Since the interaction between the abrasive grain, workpiece and nanofluids on the minimum quantity lubrication (MQL) grinding interface are difficult to observe directly, there is still lack of direct evidence to reveal the internal mechanism of carbon group nanoparticles on the abrasive grain/workpiece grinding interface. Concerning this issue, the professor Changhe Li team, from department of Mechanical and Automotive Engineering of Qingdao University of Technology, China, using molecular dynamics simulation to study the tribological mechanism of friction-reducing and anti-wear of three kinds of carbon group nanoparticles, i.e., diamond, carbon nanotubes and graphene. This research will disclose the formation mechanism of the lubrication film on the grinding interface under MQL condition. Based on this, the tribological behaviors of the nanoparticles on the interface will be further investigated. It will provide direct evidence for revealing the effect mechanism of carbon group nanoparticles on the grinding interface. This study can be found in the journal Frontiers of Mechanical Engineering on 26 April, 2023.
Carbon group nanofluids can further improve the friction-reducing and anti-wear properties of MQL. However, the formation mechanism of the lubrication film generated by carbon group nanofluids on the MQL grinding interface is not fully revealed due to lack of sufficient evidences. In this paper, molecular dynamics simulations are performed to explore the interactions on the abrasive grain/workpiece grinding interface, so as to reveal the formation mechanism of the lubrication film. Three representative kinds of carbon group nanoparticles, i.e., nano-diamond, carbon nanotube and graphene nanosheet, are taken as research targets, and [BMIM]BF4 ionic liquid is used as the base fluid of nanofluids. The research firstly discloses the formation mechanism of the lubrication film under the MQL condition using the ionic liquid only. Based on this, the tribological behaviors of the nanoparticles on the grinding interface are further investigated, so as to reveal the tribological mechanism of carbon group nanofluids on the grinding interface.
The investigation show that boundary lubrication film is formed on the grinding interface under MQL condition, via the ionic liquid molecules absorbing in the groove-like fractures on the grain wear flat face. The boundary lubrication film takes effect of friction-reduction through reducing the abrasive grain/workpiece contact area. Under nanofluid MQL conditions, carbon group nanoparticles further enhance the tribological performances of the MQL technique benefitting from their corresponding tribological behaviors on the grinding interface. The behaviors involve the rolling effect of nano-diamond, the rolling and sliding effects of carbon nanotube, and the interlayer shear effect of graphene nanosheet. Compared with the MQL condition, the tangential grinding forces are further reduced by 8.5%, 12.0%, and 14.1% under the diamond, carbon nanotube, and graphene nanofluid MQL conditions, respectively. This provides direct evidence for the effect mechanism of carbon group nanoparticles on the abrasive grain/workpiece grinding interface.
