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ENGINEERING (1119 journals)            First | 2 3 4 5 6 7 8 9 | Last

International Journal of Intelligent Engineering Informatics     Hybrid Journal  
International Journal of Intelligent Systems and Applications in Engineering     Open Access   (Followers: 1)
International Journal of Lifecycle Performance Engineering     Hybrid Journal  
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 4)
International Journal of Manufacturing Research     Hybrid Journal   (Followers: 7)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 9)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mathematical Education in Science and Technology     Hybrid Journal   (Followers: 6)
International Journal of Mathematics in Operational Research     Hybrid Journal   (Followers: 1)
International Journal of Medical Engineering and Informatics     Hybrid Journal   (Followers: 5)
International Journal of Micro Air Vehicles     Full-text available via subscription   (Followers: 3)
International Journal of Microwave and Wireless Technologies     Hybrid Journal   (Followers: 1)
International Journal of Microwave Science and Technology     Open Access   (Followers: 2)
International Journal of Mobile Network Design and Innovation     Hybrid Journal   (Followers: 3)
International Journal of Multiphase Flow     Hybrid Journal   (Followers: 2)
International Journal of Nanomanufacturing     Hybrid Journal   (Followers: 1)
International Journal of Nanoscience     Hybrid Journal   (Followers: 1)
International Journal of Nanotechnology     Hybrid Journal   (Followers: 4)
International Journal of Navigation and Observation     Open Access   (Followers: 5)
International Journal of Network Management     Hybrid Journal  
International Journal of Nonlinear Sciences and Numerical Simulation     Full-text available via subscription   (Followers: 1)
International Journal of Numerical Methods for Heat & Fluid Flow     Hybrid Journal   (Followers: 7)
International Journal of Optics     Open Access   (Followers: 1)
International Journal of Organisational Design and Engineering     Hybrid Journal   (Followers: 8)
International Journal of Pattern Recognition and Artificial Intelligence     Hybrid Journal   (Followers: 6)
International Journal of Pavement Engineering     Hybrid Journal   (Followers: 2)
International Journal of Physical Modelling in Geotechnics     Hybrid Journal   (Followers: 3)
International Journal of Plasticity     Hybrid Journal   (Followers: 6)
International Journal of Plastics Technology     Hybrid Journal  
International Journal of Polymer Analysis and Characterization     Hybrid Journal   (Followers: 3)
International Journal of Polymer Science     Open Access   (Followers: 16)
International Journal of Precision Engineering and Manufacturing     Hybrid Journal   (Followers: 7)
International Journal of Precision Technology     Hybrid Journal  
International Journal of Pressure Vessels and Piping     Hybrid Journal   (Followers: 2)
International Journal of Production Economics     Hybrid Journal   (Followers: 10)
International Journal of Quality and Innovation     Hybrid Journal   (Followers: 2)
International Journal of Quality Engineering and Technology     Hybrid Journal   (Followers: 2)
International Journal of Quantum Information     Hybrid Journal  
International Journal of Rapid Manufacturing     Hybrid Journal   (Followers: 3)
International Journal of Reliability, Quality and Safety Engineering     Hybrid Journal   (Followers: 4)
International Journal of Renewable Energy Technology     Hybrid Journal   (Followers: 7)
International Journal of Robust and Nonlinear Control     Hybrid Journal   (Followers: 2)
International Journal of Science Engineering and Advance Technology     Open Access  
International Journal of Sediment Research     Full-text available via subscription   (Followers: 1)
International Journal of Self-Propagating High-Temperature Synthesis     Hybrid Journal   (Followers: 2)
International Journal of Signal and Imaging Systems Engineering     Hybrid Journal  
International Journal of Six Sigma and Competitive Advantage     Hybrid Journal  
International Journal of Social Robotics     Hybrid Journal   (Followers: 1)
