Quasi-static multilayer piezoelectric actuators are finding more and more applications, for example, in the field of aerospace; however, their properties are still not fully characterised, in particular at a high temperature. The present study targets the full characterisation of both soft-doped and harddoped lead zirconate titanate (PZT) up to 200°C. A simple set of tests and test results are presented, focusing particularly on dielectric losses and creep effect. Dielectric losses were found to decrease with the increasing field for soft-doped PZT, while they tend to increase for hard-doped PZT. The interpretation is that soft-doped PZT has less hysteresis at high field. The creep behaviour is also significantly different. While soft-doped PZT follows a logarithmic model with low and stable creep rates, hard-doped PZT exhibits non-logarithmic creep with increasing or decreasing rates depending on the temperature. This behaviour is attributed to the generation of additional poling in the material.
In micro forming, the increased surface to volume ratio makes ejection of an extruded component to an often complicated process. The aim of this work has been to demonstrate the possibility to reduce the force required to eject the component, by controlled pre-stressing of the die, before, during and after the forming process. The level of required prestress has been evaluated by FE analysis of the interaction between the forming process and the elastic deflection of the tool-system. A test rig has been designed containing four piezo actuators mounted symmetrically around the circumference of the die cavity. Mechanical amplification has been used to increase the pressure created by the piezo actuator to reach the level required for prestressing of a bulk forming tool.The force required to eject the component from the die depends on the tribological conditions combined with the radial pressure between die and component due to elastic deflections remaining after the punch
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