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Buckling of Spherical Shells with Large Axisymmetric Imperfection and Application in Soft Robotics.

紀錄類型:	書目-電子資源 : Monograph/item
正題名/作者:	Buckling of Spherical Shells with Large Axisymmetric Imperfection and Application in Soft Robotics./
作者:	Qiao, Chuan.
面頁冊數:	1 online resource (185 pages)
附註:	Source: Dissertations Abstracts International, Volume: 83-10, Section: B.
Contained By:	Dissertations Abstracts International83-10B.
標題:	Spheres. -
電子資源:	http://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=29043545click for full text (PQDT)
ISBN:	9798209933625

Buckling of Spherical Shells with Large Axisymmetric Imperfection and Application in Soft Robotics.
Qiao, Chuan.

Buckling of Spherical Shells with Large Axisymmetric Imperfection and Application in Soft Robotics. - 1 online resource (185 pages)

Source: Dissertations Abstracts International, Volume: 83-10, Section: B.

Thesis (Ph.D.)--McGill University (Canada), 2021.

Includes bibliographical references

Spherical shells are ubiquitous in nature and engineering for their simple geometry and excellent load-bearing capacity. A long-standing topic of spherical shells subject to uniform external pressure is their highly unstable post-buckling response that leads to a catastrophic collapse. This type of failure fully exhausts the load-bearing capacity of the shell, and it is thus detrimental for traditional engineering applications. On the other hand, recent advances in soft robotics and metamaterials demonstrate that geometric nonlinearities and elastic instabilities can be harnessed to generate distinctive functions, such as shape morphing, fast motion, and logic operation.This thesis proposes the use of a large axisymmetric imperfection to control the buckling mode of spherical shells, and demonstrates its application when integrated into a soft bi-shell valve for the fast actuation of soft robots. On the first front, the proposed imperfection can escape the classical bifurcation of perfect spherical shells, and induce snap-through buckling followed by a stable post-buckling; this response provides increasing pressure resistance over a large change in volume. The buckling of the imperfect shell is investigated through a theoretical study that employs exact expressions of the middle surface strains, curvature changes, and live pressure loading along with validating experiments and numerical simulations. The post-buckling characteristics and transition between four buckling modes can be programmed by tuning the defect geometry and shell radius to thickness ratio. On the second front, a new concept for soft valves is proposed: a bi-shell valve consisting of an imperfect shell and a shallow spherical cap. The bi-shell valve harnesses the snap-through interaction of the constituent shells to convert a slowly imparted volume into a fast volume output. Upper bounds and performance metrics are presented to guide the design of the bi-shell valve, and its performance is illustrated through an application that demonstrates the fast actuation of a soft striker.Overall, the work in this thesis contributes to unveil original aspects of shell buckling with results that are promising for diverse applications. Geometric imperfections can be programmed into spherical shells to trigger new buckling modes that can be exploited for the design of soft robots, mechanical metamaterials, and soft matter. Furthermore, the bi-shell valve concept here introduced can inspire the design of future soft valves with unique actuation modes for soft pneumatic robots.

Electronic reproduction.
Ann Arbor, Mich. :
ProQuest,
2023

Mode of access: World Wide Web

ISBN: 9798209933625Subjects--Topical Terms:

