| Due to the soft nature of the underfoot conditions in an oil sand mine, mobile equipment tends to develop greater amounts of maintenance problems than similar equipment in other types of mines. This is an investigation into cracking of haul truck dump bodies in oil sand mining service using the Finite Element Method (FEM). This work identifies the damage mechanism and source causing this persistent problem, which occurs at the intersection of the widthwise and lengthwise box-style floor stiffeners. In particular, compressive, membrane stresses are setup at these intersections resulting from overall bending of the floor plate from the weight of the ore. Superimposed onto these membrane stresses are localized bending stresses caused by very slight deflections, or twist, within the frame. Depending on the magnitude of twist, these localized bending stresses can overcome the compressive membrane stress producing sufficient tension to propagate a crack in this as-welded, non-heat-treated connection. |
