Operational modal analysis and fatigue life estimation of a chisel plow arm under soil-induced random excitations

Chisel plow is an important implement for primary tillage when the soil is dry and firm. In this research, fatigue life of a prototype of chisel plow arm under soil induced random excitation is analyzed. For this purpose, first, the field test is carried out on the chisel plow arm under soil-induced random excitations and operational modal analysis of the chisel plow arm is performed using stochastic subspace identification approach. In addition, a finite element model is constructed and successfully validated by stochastic subspace identification results. Then, the validated finite element model and power spectral density results of the measured random responses are used to achieve a process of the Mises stress in the arm needed for fatigue analysis. Finally, the fatigue life estimation of chisel plow arm is carried out in frequency domain using Wirsching-Light and Dirlik methods for different values of geometrical variables. The results of operational modal analysis demonstrate the possibility of identifying modal model of chisel plow arm in its operating condition on a basis of output-only data and the results of fatigue life estimation show that Wirsching-Light method provides a marginally safer prediction for chisel plow.