Quasi-zero stiffness isolator based on bistable structures with variable cross-section

Simple and light-weighted quasi-zero stiffness (QZS) isolators can be designed based on nonlinear and negative stiffness generated by the snap-through effect of bistable structures. Traditionally, the snap-through force of the bistable structure is limited which makes the weight which can be isolated based on this mechanism very low. This paper investigates increasing loading capacity of this kind of isolator by using an optimized and varying sectional profile. Numerical models were derived for the bistable structures with variable sectional distributions. Optimized sections’ alignment of the bistable beam was derived based on the numerical model which was consequently validated by experimental results. Influences of the bistable beams with a variable section on nonlinear stiffness characteristics and performance of the isolator were at last investigated with the harmonic balance method.

Suppression of Cross-Well Oscillations for Bistable Composites Through Potential Well Elimination

Although there have been numerous efforts into harnessing the snap through dynamics of bistable structures with piezoelectric transducers to achieve large energy conversion, these same dynamics are undesirable under morphing applications where stationary control of the structure’s configuration is paramount. To suppress cross-well vibrations that primarily result from periodic excitation at low frequencies, a novel control strategy is proposed and implemented on the piezoelectrically generated bistable laminate, which consists of only macro fiber composites (MFCs) in a [0MFC/90MFC]T layup. While under cross-well regimes such as subharmonic, chaotic, or limit cycle oscillations, a single MFC is actuated to the laminate’s limit voltage to eliminate one of its potential wells and force it into the remaining stable state. Simultaneously, a positive position feedback (PPF) controller suppresses the resulting single-well oscillations through the other MFC. This dual control strategy is numerically and experimentally demonstrated through the suppression of various cross-well regimes and results in significant reduction of amplitude. The active control capability of the laminate prevents snap through instability when under large enough external vibrations.

Perceived Value Change via 3D Printed Bistable Structures

A key aspect of color change is altering perceived value or intensity. This paper presents a methodology to achieve value change through mechanical means via the deflection of bistable structures. We create mechanical pixel-based, reversible color change using 3D printed switchable bistability. Switchable bistability arises from the combination of pre-strain and shape memory, enabling us to access multiple elastically programmed shapes at elevated temperatures with fast morphing and low actuation forces, while retaining high stiffness at room temperature. Building on our previous study that achieved bistability through FDM printing with directional pre-stress, finite element analysis is conducted to design a pixel-like structure that acts as a unit cell with color change capabilities. Quantitative and qualitative analysis is conducted through image processing techniques in order to prove the viability of this approach to creating value change through geometric deformation of bistable structures. By leveraging this technique, there are numerous potential applications in fields including robotics, architecture, and interior design.