Improved Performance of Unimorph Actuators by Domain Switching Enhancement in the Piezoelectric Layer with External Loading

摘要

The tensile strength of piezoceramics is much lower than the compressive strength. Therefore, in unimorph actuator design, the ceramic layer must be in compressed state at the service temperature to avoid failure during operation. However, the high compressive stress in the piezoceramic material may cause a decrease in strain due to the induced piezoelectric effect. In addition, the compressive stress acts against the electric field to prevent domain switching. The unimorph actuator is thus designed and operated in a fashion such that the compressive stress in piezoceramic material is large enough to avoid failure in service condition but small enough to allow a large amount of domain switching. In this paper, the design and loading arrangements of unimorph piezoelectric actuators are investigated to enhance the performance by increasing non-180° domain switching. To obtain such improvement of the actuation performance for THUNDER (THin layer UNimorph DrivER and sensor) and LIPCA (Lightweight Piezoceramic Composite Actuator), external loadings should be arranged in a manner such that the stress state within the PZT wafer is in as more tension as possible to alleviate the High compressive induced stress due to the manufacturing process.