A Novel Gray-Scaled Threshold-Free Recursive Analysis Method: Revealing Tribological Behaviors and Identifying Frictional Running-In State

The aim of this study is to introduce a novel threshold-free recursive analysis method for friction-induced signals and explore its potential application in the identification of running-in state. To address some issues from recursive analysis results being influenced by the recursive threshold, a grayscale threshold-free recursive metric is investigated to measure the recursive characteristics in a tribosystem. Additionally, the visualization and quantitative measure extraction of the gray-scaled recursive matrix are discussed. Afterward, the friction-induced torque signals throughout the running-in process are extracted and then characterized by the proposed method. The results demonstrate that the morphology and quantitative features of the gray-scale recursive plots effectively reveal tribological behaviors and are closely related to the frictional running-in states. Therefore, the proposed method can be considered a reliable approach for characterizing the recursive properties of a tribosystem and identifying running-in states.