Characterization and modeling of granular jamming: models for mechanical design
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ORIGINAL PAPER
Characterization and modeling of granular jamming: models for mechanical design Loïc Blanc1,3 · Bertrand François2 · Alain Delchambre3 · Pierre Lambert1 Received: 10 April 2020 / Accepted: 26 October 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract The use of granular jamming is proposed for designing structures with tunable rigidity of their tools (with the ability of being flexible devices for shaping and deformation but rigid for shape-locking and force transmission). The granular jamming consists in modifying the apparent rigidity of a structure by controlling the vacuum in a membrane filled with granular material. When the difference of pressure is low, the grains are free to move with respect to each other and the structure is flexible. When the vacuum in the membrane is increased, the grains are blocked and the structure is more rigid. Different mechanical characterizations of the granular jamming have been performed (triaxial compression and tension and cantilever beam bending tests) for different glass bead sizes ranging between 100 μm and 1 mm (used as granular material) at different vacuum levels (between 0 kPa and 90 kPa ). The grain size slightly influences the stiffness while the pressure difference is the main parameter to tune the stiffness of the structure. Based on these experiments, analytical models have been developed and validated. The tension characteristics can be directly deduced from the compression behavior and the bending modulus can be obtained by a combination of the tension and compression moduli. The proposed analytical models present the advantage of a simple formulation and are suitable for estimating the performance of other structures based on the granular jamming. The models can estimate and predict satisfactorily the results of granular jamming and can be used for designing mechanical structures based on this mechanism. Keywords Granular jamming · Triaxial testing · Analytical model · Tunable flexural stiffness · Mechanical design
1 Introduction Currently, in the medical field, the clinicians are facing a problem about the stiffness of their tools. They need them to be as flexible as possible to travel in the human anatomy without damaging the tissues or causing pain to the patient, but once in position, they need them to be rigid to support additional tools or to perform their tasks (e.g. gripping, suturing, puncturing) [1, 2]. Therefore, the clinicians require * Loïc Blanc [email protected] Pierre Lambert [email protected] 1
TIPs Department, CP165/67, Université Libre de Bruxelles, av.FD Roosevelt 50, 1050 Brussels, Belgium
2
BATir Department, CP194/2, Université Libre de Bruxelles, av.FD Roosevelt 50, 1050 Brussels, Belgium
3
BEAMS Department, CP165/56, Université Libre de Bruxelles, av.FD Roosevelt 50, 1050 Brussels, Belgium
tunable stiffness tools. Furthermore, decreased dimensions are preferred to reduce the invasiveness of the medical devices [3]. As reduced dimensions are leading to reduced flexura
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