Executive Summary : | The structural integrity analysis of Large Diameter bearing, also referred as slewing bearings are proposed in this work. The large diameter bearing is classified based on its size, ranging from 0.5m to 1.5m. Apart from serving as the rotational connections these slewing bearings are subjected to heavy loads and the applications ranges from cranes, wind mill to nuclear reactor. In such critical applications the failure of the bearing leads to potential disastrous to the users. Unlike in classical bearings, slewing ring bearings are less firmly supported by their mounting structures and the elasticity of the upper and support structures cause an uneven distribution of external loads over the rolling bearing diameter. The unexpected excessive load on the ball due to varying load distribution causes local deformation of a bearing race way and subsequent yielding of case /core interface. The failure of rolling bearings in surface fatigue caused by this load emanates from points below the stressed surface. Therefore, it is of interest to determine the magnitude of the subsurface stresses. As the fatigue failure of the surfaces in rolling contact is a statistical phenomenon dependent on the volume of material stressed, the depths at which significant stresses occur below the surface are also of interest. The fracture occurs by the development of certain displacement discontinuity, surface/sub-surface stress within the solid while loading. It has two distinct characteristics, i.e., crack initiation and crack propagation. The crack initiation is dominated by the stress intensity factor (sIF) while the crack propagation is dominated by the fracture toughness. The assessment of fracture present in any components should be carefully carried out to avoid premature failures. The challenges in the assessment of low cycle life of slewing ring bearings task includes precise measurement of static/dynamic analysis, stiffness, contact stress, flatness, raceway relative approach, ball deformation, subsurface shear stress analysis etc. These parameters affect the bearing life and performance of the rolling elements. Correlation of fracture parameter gives an insight to the fatigue crack propagation in the structural component. The investigation of fracture parameters to characterize the crack and fatigue behaviour require thorough understanding of elastic and elastic-plastic fracture mechanics approaches. By employing design of experiment technique, a systematic analysis can be performed to correlate fracture the parameters. The preliminary analysis are carried out using lab scale samples for various conditions. The crack configurations, material model are to be varied in the lab scale model analysis followed by large diameter bearing analysis. Towards this, it is proposed to design and develop a test rigs with suitable bearing mock-ups for study the above challenges. |