Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

A new intelligent thin-shell element

Abstract: In this paper, a new three-dimensional thin-shell structure containing an integrated distributed piezoelectric sensor and actuator is proposed. The distributed piezoelectric sensor layer monitors the structural shape deformation due to the direct effect and the distributed actuator layer suppresses the deflection via the converse piezoelectric effect. A finite-element formulation is presented for modelling the dynamic as well as static response of the laminated shell with piezoelectric sensors/actuators. An eight-node and 40 degrees of freedom shell element is built. The performance of the shell elements is improved by a reduced integration technique. The shell element is verified by calculating a piezoelectric polymeric PVDF bimorph beam. The results agreed fairly well with those obtained through theoretical analysis by Tzou and Tseng and Hwang and Park.

Fast driving technique for integrated thermal bimorph actuator toward high-throughput atomic-force microscopy

Abstract: A driving scheme for improving the effective response of a microfabricated cantilever with an integrated thermal bimorph actuator is proposed for applications in high-throughput atomic-force microscopy. The essential part of the proposed scheme is a tuned boost filter (BSF), which is inserted in the setup for constant force imaging and which boosts the servo signal according to its frequency. Using this setup, an imaging bandwidth of 5 kHz was obtained within an actuation range of 1.7 μm. Constant force imaging with a tip velocity of 0.62 mm/s is demonstrated and the effectiveness of the BSF is verified. The improved bandwidth is gained at the expense of the achievable deflection range. An optimized system, therefore, requires not only a BSF but also a thermal bimorph with a large power to deflection efficiency.

In situ measurement of mechanical properties of polyimide films using micromachined resonant string structures

Abstract: Two in situ measurement schemes, using micromachined resonant string structures, for the measurement of the polyimide residual stress and polyimide/metal adhesion durability have been developed. The residual stress of polyimide films, DuPont PI-2555 and PI-2611, have been measured using a bulk micromachined string structure. According to the Rayleigh's method, the resonant frequency of a polyimide string can be related to the film stress. By measuring the resonant frequency of these polyimide strings, the residual stresses have been calculated. The measurement results of various strings have been compared with conventional measurement results, which shows that they are in good agreement. Also, a noble scheme to quantize the adhesion durability between a polyimide film and a metal film has been developed. This scheme is based on a polyimide/metal bimorph string structures, fabricated using a surface micromachining technique, vibrating with an alternating potential. The change of resonance profile of this string structure can be related to the degradation of adhesion strength at the polyimide/metal interface. Various polyimide/gold string structures have been fabricated using a surface micromachining with Cu sacrificial layers, and the resonant qualities have been monitored. Notable changes of resonant Q-factor and resonant frequency, due to the degradation of adhesion between the metal and polyimide, have been observed after 10/sup 8/ cycles (string vibration) for the polyimide/gold bimorph strings. The changes of resonant Q-factor and resonant frequency over a time period (vibration cycles) have been monitored.

Continued development of a helicopter rotor model employing smart trailing-edge flaps for vibration suppression

Abstract: The continued development of a Froude-Scale helicopter rotor model featuring a trailing-edge flap driven by piezoceramic bimorph actuators for active vibration suppression is discussed. Block force and stroke of the current actuators are evaluated using two theories and compared with experimental results. Dynamic performance of the actuator as well as the actuator-flap assembly are examined. Earlier hover tests have shown severe degradation in flap deflections with increasing rotor speed, and flap deflections were too small to be effectively utilized for significant vibration control. To investigate the causes of the performance degradation, new blades are constructed and tested in-vacuo to isolate the effects of centrifugal loading on the actuator-flap system. A beam model of the piezo bimorph including propeller moment effects is formulated to better illustrate the physical mechanisms affecting the system in a rotating environment. The cause of the reduced deflections is traced to frictional forces created at the junction where the flap is supported during rotation of the blades. The use of a thrust bearing was found to alleviate this problem and subsequent tests on a hover stand showed a dramatic increase in flap detection at high excitation frequencies.© (1995) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Biomimetic flexible plate actuators are faster and more efficient with a passive attachment

Abstract: Using three-dimensional computer simulations, we probe biomimetic free swimming of an internally actuated flexible plate in the regime near the first natural frequency. The plate is driven by an oscillating internal moment approximating the actuation mechanism of a piezoelectric macro fiber composite (MFC) bimorph. We show in our simulations that the addition of a passive attachment increases both swimming velocity and efficiency. Specifically, if the active and passive sections are of similar size, the overall performance is the best. We determine that this optimum is a result of two competing factors. If the passive section is too large, then the actuated portion is unable to generate substantial deflection to create sufficient thrust. On the other hand, a large actuated section leads to a bending pattern that is inefficient at generating thrust especially at higher frequencies.