Temperature uniformity control on specimen of material testing apparatus in hydrogen environment

A new testing apparatus in hydrogen environment was developed for studying the degradation of material properties by hydrogen which is the most common type of damages induced by gas. The temperature uniformity of specimen is the key to ensure the creditability and accuracy of the testing results. Another water-cooling structure was added on the top of the pressure vessel to take away the excessive thermal gathered at the upper specimen. A new fuzzy-PID control algorithm was proposed to enhance the accuracy of temperature uniformity. The fuzzy algorithm is used to set the power upper limit of both upper and lower resistive heater respectively, and then the traditional PID algorithm is used to control the power of each resistive heater separately. The experiment results indicate that the new heater structure and fuzzy-PID control algorithm improved the temperature uniformity of the specimen, and the temperature difference between upper and lower of the specimen was control within ±1℃, which meet the demands of material performance testing.