FEM Simulation and Life Optimization of Tandem Roller Thrust Bearing

Tandem thrust roller bearings carry high axial loads in rotary equipment such as mud pumps or extruders. Deflection of the bearing plates redistributes loads over rollers, and affects bearing life. In this study, solid finite elements modeled a shaft, housing and two stages of bearing plates. A line of spring elements represented each row of rollers. The stiffness of the line of spring elements modeled the stiffness of each roller/raceway non-Hertzian line contact. Modification of the spring element stiffness compensated for the compliance of the nodes of solid elements that modeled the bearing plates. This construct avoided computationally expensive surface-to-surface contact calculations. Further computational savings accrued from modeling the bearing and shaft assembly as axisymmetric. Program output included deflection of the bearing plates and a listing of spring element forces, which characterized the distribution of load over the length of the rollers. Bearings with optimized geometry had decreased maximum contact stress, more uniform distribution of contact stress over the length of each roller, and longer estimated rolling contact fatigue life.