International Journal of Software Engineering and Knowledge Engineering     Hybrid Journal   (Followers: 1)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Speech Technology     Hybrid Journal   (Followers: 2)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 5)
International Journal of Surface Engineering and Interdisciplinary Materials Science     Full-text available via subscription   (Followers: 1)
International Journal of Surface Science and Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Manufacturing     Hybrid Journal   (Followers: 4)
International Journal of Systems Assurance Engineering and Management     Hybrid Journal  
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 2)
International Journal of Technology Management and Sustainable Development     Hybrid Journal   (Followers: 1)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 4)
International Journal of Telemedicine and Applications     Open Access   (Followers: 2)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 4)
International Journal of Thermodynamics     Open Access   (Followers: 2)
International Journal of Turbo & Jet-Engines     Full-text available via subscription  
International Journal of Ultra Wideband Communications and Systems     Hybrid Journal  
International Journal of Vehicle Autonomous Systems     Hybrid Journal   (Followers: 1)
International Journal of Vehicle Design     Hybrid Journal   (Followers: 6)
International Journal of Vehicle Information and Communication Systems     Hybrid Journal   (Followers: 2)
International Journal of Vehicle Noise and Vibration     Hybrid Journal   (Followers: 3)
International Journal of Vehicle Safety     Hybrid Journal   (Followers: 4)
International Journal of Vehicular Technology     Open Access   (Followers: 1)
International Journal of Virtual Technology and Multimedia     Hybrid Journal   (Followers: 4)
International Journal of Wavelets, Multiresolution and Information Processing     Hybrid Journal  
International Journal on Artificial Intelligence Tools     Hybrid Journal   (Followers: 4)
International Nano Letters     Open Access   (Followers: 5)
International Review of Applied Sciences and Engineering     Full-text available via subscription  
Inverse Problems in Science and Engineering     Hybrid Journal   (Followers: 2)
Ionics     Hybrid Journal  
IPTEK The Journal for Technology and Science     Open Access  
IRBM News     Full-text available via subscription  
Ironmaking & Steelmaking     Hybrid Journal   (Followers: 2)
Irrigation and Drainage Systems     Hybrid Journal  
ISA Transactions     Full-text available via subscription  
ISRN - International Scholarly Research Notices     Open Access   (Followers: 69)
ISRN Signal Processing     Open Access  
IT Professional     Full-text available via subscription   (Followers: 2)
Journal of Biosensors & Bioelectronics     Open Access   (Followers: 1)
Journal of Advanced Manufacturing Systems     Hybrid Journal   (Followers: 8)
Journal of Aerosol Science     Hybrid Journal   (Followers: 2)
Journal of Aerospace Engineering     Full-text available via subscription   (Followers: 110)
Journal of Alloys and Compounds     Hybrid Journal   (Followers: 6)
Journal of Analytical and Applied Pyrolysis     Hybrid Journal   (Followers: 3)
Journal of Analytical Science & Technology     Open Access   (Followers: 4)
Journal of Analytical Sciences, Methods and Instrumentation     Open Access   (Followers: 1)
Journal of Applied Analysis     Full-text available via subscription  
Journal of Applied and Industrial Sciences     Open Access  
Journal of Applied Logic     Full-text available via subscription  
Journal of Applied Physics     Hybrid Journal   (Followers: 138)
Journal of Applied Probability     Full-text available via subscription   (Followers: 6)
Journal of Applied Research and Technology     Open Access  

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Journal of Computational and Nonlinear Dynamics
   [6 followers]  Follow    
   Full-text available via subscription Subscription journal
     ISSN (Print) 1555-1415 - ISSN (Online) 1555-1423
     Published by ASME International Homepage  [25 journals]   [SJR: 0.606]   [H-I: 17]
  • Motion Planning of Uncertain Ordinary Differential Equation Systems
    • Authors: Hays J; Sandu A, Sandu C, et al.
