Study On Fatigue Life Of Welded Joint Between Tube Sheet And Heat Exchange Tube

Welding is an important industrial manufacturing technology,widely used in various industries of the national economy.Due to defects and stress concentration in the welding area,it is easy to cause fatigue damage and is one of the weak links of the entire device.This topic focuses on the relationship between the fatigue life of welded joints between tubesheet and heat exchange tubes in shell and tube heat exchangers and the welded structure,which has certain significance for ensuring the safety and long-term operation of heat exchangers.This project mainly applies the notch stress method to construct a welded structure model of tube sheet heat exchange tube.Numerical simulation methods are used to conduct stress analysis on models with different structural sizes and load conditions.The Von Mises and IIW criteria are used to characterize the multi-axial stress of the welded structure.The S-N curve recommended by the International Welding Society is used to predict the fatigue life of the welded structure,and the fatigue life of different structural parameters and load forms is obtained,A comparative analysis was conducted on the effects of the position of the tube plate opening,the thickness of the tube plate,the thickness of the heat exchange tube,and the load form on the fatigue life.The results show that the location of the tube plate opening has a significant impact on the fatigue life of the welded joint between the tube plate and the heat exchange tube.When the heat exchange tube is located at the center of the tube plate,the multiaxial fatigue life of the welded joint is the largest,while the heat exchange is located at the edge of the tube plate,and the multiaxial fatigue life of the welded joint is the smallest;As the thickness of the tubesheet increases,the fatigue life of the welded structure between the tubesheet and the heat exchange tube first increases and then decreases.Therefore,under the condition of meeting the static strength of the connection between the tubesheet and the heat exchange tube,the tubesheet thickness is not as large as possible,but there is an optimal value;When the maximum axial stress on the cross-section of the heat exchange tube is the same due to external loads,the fatigue life of the connection between the tube plate and the heat exchange tube decreases with the increase of the wall thickness of the heat exchange tube.Moreover,when the wall thickness of the heat exchange tube exceeds a certain value,the fatigue life no longer changes;When the maximum axial stress generated by the external load on the cross-section of the heat exchange tube is equal,the fatigue life of the welded joint is the highest under pure tensile load,and the fatigue life is the lowest under pure bending load,indicating that bending load is more dangerous for the welded structure of the tube sheet and heat exchange tube.By studying the fatigue life of the welded structure between the tubesheet and the heat exchange tube of a shell-and-tube heat exchanger under different structural dimensions and load conditions,the effects of the position of the tubesheet opening,the tubesheet thickness,the thickness of the heat exchange tube,and the load form on the fatigue life are clarified.The relevant work can provide a certain reference for the design of the welded structure between the tubesheet and the heat exchange tube.