22. Durability Assessment of Multiaxial Strain Loads for Rural Road Condition in Time–Frequency Domain

This paper aims to characterise the multiaxial strain loading signal in order to assess the durability of the coil spring in the time–frequency domain. Coil spring experiences vertical axial loading, direct shear force, and torsion during movement when subjected to cyclic loading. The experiment was set to capture random strain signal in the different angle at x-axis (0°), 45°, and y-axis (90°) from the coil spring at operating conditions. The time history of random strain signal was assessed based on kurtosis and the power spectrum density in order to analyse strain signals in time and frequency domain. The life is predicted through the strain-life models namely Coffin-Manson (CM), Smith–Watson–Topper (SWT), and Morrow model and is correlated using linear regression to obtain the relationship of the strain signal at 0°, 45°, and 90° axis. The results indicated that the strain at 45° axis shows the highest vibrational energy content followed by the strain at 90° axis and 0° axis. The fatigue life prediction for the CM, Morrow, and SWT models showed the same trend for the strain signals at 0°, 45°, and 90° axis. The correlation of strain life at 0° and 90° axis showed a good agreement with R² value exceeding 0.9 except for 45° axis. This shows that the strain life at 45° axis is affected by the torsion. This study showed a successful establishment of the relationship between the strain signal at 0°, 45°, and 90° axis using linear regression.