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  Subjects -> ENGINEERING (Total: 2168 journals)
    - CHEMICAL ENGINEERING (185 journals)
    - CIVIL ENGINEERING (168 journals)
    - ELECTRICAL ENGINEERING (92 journals)
    - ENGINEERING (1176 journals)
    - ENGINEERING MECHANICS AND MATERIALS (356 journals)
    - HYDRAULIC ENGINEERING (56 journals)
    - INDUSTRIAL ENGINEERING (54 journals)
    - MECHANICAL ENGINEERING (81 journals)

ENGINEERING (1176 journals)            First | 2 3 4 5 6 7 8 9 | Last

International Journal of Grid and Utility Computing     Hybrid Journal  
International Journal of Heat and Fluid Flow     Hybrid Journal   (Followers: 15)
International Journal of Heat and Mass Transfer     Hybrid Journal   (Followers: 129)
International Journal of Heavy Vehicle Systems     Hybrid Journal   (Followers: 6)
International Journal of Hypersonics     Full-text available via subscription   (Followers: 3)
International Journal of Imaging Systems and Technology     Hybrid Journal   (Followers: 2)
International Journal of Impact Engineering     Hybrid Journal   (Followers: 7)
International Journal of Information Acquisition     Hybrid Journal   (Followers: 1)
International Journal of Innovation and Applied Studies     Open Access   (Followers: 2)
International Journal of Innovation Science     Full-text available via subscription   (Followers: 6)
International Journal of Innovative Technology and Research     Open Access  
International Journal of Integrated Engineering     Open Access   (Followers: 1)
International Journal of Intelligent Engineering Informatics     Hybrid Journal  
International Journal of Intelligent Systems and Applications in Engineering     Open Access  
International Journal of Lifecycle Performance Engineering     Hybrid Journal   (Followers: 1)
International Journal of Machine Tools and Manufacture     Hybrid Journal   (Followers: 5)
International Journal of Manufacturing Research     Hybrid Journal   (Followers: 5)
International Journal of Manufacturing Technology and Management     Hybrid Journal   (Followers: 7)
International Journal of Materials and Product Technology     Hybrid Journal   (Followers: 4)
International Journal of Mathematical Education in Science and Technology     Hybrid Journal   (Followers: 7)
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: 4)
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: 5)
International Journal of Nanotechnology and Molecular Computation     Full-text available via subscription   (Followers: 3)
International Journal of Navigation and Observation     Open Access   (Followers: 8)
International Journal of Network Management     Hybrid Journal  
International Journal of Nonlinear Sciences and Numerical Simulation     Hybrid Journal  
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: 10)
International Journal of Pattern Recognition and Artificial Intelligence     Hybrid Journal   (Followers: 6)
International Journal of Pavement Engineering     Hybrid Journal   (Followers: 3)
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: 5)
International Journal of Polymer Science     Open Access   (Followers: 16)
International Journal of Precision Engineering and Manufacturing     Hybrid Journal   (Followers: 5)
International Journal of Precision Engineering and Manufacturing-Green Technology     Hybrid Journal  
International Journal of Precision Technology     Hybrid Journal  
International Journal of Pressure Vessels and Piping     Hybrid Journal   (Followers: 3)
International Journal of Production Economics     Hybrid Journal   (Followers: 13)
International Journal of Quality and Innovation     Hybrid Journal   (Followers: 4)
International Journal of Quality Assurance in Engineering and Technology Education     Full-text available via subscription   (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: 2)
International Journal of Reliability, Quality and Safety Engineering     Hybrid Journal   (Followers: 7)
International Journal of Renewable Energy Technology     Hybrid Journal   (Followers: 8)
International Journal of Robust and Nonlinear Control     Hybrid Journal   (Followers: 3)
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: 2)
International Journal of Software Engineering and Knowledge Engineering     Hybrid Journal   (Followers: 2)
International Journal of Space Science and Engineering     Hybrid Journal   (Followers: 2)
International Journal of Speech Technology     Hybrid Journal   (Followers: 4)
International Journal of Spray and Combustion Dynamics     Full-text available via subscription   (Followers: 6)
International Journal of Superconductivity     Open Access  
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: 8)
International Journal of Sustainable Engineering     Hybrid Journal   (Followers: 7)
