Prediction Model for Brake-Drum Temperature of Large Trucks on Consecutive Mountain Downgrade Routes Based on Energy Conservation Law

Excessively high brake temperature may lead to brake fading and failure, resulting in truck runaway down a graded descent. The accurate prediction of the changes in the brake-drum temperature on downgrades can provide theoretical guidance for truck accident countermeasures, such as determining the maximum safe speeds and the locations of truck escape ramps. By analyzing truck accident mechanisms during graded descents and selecting the initial brake-drum temperature, downgrade percentage and length, and the truck weight and speed as independent variables, with the brake-drum temperature as a dependent variable, the downgrade process of a truck can be divided into two stages: speed control at the grade section and emergency braking at the grade end. The energy conversion process in the forms of brake and nonbrake forces in the two stages are analyzed, based on the energy conservation law. A prediction model for the brake-drum temperature of large trucks on consecutive mountain downgrade routes is established, using the heat quantity formula. The model’s numerical calculation explicitly demonstrates the effect of all the variables. The brake-drum temperature is positively related to the truck weight, and the percentage and length of the downgrade. The temperature increase in the control speed phase is negatively related to the truck speed, whereas that in the emergency braking phase is positively related. The relationship curves between the variables show that the brake-drum temperature does not change significantly with the truck speed. However, the brake-drum temperatures, under different truck weights, downgrade lengths, and percentages, at the same speed, differ considerably. Compared to the existing empirical fitting model based on specific test data, the proposed model clearly shows the effects of main variables. The proposed model can be used for determining the safe truck speeds and locations of truck escape ramps to provide guidance for drivers and builders.