Fatigue Testing Machine of Micro-Sized Specimens for MEMS Applications
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Mat. Res. Soc. Symp. Proc. Vol. 605 © 2000 Materials Research Society
SPECIFICATIONS OF FATIGUE TESTING MACHINE In this investigation, the size of specimen is anticipated to be I to 10 Rm. Therefore, the load and the displacement resolutions required are calculated to be approximately 10 IAN and 5 nm, respectively, although these values depend on materials and type of loading mode (i.e., tensile, bending). In order to satisfy these requirements, we have developed a fatigue testing machine. Figure 1 shows a block diagram of the fatigue testing machine developed in this study, and Fig. 2 shows a photograph of the testing machine. The testing machine consists of an actuator, a specimen holder, a load cell and a controller. Table I summarizes the specification of the testing machine and following are the details of this equipment. A magnetostrictive device is used as an actuator which imparts a small amount of displacement to a specimen. The magnetostrictive material used is TERFENOL-D (TbDyFe), which is able to produce displacements upto ±10 Itm with an accuracy of 5 nm, and maximum response frequency of cyclic displacement is 100 Hz. Sinusoidal, triangular and ramp waves can be used as displacement waveforms using a generator equipped in the controller. External waveform input is also possible. So far, a nano-indentor type loading system has been applied for the measurement of mechanical properties in thin film specimens. The stiffness of such system is very low and it is inadequate for applying cyclic loading. In the system used in this study, the end of the actuator is connected to a metal shaft and a diamond tip of 5 jim in radius is attached to the other end of the shaft. This makes it possible to construct a high stiffness loading fixture. The displacement of the actuator is measured by a laser displacement meter with accuracy of 5 nm and the displacement
Resolution: 0.1 ton
Fig. 1 Block diagram of fatigue testing machine for micro-sized specimens.
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Fig. 2 Photograph of the main part of fatigue testing machine developed inthis investigation.
Table 1 Specifications of fatigue testing machine for micro-sized specimen. Loading type: Static and dynamic Actuator: Magnetostrictive deveice (TERFENOL-D, TbDyFe) Maximum displacement: ±10 [im Displacement resolution: 5 nm Load cell: Strain gage type (Piezoelectric type may be also used) Maximum load: ±100 mN Load resolution: 10 [tN Maximum cyclic frequency: 100 Hz Waveform type of cyclic load: Sinusoidal, triangular, ramp or external input Feedback control: Displacement or load control Resolution of specimen position setting: 0.5 [tm
signal is used as feed back control. A micro-sized specimen is set in a specimen holder and the holder is placed on a load cell as shown in Fig. 1. This holder is interchangeable and may also be used in a focused ion beam machine for machining the micro-sized specimens, in a fatigue testing machine and in a field emission-gun type scanning electron microscope. Therefore, machining, testing and observation processes are able t
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