MEMSマイクロエンコーダを利用した水素中フレッティング疲労における新たな相対すべり計の開発

抄録

To evaluate fretting fatigue strength in hydrogen, a new method to measure the relative slip range during fretting fatigue in hydrogen environment was developed by using an optical micro-encoder fabricated by MEMS (Micro Electro Mechanical System) technology. The relative slip range is an important parameter to evaluate the fretting fatigue strength because the fretting fatigue properties are strongly affected by the relative slip range. However, there are measurement difficulties regarding the accuracy, size of the sensor, error due to elastic deformation around the measurement part and effect of hydrogen on sensor stability. The optical MEMS micro-sensor we developed showed a good reproducibility, accuracy and stability in hydrogen environment. For further improvement of the measurement accuracy, a component of an elastic deformation around the contacting part was subtracted from the measurement value based on both experiments and calculations. By applying the MEMS sensor, it was found that the relative slip range in hydrogen was significantly lower than that in air. When 5 vppm oxygen was added to hydrogen gas, the relative slip range was increased. These results were consistent with the experimental results that local adhesion between contacting surfaces occurred during fretting fatigue in hydrogen and the adhesion was prevented by the addition of oxygen to hydrogen gas.