Development of an empirical model of the spindle bearing damping in consideration of the assembly and operating condition for an application-oriented simulation of the dynamic behavior of main spindles
Final Report Abstract
The project carried out deals with the computational and experimental determination of the damping behavior of spindle bearings and thus contributes to a better understanding of the damping behavior and the methods by which it can be mapped. In section 1, experimental investigations are carried out on a bearing test rig. For this purpose, compliance frequency responses are measured in the operating condition and the damping constants of the relevant eigenmodes are determined with the aid of modal models. It is shown that the damping constants are highest in the low speed range and decrease with increasing speed until they finally remain at a constant level. In section 2, the theoretical treatment of rolling contact damping is based on the calculation of EHL contacts. The necessary equations for the description of the lubricated rolling contact are addressed and it is explained how the damping behavior can be inferred from the time-dependent rolling contact calculation. This is followed by calculations based on the design of experiments to determine the main influences on the operation-dependent damping behavior. Based on this, a simple model of the damping as a function of the operating parameters contact load, contact speed, excitation frequency and static preload is derived as an example. Finally, operation-independent parameters of the bearing are examined for their influence and presented. It is shown that the viscosity of the lubricant and the rolling element radius are the main influences on the reduction or increase of the contact-related damping capacity. Finally, a comparison is made between the test rig simulation and the experiment using the derived damping model. Good agreement is found between the amplitude heights in the compliance frequency responses for both the axial and radial directions. Section 3 presents the results of the investigations on the influence of the fit. It is shown that the fit between the outer ring and the housing has a partially significant influence on the dynamic behavior. Nevertheless, it is also found that the damping is in a similar range for all tests. The project report concludes with a prediction of the dynamic behavior of an industrially used spindle system. The damping model is again parameterized for the spindle bearings installed in the test spindle. It is shown that, despite large uncertainties resulting from the floating bearing components, for example, a good representation of the real conditions can be achieved for large parts of the operating range. Nevertheless, weak points of the model are also revealed. Especially in the high speed range, the simulated amplitude response deviates significantly from the experiment. This is attributed to the uncertainties of the floating bearing components, which have been insufficiently investigated so far. In summary, the work carried out in this project and the damping model based on it are reasonable, coherent in themselves and in relation to the existing literature in this field. Thus, important progress has been made in the field of damping prediction, which now empowers designers and computational engineers by means of a simple approach to determine damping values a priori and to use them in simulations. In a next step, the calculation results now need to be validated by further experimental investigations for a wider range of operating parameters and bearing types.
Publications
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Dämpfungsmodelle für hochdrehende Spindellager, In: Maschinenmarkt: MM, 123. Jahrgang, 2017, Nr. 44, S.: 28-32
Brecher, Christian; Motschke, Tobias & Fey, Marcel
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Dämpfungsmaße in Lagerpassungen*/Identification of damping values for spindle bearing interfaces. wt Werkstattstechnik online, 109(05), 342-346.
Brecher, C.; Motschke, T. & Fey, M.
