Assessment of Thermo-Mechanical Fatigue Performance of an Exhaust Manifold through Simulation

Exhaust manifold of an IC engine typically experiences cyclic thermal and mechanical loading and are prone to TMF failure. Thermo-mechanical fatigue resistance needs to be ensured for exhaust manifold to meet the requirement of durability in order to meet the demanding needs of recent trends in IC engine design. Considering reduced product development cycle time, more accurate design procedure for exhaust manifold through simulation route is preferred. The present work is an attempt in this direction, where methodology to carry out TMF analysis of exhaust manifold through simulation is formulated and successfully implemented. The complete simulation process involved four important stages, namely simplified 1-D simulation of engine, thermal analysis of exhaust manifold, and structural analysis of exhaust manifold and TMF life evaluation of exhaust manifold. The developed methodology has been successfully implemented considering a typical exhaust manifold. Thermal inputs obtained through simplified engine simulation using 1-D gas dynamics and engine simulation software required for thermal analysis of exhaust manifold are found to be satisfactory and has eliminated the need for complex 3-D CFD simulations. TMF life valuated at critical locations indicate that except one location all other locations have life exceeding the LCF limit.