The Experts below are selected from a list of 57 Experts worldwide ranked by ideXlab platform

Haiyang Li - One of the best experts on this subject based on the ideXlab platform.

  • extended static modeling and analysis of compliant compound parallelogram mechanisms considering the initial Internal Axial Force
    Journal of Mechanisms and Robotics, 2016
    Co-Authors: Haiyang Li
    Abstract:

    Extended nonlinear analytical modeling and analysis of compound parallelogram mechanisms are conducted in this paper to consider the effect of the initial Internal Axial Force. The nonlinear analytical model of a compound basic parallelogram mechanism (CBPM) is first derived incorporating the initial Internal Axial Force. The stiffness equations of compound multibeam parallelogram mechanisms (CMPMs) are then followed. The analytical maximal stress under the primary actuation Force only is also derived to determine the maximal primary motion (motion range). The influence of initial Internal Axial Forces on the primary motion/stiffness is further quantitatively analyzed by considering different slenderness ratios, which can be employed to consider active displacement preloading control and/or thermal effects. The criterion that the primary stiffness may be considered “constant” is defined and the initial Internal Axial Force driven by a temperature change is also formulated. A physical preloading system to control the initial Internal Axial Force is presented and testing results of the object CBPM are compared with theoretical ones.

  • Extended Nonlinear Analysis of Exactly-Constrained Compliant Compound Parallelogram Mechanisms
    Volume 5A: 39th Mechanisms and Robotics Conference, 2015
    Co-Authors: Haiyang Li, George Joseph
    Abstract:

    Extended nonlinear analysis of compliant compound parallelogram mechanisms is conducted in this paper. The analytical nonlinear model of a compound basic parallelogram mechanism (CBPM) is first derived incorporating the initial Internal Axial Force. The stiffness equations of compound multi-beam parallelogram mechanisms (CMPMs) are then followed. The effect of initial Internal Axial Forces on the primary motion is further analyzed, which can be employed to consider active displacement preloading control and thermal effects etc. It is shown that negative initial Internal Axial Force will reduce the primary stiffness, and vice versa. The criteria for which the primary stiffness may be considered “constant” is defined and the initial Internal Axial Force driven by temperature change is also formulated. The dynamic analysis of a CMPM using nonlinear finite element analysis (FEA) is finally carried out to show the modal frequency and the Forced excitation response in the primary motion direction.Copyright © 2015 by ASME

Jacek Przybylski - One of the best experts on this subject based on the ideXlab platform.

  • Shape enhancement of an eccentrically loaded column using piezoelectric actuator
    Engineering Structures, 2019
    Co-Authors: Jacek Przybylski, Krzysztof Kuliński
    Abstract:

    Abstract The stability and prebuckling enhancement of a cantilever column composed of two parallel members and subjected to a dead or partially follower load is discussed. The members are made of different materials: aluminium for the host column and a piezoceramic material for the auxiliary rod. The presence of the piezoceramic rod, offset from the centroidal axis of the host column, makes it possible to study the influence of actuation on the Internal Axial Force distribution and the diminution of the undesirable flexural displacement appearing as a result of accidental external load eccentricity. The principle of stationary value potential energy is employed to formulate a problem in which the electro-mechanical coupling is expressed in constitutive equations of the actuator's material. Nonlinear terms, which allow for the interaction of the developed in-plane Force with the out-of-plane displacements, are included in the derived equilibrium equations. The numerical results are compared to those for an uniAxial system to show that the offset distance of the actuating rod has a large impact on the behaviour of the system. It is shown that while piezoelectric actuation cannot increase the critical buckling load due to limitations resulting from the risk of material depolarization, it does have a great impact on the flexural deflection of the column. Exemplary modification of the lateral deflection resulting from representative loads characterized by opposite eccentricities are studied for increasing actuation to prove that it is possible to either minimize bending or to straighten the host column. The presented configuration may be used as an efficient tool for controlling the prebuckling response resulting from accidental load eccentricity or alternatively may be applied as a piezoelectric bender to precisely position its free end. The formulation and solution method may be extended to dynamics and vibration analyses for the actuating rod - host column system.

