Brake Squeals After Standing at Low Temperatures 2006-01-3190
Brake squeals are self-excited vibrations arising from friction, caused by an increase in the coefficient of friction (COF) or friction vs. velocity (μ-v). Although some studies were conducted on COF at low temperatures in the past, the relationship between brake squeals and the characteristics of friction after standing at low temperatures have not been adequately considered.
Hence, we performed burnishing using a brake dynamometer with an environmental chamber at various rotor temperatures, and measured brake squeals and COF at a low speed just after burnishing and braking after standing at low temperatures. In addition, Focused Ion Beam (FIB) etching was performed on the surfaces of the disc rotor after the end of the experiment to observe the quantity of adhered transfer film (T/F). Based on the results of this observation, we will suggest the factors involved in COF changes after standing at low temperatures.
Brake squeals which occurred after standing at low temperatures were more notable than those occurring just after burnishing. By standing at low temperatures, not only did the COF increase but also the negative μ-v slope increased. We surmised that these changes cause the squeals after standing at low temperatures. T/F adhered after burnishing and a phenomenon whereby part of the T/F is peeled off the disc rotor was observed after standing at low temprature. We propose that such changes in the adhesion of T/F bring about the change in COF, leading to brake squeals.