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.

Influence of Electric Current and Magnetic Flow on Firing Patterns of Pre-Bötzinger Complex Model

The dynamics of neuronal firing activity is vital for understanding the pathological respiratory rhythm. Studies on electrophysiology show that the magnetic flow is an essential factor that modulates the firing activities of neurons. By adding the magnetic flow to Butera’s neuron model, we investigate how the electric current and magnetic flow influence neuronal activities under certain parametric restrictions. Using fast-slow decomposition and bifurcation analysis, we show that the variation of external electric current and magnetic flow leads to the change of the bistable structure of the system and hence results in the switch of neuronal firing pattern from one type to another.

Transient Motion of a Piezoelectrically-Actuated Bistable Beam

Bistable structures have several applications in different areas, such as aircraft morphing wings, morphing wind turbine blades, and vibration energy harvesting, due to their unique properties. Bistable structures can be used in morphing wings and wind turbine blades since they are able to alleviate large loads by snapping from one stable position to the other one. A piezoelectric actuator can be used to bring the bistable structure back to its original position after the load is alleviated. In this paper, the transient response of a piezoelectrically actuated bistable beam is investigated experimentally for different force inputs. The goal of these experiments is to explore the ability of a commercial piezoelectric actuator to induce snap-through motion in a bistable structure. The feasibility of performing snap-through motion, and the required energy are found for different excitation force amplitudes and frequencies.

Constrained-Energy Dynamic Cross-Well Motion of Bistable Structures Subjected to Noise Disturbance

Bistable structures have two stable equilibrium positions and can be utilized to maintain a static shape with no energy consumption. This paper focuses on the minimum energy required for performing snap-through of a bistable structure subjected to noise disturbance. This paper uses the Duffing–Holmes equation as a one-degree-of-freedom representative model of a bistable structure. This equation is numerically solved to calculate the energy required for cross-well oscillation under different system and forcing conditions. The paper shows how the energy required for cross-well transfer varies as a function of damping ratio and frequency ratio at specific harmonic force amplitude when the system is externally disturbed with a band-limited noise signal. A magneto-elastic bistable beam is fabricated and tested to validate the used mathematical model. Various nondimensional parameters are used to highlight interesting phenomena. The relationships between signal-to-noise ratio (SNR), dynamic-to-static force ratio, and damping ratio to the response behavior are shown. It is found that the domain of low energy regions decreases by increasing the level of noise. Additionally, underactuated bistable and linear systems behave similarly for high levels of noise. This paper specifically identifies the critical force ratio, which allows for snap-through as a function of critical nondimensional system parameters.