  • Static and dynamic analysis of a flextensional transducer with an Axial piezoelectric actuation
    Engineering Structures, 2015
    Co-Authors: Jacek Przybylski
    Abstract:

    Abstract The objective of this paper is to describe the mathematical modelling and numerical testing of the static behaviour and natural frequency of a flexure hinge transducer. The actuator is constructed of two parallel beams mounted by stiff links with an offset to a piezoceramic rod. A monolithic hinge lever mechanism is applied by cutting constricted hinges at the links to generate and magnify the in-plane displacement created by the application of a voltage to the piezorod. This mechanism enables the piezoelectric transducers to amplify displacement efficiently. A non-linear analytical model of the actuator is developed on the basis of Hamilton’s principle and solved with use of the perturbation method. During the numerical analysis, the static deflection and Internal Axial Force generated by the electric field application are determined by changing actuator properties such as the distance between the beams and the rod as well as the stiffness of the constricted hinges. It is shown that for the flextensional actuator with a very high flexibility of constricted hinges, the generated transverse displacement is limited by the maximum electric field as the characteristic property for each piezoceramic material. In the dynamic analysis, the fundamental vibration frequency and the adequate modes are studied in relation to the piezoelectric Force. The natural vibration frequency, affected by the piezoelectric Force, also depends on the stiffness of the beam supports, the matched beam and rod materials, the ratio of the cross section of the rod to the beam and the direction of the electric field.

  • Piezoelectric control of the static behaviour of flextensional actuators with constricted hinges
    Smart Materials and Structures, 2014
    Co-Authors: Jacek Przybylski
    Abstract:

    The objective of this paper is to present the mathematical modelling and computational testing of the static operational performance and effectiveness of flextensional actuators comprised of two rectilinear or initially deflected beams placed equidistantly from a centrally located piezoceramic stack in the form of a rod. The beams are mounted by stiff links with an offset to a piezoelectric transformer. A monolithic hinge lever mechanism is applied by cutting constricted hinges at the links to generate and magnify the in-plane displacement created by the application of a voltage to the piezorod. Structures of such a type have been commonly used as passive or active actuators since the manufacturing of the mechanism’s prototypes in the form of Moonie or cymbal actuators. An analytical model of the actuator is developed on the basis of stationary values of the total potential energy principle with the use of the von Karman non-linear strains theory. During the numerical computations, the deflection and Internal Axial Force generated by both the externally distributed load and the the application of an electric field are determined by changing the actuator properties such as the distance between the beams and the rod, the amplitude of the beam’s initial displacement as well as the stiffness of the constricted hinges. Additionally, the application of structure prestressing is considered to avoid an undesired stretching of the piezo stack. It has been shown that for the flextensional actuator with a very high flexibility of constricted hinges, the generated transverse displacement is limited by the maximum electric field as the characteristic property for each piezoceramic material. A vast number of numerical results exhibit the mechanical responses of the transducer of different geometrical and physical properties to piezoelectric stimulation; this has potential applications in the design process of such actuators.

Jun-hyeok Choi - One of the best experts on this subject based on the ideXlab platform.

  • Approximate Analysis of Simply Supported Composite Beams with Partial Interaction
    Advances in Structural Engineering, 2020
    Co-Authors: Jun-hyeok Choi
    Abstract:

    An approximate analysis method was presented for the analysis and design of a simply supported composite beam with partial interaction. To solve the governing differential equation in linear elastic partial interaction theory, the Internal Axial Force was approximated by Fourier series. In case studies, the Internal Axial Force, slip and displacement of the beam were obtained for some load cases such as temperature load, end moment, point load and uniformly distributed load. From the study for convergence of the approximate solution, the relative error for the displacement was converged below about 0.1% at more than the fifth order of Fourier series. This method can be applied to arbitrary loading conditions. Also, the results are sufficiently accurate for determining the behavior of the composite beam with partial interaction for the design purpose.

  • Approximate analysis method for composite beams with partial interaction using Fourier series
    International Journal of Steel Structures, 2013
    Co-Authors: Young-hoon Park, Jun-hyeok Choi
    Abstract:

    This paper presents an alternate analysis method for calculating the deflection and Internal Forces for arbitrary boundary and loading conditions of composite beams with partial interaction. The Internal Axial Force was approximated by the Fourier series to solve the governing equation of composite beam. Then, the coefficients of the Fourier series were determined using the Euler-Lagrange equation of minimizing a definite integral. An evaluation of the convergence and the accuracy for the proposed method in the determination of the deflection for four types of boundary conditions with four types of loading cases was made. The results were agreed with those obtained by other analytical methods. The displacement of the partial composite beam depends on the stiffness of shear connectors, boundary conditions and loading conditions.

