汽轮机高温螺栓蠕变和应力松弛研究

Research on Creep and Stress Relaxation of Bolts in Steam Turbine at High Temperature

为研究高参数汽轮机组螺栓的高温蠕变与松弛特性,解决汽轮机高压缸因紧固螺栓的蠕变导致的结合面密封性问题,建立了螺栓法兰联接的三维模型,采用ANSYS软件中自带的Norton模型,仿真模拟螺栓的蠕变与应力松弛。结果表明:螺栓蠕变先快后慢,在不同温度、相同初始预紧力的条件下,温度越高,螺栓残余预紧力越小;在相同温度、不同初始预紧力的条件下,初始预紧力越大,在蠕变初期螺栓残余预紧力也越大,但螺栓最终残余预紧力基本相同,与初始预紧力大小无关。仿真结果与试验结果吻合较好,说明使用Norton模型来预测螺栓残余预紧力随时间的变化是合适的。

In order to study the creep and relaxation characteristics of bolts in high-parameter steam turbine, and to solve sealing problem of joint surface of high-pressure casing caused by the creep of the fastening bolts, a three-dimensional model of bolt-flange connection was established, and the Norton model in ANSYS software was used to simulate the creep and stress relaxation of bolts. Results show that the creep of bolts is fast at the beginning and then slow down.Under the condition of the same initial pre-tightening force but different temperature, the higher the temperature, the smaller the residual pre-tightening force of the bolt. Under the condition of the same temperature but different initial pre-tightening force, the greater the initial pre-tightening force, the greater the residual pre-tightening force of the bolt at the initial stage of creep, but the final residual pre-tightening force of the bolts is basically the same, regardless of the size of the initial pre-tightening force. The simulation results are in good agreement with the experimental results, indicating that it is appropriate to use the Norton model to predict the change of the bolt residual pre-tightening force over time.