Evolution of chaotic stick–slip frictional behavior affected by dynamic normal stress disturbances: parameter study based on spring-block model

Frictional sliding is ubiquitous in both natural phenomena and engineering systems, often occurring under dynamic normal stress conditions, yet the theoretical understanding of such scenarios remains limited. This study employs a verified one-dimensional spring-block model, incorporating rate- and state-dependent friction law, to investigate the evolution of stick–slip behavior under cyclic normal stress perturbations. We conduct a systematic parametric analysis to explore how the normalized amplitude and frequency of the normal stress oscillations influence the chaotic frictional behavior. The results demonstrate that cyclic normal stress dramatically alters the frictional style. While the model exhibits periodic stick slip under constant normal stress, specific combinations of intermediate amplitude and frequency drive the frictional style into a chaotic regime characterized by irregular and unpredictable stress drops. We employ a Schuster test to reveal that the timing of chaotic slip events can be statistically correlated with the phase angle of normal unloading beyond critical perturbation amplitude. The estimated largest Lyapunov exponent in the specific space supports the presence of chaotic sensitivity in the observable response, underscoring the sensitivity of frictional process to external loading conditions. These findings preliminarily highlight the intrinsic potential for deterministic chaos during frictional sliding, with implications for predicting frictional instabilities in engineering safety and seismology.