• Title/Summary/Keyword: Timoshenko Theory

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A unified consistent couple stress beam theory for functionally graded microscale beams

  • Chih-Ping Wu;Zhen Huang
    • Steel and Composite Structures
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    • v.51 no.2
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    • pp.103-116
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    • 2024
  • Based on the consistent couple stress theory (CCST), we develop a unified formulation for analyzing the static bending and free vibration behaviors of functionally graded (FG) microscale beams (MBs). The strong forms of the CCST-based Euler-Bernoulli, Timoshenko, and Reddy beam theories, as well as the CCST-based sinusoidal, exponential, and hyperbolic shear deformation beam theories, can be obtained by assigning some specific shape functions of the shear deformations varying through the thickness direction of the FGMBs in the unified formulation. The above theories are thus included as special cases of the unified CCST. A comparative study between the results obtained using a variety of CCST-based beam theories and those obtained using their modified couple stress theory-based counterparts is carried out. The impacts of some essential factors on the deformation, stress, and natural frequency parameters of the FGMBs are examined, including the material length-scale parameter, the aspect ratio, and the material-property gradient index.

Forced vibration of a sandwich Timoshenko beam made of GPLRC and porous core

  • Mohammad Safari;Mehdi Mohammadimehr;Hossein Ashrafi
    • Structural Engineering and Mechanics
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    • v.88 no.1
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    • pp.1-12
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    • 2023
  • In this study, forced vibration behavior of a piezo magneto electric sandwich Timoshenko beam is investigated. It is assumed a sandwich beam with porous core and graphene platelet reinforced composite (GPLRC) in facesheets subjected to magneto-electro-elastic and temperature-dependent material properties. The magneto electro platelets are under linear function along with the thickness that includes a cosine function and magnetic and electric constant potentials. The governing equations of motion are derived using modified strain gradient theory for microstructures. The effects of material length scale parameters, temperature change, different distributions of porous, various patterns of graphene platelets, and the core to face sheets thickness ratio on the natural frequency and excited frequency of a sandwich Timoshenko beam are scrutinized. Various size-dependent methods effects such as MSGT, MCST, and CT on the natural frequency is considered. Moreover, the final results affirm that the increase in porosity coefficient and volume fractions lead to an increase in the amount of natural frequency; while vice versa for the increment in the aspect ratio. From forced vibration analysis, it is understood that by increasing the values of volume fraction and the length thickness of GPL, the maximum deflection of a sandwich beam decreases. Also, it is concluded that increasing the temperature, the thickness of GPL, and the initial force leads to a decrease in the maximum deflection of GPL. It is also shown that resonance phenomenon occurs when the natural and excitation frequencies become equal to each other. Outcomes also reveal that the third natural frequency owns the minimum value of both deflection and frequency ratio and the first natural frequency has the maximum.

A refined discrete triangular Mindlin element for laminated composite plates

  • Ge, Zengjie;Chen, Wanji
    • Structural Engineering and Mechanics
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    • v.14 no.5
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    • pp.575-593
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    • 2002
  • Based on the Mindlin plate theory, a refined discrete 15-DOF triangular laminated composite plate finite element RDTMLC with the re-constitution of the shear strain is proposed. For constituting the element displacement function, the exact displacement function of the Timoshenko's laminated composite beam as the displacement on the element boundary is used to derive the element displacements. The proposed element can be used for the analysis of both moderately thick and thin laminated composite plate, and the convergence for the very thin situation can be ensured theoretically. Numerical examples presented show that the present model indeed possesses the properties of higher accuracy for anisotropic laminated composite plates and is free of locking even for extremely thin laminated plates.

Bending and stability analysis of size-dependent compositionally graded Timoshenko nanobeams with porosities

  • Bensaid, Ismail;Guenanou, Ahmed
    • Advances in materials Research
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    • v.6 no.1
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    • pp.45-63
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    • 2017
  • In this article, static deflection and buckling of functionally graded (FG) nanoscale beams made of porous material are carried out based on the nonlocal Timoshenko beam model which captures the small scale influences. The exact position of neutral axis is fixed, to eliminate the stretching and bending coupling due to the unsymmetrical material change along the FG nanobeams thickness. The material properties of FG beam are graded through the thickness on the basis of the power-law form, which is modified to approximate the material properties with two models of porosity phases. By employing Hamilton's principle, the nonlocal governing equations of FG nanobeams are obtained and solved analytically for simply-supported boundary conditions via the Navier-type procedure. Numerical results for deflection and buckling of FG nanoscale beams are presented and validated with those existing in the literature. The influences of small scale parameter, power law index, porosity distribution and slenderness ratio on the static and stability responses of the FG nanobeams are all explored.