International Journal of Sustainable Manufacturing     Hybrid Journal   (Followers: 4)
International Journal of Systems and Service-Oriented Engineering     Full-text available via subscription  
International Journal of Systems Assurance Engineering and Management     Hybrid Journal  
International Journal of Systems, Control and Communications     Hybrid Journal   (Followers: 2)
International Journal of Technoethics     Full-text available via subscription   (Followers: 1)
International Journal of Technology Management and Sustainable Development     Hybrid Journal   (Followers: 1)
International Journal of Technology Policy and Law     Hybrid Journal   (Followers: 5)
International Journal of Telemedicine and Applications     Open Access   (Followers: 2)
International Journal of Thermal Sciences     Hybrid Journal   (Followers: 7)
International Journal of Thermodynamics     Open Access   (Followers: 2)
International Journal of Turbo & Jet-Engines     Hybrid Journal  
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: 5)
International Journal of Vehicular Technology     Open Access   (Followers: 2)
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: 9)
International Review of Applied Sciences and Engineering     Full-text available via subscription  
International Scholarly Research Notices     Open Access   (Followers: 222)
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)

  First | 2 3 4 5 6 7 8 9 | Last

  Journal of Computational and Nonlinear Dynamics
  [SJR: 0.729]   [H-I: 21]   [5 followers]  Follow
    
   Full-text available via subscription Subscription journal
   ISSN (Print) 1555-1415 - ISSN (Online) 1555-1423
   Published by ASME International Homepage  [25 journals]
  • A New Generalized-Type of Synchronization for Discrete-Time Chaotic
           Dynamical Systems
    • Authors: Ouannas A.
      Abstract: In this paper, a new type of chaos synchronization in discrete-time is proposed by combining matrix projective synchronization (MPS) and generalized synchronization (GS). This new chaos synchronization type allows us to study synchronization between different dimensional discrete-time chaotic systems in different dimensions. Based on nonlinear controllers and Lyapunov stability theory, effective control schemes are introduced and new synchronization criterions are derived. Numerical simulations are used to validate the theoretical results and to verify the effectiveness of the proposed schemes.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Global Analysis of Gravity Gradient Satellite's Pitch Motion in an
           Elliptic Orbit
    • Authors: Koh D; Flashner H.
      Abstract: Pitch motion of a gravity gradient satellite in an elliptical orbit is studied. The cell mapping method is employed to find periodic solutions and analyze the global behavior of the system. Stability characteristics of the solutions are established using a point mapping approximation algorithm. The proposed approach does not depend on existence of a small parameter and, therefore, no limitations are imposed on the magnitudes of eccentricity or amplitude of motion. This is in contrast to the perturbation based approaches that require assumptions of small orbital eccentricity and small motion. As a result, stable periodic solutions of twice and three times the orbital period are found for some different eccentricities and inertia parameters. Global behavior and evolution of periodic solutions are also demonstrated using invariant surfaces and bifurcation diagrams.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Computing Schemes for Longitudinal Train Dynamics: Sequential, Parallel
           and Hybrid
    • Authors: Wu Q; Cole C.
      Abstract: Conventionally, force elements in longitudinal train dynamics (LTD) are determined sequentially. Actually, all these force elements are independent from each other, i.e., determination of each one does not require inputs from others. This independent feature makes LTD feasible for parallel computing. A parallel scheme has been proposed and compared with the conventional sequential scheme in regard to computational efficiency. The parallel scheme is tested as not suitable for LTD; computing time of the parallel scheme is about 165% of the sequential scheme on a four-CPU personal computer (PC). A modified parallel scheme named the hybrid scheme was then proposed. The computing time of the hybrid scheme is only 70% of the sequential scheme. The other advantage of the hybrid scheme is that only two processors are required, which means the hybrid scheme can be implemented on PCs.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Bifurcation Transition and Nonlinear Response in a Fractional-Order System
    • Authors: Yang JH; Sanjuán MF, Liu HG, et al.
