Simulation On The Process Of Hydraulic Expansion Technology Of Heat Exchangers And The Quality Analysis Of The Joint In Nuclear Power Auxiliary System

Hydraulic expansion can cause high residual stress at the transition zones of the tube-to-tubesheet joints, so that’s why the transition zones have extreme high trend to SCC. Nowadays, some foreign modern nuclear station codes have clear requirement on the residual stress in the stainless tube, and domestic nuclear and military industries also put a lot of focus on the stress level in the stainless tube. In conclusion, it has great significance to analyze and control the stress in the expansion joint of the heat ex-changer with stainless tubes in the Nuclear Power Auxiliary System.The theoretic formula based on the material model of linear strain-hardening about the relation between expansion pressure and residual contact pressure is obtained in the research, and has been verified its accuracy. A FEA has been carried out to analyze the stress in a given tube-to-tubesheet joint with ANSYS as well as the SCC test. The FEA and experiment indicate that the expansion joint has high SCC trend theoretically and experimentally. To decrease the residual stress in the tube, some methods are provided with FEA and experiment verification in this paper. At the end of this paper, the insecure problems in the joint expanded prior to the welding and that welded prior to expansion have been discussed.The research work in this paper has great value to engineering. It not only provides a simplified formula on hydraulic expansion for engineering practice, but also offers meaningful methods to decrease the stress lin the tube.