:Establishing an accurate and effective joint contact stiffness model is the basis for further modeling and analysis of machine tool dynamics characteristics. A new elastic contact stiffness model is proposed, which considers the bulk substrate deformation and modifies the Greenwood and Williamson microcontact model (GW model) of rough surfaces. In order to analyze the influence of the bulk substrate on the contact deformation, a single asperity contact model containing the bulk substrate is first established, and the contact parameters of the joint surface are obtained based on the Hertz contact theory. Then, the new elastic contact stiffness model is proposed by introducing a triangular distribution function and making up for the defects of the GW model. The effects of distribution function, bulk substrate deformation and surface roughness on the contact characteristics of the joint surface are analyzed. The research shows that the triangular distribution function can effectively characterize asperity heights distribution. The influence of the bulk substrate deformation is caused by the interaction between the bulk substrate and the asperity, which is obvious as the normal load increases. In addition, surface roughness is the main factor affecting the contact stiffness. When the joint surface is applied with the same load, the surface roughness is larger, the contact deformation is larger, and the contact stiffness is smaller.
The joint surfaces have a significant effect on the behavior of mechanical structures. Strong demand exists for the development of a model that can include the contact characteristics of joint surfaces. In this article, a new contact model considering asperity interaction and surface waviness is proposed. The roughness and waviness of the surface are separated by the Fourier series, and a contact model for an asperity is first established to obtain the displacement caused by asperity interaction. The joint surface is then treated as the contact between a rough surface and a smooth waviness to obtain a new model which considers asperity interaction and surface waviness. Simulation results show that when the normal load is fixed, the contact deformation decreases with the increasing radius of the waviness peak, but increases with the increasing surface roughness. In addition, asperity interaction will lead to a lower contact stiffness and a larger real contact area. Compared with other models, the results obtained from the proposed model are closer to the experimental results.
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