Comparison of Fatigue Reliability Life of Telescopic Rod of an Eccentric Telescopic Rod Conveyor with and without Strength Degradation

Abstract

Eccentric telescopic rod conveyors are used to convey straw from chain conveyors to the feeding and compression mechanism of the 4FZ-2000A type self-propelled straw harvesting baler. As the main working component, the telescopic rod endures higher dynamic loads while conveying the straw. This will make the telescopic rod prone to fatigue fracture. Therefore, it is necessary to find a feasible model that can accurately estimate the fatigue reliability life of the telescopic rod. In order to ensure the safe working of the eccentric telescopic rod conveyer, a mechanical model of the main bearing parts of the telescopic rod is established, and virtual prototype technology is used to obtain the work load spectrum borne by the telescopic rod. Static analysis of the telescopic rod using the finite element method shows that the telescopic rod experiences multi-axial stress fatigue, and the critical section is determined. The S-N curve equation of the structure modified by the surface mass and stress gradient, critical plane approach, Miner's cumulative fatigue linear damage model, and Gaussian normal distribution model of fatigue life are used to estimate the fatigue life of the telescopic rod. In order to predict the fatigue life of the telescopic rod accurately, fatigue reliability lives are calculated with and without consideration of the strength degradation. The results show that: (1) the fatigue life prediction without considering the strength degradation is far different from practical experience; the results obtained after considering the strength degradation are more conservative and more consistent with the actual fatigue lives. The prediction results are more accurate. (2) When the strength degradation is considered, the modified Gerber correction method is more accurate than the Goodman correction method. The results of this study can provide a reference for the fatigue reliability analysis and optimization of eccentric telescopic rod conveyors.