      Abstract: We extend a typical system that possesses a transcritical bifurcation to a fractional-order version. The bifurcation and the resonance phenomenon in the considered system are investigated by both analytical and numerical methods. In the absence of external excitations or simply considering only one low-frequency excitation, the system parameter induces a continuous transcritical bifurcation. When both low- and high-frequency forces are acting, the high-frequency force has a biasing effect and it makes the continuous transcritical bifurcation transit to a discontinuous saddle-node bifurcation. For this case, the system parameter, the high-frequency force, and the fractional-order have effects on the saddle-node bifurcation. The system parameter induces twice a saddle-node bifurcation. The amplitude of the high-frequency force and the fractional-order induce only once a saddle-node bifurcation in the subcritical and the supercritical case, respectively. The system presents a nonlinear response to the low-frequency force. The system parameter and the low-frequency can induce a resonance-like behavior, though the high-frequency force and the fractional-order cannot induce it. We believe that the results of this paper might contribute to a better understanding of the bifurcation and resonance in the excited fractional-order system.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • A Novel Lattice Model on a Gradient Road With the Consideration of
           Relative Current
    • Authors: Cao J; Shi Z.
      Abstract: In this paper, a novel lattice model on a single-lane gradient road is proposed with the consideration of relative current. The stability condition is obtained by using linear stability theory. It is shown that the stability of traffic flow on the gradient road varies with the slope and the sensitivity of response to the relative current: when the slope is constant, the stable region increases with the increasing of the sensitivity of response to the relative current; when the sensitivity of response to the relative current is constant, the stable region increases with the increasing of the slope in uphill and decreases with the increasing of the slope in downhill. A series of numerical simulations show a good agreement with the analytical result and show that the sensitivity of response to the relative current is better than the slope in stabilizing traffic flow and suppressing traffic congestion. By using nonlinear analysis, the Burgers, Korteweg–de Vries (KdV), and modified Korteweg–de Vries (mKdV) equations are derived to describe the triangular shock waves, soliton waves, and kink–antikink waves in the stable, metastable, and unstable region, respectively, which can explain the phase transitions from free traffic to stop-and-go traffic, and finally to congested traffic. One conclusion is drawn that the traffic congestion on the gradient road can be suppressed efficiently by introducing the relative velocity.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Effect of Electromagnetic Actuation on Contact Loss in a Hertzian Contact
           Oscillator
    • Authors: Bichri A; Belhaq M, Perret-Liaudet J.
      Abstract: The effect of electromagnetic actuation (EMA) on the dynamic of a single-sided Hertzian contact forced oscillator is studied near primary and secondary resonances. Emphasis is put on the case where two symmetric EMAs are introduced, such that one is driven by a DC actuation and the other is actuated by AC actuation with a fast frequency. An averaging technique and a perturbation analysis are performed to obtain the frequency response of the system. It is shown that for appropriate values of AC, forced Hertzian contact systems are more likely to remain operating in the linear regime without the loss of contact near certain resonances.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • A Deflated Assembly Free Approach to Large-Scale Implicit Structural
           Dynamics
    • Authors: Mirzendehdel AM; Suresh K.
