Fatigue Evaluation for Innovative Excavator Arms Made of Composite Material

Abstract

This research reports the results related to the evaluation of the fatigue phenomenon of the arms of a medium–large excavator made of composite material (carbon fiber) instead of the classic constructional steel S355 (UNI EN 10025-3). In the numerical sizing phase, it was obtained that the overall weight of the excavator’s arms made of composite material is about 35% of the same components made of steel, obviously with equal performance in terms of the safety static coefficient, rigidity, and critical buckling load. The evaluation of the fatigue behaviour (assuming 5.25 × 106 load cycles) applied for each load condition analyzed (levelling from the maximum distance to the minimum, lifting at the maximum distance, lifting at the minimum distance and rotation) shows the magnitude of the safety coefficients both related to the allowable stress and relative to the number of cycles acceptable. The assumption instead of combined cycles (involving one or more load conditions) leads to a significant reduction in the magnitude of the safety coefficients. The implementation of a loading cycle plan resulting from the different load conditions must be reliably assessed to evaluate as accurately as possible the fatigue behavior of the excavator arms made of composite material.