Fatigue in the shell of a conveyor drum

The shell of a belt conveyor broke in operation due to fatigue in the area of the weld seam between the axle disk and the cylindrical shell. The investigation had to provide evidence whether an overloading of the drum, or a deficient design or fabrication lead to the failure. After the first damage hypothesis had been ruled out, two finite element models were built to compare the original design with the actually manufactured drum by means of nonlinear calculations.Based on the stress components of the ‘hot spot’ on the circumference, the service life of the drum was calculated for the given loading conditions. For the design according to the drawing, a sufficient service life was verified. The estimated service life of the failed drum corresponded with the effective operation time of the conveyer. High shear stresses contributed significantly to the deterioration. Since the realisation of the design proved to be problematic regarding the welding technique in the area of the seam root and at the shoulder of the axle disk, an optimised design was developed and proposed.