Development of Curved Beam Element with Shear Effect (전단효과를 고려한 곡선보 요소 개발)

  • 이석순;구정서;최진민
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.10
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    • pp.2535-2542
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    • 1993
  • Two-noded curved beam elements, CMLC (field-consistent membrane and linear curvature) and IMLC(field-inconsistent membrane and linear curvature) are developed on the basis of Timoshenko's beam theory and curvilinear coordinate. The curved beam element is developed by the separation of the radial deflection into the bending deflection. In the CMLC element, field-consistent axial strain interpolation is adapted for removing the membrane locking. The CMLC element shows the rapid and stable convergence on the wide range of curved beam radius to thickness. The field-consistent axial strain and the separation of radial deformation produces the most efficient linear element possible.

Out of Plane Free Vibrations of Circular Curved Beams (원호형 곡선보의 면외 자유진동에 관한 수치해석적 연구)

  • 이병구;오상진
    • Computational Structural Engineering
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    • v.9 no.1
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    • pp.133-139
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    • 1996
  • In this paper, an approximate method is developed to obtain the natural frequencies of the out of plane vibration of circular curved beams. The governing differential equations are derived using the dynamic equilibrium equations with the Timoshenko theory, and solved numerically. The Runge-Kutta method and Regula-Falsi method are used to integrate the differential equations and to determine the natural frequencies, respectively. In numerical examples, the hinged-hinged and clamped-clamped end constraints are considered. For each case, the four lowest natural frequencies are reported as functions of four non-dimensional system parameters.

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Free Vibration Analysis of Stepped Parabolic Arches with Timoshenko's Theory (Timoshenko 이론에 의한 불연속 변단면 포물선 아치의 자유진동 해석)

  • 오상진;진태기;모정만
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2004.05a
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    • pp.942-947
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    • 2004
  • The differential equations governing free, in-plane vibrations of stepped non-circuiar arches are derived as nondimensional forms including the effects of rotatory inertia, shear deformation and axial deformation. The governing equations are solved numerically to obtain frequencies and mode shapes. The lowest four natural frequencies and mode shapes are calculated for the stepped parabolic arches with hinged-hinged, hinged-clamped, and clamped-clamped end constraints. A wide range of arch rise to span length ratios, slenderness ratios, section ratios, and discontinuous sector ratios are considered. The effect of rotatory inertia and shear deformation on natural frequencies is reported. Typical mode shapes of vibrating arches are also presented.

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Effective Analysis of Beams and Plates using the RKPM (무요소법을 이용한 보와 판의 효과적인 해석)

  • Song, Tae-Han;Seog, Byung-Ho;Lim, Jang-Keun
    • Proceedings of the KSME Conference
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    • 2001.06a
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    • pp.680-685
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    • 2001
  • In this paper, RKPM is extended for solving moderately thick and thin structures. General Timoshenko beam and Mindlin plate theory are used far formulation. Shear locking is the main difficulty in analysis of these kinds of structures. Shear relaxation factor, which is formulated using the difference between bending and shear strain energy, is introduced to overcome shear locking. Analysis results obtained reveal that RKPM using introduced method is free of locking and very effectively applicable to deeply as well as shallowly beams and plates.

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Wave Motion of Helical Springs with a Circular Section (원형 단면을 갖는 헬리컬 스프링에 대한 파동)

  • Lee, Jae-Hyeong;Heo, Seung-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.25 no.5
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    • pp.866-873
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    • 2001
  • The governing partial differential equations of a helical spring with a circular section were derived from Frenet formulas and Timoshenko beam theory. These were solved to give the dispersion relationship between wave number and frequency along with wave form. Wave motions of helical springs are categorized by 4 regimes. In the first regime, the lower frequency area, the torsional and extensional waves of the spring are predominant and two waves are composite wave motions involving lateral motion of the coils and rotation of the coils about a horizontal axis. All waves are propagating in the second regime. The wave of the extensional motion of the spring and one wave of transverse motion of a wire change from travelling waves to near field waves in the third regime. Both waves excited by both axial and transverse motion are predominant in the fourth regime.

Elasto-Plastic Analysis of Plane Frame Structures using Timoshenko Beam Element (Timoshenko보 요소를 이용한 평면 뼈대구조의 탄-소성 해석)

  • 정동영;이정석;신영식
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2001.10a
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    • pp.327-334
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    • 2001
  • This paper presents a non-linear analysis procedure for plane frame structures by finite element formulation with assumptions of Timoshenko beam theory. Finite element displacement method based on Lagrangian formulation is used and two-noded and isoparametric line element is adopted to represent finite element model. The layered approach is used for the elasto-plastic analysis of the plane frame structures with rectangular and I cross sections. A load incremental method combined with the tangent stiffness and the initial stiffness methods for each load increment is used for the solution of non-linear equations. Numerical examples are presented to investigate the behavior and the accuracy of the elasto-plastic non-linear application and the results of this study are compared with other solutions using the concept of plastic hinge.

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