      Abstract: This work presents a novel motion planning framework, rooted in nonlinear programming theory, that treats uncertain fully and underactuated dynamical systems described by ordinary differential equations. Uncertainty in multibody dynamical systems comes from various sources, such as system parameters, initial conditions, sensor and actuator noise, and external forcing. Treatment of uncertainty in design is of paramount practical importance because all real-life systems are affected by it, and poor robustness and suboptimal performance result if it is not accounted for in a given design. In this work uncertainties are modeled using generalized polynomial chaos and are solved quantitatively using a least-square collocation method. The computational efficiency of this approach enables the inclusion of uncertainty statistics in the nonlinear programming optimization process. As such, the proposed framework allows the user to pose, and answer, new design questions related to uncertain dynamical systems. Specifically, the new framework is explained in the context of forward, inverse, and hybrid dynamics formulations. The forward dynamics formulation, applicable to both fully and underactuated systems, prescribes deterministic actuator inputs that yield uncertain state trajectories. The inverse dynamics formulation is the dual to that of forward dynamics, and is only applicable to fully actuated systems; deterministic state trajectories are prescribed and yield uncertain actuator inputs. The inverse dynamics formulation is more computationally efficient as it requires only algebraic evaluations and completely avoids numerical integration. Finally, the hybrid dynamics formulation is applicable to underactuated systems where it leverages the benefits of inverse dynamics for actuated joints and forward dynamics for unactuated joints; it prescribes actuated state and unactuated input trajectories that yield uncertain unactuated states and uncertain actuated inputs. The benefits of the ability to quantify uncertainty when planning the motion of multibody dynamic systems are illustrated through several case studies. The resulting designs determine optimal motion plans—subject to deterministic and statistical constraints—for all possible systems within the probability space.
      PubDate: Tue, 13 May 2014 00:00:00 GMT
  • A Numerical Model to Study the Effects of Aluminum Foam Filler on the
           Dynamic Behavior of a Steel Tubular Energy Absorber Using a Multi-Node
           Displacement Evaluation Procedure
    • Authors: Veloso V, Almeida Magalhães P, Jr; Landre J, Jr..
      Abstract: Tubular energy absorbers are usually found in the structures of cars, trains, and other means of transportation. They can absorb high levels of impact energy by plastic deformation during axial folding. The key advantages of this type of energy absorber are the compact dimensions, simple manufacturing, and good energy absorption efficiency. The dynamic behavior of the tube during collapse has a great influence on the total energy absorbed and, consequently, the force transmitted during folding. The optimization of this process may lead to improved energy absorption efficiency, allowing us to reduce the dimensions and costs of the component or improve the crashworthiness of pre-existing structures. Foam materials are used in most applications to improve the impact absorption of structures due to its constant load pattern during crushing. They are used, in most cases, as fillers inside empty absorbers such as tubes. In this paper, a numerical model was developed in order to study the possible interactions of foam and tube walls, providing information onhow this relation can influence the deformation modes of the tube. The obtained results showed a direct influence of the foam interaction with the tube walls under the energy absorption and load transmitting characteristics of the component.
      PubDate: Thu, 13 Mar 2014 00:00:00 GMT
  • Complex Dynamics of Spring-Block Earthquake Model Under Periodic Parameter
    • Authors: Kostić S; Vasović N, Franović I, et al.
      Abstract: A simple model of earthquake nucleation that may account for the onset of chaotic dynamics is proposed and analyzed. It represents a generalization of the Burridge–Knopoff single-block model with Dieterich–Ruina's rate- and state-dependent friction law. It is demonstrated that deterministic chaos may emerge when some of the parameters are assumed to undergo small oscillations about their equilibrium values. Implementing the standard numerical methods from the theory of dynamical systems, the analysis is carried out for the cases having one or two periodically variable parameters, such that the appropriate bifurcation diagrams, phase portraits, power spectra, and the Lyapunov exponents are obtained. The results of analysis indicate two different scenarios to chaos. On one side, the Ruelle–Takens–Newhouse route to chaos is observed for the cases of limit amplitude perturbations. On the other side, when the angular frequency is assumed constant for the value near the periodic motion of the block in an unperturbed case, variation of oscillation amplitudes probably gives rise to global bifurcations, with immediate occurrence of chaotic behavior. Further analysis shows that chaotic behavior emerges only for small oscillation frequencies and higher perturbation amplitudes when two perturbed parameters are brought into play. If higher oscillation frequencies are assumed, no bifurcation occurs, and the system under study exhibits only the periodic motion. In contrast to the previous research, the onset of chaos is observed for much smaller values of the stress ratio parameter. In other words, even the relatively small perturbations of the control parameters could lead to deterministic chaos and, thus, to instabilities and earthquakes.
      PubDate: Thu, 13 Mar 2014 00:00:00 GMT
  • Forward Dynamic Optimization of Human Gait Simulations: A Global
           Parameterization Approach
    • Authors: Sharif Shourijeh M; McPhee J.