      Abstract: The primary computational bottle-neck in implicit structural dynamics is the repeated inversion of the underlying stiffness matrix. In this paper, a fast inversion technique is proposed by merging four distinct but complementary concepts: (1) voxelization with adaptive local refinement, (2) assembly-free (a.k.a. matrix-free or element-by-element) finite element analysis (FEA), (3) assembly-free deflated conjugate gradient (AF-DCG), and (4) multicore parallelization. In particular, we apply these concepts to the well-known Newmark-beta method, and the resulting AF-DCG is well-suited for large-scale problems. It can be easily ported to many-core central processing unit (CPU) and multicore graphics-programmable unit (GPU) architectures, as demonstrated through numerical experiments.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Solving Nonlinear Fractional Integro-Differential Equations of Volterra
           Type Using Novel Mathematical Matrices
    • Authors: Mirzaee F; Bimesl S, Tohidi E.
      Abstract: In this paper, the operational matrix of Euler functions for fractional derivative of order β in the Caputo sense is derived. Via this matrix, we develop an efficient collocation method for solving nonlinear fractional Volterra integro-differential equations. Illustrative examples are given to demonstrate the validity and applicability of the proposed method, and the comparisons are made with the existing results.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Fuzzy Speed Control of Networked Motion Control Systems
    • Authors: Zhang S; Zhao D, Li C, et al.
      Abstract: This paper proposed an integrated scheme for the modeling and control of induction motors in the networked environment. The networked control system (NCS) is built in hierarchical structure, which consists of a networked speed controller and a local controller. In the networked speed controller, fuzzy gain scheduling is applied to guarantee the robustness against communication constraints. Furthermore, a state predictor is designed to compensate the time delay occurred in data transmission from the sensor to the controller, as a component of the networked speed controller. Simulation and experimental results are given to illustrate the effectiveness of the proposed approach.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Nonlinear Dynamics of a Rotating Flexible Link
    • Authors: Sandeep Reddy BB; Ghosal A.
      Abstract: This paper deals with the study of the nonlinear dynamics of a rotating flexible link modeled as a one dimensional beam, undergoing large deformation and with geometric nonlinearities. The partial differential equation of motion is discretized using a finite element approach to yield four nonlinear, nonautonomous and coupled ordinary differential equations (ODEs). The equations are nondimensionalized using two characteristic velocities—the speed of sound in the material and a velocity associated with the transverse bending vibration of the beam. The method of multiple scales is used to perform a detailed study of the system. A set of four autonomous equations of the first-order are derived considering primary resonances of the external excitation and one-to-one internal resonances between the natural frequencies of the equations. Numerical simulations show that for certain ranges of values of these characteristic velocities, the slow flow equations can exhibit chaotic motions. The numerical simulations and the results are related to a rotating wind turbine blade and the approach can be used for the study of the nonlinear dynamics of a single link flexible manipulator.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • The Use of the Adjoint Method for Solving Typical Optimization Problems in
           Multibody Dynamics
    • Authors: Nachbagauer K; Oberpeilsteiner S, Sherif K, et al.
      Abstract: The present paper illustrates the potential of the adjoint method for a wide range of optimization problems in multibody dynamics such as inverse dynamics and parameter identification. Although the equations and matrices included show a complicated structure, the additional effort when combining the standard forward solver to the adjoint backward solver is kept in limits. Therefore, the adjoint method shows an efficient way to incorporate inverse dynamics to engineering multibody applications, e.g., trajectory tracking or parameter identification in the field of robotics. The present paper studies examples for both, parameter identification and optimal control, and shows the potential of the adjoint method in solving classical optimization problems in multibody dynamics.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Novel Hyperchaotic System and Its Circuit Implementation
    • Authors: Feng C; Cai L, Kang Q, et al.
      Abstract: It is very important to generate hyperchaos with more complicated dynamics as a model for theoretical research and practical application. A new hyperchaotic system with double piecewise-linear functions in state equations is presented and physically implemented by circuit design. Based on the theoretical analyses and simulations, the hyperchaotic dynamical properties of this nonlinear system are revealed by equilibria, Lyapunov exponents, and bifurcations, verifying its unusual random nature and indicating its great potential for some relevant engineering applications such as secure communications.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Stability Analysis of Sliding–Grazing Phenomenon in Dry-Friction
           Oscillator Using Takagi–Sugeno Fuzzy Approach
    • Authors: Mehran K; Zahawi B, Giaouris D, et al.
