Structural acoustic model for the rough rolling contact in bearings based on real surface conditions

The interest in bearing diagnostic techniques is increasing, due to the necessity of an early evaluation of the surface condition and remaining operating time. This work presents a procedure for the simulation of structural-borne sound resulting from the dry interaction of surfaces during rolling contact. It is based on the elastic rough theory of contact and considers the operational conditions of the machine and the dynamics of rolling bearings for the calculations, as well as on the actual roughness profiles of the surfaces in contact as input parameters. The model makes no prior assumption about the height distribution of the asperities. It is therefore suitable for the calculation of the contact between any kind of surface, provided that its roughness profile is known. The main interest lies in the investigation of how the condition of the surfaces in bearings affects the vibration signal generated by the contact between them. For that purpose a physical model of this interaction was developed. The model delivers a time evolution of the vibration of the bearing based on the actual condition of its surfaces. This allows, among other things, to follow de degradation of the bearing's races and to calculate the influence of this degradation over the vibration produced by the bearing. Additionally, in this work, a rough parameter study is made on surfaces with different finishes as well as on bearing surfaces in different stages of degradation. A set of cylindrical and ball bearings is run until different surface conditions are reached. Their surface roughness is measured and used as input to the physical model to simulate the structure-borne sound produced by this machine element and imposed as excitation to the surrounding structure. The model proves to be sensible to very early stages of wear in bearing's races, where massive material removal did not already occur. Furthermore, it addresses the problem of vibration generation during to rolling interaction of mechanical components in rolling bearings.