摘要
某电厂新建机组中压外缸螺栓在168试运行过程中发生断裂,并有多条螺栓的螺纹处产生裂纹。失效分析认为该螺栓基本属于轴向大应力脆性断裂,为分析螺栓受力情况,采用有限元的方法对螺栓螺纹及螺柱的受力状况进行计算。为得到较高的精度,采用全螺纹、精细分网模型进行计算,结果表明螺纹的受力与螺柱内平均应力及螺栓材料的应力应变曲线有紧密联系;接触的前3阶螺纹承受的应力较大,最大应力约为螺杆平均应力的2. 5倍,工况下达到了屈服强度的82. 8%,往后各阶螺纹应力逐步递减;对螺栓加载过程进行了模拟,发现应力水平受加载历史影响。结合螺栓服役条件,认为本次螺栓裂纹与安全裕度不足有关,在附加应力的影响下造成螺栓开裂失效。
The intermediate pressure outer cylinder of steam-turbine of new units fractured during the 168 h running. The cracks were also found on the other bolts used on the intermediate pressure outer cylinder. It showed by the failure analysis that the brittle fracture occurred because of the high axial stress. The stress distribution was studied based on finite element analysis.The full screw thread and fine grid blocks were used to gain the higher calculation accuracy. It said that the stress of the screw thread was closely influenced by the stress of the mean stress of screw and the stress-strain curve. The force on the three screw threads which near the screw was higher than other screw threads.The maximum stress on the screw threads was 2.5 times of the screw and reached 82.8% of yield strength at the operating condition. The loading process was simulated and it showed that the stess was influenced by the loading process. Considering the service condition of the bolts,the fracture of the bolts was mainly caused by the lack of safety tolerance and the additional stress.
作者
刘长福
蔡文河
代小号
陈鑫
董树青
杜双明
宁玉恒
LIU ChangFu;CAI WenHe;DAI XiaoHao;CHEN Xin;DONG ShuQing;DU ShuangMing;NING YuHeng(China Datang Corporation Science and Technology Research Institute Thermal Power Research Institute,Beijing 100040,China;Guodian Boiler and Pressure Vessel Inspection Center,Beijing 102209,China;Datang Notheast Electric Power Test&Research Institute,Changchun 130012,China)
出处
《机械强度》
CAS
CSCD
北大核心
2019年第1期238-243,共6页
Journal of Mechanical Strength
关键词
螺栓
安全裕度
应力
螺栓伸长量
有限元
应力分布
失效分析
Bolt
Safety
Tolerance
Stress
Elongation of bol
Finite element
Stress distribution
Failure analysis
