| Summary: | 碩士 === 中華大學 === 機械與航太工程研究所 === 95 === In this study, micro strain gauge is designed in the polyurethane (PU) thin film to measure the stress/strain in situ. In our design, the strain gauge is embedded in PU which is different to the commercial strain gauge of sticking to the sample. The metal layer of strain gauge used in this study is gold. The overall size of the designed strain gauge is 1 mm x 1 mm x 0.1 μm and the resistance value was measured to be 200±30Ω. The static test of strain gauge without damp proof shows that the gauge sensitivity G was measured to be G=4 when strain range is less than 1%. While G was measurement to be 1.8 when the strain range is between 1~1.5%. The static test of strain gauge with damp proof shows that the G was measurement to be G=2.6 when strain range is less than 1.2%. The dynamic test of strain gauge demonstrates that the strain is reverse proportion with frequency when strain is 0.75%. However, when the strain is 1.5% the strain is direct proportion to the frequency. The possible reason was the plastic deformation of gold was induced. After testing, the microfabricated strain gauge was found having stable problem. There are three possible reasons: 1. The adhesion of gold thin film and the substrate is poor. 2. The surface gold coated layer has many defects. 3. The strain of gold thin film has to be limited in a very low level. As a conclusion, the designed strain gauge in this study can measure more exact data when strain range is less than 1%. In dynamic test, it is suitable only measuring in a short time. Keywords: foil strain gauge, polyurethane (PU), gold, gauge sensitivity
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