Estimated S-N curve for nodular cast iron: A steering knuckle case study

Durability assessment is performed to establish the damage applied by loads and the number of load cycles versus S-N curves. This information is evaluated using a fatigue damage hypothesis. A new relationship is proposed to estimate the S-N curve of nodular cast iron, based on its ultimate strength, using a case study of a steering knuckle component under bending load. Finite element simulation was performed to obtain the maximum stresses in the component using Patran V2012.2 and Nastran V2008 software. Correction factors accounted for surface finish, type of load and level of reliability. Actual and proposed predictions were evaluated using experimental results. The main aim of this work was to design a fatigue test, with a limited amount of information, through finite element simulation and tensile strength. The main advantage of this relationship over the other methods for estimating an S-N curve, is to improve life prediction at the boundary of low and high cycle fatigue with a simple relationship and without a series of tests to identify the S-N curve, thus simplifying durability assessment with a limited amount of information. The proposed relationship improved the life prediction by an average of 10% in the case study.