Fatigue Life Prediction of a Commercial Vehicle Radiator under Internal Pressure Cycling Loading

Objectives: The study is conducted to find the hot spot stresses in the commercial vehicle heavy duty radiator subjected to internal pressure loading and predict the pressure cycle life. Methods/Statistical Analysis: The finite element analysis technique is employed to predict the hot spot stress and pressure cycle life of the radiator. Finite element model of the radiator is built by the including the mass and stiffness of the radiator component. Header tube joint is the critical area which affects the pressure cycle life and needs to be analyzed. The critical joint area is captured with a good mesh pattern and better element quality to avoid stress singularities and spurious stresses. Findings: Deformation and stresses are the studied in detail to evaluate the finite element analysis result. The radiator deformation shows core side to side expansion which correlates well with the pressure cycle test. Then von-mises stresses are measured at various locations, the header tube stress is found to at 75MPa. Since the radiator core material is ductile material, von-mises stress criterion is employed. To calculate the pressure cycle life, three components such as geometry, loading and material are required. The geometry component is represented by the stress concentration factor (kt) at the header tube joint. The Kt value can be measured based on test failure history. The loading is represented by the internal pressure loading. The S-N curve and cyclic stressstrain properties for the aluminium material is required. Once the above three parameters are known, we can calculate the pressure cycle life at the header tube joint using strain life approach. Calculated pressure cycle life at the critical joint is found to be 150,000 cycles to failure. The virtual life meets the typical pressure cycle life at the header tube joint. Application/Improvements: Prototypes for the pressure cycle test can be reduced. The approach identifies the weak areas early in the design phase. Approximate pressure cycle life at header tube joint is estimated.