3684734
Spheres.
Index Terms--Genre/Form:

542853
Electronic books.

Buckling of Spherical Shells with Large Axisymmetric Imperfection and Application in Soft Robotics.
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500 $a Source: Dissertations Abstracts International, Volume: 83-10, Section: B.
500 $a Advisor: Pasini, Damiano.
502 $a Thesis (Ph.D.)--McGill University (Canada), 2021.
504 $a Includes bibliographical references
520 $a Spherical shells are ubiquitous in nature and engineering for their simple geometry and excellent load-bearing capacity. A long-standing topic of spherical shells subject to uniform external pressure is their highly unstable post-buckling response that leads to a catastrophic collapse. This type of failure fully exhausts the load-bearing capacity of the shell, and it is thus detrimental for traditional engineering applications. On the other hand, recent advances in soft robotics and metamaterials demonstrate that geometric nonlinearities and elastic instabilities can be harnessed to generate distinctive functions, such as shape morphing, fast motion, and logic operation.This thesis proposes the use of a large axisymmetric imperfection to control the buckling mode of spherical shells, and demonstrates its application when integrated into a soft bi-shell valve for the fast actuation of soft robots. On the first front, the proposed imperfection can escape the classical bifurcation of perfect spherical shells, and induce snap-through buckling followed by a stable post-buckling; this response provides increasing pressure resistance over a large change in volume. The buckling of the imperfect shell is investigated through a theoretical study that employs exact expressions of the middle surface strains, curvature changes, and live pressure loading along with validating experiments and numerical simulations. The post-buckling characteristics and transition between four buckling modes can be programmed by tuning the defect geometry and shell radius to thickness ratio. On the second front, a new concept for soft valves is proposed: a bi-shell valve consisting of an imperfect shell and a shallow spherical cap. The bi-shell valve harnesses the snap-through interaction of the constituent shells to convert a slowly imparted volume into a fast volume output. Upper bounds and performance metrics are presented to guide the design of the bi-shell valve, and its performance is illustrated through an application that demonstrates the fast actuation of a soft striker.Overall, the work in this thesis contributes to unveil original aspects of shell buckling with results that are promising for diverse applications. Geometric imperfections can be programmed into spherical shells to trigger new buckling modes that can be exploited for the design of soft robots, mechanical metamaterials, and soft matter. Furthermore, the bi-shell valve concept here introduced can inspire the design of future soft valves with unique actuation modes for soft pneumatic robots.
520 $a Les coques spheriques sont omnipresentes en sciences naturelles et en ingenierie en raison de leur geometrie simple et leurs excellentes proprietes mecaniques. En particulier, les coques spheriques soumises a une pression externe uniforme sont etudiees exhaustivement pour leur regime post-flambement instable qui resulte en une defaillance catastrophique. Ce mode de defaillance doit etre evite pour les structures d'ingenierie traditionnelles puisqu'il limite leur capacite de support de charge. Cependant, les avancees dans le domaine des robots souples et des metamateriaux permettent d'utiliser les instabilites elastiques afin de generer de nouvelles fonctionnalites comme la transformation de forme et l'amplification de la reponse des structures.Cette these formalise l'utilisation d'imperfections axisymetriques pour controler le flambement de coques spheriques. Une application sur une valve bi-coque souple est mise de l'avant pour illustrer que le concept permet d'augmenter la reponse des robots souples. En premier lieu, il est demontre qu'en raison de l'imperfection axisymetrique, la reponse de la coque differe du resultat classique de bifurcation pour une coque sans imperfection. L'imperfection produit un flambement a pression constante suivi d'un regime post-flambement stable. Cette reponse non-lineaire de la coque fournit une augmentation de la resistance a la pression externe associee a un grand changement de volume. Le flambement de la coque imparfaite est etudie theoriquement a l'aide d'une formulation exacte de la deformation de la surface moyenne, des changements du rayon de courbure et de la pression. Cette approche theorique est par la suite validee par des experiences sur des prototypes et des simulations numeriques. Le regime post-flambement et la transition entre quatre modes de flambement peuvent etre programmes en modifiant le defaut de geometrie ainsi que le rapport entre le rayon et l'epaisseur de la coque. En deuxieme lieu, il est propose un nouveau concept pour une valve souple: une valve bi-coque construite a partir d'une coque avec une imperfection axisymetrique et une autre coque sans imperfections, mais avec un angle polaire tres faible. Cette bi-coque utilise l'instabilite de flambement afin de convertir un debit de volume d'entree lent en un debit de sortie rapide. Il est aussi presente les limites du concept ainsi que des metriques de performance pour comparer le design avec la litterature scientifique. Le potentiel de la bi-coque flexible est demontre a travers l'actuation rapide d'un robot souple perforeur.Cette these met de l'avant le flambement elastique de coques ainsi que les imperfections de geomterie qui peuvent etre utilises dans le design de robots souples, de metamateriaux, et de matiere desordonnee. Finalement, le concept de bi-coque presente dans cette these pourrait alimenter le developpement de valves souples munies de nouvelles fonctionnalites.
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