Hinges and Curved Lamina Emergent Torsional Joints in Cylindrical Developable Mechanisms

2020 ◽

Author(s):

Kendall Seymour ◽

Pietro Bilancia ◽

Spencer Magleby ◽

Larry Howell

Keyword(s):

Cylindrical Surface ◽

Small Scale ◽

Membrane Thickness ◽

Cylinder Wall ◽

Small Length ◽

Curved Beams ◽

Modeling Assumption ◽

Thin Walled

Abstract Cylindrical developable mechanisms are devices that conform to and emerge from a cylindrical surface. These mechanisms can be formed or cut from the cylinder wall itself. This paper presents a study on adapting traditional hinge options to achieve revolute motion in these mechanisms. A brief overview of options is given, including classical pin hinges, small-length flexural pivots, initially curved beams, and an adaptation of the membrane thickness-accommodation technique. Curved Lamina Emergent Torsional (LET) joints are then evaluated in detail, and a thin-walled modeling assumption is checked analytically and empirically. A small-scale cylindrical developable mechanism is then evaluated with Nitinol curved LET joints.

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Stress-driven two-phase integral elasticity for Timoshenko curved beams

Proceedings of the Institution of Mechanical Engineers Part N Journal of Nanomaterials Nanoengineering and Nanosystems ◽

10.1177/2397791421990514 ◽

2021 ◽

pp. 239779142199051

Author(s):

Marzia S Vaccaro ◽

Francesco P Pinnola ◽

Francesco Marotti de Sciarra ◽

Marko Canadija ◽

Raffaele Barretta

Keyword(s):

Solution Procedure ◽

Small Scale ◽

Curved Beams ◽

Sensors And Actuators ◽

Two Phase ◽

Design And Optimization ◽

Local Responses ◽

Size Dependent ◽

Classical Boundary ◽

Phase Integral

In this research, the size-dependent static behaviour of elastic curved stubby beams is investigated by Timoshenko kinematics. Stress-driven two-phase integral elasticity is adopted to model size effects which soften or stiffen classical local responses. The corresponding governing equations of nonlocal elasticity are established and discussed, non-classical boundary conditions are detected and an effective coordinate-free solution procedure is proposed. The presented mixture approach is elucidated by solving simple curved small-scale beams of current interest in Nanotechnology. The contributed results could be useful for design and optimization of modern sensors and actuators.

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Pretwisted Curved Beams of Thin-Walled Open Section

Journal of Applied Mechanics ◽

10.1115/1.3422788 ◽

1972 ◽

Vol 39 (3) ◽

pp. 779-785 ◽

Cited By ~ 2

Author(s):

A. I. Soler

Keyword(s):

Numerical Technique ◽

Equations Of Motion ◽

Highway Bridges ◽

Major Effect ◽

Curved Beams ◽

Open Section ◽

Straight Beam ◽

Thin Walled ◽

Bending Modes ◽

Axes Of Symmetry

Equations of motion are derived for coupled extension, flexure, and torsion of pretwisted curved bars of thin-walled, open section. The derivation is based on energy principles and includes inertia terms. The major effect of initial pretwist is to allow coupling of all possible beam deformation modes; however, if the bar is straight and has two axes of symmetry, pretwist causes coupling only between the two bending modes, and between extension and torsion. The governing equations are presented in first-order form, and a numerical technique is suggested for the case of space varying pretwist. It is suggested that these equations may form the basis for a simplified study of the effect of superelevation on the static and dynamic response of curved highway bridges. Finally, a simple straight beam with uniform pretwist is studied to compare effects of pretwist and restrained torsion in a thin-walled beam of open section.

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Discussion: Thin-Walled Curved Beams. I: Formulation of Nonlinear Equations

Journal of Engineering Mechanics ◽

10.1061/(asce)0733-9399(1996)122:5(482) ◽

1996 ◽

Vol 122 (5) ◽

pp. 482-484 ◽

Cited By ~ 2

Author(s):

Yeong-Bin Yang ◽

Shyh-Rong Kuo

Keyword(s):

Nonlinear Equations ◽

Curved Beams ◽

Thin Walled

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Buckling of Thin-Walled Long Steel Cylinders Subjected to Bending

Journal of Pressure Vessel Technology ◽

10.1115/1.4002902 ◽

2010 ◽

Vol 133 (1) ◽

Cited By ~ 9

Author(s):

Sotiria Houliara ◽

Spyros A. Karamanos

Keyword(s):

Structural Response ◽

Cylinder Wall ◽

Imperfection Sensitivity ◽

Bifurcation Instability ◽

Buckling Mode ◽

Cross Sectional ◽

Moment Capacity ◽

Thin Walled ◽

Cylindrical Steel ◽

Element Technique

The present paper investigates structural response and buckling of long unstiffened thin-walled cylindrical steel shells, subjected to bending moments, with particular emphasis on stability design. The cylinder response is characterized by cross-sectional ovalization, followed by buckling (bifurcation instability), which occurs on the compression side of the cylinder wall. Using a nonlinear finite element technique, the bifurcation moment is calculated, the post-buckling response is determined, and the imperfection sensitivity with respect to the governing buckling mode is examined. The results show that the buckling moment capacity is affected by cross-sectional ovalization. It is also shown that buckling of bent elastic long cylinders can be described quite accurately through a simple analytical model that considers the ovalized prebuckling configuration and results in very useful closed-form expressions. Using this analytical solution, the incorporation of the ovalization effects in the design of thin-walled cylinders under bending is thoroughly examined and discussed, considering the framework of the provisions of the new European Standard EN1993-1-6.

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