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Clermont-Ferrand, France

Le Cam J.-B.,French Institute for Advanced Mechanics
Rubber Chemistry and Technology | Year: 2010

Elastomeric materials are subjected to significant change in volume during their deformation. This paper proposes to review the change in volume of stretched rubber and to highlight why volume change can be considered as a relevant mechanical quantity to characterize rubbery materials in terms of microstructure evolution. The first part of the present review examines experimental measurements of volume change reported from the end of the 19th century until now. The second part reports the models proposed to predict the change in volume of stretched rubbers. These are formulated for small deformations. Some of them account for the decrease in volume due to crystallization. Source


Gogu G.,French Institute for Advanced Mechanics
Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science | Year: 2010

The current article presents a new family of T2R1-type spatial parallel mechanisms (PMs) with decoupled and unlimited rotation of the moving platform in planar motion. The moving platform performs two independent translations (T2) and one independent unlimited rotation (R1) whose axis is perpendicular to the plane of translations. A method is proposed for structural synthesis of T2R1-type PMs based on the theory of linear transformations. The moving platform has unlimited rotational capabilities and is decoupled with respect to translational motion. To the best of the author's knowledge, this article presents for the first time solutions of T2R1-type spatial PMs with decoupled and unlimited rotation of the moving platform in planar motion. Source


Gogu G.,French Institute for Advanced Mechanics
Meccanica | Year: 2011

The paper addresses bifurcation in constraint singularities in connection with structural parameters of parallel mechanisms. The new formulae of mobility, connectivity, overconstraint and redundancy of parallel robots, recently proposed by the author, are used to characterize the bifurcation in constraint singularities. By using these formulae, we have demonstrated that, in a constraint singularity, the instantaneous values of mobility, connectivity of the moving platform and degree of overconstraint increase with no changes in limb connectivity. When bifurcation occurs in a constraint singularity, the mechanism can reach different branches characterized by different independent motions of the moving platform. Bifurcation in constraint singularities is easily identified by inspection with no need to calculate the augmented Jacobian. © 2010 Springer Science+Business Media B.V. Source


Gogu G.,French Institute for Advanced Mechanics
European Journal of Mechanics, A/Solids | Year: 2012

This paper presents a new family of T2R1-type parallel manipulators with bifurcated planar-spatial motion of the moving platform. In each branch, the moving platform has two independent translations (T) and one rotation (R) driven by three actuators mounted on the fixed base or on a moving link. The rotation axis is perpendicular to the plane of translations or parallel to this plane. In the first case, the moving platform has a planar motion, and in the second case, a spatial motion. The bifurcation between planar and spatial motion occurs in a constraint singularity in which the connectivity between the moving and fixed platforms increases instantaneously with no change in limb connectivity. Overconstrained/isostatic parallel manipulators with decoupled/uncoupled motions and maximally regular solutions with bifurcated planar-spatial motion of the moving platform are presented for the first time. © 2011 Elsevier Masson SAS. All rights reserved. Source


Gogu G.,French Institute for Advanced Mechanics
Journal of Mechanisms and Robotics | Year: 2011

This paper presents a new family of maximally regular T2R1-type parallel manipulators with bifurcated spatial motion. In each branch, the moving platform has two independent translations (T2) and one rotation (R1) driven by three actuators mounted on the fixed base. The rotation axis is situated in the plane of translation and can bifurcate in two orthogonal directions. This bifurcation occurs in a constraint singularity in which the connectivity between the moving and fixed platforms increases instantaneously, incurring no change in limb connectivity. The Jacobian matrix of the maximally regular solutions presented in this paper is a 3×3 identity matrix in the entire workspace of each branch. This paper presents for the first time a family of maximally regular T2R1-type parallel manipulators with bifurcated spatial motion of the moving platform along with solutions using uncoupled motions. © 2010 American Society of Mechanical Engineers. Source

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