      Abstract: This study presents a 2D gait model that uses global parameterization within an optimal control approach and a hyper-volumetric foot contact model. The model is simulated for an entire gait stride, i.e., two full steps. Fourier series are utilized to represent muscle forces to provide a periodic gait with bilateral symmetry. The objectives of this study were to develop a predictive gait simulation and to validate the predictions. The comparison of simulation results of optimal muscle activations, joint angles, and ground reaction forces against experimental data showed a reasonable agreement.
      PubDate: Thu, 06 Mar 2014 00:00:00 GMT
  • On the Relation of the Principle of Maximum Dissipation to the Principles
           of Jourdain and Gauss for Rigid Body Systems
    • Authors: Yunt K.
      Abstract: A dissipation based definition of the principle of Jourdain is presented for rheonomic (explicitly time dependent) mechanical systems, which evolve under the influence of convex dissipation potentials. It is shown, that the variational condition of the dissipative principle of Jourdain is the necessary condition for the maximization of the total dissipated power with respect to generalized velocities. The principle of maximum dissipation is shown to be the dual principle of the dissipative principle of Jourdain. A dissipative principle of Gauss is formulated by making use of nonsmooth analysis and potential theory and its dual principle is formulated.
      PubDate: Fri, 14 Feb 2014 00:00:00 GMT
  • Modeling and Analysis of an Electrically Actuated Microbeam Based on
           Nonclassical Beam Theory
    • Authors: Belardinelli P; Lenci S, Brocchini M.
      Abstract: This work investigates the mechanical behavior of a clamped-clamped microbeam modeled within the framework of the strain-gradient elasticity theory. The governing equation of motion gives proper account of both the effect of the nonlinear midplane stretching and of an applied axial load. An electric-voltage difference, introducing into the model a further source of nonlinearity, is considered, including also a correction term for fringing field effects. The electric force acting on the microbeam is rearranged by means of the Chebyshev method, verifying the accuracy of the proposed approximation. The results show that a uniform error on the whole domain can be achieved. The static solution is obtained by a numerical differential quadrature method. The paper looks into the variation of the maximal deflection of the microbeam with respect to several parameters. Study of the pull-in limit on the high-order material parameters introduced by the nonclassical approach and a comparison with respect to the classical beam theory are also carried out. The numerical simulation indicates that the static response is larger, affected by the use of a nonclassical theory near the pull-in instability regime. The dynamical problem is, finally, analyzed, deriving the multi degree-of-freedom problem through a Galerkin-based approach. The study on the single degree-of-freedom model enables us to note the large influence of the nonlinear terms.
      PubDate: Fri, 14 Feb 2014 00:00:00 GMT
  • Nonlinear Analysis of a New Extended Lattice Model With Consideration of
           Multi-Anticipation and Driver Reaction Delays
    • Authors: Chen J; Shi Z, Yu L, et al.
      Abstract: A new extended lattice model of traffic flow is presented by taking into account both multianticipative behavior and the reaction-time delay of drivers. The linear stability theory and the nonlinear analysis method are applied to the model. The linear stability condition is obtained. The Korteweg–de Vries (KdV) equation near the neutral stability line and the modified Korteweg–de Vries (mKdV) equation near the critical point are derived. The numerical results show that the stability of traffic flow will be enhanced by multianticipative consideration and will be weakened with the increase of the reaction-time delay. The unfavorable effect induced by driver reaction delays can be partly compensated by considering multianticipative behavior.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Third-Order Continuous-Discrete Filtering for a Nonlinear Dynamical System
    • Authors: Patel HG; Sharma SN.
      Abstract: Approximate higher-order filters are more attractive and popular in control and signal processing literature in contrast to the exact filter, since the analytical and numerical solutions of the nonlinear exact filter are not possible. The filtering model of this paper involves stochastic differential equation (SDE) formalism in combination with a nonlinear discrete observation equation. The theory of this paper is developed by adopting a unified systematic approach involving celebrated results of stochastic calculus. The Kolmogorov–Fokker–Planck equation in combination with the Kolmogorov backward equation plays the pivotal role to construct the theory of this paper “between the observations.” The conditional characteristic function is exploited to develop “filtering” at the observation instant. Subsequently, the efficacy of the filtering method of this paper is examined on the basis of its comparison with extended Kalman filtering and true state trajectories. This paper will be of interest to applied mathematicians and research communities in systems and control looking for stochastic filtering methods in theoretical studies as well as their application to real physical systems.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • A Simple Procedure for the Solution of Three-Dimensional Wheel/Rail
           Conformal Contact Problem
    • Authors: Recuero AM; Shabana AA.
