• Geomechanics and Engineering
• /
• v.33 no.5
• /
• pp.427-437
• /
• 2023

The objective of this work is to study the wave propagation of an FGM plate via a new integral inverse shear model with temperature-dependent material properties. In this contribution, a new model based on a high-order theory field of displacement is included by introducing indeterminate integral variables and inverse co-tangential functions for the presentation of shear stress. The temperature-dependent properties of the FGM plate are assumed mixture of metal and ceramic, and its properties change by the power functions of the thickness of the plate. By applying Hamilton's principle, general formulas of wave propagation were obtained to plot the phase velocity curves and wave modes of the FGM plate with simply supported edges. The effects of the temperature and volume fraction by distributions on wave propagation of the FGM plate are investigated in detail. The results of the dispersion and the phase velocity curves of the propagation wave in the functionally graded plate are compared with previous research.

• Smart Structures and Systems
• /
• v.11 no.2
• /
• pp.135-161
• /
• 2013

This work presents a test platform for the assessment and benchmarking of modern actuators which have been specifically developed for the new field and service robotics applications. This versatile platform has been designed for the comparative analysis of actuators of dissimilar technology and operating conditions. It combines a modular design to adapt to linear and rotational actuators of different sizes, shapes and functions, as well as those with different load capacities, power and displacement. This test platform emulates the kinematics of robotic joints while an adaptive antagonist-load actuator allows reproducing the variable dynamic loads that actuators used in real robotics applications will be subjected to. A data acquisition system is used for monitoring and analyzing test actuator performance. The test platform combines hardware and software in the loop to allow actuator performance characterization. The use of the proposed test platform is demonstrated through the characterization and benchmarking of three controllable impedance actuators recently being incorporated into modern robotics.

• Earthquakes and Structures
• /
• v.26 no.2
• /
• pp.163-174
• /
• 2024

Dynamic equilibrium equations for finite element analysis were derived for the free field one-dimensional shear wave propagation through the horizontally layered soil deposits with the elastic half-space. We expressed Rayleigh's viscous damping consisting of mass and stiffness proportional terms. We considered two cases where damping matrices are defined in the total and relative displacement fields. Two forms of equilibrium equations are presented; one in terms of total motions and the other in terms of relative motions. To evaluate the performance of new equilibrium equations, we conducted two sets of site response analyses and directly compared them with the exact closed-form frequency domain solution. Results show that the base shear force as earthquake load represents the simpler form of equilibrium equation to be used for the finite element method. Conventional finite element procedure using base acceleration as earthquake load predicts exact solution reasonably well even in soil deposits with unrealistically high damping.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.10 no.4
• /
• pp.337-347
• /
• 2008

Critical strain is a new material property of the ground. Critical strain concept which was established in tunnel engineering can be applied to deformation limits in the ground due to tunneling by using the measured displacement at the tunnel construction site. In this study, quantitative evaluations for the tunnel stability are conducted by analysing the displacement results obtained at the construction field. Especially, critical stain concept was reviewed from a total displacement point of view using the displacements occurring before excavation. As a results, the variation characteristics of the tunnel stability are presented on the critical strain diagram with or without the preceeding displacements.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.5 no.2
• /
• pp.19-25
• /
• 1985

By the combined use of reduced integration and addition of nonconforming displacement modes, a highly effective new plate element has been established. The displacement field of this element was formed by adding nonconforming modes only to transverse displacement component of Ahmad-Irons' element and the element matrices are computed by the numerical integrations with modified orders. Comparing with other elements, the superiority of the both NC 8-4.1 and NC 8-5.1 elements over the elements previously studied has been observed. The solutions with these elements converge to the true solutions very rapidly as the mesh is refined. These elements are also shown to be applicable to the wide range of thick and very thin plate problems.

• Geomechanics and Engineering
• /
• v.16 no.2
• /
• pp.141-150
• /
• 2018

In this current work a quasi 3D "trigonometric shear deformation theory" is proposed and discussed for the dynamic of thick orthotropic plates. Contrary to the classical "higher order shear deformation theories" (HSDT) and the "first shear deformation theory" (FSDT), the constructed theory utilizes a new displacement field which includes "undetermined integral terms" and presents only three "variables". In this model the axial displacement utilizes sinusoidal mathematical function in terms of z coordinate to introduce the shear strain impact. The cosine mathematical function in terms of z coordinate is employed in vertical displacement to introduce the impact of transverse "normal deformation". The motion equations of the model are found via the concept of virtual work. Numerical results found for frequency of "flexural mode", mode of shear and mode of thickness stretch impact of dynamic of simply supported "orthotropic" structures are compared and verified with those of other HSDTs and method of elasticity wherever considered.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.3
• /
• pp.222-227
• /
• 2006

