Toughening mechanisms for the dynamic perforation behavior of laminar aluminum alloy with lubricated frictional interfaces

Abstract

Lubricant has been well-recognized in reducing friction/wear resistance and subsequently facilitating the movement of objects. However, the so-called lubricant inclines to increase the transverse dynamic piercing resistant properties of laminar aluminum over a wide range of high-velocity from 60 m/s to 230 m/s. The underlying mechanism in the high-speed perforation process of laminar structural raises confusion about the traditional concept that the lubricant did not act in reducing the frictional effect. Lubricant, such as high vacuum grease, smeared on the thinner metal laminar show the ‘slippery but bulletproof’ behavior. A specially designed dynamic sliding experiment provides further evidence that the lubricants act as a strengthening factor under the lower normal load state, but have no significant effect under a heavy normal load during the sliding initiation stage. The lubricant film avoids direct metallic contacting, reducing the stress concentration, postponing the failure displacement, and increasing the dissipated energy. This abnormal lubricant phenomenon in terms of strengthening and toughening should be taken into consideration as the thickness of the anti-bullet protective structure has been decreasing. These findings provide physical insights into the evolution of friction and fracture for developing membrane-like protective structures.

Keywords

• Dynamic behavior
• Friction and fracture
• Lubricate
• Velocity dependence