      Abstract: This paper describes a simple and efficient procedure for the treatment of conformal contact conditions with special emphasis on railroad wheel/rail contacts. The general three-dimensional nonconformal contact conditions are briefly reviewed. These nonconformal contact conditions, which are widely used in many applications because of their generality, allow for predicting online one point of contact, provided that the two surfaces in contact satisfy certain geometric requirements. These nonconformal contact conditions fail when the solution is not unique as the result of using conformal surface profiles or surface flatness, situations often encountered in many applications including railroad wheel/rail contacts. In these cases, the Jacobian matrix obtained from the differentiation of the nonconformal contact conditions with respect to the surface parameters suffer from singularity that causes interruption of the computer simulations. The singularities and the fundamental issues that arise in the case of conformal contact are discussed, and a simple and computationally efficient procedure for avoiding such singularities in general multibody systems (MBS) algorithms is proposed. In order to demonstrate the use of the proposed procedure, the wheel climb of a wheelset as the result of an external lateral force is considered as an example. In this example, the wheel and rail profiles lead to conformal contact scenarios that could not be simulated using the nonconformal contact conditions.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Response of Fractional Oscillators With Viscoelastic Term Under Random
    • Authors: Xu Y; Li Y, Liu D.
      Abstract: A system with fractional damping and a viscoelastic term subject to narrow-band noise is considered in this paper. Based on the revisit of the Lindstedt–Poincaré (LP) and multiple scales method, we present a new procedure to obtain the second-order approximate analytical solution, and then the frequency–amplitude response equations in the deterministic case and the first- and second-order steady-state moments in the stochastic case are derived theoretically. Numerical simulation is applied to verify the effectiveness of the proposed method, which shows good agreement with the analytical results. Specially, we find that the new method is valid for strongly nonlinear systems. In addition, the influences of fractional order and the viscoelastic parameter on the system are explored, and the results indicate that the steady-state amplitude will increase at a fixed point with the increase of fractional order or viscoelastic parameter. At last, stochastic jump is investigated via the received Fokker–Planck–Kolmogorov (FPK) equation to compute the stationary solution of probability density functions with its shape changing from one peak to two peaks with the increase of noise intensity, and the phenomena of stochastic jump is consistent with the solution of frequency–amplitude response equations.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • A Mechanistic Multibody Model for Simulating the Dynamics of a Vertical
           Piano Action
    • Authors: Masoudi R; Birkett S, McPhee J.
      Abstract: The theoretical framework for constructing a fully mechanistic multibody dynamic model of a vertical piano action is described, and its general validity is established. Equations of motion are derived symbolically using a graph-theoretic formulation. Model fidelity is increased by introducing several novel features: (i) a new contact model for representing the compression of the felt-lined interfaces between interacting parts, capable of capturing the intermittent loading and unloading of these contacts occurring through the key stroke, as well as providing smooth transitions between these states; (ii) models for two important components that are unique to the vertical action, the bridle strap and the butt spring; (iii) a sophisticated key pivot model that captures both the rotational motion and the vertical translation of the key as it can lift off the balance rail under some conditions; (iv) flexible beam models for backcheck wire and hammer shank so as to predict observed vibrations in the response accurately; and (v) coupling of the mechanism model to a flexible stiff string model for realistic hammer impact. For simulation, parameters were obtained by experimental testing and measurement of a physical prototype vertical action. Techniques are described for the virtual regulation of the model to ensure that initial conditions and pseudostatic response accurately represent the precise configuration and desired relationships between the parts during the key stroke. Two input force profiles were used for simulations, a forte pressed (hard) and piano pressed touch (soft), typical of those measured at the key surface when activated by a pianist. Simulated response to these quite different inputs is described, and compared to experimental observations obtained from a physical prototype.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • A Kriging Model for Dynamics of Mechanical Systems With Revolute Joint
    • Authors: Zhang Z; Xu L, Flores P, et al.