      Abstract: Dry-friction oscillators are mechanical systems with dry friction and stick-slip vibrations. In the context of control theory, the stability analysis of this type of dynamical systems is important since they exhibit nonsmooth bifurcations, or most famously a sliding–grazing bifurcation inducing abrupt chaos. This paper develops a Lyapunov-based framework to study the so-called structural stability of the system, predicting the onset of such unique bifurcations. To achieve this, the nonlinear system is first represented as a nonsmooth Takagi–Sugeno (TS) fuzzy model, and the structural stability is then formulated as linear matrix inequalities (LMI) feasibility problems with less conservative formulation. Solving the resulting LMI problem, the onset of sliding–grazing bifurcation can be accurately predicted.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Accuracy and Computational Efficiency of Finite Element Models for Low
           Velocity Impact on Composite Structures Subject to Progressive Damage and
           Delamination 1
    • Authors: Ibrahim AA; Yigit AS.
      Abstract: There has been growing interest to use composites in load carrying structures where high strength and light weight are of major concern, e.g., oil industry (offshore structures and platforms, pipe systems, and tubings), sports equipment, automobiles, and aircraft industries. Despite extensive research in the last two decades, mechanical behavior of composite structures subject to contact and impact loading is still not well understood. It is well known that composites are highly vulnerable to various modes of failure and damage due to impact by foreign objects. Such impact events are not only dependent on the material behavior but also on the dynamics of the structure. Finite element (FE) packages are capable of simulating impact response of composite structures subject to impact. It requires extensive training and in-depth knowledge to obtain an adequate FE model with proper impact response prediction and acceptable computational efficiency. Limited FE models have the ability to capture composite damage due to impact when internal delamination or fiber/matrix failures are present. Severe nonlinearities are encountered during FE analysis to capture composite damage progression or material degradation. This work investigates different FE modeling approaches by analyzing their prediction of force–time history and force–indentation curve occurring in composite plates as a result of low velocity impact. The objective is to provide guidelines on selecting the most appropriate approach for a given impact situation. Moreover, a computationally efficient approach in contact modeling is presented. The proposed approach yields better computation efficiency for contact modeling on both isotropic and composite materials.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Continuous Galerkin Petrov Time Discretization Scheme for the Solutions of
           the Chen System
    • Authors: Hussain SS; Salleh ZZ.
      Abstract: In this paper, the continuous Galerkin Petrov time discretization (cGP) scheme is applied to the Chen system, which is a three-dimensional system of ordinary differential equations (ODEs) with quadratic nonlinearities. In particular, we implement and analyze numerically the higher order cGP(2)-method which is found to be of fourth order at the discrete time points. A numerical comparison with classical fourth-order Runge–Kutta (RK4) is given for the presented problem. We look at the accuracy of the cGP(2) as the Chen system changes from a nonchaotic system to a chaotic one. It is shown that the cGP(2) method gains accurate results at larger time step sizes for both cases.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Galerkin Approximations for Stability of Delay Differential Equations With
           Time Periodic Delays
    • Authors: Sadath A; Vyasarayani CP.
      Abstract: In this paper, we develop Galerkin approximations for determining the stability of delay differential equations (DDEs) with time periodic coefficients and time periodic delays. Using a transformation, we convert the DDE into a partial differential equation (PDE) along with a boundary condition (BC). The PDE and BC we obtain have time periodic coefficients. The PDE is discretized into a system of ordinary differential equations (ODEs) using the Galerkin method with Legendre polynomials as the basis functions. The BC is imposed using the tau method. The resulting ODEs are time periodic in nature; thus, we resort to Floquet theory to determine the stability of the ODEs. We show through several numerical examples that the stability charts obtained from the Galerkin method agree closely with those obtained from direct numerical simulations.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Energy Storage and Loss in Fractional-Order Systems
    • Authors: Hartley TT; Trigeassou J, Lorenzo CF, et al.
