Fatigue failure modeling and life expectancy of the dipper-teeth assembly of a mining shovel

Abstract

Large mining shovels are used to achieve economic bulk production in surface mining operations. The suspended payload for these large capacity mining shovels combined with dipper weight, and harsh digging environment may result in severe stress loading of the shovel front-end assembly. Material flaws, high stresses and harsh operating environment can initiate cracks in the dipper-teeth assembly that can propagate to critical lengths resulting in fatigue failure, unscheduled downtimes, costly unplanned repairs, and downstream processing circuit problems. The existing shovel research has been restricted to shovel dynamic modeling and stress measurement for the boom only and the fatigue life estimation has been ignored so far. In this research, we provided a framework for modeling the fatigue failure based on crack propagation studies for the dipper-teeth assembly. We proposed a step-by-step scheme that includes the modeling of the formation resistive forces, kinematic and dynamic modeling of the shovel front-end assembly, virtual prototyping, and crack propagation and life expectancy studies. We implemented this framework for a large mining shovel. A virtual P&H 4100XPC shovel prototype was built in ANSYS (R15) software for stress and fatigue failure modeling studies. We introduced crack at various locations of the dipper. These cracks were incremented gradually. Crack propagation simulation studies show that a 100 mm crack-length is a critical crack-length for the shovel dipper. A 75 mm bottom-plate crack can propagate to the critical length in 16 days. These initial but pioneering insights can provide a scientific basis for shovel maintenance and care and contribute towards shovel health and longevity.