Numerical investigation on fatigue life of aluminum brazing structure with fin-plate-side bar under the low temperature thermal-structure cyclic stress

Abstract A stress analysis model was established to analyze the thermal and structural stress of aluminum brazing structure with fin-plate-side bar (ABS) in the LNG plate-fin heat exchanger. The fatigue life of ABS was evaluated based on the above stress analysis results by the different standard. The result shows that the thermal and structural stress concentration is generated at the brazed joint of ABS. Under the common action of thermal and structural stress, the equivalent stress is influenced mainly by the equivalent thermal stress. The equivalent alternating stress was calculated to be 153.5 MPa based on thermal and structural stress. The permissible cycle numbers at the brazed joint of ABS, which is calculated by the fatigue assessment procedure of ASME and JB4732, are 3311 and 2953, respectively. The fatigue assessment results based on the third strength theory is more conservative for the ABS. The influence of operation parameters is also analyzed for the fatigue life of ABS. The temperature difference between NG and MR, MR temperature and NG pressure will be the main factors to impact the fatigue life of that. And a method is proposed to predict the fatigue life of ABS according to the main factors. The error will be less than 10% between the prediction results and the simulation results.