      Abstract: As fractional-order systems are becoming more widely accepted and their usage is increasing, it is important to understand their energy storage and loss properties. Fractional-order operators can be implemented using a distributed state representation, which has been shown to be equivalent to the Riemann–Liouville representation. In this paper, the distributed state for a fractional-order integrator is represented using an infinite resistor–capacitor network such that the energy storage and loss properties can be readily determined. This derivation is repeated for fractional-order derivatives using an infinite resistor–inductor network. An analytical example is included to verify the results for a half-order integrator. Approximation methods are included.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • A Simple Absolute Nodal Coordinate Formulation for Thin Beams With Large
           Deformations and Large Rotations
    • Authors: Ren H.
      Abstract: A simple but effective formulation of beams with large deformation and large rotation is derived from the principles of continuum mechanics. Proper assumptions are imposed, and the beam strain tensors are formulated from the Green strain tensors. The mass matrix is constant, and the elastic forces and the stiffness matrix entries are polynomials of the generalized coordinates, so numerical quadratures are not required in each time step of simulation, which makes the current approach much more superior in numerical efficiency than other formulations. The shape of the cross sections can be arbitrary, either uniform or nonuniform, and the beam can be either straight or curved. The generalized free of traction assumption ensures the strains in the cross section and the beam strains are independent, which resolves the Possion's locking issue and renders this approach can be accurately applied to general composite material beams. The elastic line approach (ELA) in the absolute nodal coordinate formulation (ANCF) can be derived from the current formulation.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Experimental Validation of a Mechanistic Multibody Model of a Vertical
           Piano Action
    • Authors: Masoudi R; Birkett S.
      Abstract: The validity and accuracy of a high-fidelity mechanistic multibody model of a vertical piano action mechanism is examined experimentally and through simulation. An overview of the theoretical and computational framework of this previously presented model is given first. A dynamically realistic benchtop prototype mechanism was constructed and driven by a mechanical actuator pressing the key. For simulations, a parameterization based on geometric and dynamic component properties and configuration is used; initial conditions are established by a virtual regulation that mimics a piano technician's procedure. The motion of each component is obtained experimentally by high-speed imaging and automated tracking. Simulated response is shown to accurately represent that of the real action for two different (pressed) key inputs using a single fixed parameterization. Various specialized model features are separately evaluated. Proper simulated dynamic behavior supports the accuracy of the friction representation; this is especially so for softer key inputs which demand a more actively controlled playing technique. The accuracy of the contact model is confirmed by the proper timing and function of the mechanism, as the relationship between components is strongly dependent on the state of compression of the interface between them. The value of including three flexible components is weighed against their significant computational cost. Compared to a rigid fixed ground point target, hammer impact on a compliant string reduces impact force, contact duration, and postimpact hammer velocity to improve accuracy. Flexibility of the backcheck wire and hammer shank also strongly affects postimpact behavior of the mechanism. The sophisticated balance pivot model is seen to be valuable in creating a realistic key response, with compression of felt balance punching and lift-off of the key, very important for achieving the proper key–hammer relationship. Finally, two components unique to the vertical mechanism—the bridle strap and butt spring—are shown to be essential in controlling the hammer for detached key inputs, where the key is released before it has reached the front punching. Accurate postimpact response is important for proper simulation of repeated notes, as well as the “feel” of the action. In general, the results reported can be considered as a validation of the method for constructing and parameterizing a dynamically accurate multibody model of a specific prototype mechanism or system including compliant contacts and flexibility of some components, as well as ad hoc components to cover unusual dynamic behavior.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Mixed-Coordinate ANCF Rectangular Plate Finite Element
    • Authors: Yu Z; Shabana AA.
