Abstract
Comprehension of stick-slip motion is very important for understanding tribological principles. The transition from creep-dominated to inertia-dominated stick-slip as the increase of sliding velocity has been described by researchers. However, the associated micro-contact behavior during this transition has not been fully disclosed yet. In this study, we investigated the stick-slip behaviors of two polymethyl methacrylate blocks actively modulated from the creep-dominated to inertia-dominated dynamics through a non-uniform loading along the interface by slightly tilting the angle of the two blocks. Increasing the tilt angle increases the critical transition velocity from creep-dominated to inertia-dominated stick-slip behaviors. Results from finite element simulation disclosed that a positive tilt angle led to a higher normal stress and a higher temperature on blocks at the opposite side of the crack initiating edge, which enhanced the creep of asperities during sliding friction. Acoustic emission (AE) during the stick-slip has also been measured, which is closely related to the different rupture modes regulated by the distribution of the ratio of shear to normal stress along the sliding interface. This study provided a more comprehensive understanding of the effect of tilted non-uniform loading on the local stress ratio, the local temperature, and the stick-slip behaviors.
Highlights
Stick-slip, acoustic emission (AE) has been widely used in the study of stick-slip especially in the crack of rocks concerning earthquake[23,24,25,26,27]
Considering the rupture dynamics of micro-contacts was controllable by external loading condition[30], we changed the load distribution along the sliding interface by slightly tilting the upper PMMA block with a small tilt angle α under a certain sliding velocity v
ΔF is the difference between the maximum static friction force FS and the minimum tangential force Fd after slip
Summary
The energy of AE2 decreased monotonically with the sliding velocity (Fig. 4B) in accordance with ΔF/FS (for negative tilt angles, AE2 was too weak to be distinguished from the background noise) This indicates that AE in stage 2 is only determined by the stick-slip intensity. When α < 0, decreasing the tilt angle, the stress ratio would decrease from the trailing edge but increase on the other side The dynamics of stick-slip motion from creep-dominated to inertia-dominated was modulated by the tilt angle between the contact surfaces through changing the normal stress distribution by the FS induced torque. The tilt angle modulated stick-slip was affected by the non-uniform loading and the resulted non-uniform interfacial temperature distribution and their effects on the mechanical properties of materials at the sliding interface
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