Design Optimization and Numerical Analysis of FGM Mono-Leaf Springs Under Static, Dynamic, and Fatigue Loading

This study evaluates the static, dynamic, fatigue, and multi-objective performance of an Aluminum-Alumina functionally graded material (FGM) mono-leaf spring relative to a conventional 50R steel spring. Six power-law indices (k = 0.2, 0.5, 1, 2, 5, and 10) were analyzed using ANSYS Workbench. The FGM designs reduced mass by 60.5-65.1% while maintaining maximum von Mises stresses of 28.718-30.897 MPa, close to the steel value of approximately 28.6 MPa. All FGM cases exhibited higher natural frequencies, with the first mode increasing from 310.58 Hz for steel to 430.29-550.14 Hz for the FGM designs. Total elastic strain energy decreased from 327 mJ at k = 0.2 to 91 mJ at k = 10. The Basquin S-N model indicated superior high-cycle fatigue strength for steel, while the ANSYS fatigue-life predictions for the FGM cases were treated as model-dependent because they extend beyond the adopted S-N data range. A four-objective design assessment minimized mass and maximized fatigue factor of safety, first natural frequency, and total strain energy. All FGM designs satisfied the imposed constraints, and equal 25% weighting identified k = 0.2 as the best-balanced configuration, with a combined normalized score of 0.75. The results demonstrate that FGM gradation provides substantial lightweighting while introducing trade-offs among static, dynamic, energy-storage, and fatigue-related performance.