Necessary condition for creep groan occurrence on a simple caliper-slider model

Brake creep groan is a unique stick-slip vibration that has not fully understood yet. The present paper discusses necessary condition for creep groan generation by introducing a simple caliper-slider experiment model. The model is developed based on the principle operation of a brake system so that the simulated creep groan has quantitatively similar time history to that of the real brake system. The main advantage of the model is that it enables various parameters to be taken into consideration, such as contact condition (surface roughness, material properties, and contact area), forces, and stiffness of the structure. Therefore, this paper, instead of focusing on the limit cycle of creep groan time history, approaches the problem using the effect of various parameters on creep groan occurrence. The main objective is to identify the necessary condition that promotes creep groan generation on the test model and therefore provides some understanding about how to avoid creep groan at brake system. The results show that creep groan seems to generate when the contact is smooth, particularly when the stiffness of the structure is relatively low. The result of the analysis is concluded in a map of creep groan, showing the necessary condition that is susceptible to creep groan generation. According to the map, creep groan occurrence is controlled by two dimensionless parameters. The first parameter is the ratio between stiffness of the model's structure to the stiffness of the contact interface, r_k. The second parameter is the difference between static and dynamic coefficient of friction, Δμ. Creep groan tends to generate at the region of higher stiffness ratio, r _k, meaning that either the contact stiffness is high or the structure's stiffness is low. On the other hands, the region of low stiffness ratio, r_k, is not suitable to creep groan generation because of the reason vice versa. However, creep groan in this region is still possible only if the difference between static and dynamic coefficient of friction, Δμ, is large enough.