Computation and Field Dynamic Stress Simulation of Shovel Crawler Shoes

Electric cable shovel excavator is widely used in the surface mining operations of oil sand and other highly abrasive formations. The oil sands mines in Alberta use P&H 4100 C Boss shovel [1,2] for their loading operations. The lower works of this shovel consist of propel and crawler systems [3-7]. The crawler system consists of a crawler track assembly, front and rear idlers, lower rollers and guide rails [3]. The crawler track assembly is made up of shoes that are connected together by link pins to form a continuous chain. The efficiency and reliability of the shovel during the excavation of oil sands depends on the service life of the crawler track. The two crawler tracks interact with the abrasive terrain and distribute the machine and dipper loads to the ground during both propel and loading duty cycles. This interaction generates dynamic loads which can cause stress loading, wear, and crack and fatigue failure of the crawler shoes. The only published study on dynamic stress simulation of shovel crawler shoes was conducted by Frimpong et al. [4-7]. They developed the 3-D virtual prototype model of the rigid-flexible open chain crawler track assembly interacting with oil sands to study stress distribution in the crawler shoes during shovel propel and loading operations. The load due to machine weight and dipper pay load were distributed on each crawler shoe based on the assumptions obtained from on-field observation. The cyclic ground pressure acting under the P&H 4100C Boss shovel during the loading duty cycle is reported in the field study undertaken by Joseph [8], Joseph et al. [9] & Sharif Abadi et al. [10]. They measured ground bearing pressure acting under shovel front and rear track for three idealized shovel-truck loading duty cycles using passive seismic instrumentation. The present study uses the field data [8-10] to distribute load on the crawler track to determine dynamic stress distribution in the crawler shoes during propel and loading within MSC.ADAMS VIEW/FLEX/ DURABILITY and MSC.NASTRAN [1115]. This stress results can be used in the subsequent study of crawler shoes for investigating its crack and fatigue failure.