| Summary: | 碩士 === 國立中興大學 === 機械工程學系所 === 95 === Gothic profile surface is a special surface that provides multi contact points with other surface and thus widely used in precise transmission components, such as ballscrew and linear guide. However, as the transmission component needs preload between moving elements to provide motion stiffness, interference assembly is introduced in these transmission compoments. This research is aimed to investigate the relationship between the preload and the interference of Gothic and spherical surfaces. Experiments are also designed and conducted as a comparison with the theoretical analysis.
The contact model of Gothic and spherical surfaces is first constructed and analyzed by Hertz contact model as well as by finite element method. The results reveal that the contact force increases, non-linearly, as the interference increases. Experiments measuring the force and the deformation of a fixture, with dual-spherical Gothic surfaces of radius 10.287mm, in contact with different steel balls are designed and conducted. The diameters of these steel balls are from 19.035mm to 19.06mm in 5μm increment with contact forces ranging from 21.2N to 282.2N. The experimental results showed that the deformation increases nonlinearly when contact force increases, in consistent with Hertz model. Nevertheless, the measured deformations are higher than theoretical values due to slippings between the contact elements in the experiments. The experience formula of deformation and stiffness with respect to the contact force for different profiles form factor are derived from the experimental data as a reference for the design and analysis of transmission components.
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