Chen Xuewen, Du Kexue, Du Yuqing, Lian Tingting, Liu Jiqi, Bai Rongren, Li Zhipeng, Yang Yisi, Jung Dongwon
School of Materials Science and Engineering, Henan University of Science and Technology, 263 Kaiyuan Avenue, Luoyang 471023, China.
Faculty of Mechanical, Jeju National University, 102 Jejudaehak-ro, Jeju-si 63243, Korea.
Materials (Basel). 2021 Feb 2;14(3):695. doi: 10.3390/ma14030695.
X12 alloy steel is a new generation material for manufacturing ultra-supercritical generator rotors. Cracks will appear on the forgings during the forging process and the rotors will be scrapped in serious cases. To optimize the forging process of the rotor and avoid the occurrence of crack defects in the hot forming process, based on Oyane damage model, a high temperature damage model of X12 alloy steel was proposed by introducing the influences of temperature and strain rate on the damage evolution. A reverse analysis method was proposed to determine the critical damage value of Oyane damage model by comparing experimental and simulated fracture displacement in the tensile tests. Then, the critical damage value was determined as a function of temperature and strain rate. The high temperature damage model was combined to the commercial finite element software FORGE to simulate the high temperature tensile test. The accuracy of the damage model was verified by comparing the difference of the fracture displacement between simulated and experimental samples. Additionally, as stress triaxiality is a significant factor influencing the damage behavior of ductile materials, the effects of temperature and strain rate on the stress triaxiality of X12 alloy steel was analyzed by simulating the high temperature tensile process, and the damage mechanism of X12 alloy steel under high stress triaxiality was analyzed by SEM (Scanning Electron Microscope).
X12合金钢是制造超超临界发电机转子的新一代材料。在锻造过程中，锻件会出现裂纹，严重时转子将报废。为优化转子锻造工艺，避免热成形过程中出现裂纹缺陷，基于Oyane损伤模型，通过引入温度和应变速率对损伤演化的影响，提出了X12合金钢高温损伤模型。提出了一种反向分析方法，通过比较拉伸试验中实验和模拟的断裂位移来确定Oyane损伤模型的临界损伤值。然后，将临界损伤值确定为温度和应变速率的函数。将高温损伤模型与商业有限元软件FORGE相结合，模拟高温拉伸试验。通过比较模拟样品和实验样品的断裂位移差异，验证了损伤模型的准确性。此外，由于应力三轴度是影响韧性材料损伤行为的重要因素，通过模拟高温拉伸过程分析了温度和应变速率对X12合金钢应力三轴度的影响，并通过扫描电子显微镜（SEM）分析了高应力三轴度下X12合金钢的损伤机制。
