Synthesis of Bistable Periodic Structures Using Topology Optimization and a Genetic Algorithm

Prasad, Jitendra; Diaz, Alfredo Peña

doi:10.1115/1.2338576

Cited by 42 publications

(21 citation statements)

References 20 publications

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“…It is well established that a constrained bi-stable structure such as a buckled beam can exhibit negative stiffness under certain circumstances [1]. From negative stiffness one may expect the material/structure to displace opposite to the direction of the applied force.…”

Section: Introductionmentioning

confidence: 99%

A Novel In-Situ Nanoindentation Characterization of Phase Transforming Materials

2015

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Materials with different allotropes can undergo one or more phase transformations based on the changes in the thermodynamic states. Each phase is stable in a certain temperature/pressure range and can possess different physical and mechanical properties compared to the other phases. The majority of material characterizations have been carried out for materials under equilibrium conditions where the material is stabilized in a certain phase and a lesser portion is devoted for onset of transformation. Alternatively, in situ measurements can be utilized to characterize materials while undergoing phase transformation. However, most of the in situ methods are aimed at measuring the physical properties such as dielectric constant, thermal/electrical conductivity and optical properties. Changes in material dimensions associated with phase transformation, makes direct measurement of the mechanical properties very challenging if not impossible. In this study a novel non-isothermal nanoindentation technique is introduced to directly measure the mechanical properties such as stiffness and creep compliance of a material at the phase transformation point. Single crystal ferroelectric triglycine sulfate (TGS) was synthetized and tested with this method using a temperature controlled nanoindentation instrument. The results reveal that the material, at the transformation point, exhibits structural instabilities such as negative stiffness and negative creep compliance which is in agreement with the findings of published works on the composites with ferroelectric inclusions.

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Section: Introductionmentioning

confidence: 99%

A Novel In-Situ Nanoindentation Characterization of Phase Transforming Materials

2015

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“…However, in their method, the contact is used for changing the mode of deformation, and geometrical nonlinearity or bistability is not considered. Prasad and Diaz (2006) developed a ground structure approach using nonlinear beam elements to generate bistable periodic frame structures. Optimization is carried out by genetic algorithms.…”

Section: Introductionmentioning

confidence: 99%

Enumeration of optimal pin-jointed bistable compliant mechanisms with non-crossing members

Ohsaki

Katoh

Kinoshita

et al. 2008

Struct Multidisc Optim

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An optimization approach is presented for enumerating pin-jointed bistable compliant mechanisms. In the first stage, the statically determinate trusses with non-crossing members containing a given set of nodes and some pre-defined members are regarded as minimally rigid framework or a Laman framework, and are enumerated without repetitions by the graph enumeration algorithm. In the second stage, the nodal locations and the cross-sectional areas are optimized under mechanical constraints, where the snapthrough behavior is extensively utilized to produce a pin-jointed bistable compliant mechanism. In the numerical examples, many bistable compliant mechanisms are generated to show the effectiveness of the proposed method.

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“…Such irregularity was first observed in constrained bi-stable structures such as buckled beams. 4,5 Capitalizing on such phenomenon can facilitate elevated vibrational damping, 6 composites with infinite stiffness, 7,8 and acoustical absorbers. 9 Further, applications are still evolving ranging from meta-materials to seismic protection of structures 10 and strings with negative stiffness and hyperfine structure.…”

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confidence: 99%

“…11 While the evaluation of bi-stable structures has been studied thoroughly, the investigation of materials with negative stiffness stands at the proof of the concept. 4,12 Lakes et al 7,13 showed that materials undergoing phase transformations, while embedded within a stiff constraining matrix, display negative stiffness. They also showed that the concept of the negative stiffness is fundamentally different from the negative Poisson's ratio.…”

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confidence: 99%

Nanocharacterization of the negative stiffness of ferroelectric materials

Skandani

Čtvrtlík

Al-Haik

2014

Applied Physics Letters

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Phase changing materials such as ferroelectric materials could exhibit negative stiffness under certain thermomechanical environments. This negative stiffness is embodied by a deflection along the opposite direction of the applied load. So far negative stiffness materials were investigated with the specific morphology of embedded inclusions in stiff matrices then the resulting composite is studied to measure the behavior of each constituent indirectly. In this study, a modified nonisothermal nanoindentation method is developed to measure the negative stiffness of triglycine sulfate single crystal directly. This in-situ method is intended to first demonstrate the feasibility of detecting the negative stiffness via nanoindentation and nanocreep of a ferroelectric material at its Curie point and then to quantify the negative stiffness without the need for embedding the crystal within a stiffer matrix. V C 2014 AIP Publishing LLC. [http://dx.

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Synthesis of Bistable Periodic Structures Using Topology Optimization and a Genetic Algorithm

Cited by 42 publications

References 20 publications

A Novel In-Situ Nanoindentation Characterization of Phase Transforming Materials

A Novel In-Situ Nanoindentation Characterization of Phase Transforming Materials

Enumeration of optimal pin-jointed bistable compliant mechanisms with non-crossing members

Nanocharacterization of the negative stiffness of ferroelectric materials

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