Abstract
The contact stiffness of a mechanical bonding surface is an important parameter in determining the normal and radial contact force. To improve the calculation accuracy of the contact force model, the surface roughness of the bonding surface and the energy loss that necessarily occurs during the impact process should be considered comprehensively. To study the normal contact force of a revolute joint with clearance more accurately in the case of dry friction, a nonlinear stiffness coefficient model considering the surface roughness was established based on fractal theory, which considers the elastic, elastic-plastic, and plastic deformations of the asperities of the contact surface during the contact process. On this basis, a modified nonlinear spring damping model was established based on the Lankarani–Nikravesh contact force model. The laws influencing the surface roughness, recovery coefficient, initial velocity, and clearance size on the impact force were revealed, and were compared with the Lankarani–Nikravesh model and a hybrid model using MATLAB. The maximum impact force was obtained using a modified contact force model under different initial velocities, different clearances, and different degrees of surface roughness, and the calculated results were then compared with the experiment results. This study indicates that the modified model can be used more widely than other models, and is suitable for both large and small clearances. In particular, the modified model is more accurate when calculating the contact force of a revolute joint with a small clearance.
Highlights
In recent years, many scholars domestically and abroad have conducted a number of studies on the contact impact problem of dynamics with clearance
A common contact theory is the Hertz contact theory [1]; this theory can only describe the elastic deformation of the material during the contact process, and does not consider the energy dissipation
A contact force model with nonlinear damping (Hunt– Crossley model) was proposed by Hunt et al [2], which considers the dissipation of energy during the contact process
Summary
Many scholars domestically and abroad have conducted a number of studies on the contact impact problem of dynamics with clearance. A rough surface morphology has an important influence on the contact stiffness coefficient [9, 10], and affects the contact impact force during an actual contact collision. Wang et al [20] established a deterministic model for the elastoplastic contact of rough surfaces under combined loads, and obtained the actual contact area, pressure distribution, and plastic deformation of the micro-convex peaks. The contact stiffness coefficient was derived when considering the surface roughness of the contact surface, and a modified contact force model was obtained. Based on the fractal theory, a modified normal contact stiffness coefficient model was established, which considers the contact surface roughness, as well as the elastic, elastic-plastic, and plastic deformations of the asperities during the contact process. An experimental system was developed, and the correctness of the model was verified through an experimental study
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