高温氢气环境蠕变持久试验装置的试样均温性控制

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

试验过程中,试样有效段的温度均匀性(即均温性)直接影响测试结果的可信性与精度.为此,从装置的热结构和温控策略两个方面入手以保证试验过程中试样有效段的均温性.通过分析原有热结构热场分布找出试样上段温度过高的原因,在密封钟罩顶端增加水冷结构以带走聚集热量;提出Fuzzy-PID混合控制策略,采用Fuzzy控制调整上、下段加热电阻丝输入功率上限,再结合传统PID控制实现加热过程中输入功率的智能控制.结果表明,相对原有热结构及传统PID温控策略新结构,Fuzzy-PID温控策略有效的提高了试样有效段均温性,将其上、下段温差控制在±1℃以内,满足蠕变持久测试需求.

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.