Determination of Material Coefficients for SA-317 and for 2.25 Cr-1 Mo at 450 °C in Chaboche Unified Model

热疲劳是公认的冷热流体混合点的重要损伤机制。这种现象是炼油厂和发电厂管道部件全寿命管理中的一个重要课题。特别是，由于冷热流体的混合，三通接头的高频温度波动可能导致材料降解，导致开裂，从而影响系统的完整性。为了预测循环热载荷引起的失效，需要一个应变基疲劳曲线。特别是针对两组管道钢，300系列不锈钢和2.25 Cr-1Mo钢。对于前者，将在不同温度下进行基于应变的疲劳试验，以扩展ASMEcode在更高温度下更高应变范围的疲劳设计中的应用。对于后者，ASME规范的温度范围将被扩展，以考虑在混合三通处看到的温度升高。提出的研究结果将用于捕获Chaboche粘弹性材料模型，该模型将用于有限元程序中预测管道钢在混合三通处的热疲劳失效。这将有助于减少疲劳失效的可能性，从而提高炼油厂和发电厂管道部件的结构完整性。

Thermal fatigue is widely recognized as an important damage mechanism in mixing points of hot and coldfluids. This phenomenon is an important subject in the life-time management of piping components ofrefineries and power plants. In particular, high frequency temperature fluctuations in tee connections as a resultof mixing the hot and cold fluids may cause material degradation with consequence of cracking and thus affectthe system integrity.In order to predict failure caused by cyclic thermal loading, a strain base fatigue curve is needed. In particular,two group of pipeline steels will be targeted, the 300series stainless steel and 2.25 Cr-1Mo steel. For the formerones, strain-based fatigue tests will be conducted at different temperatures to extend the application of ASMEcode for fatigue design for higher strain ranges at higher temperature. For the latter, the temperature range ofthe ASME code will be extended to account for the elevated temperature as seen at the mixing tees.The results of the proposed research will be used to capture the Chaboche viscoelastic material model whichwill be used in the finite element code to predict thermal fatigue failure of pipeline steels at the mixing tees.This will help minimize the likelihood of fatigue failure, and therefore, improve the structural integrity ofpiping components of refineries and power plants.