A study conducted at the University of Toledo, sponsored by the Bar Applications Group of American Iron and Steel Institute (AISI) and the Forging Industry Educational and Research Foundation (FIERF), demonstrated the superior fatigue properties of forged steel over aluminum and iron castings.
The study focused on safety-critical steering knuckles, and it explored forged versus competiting material and manufacturing processes technologies using experimental, numerical, and analytical tools. It showed that forged steel was superior in terms of strength, durability, and cost. It demonstrated that optimization of steering knuckles can achieve weight and cost reductions of at least 12% and 5%, respectively with no performance degradation.
For specimen testing, strain-controlled monotonic and fatigue tests were based on ASTM standard test methods and recommended practices. Data obtained made it possible to compare deformation response, fatigue performance, and failure mechanisms of the base materials and manufacturing processes, without introducing the effects and interaction of complex design parameters.
Analytical work consisted of finite element analysis (FEA), durability assessment, and optimization analysis. Linear and non-linear FEAs of the steering knuckles were conducted to obtain critical locations, and stress and strain distributions, of each component. A general life prediction methodology for the subject components was developed, where material monotonic and cyclic data and results of the FEA were used in life prediction methods applicable to safety-critical automotive components.
Professor Ali Fatemi and research assistant Mehrdad Zoroufi, Department of Mechanical, Industrial, and Manufacturing Engineering, University of Toledo conducted the study and prepared the report for the FIERF and AISI.
For more information, contact AISI, Southfield MI.