An investigation on the fatigue performance of austempered ductile iron steering knuckle

Steering knuckles are the important components that connect the wheel in a car to the steering system subjected to time varying load during their life leading to fatigue failure. The study reports on the fatigue performance of the austempered ductile iron (ADI). SG iron can be made up of three compositions: without alloying elements (X), SG + 0.22% (X1) and SG + 0.34% (X2) of nickel. Three sets of knuckles were heat treated and specimens were cut from steering arm and converted into test sample (tensile and fatigue) form. The tensile test and fatigue test were done using 250 kN universal testing machine (UTM) and axial fatigue machine at constant load condition for different loads, respectively. The corresponding cycle stresses were recorded and S-N curve drawn. The same composition of steering knuckle was used for component level fatigue test at a load of ±4.7 kN constant amplitude mode up to 1 × 107 cycles, but no damage was found.