      Abstract: Over the past two decades, extensive work has been conducted on the dynamic effect of joint clearances in multibody mechanical systems. In contrast, little work has been devoted to optimizing the performance of these systems. In this study, the analysis of revolute joint clearance is formulated in terms of a Hertzian-based contact force model. For illustration, the classical slider-crank mechanism with a revolute clearance joint at the piston pin is presented and a simulation model is developed using the analysis/design software MSC.ADAMS. The clearance is modeled as a pin-in-a-hole surface-to-surface dry contact, with an appropriate contact force model between the joint and bearing surfaces. Different simulations are performed to demonstrate the influence of the joint clearance size and the input crank speed on the dynamic behavior of the system with the joint clearance. In the modeling and simulation of the experimental setup and in the followed parametric study with a slightly revised system, both the Hertzian normal contact force model and a Coulomb-type friction force model were utilized. The kinetic coefficient of friction was chosen as constant throughout the study. An innovative design-of-experiment (DOE)-based method for optimizing the performance of a mechanical system with the revolute joint clearance for different ranges of design parameters is then proposed. Based on the simulation model results from sample points, which are selected by a Latin hypercube sampling (LHS) method, a polynomial function Kriging meta-model is established instead of the actual simulation model. The reason for the development and use of the meta-model is to bypass computationally intensive simulations of a computer model for different design parameter values in place of a more efficient and cost-effective mathematical model. Finally, numerical results obtained from two application examples with different design parameters, including the joint clearance size, crank speed, and contact stiffness, are presented for the further analysis of the dynamics of the revolute clearance joint in a mechanical system. This allows for predicting the influence of design parameter changes, in order to minimize contact forces, accelerations, and power requirements due to the existence of joint clearance.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Model Predictive Control of Fractional Order Systems
    • Authors: Rhouma A; Bouani F, Bouzouita B, et al.
      Abstract: This paper provides the model predictive control (MPC) of fractional order systems. The direct method will be used as internal model to predict the future dynamic behavior of the process, which is used to achieve the control law. This method is based on the Grünwald–Letnikov's definition that consists of replacing the noninteger derivation operator of the adopted system representation by a discrete approximation. The performances and the efficiency of this approach are illustrated with practical results on a thermal system and compared to the MPC based on the integer ARX model.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Adaptive Consensus Tracking for Fractional-Order Linear Time Invariant
           Swarm Systems
    • Authors: Naderi Soorki M; Saleh Tavazoei M.
      Abstract: This paper presents an adaptive controller to achieve consensus tracking for the fractional-order linear time invariant swarm systems in which the matrices describing the agent dynamics and the interactive dynamics between agents are unknown. This controller consists of two parts: an adaptive stabilizer and an adaptive tracker. The adaptive stabilizer guarantees the asymptotic swarm stability of the considered swarm system. Also, the adaptive tracker enforces the system agents to track a desired trajectory while achieving consensus. Numerical simulation results are presented to show the effectiveness of the proposed controller.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Experimental and Numerical Investigation of the Mechanism of Blast Wave
           Transmission Through a Surrogate Head
    • Authors: Hua Y; Kumar Akula P, Gu L, et al.
      Abstract: This work is to develop an experiment-validated numerical model to elucidate the wave transmission mechanisms through a surrogate head under blast loading. Repeated shock tube tests were conducted on a surrogate head, i.e., water-filled polycarbonate shell. Surface strain on the skull simulant and pressure inside the brain simulant were recorded at multiple locations. A numerical model was developed to capture the shock wave propagation within the shock tube and the fluid-structure interaction between the shock wave and the surrogate head. The obtained numerical results were compared with the experimental measurements. The experiment-validated numerical model was then used to further understand the wave transmission mechanisms from the blast to the surrogate head, including the flow field around the head, structural response of the skull simulant, and pressure distributions inside the brain simulant. Results demonstrated that intracranial pressure in the anterior part of the brain simulant was dominated by the direct blast wave propagation, while in the posterior part it was attributed to both direct blast wave propagation and skull flexure, which took effect at a later time. This study served as an exploration of the physics of blast-surrogate interaction and a precursor to a realistic head model.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Bioaeroservoelastic Analysis of Involuntary Rotorcraft-Pilot Interaction
    • Authors: Masarati P; Quaranta G.
