Research On Fatigue Cracking Of Tube And Pipe Gate Braze Joint Of Ribbon-tubular Radiator

The radiator is one of the important components of the vehicle cooling system,and its structural strength directly affects the reliability of the engine cooling system.In this paper,the phenomenon of cracking of tube and pipe gate joint of a two-pass radiator is studied.A water leakage phenomenon happened in the root zone of tube and pipe gate joint of the radiator sample under the temperature cycling test.Leakage failure occurred mainly in the root of tube and pipe gate joint of the connection of radiator water inlet chamber and core.Based on fatigue analysis theory and numerical simulation methods,fatigue simulation analysis was used for exploring the solution to the cracking phenomenon of the tube and pipe gate joint of radiator.Firstly,a model of a radiator-matched engine cooling system was established based on the graphic modeling software AMESim.In order to carry out the thermal management of the cooling system,the heat transfer characteristics of the radiator were studied.The simulation results were used as reference to set the temperature load input conditions of transient thermal analysis of the tube and pipe gate.Secondly,a finite element model of pipe and pipe joint was established.According to the actual working condition of the radiator,the tube and pipe gate of radiator was applied to pressure loads to achieve alternating pressure conditions.Alternating stress fatigue analysis of the tube and the pipe gate joint was performed by ANSYS.By compositing simulation results and test results,it is concluded that the pressure alternating condition has little effect on the strength of tube and the pipe gate joint of radiator.To fatigue cracking phenomenon of the tube and pipe gate joint,thermal fatigue effect should be paid more attention.Finally,the simulation results of the temperature characteristics of the radiator in the thermal management of cooling system based on AMESim were used as the reference to set the temperature boundary conditions of transient analysis.The thermal stress and strain distribution of the tube and the pipe joint are obtained by the thermo-solid coupling analysis of the tube and the pipe gate joint based on the ANSYS.Thermal fatigue simulation analysis for the tube and the pipe joint of radiator was performed based on the strain life theory based on LMS.The results show that the reason for the cracking of the tube and pipe gate is mainly caused by excessive thermal stress.The structural improvement measures for the cause of fatigue failure have been proposed,the simulation verification has been completed,and the improvement measure to meet the optimization requirements.The conclusion of this paper can provide a reference for the design of the fatigue durability of the tube and pipe joint of radiator,which is helpful to shorten the development cycle of the fatigue life design of the tube and the pipe joint structure of the radiator.