      Abstract: Higher order finite elements (FEs) based on the absolute nodal coordinate formulation (ANCF) may require the use of curvature vectors as nodal coordinates. The curvature vectors, however, can be difficult to define at the reference configuration, making such higher order ANCF FEs less attractive to use. It is the objective of this investigation to use the concept of the mixed-coordinate ANCF FEs to ensure that the gradient vectors are the highest spatial derivatives in the element nodal coordinate vector regardless of the order of the interpolating polynomials used. This concept is used to convert the curvature vectors to nodes, called position nodes, which have only position coordinates. These new position nodes can be defined at a preprocessing stage, leading to two different sets of nodes: one set of nodes has position and gradient coordinates, while the second set of nodes has position coordinates only. The new position nodes can be used to obtain better distribution of the forces, including contact forces. Higher degree of continuity, including curvature continuity, can still be achieved at the element interface by using, at a preprocessing stage, linear algebraic equations that can reduce significantly the model dimension and ensure higher degree of smoothness. The procedure proposed in this investigation also allows for the formulation of mechanical joints at arbitrary points and nodes using linear algebraic constraint equations. The difficulties that arise when formulating these joint constraints using B-spline and NURBS (Nonuniform Rational B-Splines) representations are discussed. In order to explain the concepts introduced in this paper, low and high order ANCF thin plate elements are used. For the high order thin plate element, the curvature vectors at the interface nodes are converted to internal nodes with position coordinates only, leading to a mixed-coordinate ANCF thin plate element. This element preserves the desirable ANCF features including a constant mass matrix and zero Coriolis and centrifugal forces. Kirchhoff plate theory is used to formulate the element elastic forces. The equations of motion of the structure are formulated in terms of an independent set of structure coordinates. The resulting mass matrix associated with the independent coordinates remains constant. Numerical examples are presented in order to demonstrate the use of the mixed-coordinate ANCF thin plate element when the continuity constraints are imposed.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Fractional Derivative Constitutive Models for Finite Deformation of
           Viscoelastic Materials
    • Authors: Fukunaga M; Shimizu N.
      Abstract: A methodology to derive fractional derivative constitutive models for finite deformation of viscoelastic materials is proposed in a continuum mechanics treatment. Fractional derivative models are generalizations of the models given by the objective rates. The method of generalization is applied to the case in which the objective rate of the Cauchy stress is given by the Truesdell rate. Then, a fractional derivative model is obtained in terms of the second Piola–Kirchhoff stress tensor and the right Cauchy-Green strain tensor. Under the assumption that the dynamical behavior of the viscoelastic materials comes from a complex combination of elastic and viscous elements, it is shown that the strain energy of the elastic elements plays a fundamental role in determining the fractional derivative constitutive equation. As another example of the methodology, a fractional constitutive model is derived in terms of the Biot stress tensor. The constitutive models derived in this paper are compared and discussed with already existing models. From the above studies, it has been proved that the methodology proposed in this paper is fully applicable and effective.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
  • Aeroelastic Tailoring of Helicopter Blades
    • Authors: Cornette D; Kerdreux B, Michon G, et al.
      Abstract: The dynamic loads transmitted from the rotor to the airframe are responsible for vibrations, discomfort and alternate stress on components. A new and promising way to minimize vibration is to reduce dynamic loads at their source by performing an aeroelastic optimization of the rotor. This optimization uses couplings between the flapwise-bending motion and the torsion motion. The impacts of elastic couplings (composite anisotropy) and inertial couplings (center-of-gravity offset) on blade dynamic behavior and on dynamic loads are evaluated in this paper. First, analytical results, based on a purely linear modal approach, are given to understand the influence of these couplings on blade dynamic behavior. Then, a complete nonlinear aeroelastic model of the rotor, including elastic and inertial couplings, is derived. Finally, this last model is used to improve a simplified but representative blade (homogeneous beam with constant chord) and results are presented.
      PubDate: Sun, 01 Nov 2015 00:00:00 GMT
       
 
 
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