Stiffness matrix of thin-walled curved beam for spatially coupled stability analysis

2008 ◽  
Vol 50 (4) ◽  
pp. 788-803 ◽  
Author(s):  
Nam-Il Kim ◽  
Young-Suk Park ◽  
Chung C. Fu ◽  
Moon-Young Kim
Keyword(s):  
Stability Analysis ◽  
Stiffness Matrix ◽  
Curved Beam ◽  
Thin Walled

Stiffness of Cable-based Parallel Manipulators With Application to Stability Analysis

2005 ◽  
Vol 128 (1) ◽  
pp. 303-310 ◽  
Author(s):  
Saeed Behzadipour ◽  
Amir Khajepour
Keyword(s):  
Stability Analysis ◽  
Trajectory Planning ◽  
Stiffness Matrix ◽  
Sufficient Conditions ◽  
Parallel Manipulators ◽  
Rotational Stiffness ◽  
New Approach ◽  
Cable Forces

The stiffness of cable-based robots is studied in this paper. Since antagonistic forces are essential for the operation of cable-based manipulators, their effects on the stiffness should be considered in the design, control, and trajectory planning of these manipulators. This paper studies this issue and derives the conditions under which a cable-based manipulator may become unstable because of the antagonistic forces. For this purpose, a new approach is introduced to calculate the total stiffness matrix. This approach shows that, for a cable-based manipulator with all cables in tension, the root of instability is a rotational stiffness caused by the internal cable forces. A set of sufficient conditions are derived to ensure the manipulator is stabilizable meaning that it never becomes unstable upon increasing the antagonistic forces. Stabilizability of a planar cable-based manipulator is studied as an example to illustrate this approach.

Geometrical Stiffness of Thin-Walled I-Beam Element Based on Rigid-Beam Assemblage Concept

2012 ◽  
Vol 28 (1) ◽  
pp. 97-106 ◽  
Author(s):  
J. D. Yau ◽  
S.-R. Kuo
Keyword(s):  
Stiffness Matrix ◽  
Virtual Work ◽  
Bending Moment ◽  
Beam Element ◽  
Narrow Beam ◽  
Cross Sectional ◽  
Geometric Stiffness ◽  
Buckling Behavior ◽  
Post Buckling ◽  
Thin Walled

ABSTRACTUsing conventional virtual work method to derive geometric stiffness of a thin-walled beam element, researchers usually have to deal with nonlinear strains with high order terms and the induced moments caused by cross sectional stress results under rotations. To simplify the laborious procedure, this study decomposes an I-beam element into three narrow beam components in conjunction with geometrical hypothesis of rigid cross section. Then let us adopt Yanget al.'s simplified geometric stiffness matrix [kg]12×12of a rigid beam element as the basis of geometric stiffness of a narrow beam element. Finally, we can use rigid beam assemblage and stiffness transformation procedure to derivate the geometric stiffness matrix [kg]14×14of an I-beam element, in which two nodal warping deformations are included. From the derived [kg]14×14matrix, it can take into account the nature of various rotational moments, such as semi-tangential (ST) property for St. Venant torque and quasi-tangential (QT) property for both bending moment and warping torque. The applicability of the proposed [kg]14×14matrix to buckling problem and geometric nonlinear analysis of loaded I-shaped beam structures will be verified and compared with the results presented in existing literatures. Moreover, the post-buckling behavior of a centrally-load web-tapered I-beam with warping restraints will be investigated as well.

Discussion of “Thin-Walled Curved Beam Finite Element”

1978 ◽  
Vol 104 (5) ◽  
pp. 1303-1304
Author(s):  
Sundaramoorthy Rajasekaran ◽  
Mahadevan Padmanabhan
Keyword(s):  
Finite Element ◽  
Curved Beam ◽  
Thin Walled
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