Mechanics of Electric Rope Shovel Performance and Reliability in Formation Excavation

Large-capacity rope shovels are used as primary production equipment in many surface mining operations. Current rope shovels have payload capacities in excess of 100 tons per pass. The dynamic payload and formation resistive forces result in severe stress loading of the shovel front-end assembly. Material flaws, high stresses, and harsh excavation conditions can initiate cracks in the dipper-teeth assembly. These cracks, under high stresses, can propagate to critical lengths resulting in fatigue failure of frontend assembly. Dipper-related problems can significantly reduce shovel availability. There is no fundamental research for understanding dipper fatigue failure resulting from high stress intensity, crack initiation, and propagation, the subject matter of this study. The Newton-Euler algorithm is used to build kinematics and dynamic models of the cable shovel front-end assembly. The models incorporate the dynamic resistive forces on the dipper-teeth assembly. Numerical simulations are used to generate the dynamic payload force and its dynamic left. Virtual simulation, based on the P&H 4100XPC shovel prototype in ANSYS (R15), is run to generate stress loading of the dipper-teeth assembly and equivalent (von Mises) stresses. Stress intensity factors are computed for various crack lengths in the dipper-teeth assembly, and the crackpropagation lives are computed for these cracks. The results show that a 75-mm crack can propagate to the critical length in 16 days. This research study provides a pioneering effort toward understanding shovel dipper fatigue failure due to high stress intensity, crack initiation, and propagation for understanding shovel reliability and availability for production efficiency and bulk production economics.