George Joseph - One of the best experts on this subject based on the ideXlab platform.

  • Extended Nonlinear Analysis of Exactly-Constrained Compliant Compound Parallelogram Mechanisms
    Volume 5A: 39th Mechanisms and Robotics Conference, 2015
    Co-Authors: Haiyang Li, George Joseph
    Abstract:

    Extended nonlinear analysis of compliant compound parallelogram mechanisms is conducted in this paper. The analytical nonlinear model of a compound basic parallelogram mechanism (CBPM) is first derived incorporating the initial Internal Axial Force. The stiffness equations of compound multi-beam parallelogram mechanisms (CMPMs) are then followed. The effect of initial Internal Axial Forces on the primary motion is further analyzed, which can be employed to consider active displacement preloading control and thermal effects etc. It is shown that negative initial Internal Axial Force will reduce the primary stiffness, and vice versa. The criteria for which the primary stiffness may be considered “constant” is defined and the initial Internal Axial Force driven by temperature change is also formulated. The dynamic analysis of a CMPM using nonlinear finite element analysis (FEA) is finally carried out to show the modal frequency and the Forced excitation response in the primary motion direction.Copyright © 2015 by ASME

Jin S. Chung - One of the best experts on this subject based on the ideXlab platform.

  • 3-D responses of vertical pipe bottom pin-joined to a horizontal pipe to ship motion and thrust on pipe: Part I: MSE and FEM modeling
    1999
    Co-Authors: Jin S. Chung, B. Cheng
    Abstract:

    The present entire pipe system consists of a very long vertical pipe with elastic joints, pin-joining the buffer (mass) at its bottom end to a much shorter horizontal pipe. Opposite end of the horizontal pipe is pin-joined to a vehicle maneuvering on the seafloor, and it can be subject to the planar (x, y) motion of the seafloor vehicle. The motion of the horizontal pipe can be restrained by the motion of the seafloor vehicle, requiring more elaborate computational modeling of the joints and the entire pipe system. Thrust vectors are applied to the elastic joints on the vertical pipe and the pin joints of the horizontal pipe. Elastic joints on the vertical pipe were previously modeled by 2 computational methods: the mass-spring elements (MSE) and finite elements (FEM). As the pin joint allows the horizontal pipe to rotate about the vertical axis, the entire pipe system has one zero eigenvalue associated with the rigid-body modes. Thus, the shift technique is utilized to solve the zero-eigenvalue problem. Moreover, the weight, generating the Internal Axial Force of the vertical pipe, influences the eigenvalues of the entire system. Preliminary results indicate that the accuracy and advantages of the MSE modeling over FEM are more obvious for the entire system than for the previous vertical pipe system alone, and the two models are compared with numerical examples in Part II.

  • Effects of Elastic Joints On 3-D Nonlinear Responses of a Deep-Ocean Pipe: Modeling And Boundary Conditions
    International Journal of Offshore and Polar Engineering, 1996
    Co-Authors: Jin S. Chung, Bao-rong Cheng
    Abstract:

    Pipe vibration is often excited in the deep ocean by ship motions, wave Forces and vortex shedding. Elastic joints along the pipe are modeled in an attempt to move the resonance frequencies away from the pipe system. The numerical examples focus on the investigation of single and multiple elastic joints along a long pipe and their effect on three-dimensional (3-D) nonlinear coupled pipe responses, including torsional coupling. The multi-substructure technique is introduced in order to get the governing equation of the entire pipe system. The pipe is subjected to a vertically varying current flow in establishing the static equilibrium configuration. Dynamic responses are excited by large-amplitude horizontal as well as vertical ship or pipe-top motion. Ocean-mining pipes 4,000 ft and 18,000 ft in length are used to investigate the effects of the joint stiffness and position on the pipe responses. The bending stiffness can affect the bending moments along the pipe and the associated maximum values, but has little influence on the bending deflection. However, the Axial stiffness of the joint can greatly change the Axial fundamental frequency, as well as static Axial displacement, while it has little effect on the static Internal Axial Force. The appropriate position of joints can have a greater influence on the static responses. The dynamic responses to the external excitation of a pipe with multiple elastic joints can be greatly reduced. The results are presented for both free and pinned bottom-end conditions of the pipe.