      Abstract: This work presents the integration of a detailed biomechanical model of the arm of a helicopter pilot and an equivalently detailed aeroservoelastic model of a helicopter, resulting in what has been called a ‘bioaeroservoelastic’ analysis. The purpose of this analysis is to investigate potential adverse interactions, called rotorcraft-pilot couplings, between the aeroservoelastic system and the controls involuntarily introduced by the pilot into the control system in response to rotorcraft vibrations transmitted to the pilot through the cockpit: the so-called biodynamic feedthrough. The force exerted by the pilot on the controls results from the activation of the muscles of the arms according to specific patterns. The reference muscular activation value as a function of the prescribed action on the controls is computed using an inverse kinetostatics/inverse dynamics approach. A first-order quasi-steady correction is adopted to mimic the reflexive contribution to muscle activation. Muscular activation is further augmented by activation patterns that produce elementary actions on the control inceptors. These muscular activation patterns, inferred using perturbation analysis, are applied to control the aircraft through the pilot's limbs. The resulting biomechanical pilot model is applied to the aeroservoelastic analysis of a helicopter model expressly developed within the same multibody modeling environment to investigate adverse rotorcraft pilot couplings. The model consists of the detailed aeroelastic model of the main rotor, using nonlinear beams and blade element/momentum theory aerodynamics, a component mode synthesis model of the airframe structural dynamics, and servoactuator dynamics. Results in terms of the stability analysis of the coupled system are presented in comparison with analogous results obtained using biodynamic feedthrough transfer functions identified from experimental data.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Nonintrusive Structural Dynamic Reduced Order Modeling for Large
           Deformations: Enhancements for Complex Structures
    • Authors: Perez R; Wang XQ, Mignolet MP.
      Abstract: This paper focuses on the development of nonlinear reduced order modeling techniques for the prediction of the response of complex structures exhibiting “large” deformations, i.e., a geometrically nonlinear behavior, which are nonintrusive, i.e., the structure is originally modeled within a commercial finite element code. The present investigation builds on a general methodology successfully validated in recent years on simpler beam and plate structures by: (i) developing a novel identification strategy of the reduced order model parameters that enables the consideration of the large number of modes (>50 say) that would be needed for complex structures, and (ii) extending a step-by-step strategy for the selection of the basis functions used to represent accurately the displacement field. The above novel developments are successfully validated on the nonlinear static response of a nine-bay panel structure modeled with 96,000 degrees of freedom within Nastran.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Air Suspension System Model Coupled With Leveling and Differential
           Pressure Valves for Railroad Vehicle Dynamics Simulation
    • Authors: Nakajima T; Shimokawa Y, Mizuno M, et al.
      Abstract: In this investigation, a nonlinear air suspension system model that accounts for the coupling between air springs, leveling valves, and differential pressure valves is developed and integrated into general-purpose multibody dynamics computer algorithms. It is demonstrated that the proposed model can capture highly nonlinear air suspension characteristics resulting from the coupling with leveling and differential pressure valves, and good agreements are obtained between the numerical and on-track test results. Furthermore, the effect of flow characteristics of leveling valves on the wheel load unbalance on spiral curve sections is discussed. The numerical results obtained by the proposed model clearly indicate the importance of modeling the nonlinear flow characteristics of the leveling and differential pressure valves for assessing the vehicle safety in low speed operations on a small radius curved track.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Nonlinear Frequency Response Analysis of a Multistage Clutch Damper With
           Multiple Nonlinearities
    • Authors: Yoon J; Yoon H.
      Abstract: This paper presents the nonlinear frequency response of a multistage clutch damper system in the framework of the harmonic balance method. For the numerical analysis, a multistage clutch damper with multiple nonlinearities is modeled as a single degree-of-freedom torsional system subjected to sinusoidal excitations. The nonlinearities include piecewise-linear stiffness, hysteresis, and preload all with asymmetric transition angles. Then, the nonlinear frequency response of the system is numerically obtained by applying the Newton–Raphson method to a system equation formulated by using the harmonic balance method. The resulting nonlinear frequency response is then compared with that obtained by direct numerical simulation of the system in the time domain. Using the simulation results, the stability characteristics and existence of quasi-harmonic response of the system are investigated. Also, the effect of stiffness values on the dynamic performance of the system is examined.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Alternative Criterion for Investigation of Pitchfork Bifurcations of Limit
           Cycle in Relay Feedback Systems
    • Authors: Xu H; Wen G.
