Design Improvement and Failure Simulation of Thermostat Vent using Fatigue Test method

Currently the Automotive industry demands highly competitive product to survive in the global tough competition. Even if there is a slight reduction in product cost and time has a high significant impact on business. Engineers are under tremendous pressure to develop competitive and give better product resolution at the earliest. The paper focuses on the thermostat, that is placed between the engine and the radiator. The thermostat has a function is to block the flow of coolant to the radiator until the engine has warmed up. When the engine is cold, no coolant flows through the Radiator. Once the engine reaches its operating temperature (In our case, SOT 88°C to FOT 98° C), the thermostat opens. The thermostat helps to warm-up the engine coolant quickly and thus the thermostat reduces engine wear, and emissions. The thermostat mechanism consist of cylinder is filled with a wax that begins to melt at designed SOT. A rod connected to the valve presses into this wax. When the wax melts, it expands significantly and pushes the rod out of the cylinder, opening the valve. The thermostat also has a vent, which is placed on the topmost point of the engine coolant jacket. The function of this vent is to send all the air bubbles in the engine coolant circuit to the degassing tank. To arrest the failure of this vent, an innovative approach was used to move the design of the de-aeration restrictor to the thermostat root. Thus, increasing the strength of the vent at root and providing good business impact on cost savings. Physical testing has provided an effective way to smoothen product development for concern resolution. This Paper highlights approach on an attempt to field failure simulation with existing and modified design with lab test results. This lab test has helped to improve product quality and establish aligned and correlated load case in simulation for quicker failure resolution. Keywords: SOT – Start Opening Temperature, FOT - Full Opening temperature, Thermostat, Reliability, Fatigue.