Creep Damage Analysis and Remaining Life Assessment of Ferromagnetic Materials Exposed to High Temperatures

J.印度大学。伊利诺伊州，芝加哥-这项研究旨在建立一种可行的方法，通过使用UIC开发的磁弹性传感器来测量高温下使用的低合金铁磁钢的蠕变损伤。磁弹性现象和铁磁材料内部结构变化之间的基本关系将被用来评估蠕变。通过了解微结构变化对材料磁响应的作用，可以对传感器设计进行调整，以提高其灵敏度。对两种类型的铁磁钢的几个样品进行蠕变测试；系统地使用传感器测量每个样品的相应磁响应。将产生“蠕变-磁响应”的校准曲线，以评估与蠕变损伤有关的铁磁钢的渐进磁行为。用光学显微镜、扫描电子显微镜、透射电子显微镜、能谱仪、X射线衍射仪和显微硬度计对铁磁材料的冶金变化进行了表征。围绕国内能源供应和针对基础设施干扰的保护问题，需要对材料进行更密切的评估和实时系统监测，以确保可靠性。期望得到一种测量低合金铁磁钢蠕变损伤的实用方法。开发无损检测设备来评估材料状态是延长能源生产系统使用寿命的关键。

ABSTRACT0434516 J. IndacocheaUniv. Illinois, ChicagoThis study intends to establish a viable method to measure creep damage of low alloy ferromagnetic steels used at elevated temperatures, by using a magnetoelastic sensor developed at UIC. A basic relationship between magnetoelastic phenomena and structural changes within the ferromagnetic materials will be developed to assess creep. By understanding the role of microstructure changes on the material's magnetic response, adjustments to the sensor design can be made to enhance its sensitivity. Creep testing is performed on several samples pertaining to two types of ferromagnetic steels; systematically the corresponding magnetic responses of each sample will be measured using the sensor. A calibration curve of "creep-magnetic response" will be produced to evaluate the progressive magnetic behavior of the ferromagnetic steels in relation to creep damage. The metallurgical changes of the ferromagnetic materials are characterized by light, scanning, and transmission electron microscopy with EDS, x-ray diffraction and microhardness measurements. Issues surrounding domestic energy supply and protection against infrastructure disturbances demand a closer evaluation and real time system monitoring of materials to ensure reliability. A practical method to measure creep damage of low alloy ferromagnetic steels is expected to result. Development of NDE devices to evaluate the materials status is key to extending the service life of energy producing systems.