镍钛形状记忆合金压缩力学行为及其密封性能

法兰密封连接是过程工业装置中最常见的可拆连接形式,在保证法兰连接良好的密封性能及长久的使用寿命上,密封新材料的开发和应用具有重要意义。以Ni_(50.9)Ti_(49.1)(原子分数)形状记忆合金为对象,研究其在压缩载荷作用下的力学行为;加工了镍钛合金平垫片,研究密封连接结构泄漏率随预紧力、介质压力及温度的变化规律。试验结果表明:镍钛合金压缩载荷作用下具有超弹性特性,马氏体相变初始应力为270 MPa,不同压紧应力下试样的回弹率都达到99%以上。在恒定预紧力下,随着介质压力的提高,密封连接的泄漏率呈增加的趋势;随着温度的增加,泄漏率呈下降的趋势。最终,依据不同的工况条件获得了最佳的预紧力范围。

Compressive Mechanical Behavior and Sealing Property of NiTi Shape Memory Alloy

Flange joints are most popular removable connection in process industry devices. The development and application of new sealing materials have profound significance on good sealing performance and long service life for flange joints. The mechanical behavior of Ni50.9Ti49.1 shape memory alloy was studied under the compressive loading. The NiTi flat gaskets were processed and the leakage rate varying with medium pressure and pretightening force was researched. The experimental results show that, the NiTi alloy has the property of super-elasticity during the compressive loading. The initial stress of martensitic phase transition is 270 MPa and the resilience rates of NiTi alloy can reach to 99% under the compressive loading. Under constant pretightening force, the leakage increases obviously with the increasement of the medium pressure and the leakage decreases as the temperature rises. Finally, the optimal pretightening force is obtained according to the different working conditions.