Fatigue & Creep validation process for Pressurized Plastic Tanks

Most of the coolant plastic tanks in the Commercial vehicles industry are manufactured using injection molding process. There is a well-defined process for pressurized coolant tank evaluation for Fatigue & Creep loads. This paper involves the study and process defined to evaluate the Fatigue & Creep loads on Rotomolded Pressurized coolant tank. The loads acting on the coolant tank & boundary conditions are completely new and for these the fatigue & creep evaluation criteria are developed and validated using both simulation & bench test results. Roto-molding is a cost-effective method to manufacture plastic tanks. For manufacturing a pressurized tank, the process involves after the Roto-molding of the main tank is completed, spin welding is adapted to join features such as ventilation ports & level sensor. This in turn drives complexity to ensure the tank is manufactured with desired quality, finish & strength. This means the tank should be durable after this operation for the number of defined cycles. Additionally mounting features and internal geometry posted more challenges during the development of the tank. CAE inputs The Transient load cases were simulated using 1D simulation tool and used as input for defining the boundary conditions. This helped to define a new creep & fatigue criterion. The vehicle test results proved the defined criteria was the successful to evaluate the design of Rotomolded coolant tank. Poly propylene (PP141) material creep simulation performed at 90°C with 140kpa pressure for different strain rates. This helped to define a new creep & fatigue criterion for Rotomolded coolant tank. Both Test & CAE results were matching with Hot spots identified in Rotomolded coolant tank.