      Abstract: Relay feedback systems are strongly nonlinear due to their switching properties. Some nonlinear properties of relay feedback systems have been verified to be preferable to modern control engineering, whereas others might drive the system to be more complex or even unpredictable. An alternative criterion is proposed to investigate the pitchfork bifurcations of the limit cycle of relay feedback systems in this paper. The proposed critical criterion is explicitly formulated by the coefficients of the characteristic polynomial equation instead of the eigenvalues of the Jacobian matrix. It is more convenient and efficient for detecting the existence of this type of bifurcation than the classical critical criterion. Numerical simulations show the pitchfork bifurcation behaviors in relay feedback systems and demonstrate that the proposed criterion is a general and exact analytic method for determining pitchfork bifurcations in maps.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Control of Fractional-Order Systems Using Chatter-Free Sliding Mode
    • Authors: Pourmahmood Aghababa M.
      Abstract: The problem of stabilization of nonlinear fractional systems in spite of system uncertainties is investigated in this paper. First, a proper fractional derivative type sliding manifold with desired stability and convergence properties is designed. Then, the fractional stability theory is adopted to derive a robust sliding control law to force the system trajectories to attain the proposed sliding manifold and remain on it evermore. The existence of the sliding motion is mathematically proven. Furthermore, the sign function in the control input, which is responsible to the being of harmful chattering, is transferred into the fractional derivative of the control input. Therefore, the resulted control input becomes smooth and free of the chattering. Some numerical simulations are presented to illustrate the efficient performance of the proposed chattering-free fractional variable structure controller.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • Influence of the Fastening Modeling on the Vehicle-Track Interaction at
           Singular Rail Surface Defects
    • Authors: Zhao X; Li Z, Dollevoet R.
      Abstract: With up to 12 spring-damper groups distributed in the actual area of a rail pad, different fastening models are developed in this paper to include the nonuniform pressure distribution within a fastening system and model the constraints at the rail bottom more realistically for the purpose of high frequency dynamics between vehicle and track. Applied to a 3D transient FE model of the vehicle-track interaction, influence of the fastening modeling on the high frequency dynamic contact forces at singular rail surface defects (SRSDs) is examined. Two defect models, one is relatively large and the other is small, are employed. Such a work is of practical significance because squats, as a kind of SRSD, have become a wide spread problem. Results show that the fastening modeling plays an important role in the high frequency dynamic contact forces at SRSDs. Supports in the middle of the rail bottom, modeled as spring-damper groups located under rail web, are found to be most important. The less the rail bottom is constrained or supported, the more isolated the sleepers and substructure are from the wheel-rail interaction, and the more kinetic energy is kept in the rail after impact at a SRSD. Rolling speed is also varied to take into account its influence. Finally, based on the results of this work, influence of the service states of the fastening system on growth of relatively small SRSDs is discussed.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
  • An Approximate Solution for Period-1 Motions in a Periodically Forced van
           der Pol Oscillator
    • Authors: Luo AJ; Baghaei Lakeh A.
      Abstract: In this paper the approximate analytical solutions of period-1 motion in the periodically forced van der Pol oscillator are obtained by the generalized harmonic balance (HB) method. Such an approximate solution of periodic motion is given by the Fourier series expression, and the convergence of such an expression is guaranteed by the Fourier series theory of periodic functions. The approximate solution is different from traditional, approximate solution because the number of total harmonic terms (N) is determined by the precision of harmonic amplitude quantity level, set by the investigator (e.g., AN≤ɛ and ɛ=10-8). The stability and bifurcation analysis of the period-1 solutions is completed through the eigenvalue analysis of the coefficient dynamical systems of the Fourier series expressions of periodic solutions, and numerical illustrations of period-1 motions are compared to verify the analytical solutions of periodic motions. The trajectories and analytical harmonic amplitude spectrum for stable and unstable periodic motions are presented. The harmonic amplitude spectrum shows the harmonic term effects on periodic motions, and one can directly know which harmonic terms contribute on periodic motions and the convergence of the Fourier series expression is clearly illustrated.
      PubDate: Thu, 13 Feb 2014 00:00:00 GMT
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