Probabilistic–Experimental Assessment of Parametric Reliability of Friction Pairs in Braking Systems of Lifting and Transportation Machinery

This study provides a computational and experimental assessment of the parametric reliability of friction pairs in brake devices for lifting and transport technology. The computational and experimental method for assessing the parametric reliability of various friction units in lifting and transport equipment, based on operational and experimental research data with their permissible dynamic and thermal load of disc-drum and band-shoe brake devices, was developed to evaluate the influence of coupled dynamic and thermal loads on brake friction pair reliability. The operational parameters of the band-shoe brake, considered as a multi-pair friction system, were classified into four functional groups. The external operational parameters of their materials are determined, and the relationship between dynamic and thermal processes, phenomena and effects is established. A new quantitative indicator, the relative coefficient of parameter (RCP), was introduced to characterize the stochastic variability in friction pair performance and to assess parametric reliability. The meaning of parametric reliability for friction pairs is revealed with the subsequent classification of parameters that fit into the structural diagram of its computational and experimental assessment. Based on reliability conditions, the optimal thickness of the transverse or longitudinal section of the metal friction element has been determined, ensuring it does not exceed the permissible level of thermal stress. Experimental investigations of drilling rig winch brakes demonstrated that the RCP values ranged from 0.008 to 0.051 depending on operating conditions. The proposed probabilistic model enables the optimization of metal friction element dimensions while maintaining thermal stresses below critical levels.