used a technique based on Chebyshev polynomial expansion, the iterative Picard and transformation of Lyapunov-Floquet (L–F). For the analysis of the dynamic of the micro electro-mechanical system gyroscope, we did the diagram of stability, phase planes and time history of transfer of energy. Finally, we did the control of the unstable orbit to a desired periodic one and compared the phase planes of orbits desired and controlled and time histories of energy transfer of the controlled and non-controlled system.
Machining With Redundant Kinematics
Authors: Neugebauer Reimund , Drossel Welf-Guntram , Ihlenfeldt Steffen , Rentzsch Hendrik
Published: June 2012

The demand for high productivity and quality combined with the need for decreasing energy consumption will substantially affect machine tool design in the future. This development is driven by a modification of process chains which is focused on resource conservation. One important contribution for that purpose is the transition towards complete machining. This approach calls for a configuration targeting major process stability as well as a structure geared towards accuracy and dynamism. The compromise between potential dynamism and machine size can be improved by using redundant drives. This paper describes models, simulation tools and the method of the development process for redundant kinematics. To highlight the different aspects of designing such machine tool structures, their development process is demonstrated on the basis of two examples, complete machining for tool- and die making and an adaptive spindle holder for micro contouring and -structuring.