RAINBOW(Reduced And Internally Biased Oxide Wafers) are a new class of high-displacement, piezoelectric actuator produced by selectively removing oxygen from one surface of ceramic using a high-temperature chemical reduction process. In this paper, RAINBOW actuator materials of $0.4Pb(Ni_{1/3}Nb_{2/3})O_3-0.6Pb(Zr_{x}Ti_{1-x})O_3$ ceramics were prepared. Its dielectric and piezoelectric properties were investigated in the vicinity of MPB. The piezoelectric properties showed the maximum value of ${\epsilon}r$ = 4871, $d_{33}$ = 610 ($10^{-12}$ m/V), $d_{31}$ = -299 ($10^{-12}$ m/V), $k_{33}$ = $71\%$, Qm = 70, in $0.4Pb(Ni_{1/3}Nb_{2/3})O_{3}-0.6Pb(Zr_{405}Ti_{595})O_3$ composition sintered at $1250^{\circ}C$. The strain - electric field characteristics of RAINBOW actuator were significantly improved comparison with the conventional bulk actuator. The prepared RAINBOW actuator showed about $390\;{\mu}m/100\;V$ displacement.

• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.51 no.9
• /
• pp.455-463
• /
• 2002

Ionic Polymer metal composite(IPMC), one of new actuation materials of EAPs is fabricated by electroless plating of platinum on both sides of the perfluorosulfonic acid film or Nafion film and its electromechanical characteristics are investigated. The IPMC strip bends towards anode under electrical field. As the number of plating cycle increases, the distance between plated platinum electrodes on both sides of Nafion membrane decreases and also the displacement is almost inversely proportional to the number of plating. The displacement of IPMC strip depends on voltage magnitude and applied signal frequency and its maximum deformation is observed at a critical frequency, resonant frequency. Low pressure sandblasting is used for surface treatment of Nafion membrane and at 8 times of plating cycle produced actuator with high displacement performance. For more efficiency of fabricated IPMC, it is useful to add one or two surface developing step which is the second reduction process using hydrazine.

• Structural Engineering and Mechanics
• /
• v.71 no.5
• /
• pp.469-483
• /
• 2019

In this paper, an improved mathematical model is presented for the bending analysis of doubly curved functionally graded material (FGM) sandwich rhombic conoids. The mathematical model includes expansion of Taylor's series up to the third degree in thickness coordinate and normal curvatures in in-plane displacement fields. The condition of zero-transverse shear strain at upper and lower surface of rhombic conoids is implemented in the present model. The newly introduced feature in the present mathematical model is the simultaneous inclusion of normal curvatures in deformation field and twist curvature in strain-displacement equations. This unique introduction permits the new 2D mathematical model to solve problems of moderately thick and deep doubly curved FGM sandwich rhombic conoids. The distinguishing feature of present shell from the other shells is that maximum transverse deflection does not occur at its center. The proposed new mathematical model is implemented in finite element code written in FORTRAN. The obtained numerical results are compared with the results available in the literature. Once validated, the current model was employed to solve numerous bending problems by varying different parameters like volume fraction indices, skew angles, boundary conditions, thickness scheme, and several geometric parameters.

• Smart Structures and Systems
• /
• v.29 no.3
• /
• pp.395-420
• /
• 2022

A new hybrid quasi-3D and 2D high-order shear deformation theory is studied in this mathematical formulation, for an investigation of the bending, free vibrations and buckling influences on a functionally graded material plate. The theoretical formulation has been begun by a displacement field of five unknowns, governing the transverse displacement across the thickness of the plate by bending, shearing and stretching. The transverse shear deformation effect has been taken into consideration, satisfying the stress-free boundary conditions, especially on plate free surfaces as parabolic variation through its thickness. Thus, the mechanical properties of the functionally graded plate vary across the plate thickness, following three distributions forms: the power law, exponential form and the Mori-Tanaka scheme. The mechanical properties are used to develop the equations of motion, obtained from the Hamilton principle, and solved by applying the Navier-type solution for simply supported boundary conditions. The results obtained are compared with other solutions of 2D, 3D and quasi-3D plate theories have been found in the literature.