Oluwajobi, Akinjide O. (2012) Nanomachining Technology Development. Doctoral thesis, University of Huddersfield.

Miniaturization towards the nanoscale is now the trend of technological developments in products and devices for mechanical, optical and electronic applications. Normally, good engineering functional components should have their form and surface tolerances less than one hundredth or even one thousandth of their feature sizes. However the structure fabricated by current nanotechnology can rarely achieve such tolerance ratio in a controllable way. Because of this, the kinematical and dynamical performances of these nano-structured mechanisms are far from ideal. Consequently, this research aims to identify the limit of micro and nano material removal under machining conditions.

There are still many fundamental questions which need to be addressed in nanometric machining. Some of them are the following, name; what are the fundamental mechanisms underlying nanomachining processes? What is the limit of machining? What is the minimum depth of cut and how do you evaluate atomic surface roughness from nanomachining simulations? This study attempts to find some answers to the above questions or to point the direction towards the answers.

Nanomachining has been modelled using the Molecular Dynamics (MD) method because it has proved to be an effective tool for the prediction and the analysis of these processes at the nanometre scale. Through this investigation, it is identified that the EAM potential is the most appropriate of the 3 potentials commonly used for the modelling of nanomachining of copper with diamond tool. This is because the EAM potential provides the best description of the metallic bonding in the workpiece, also, the cutting forces variation is smallest; the potential and total energies are most stable for the depth of cut considered. Therefore, the EAM potential should be used, rather than LJ and Morse potentials for the modelling of copper and other fcc metals in MD simulations of nanomachining. For potential pairs; it was observed that the tangential cutting force components are considerably affected by the interatomic potential pair used, but they are not greatly affected by whether the tool is rigid or deformable. The total energy of the system on the other hand is much lower when the tool is non rigid than when it is rigid.

Various MD simulations have been carried out. Results of the investigation of the minimum depth cut (MDC) nanomachining show the nano material removal phenomena of rubbing, ploughing and cutting. In a copper material removal simulation, ploughing starts from 0.2~0.3nm and the formation of chips starts to occur from the depth of cut thickness of 1.5nm. So it can be suggested that the extreme accuracy attainable or MDC for copper atoms workpiece, machined with extremely sharp diamond tool is around 1.5nm to 3nm. The onset of plasticity for copper atom workpiece machined with extremely sharp diamond tool is around 0.1nm ~ 0.3nm.

In the investigation of the effect of various tool ends on the initiation of the phenomena of rubbing and ploughing; all the tools clearly show the phenomena of rubbing and ploughing in the depth of cut range of 0.05 to 0.5 nm. The tool with the pointed end has the lowest average cutting force and the tool with the flat end has the highest average cutting force. It is important to note that in nanomachining the tool with sharpest end may not necessarily cause the greatest material removal! The different tool ends may be suitable for different machining applications.

On the velocity variation in nanomachining simulations, it can be concluded that the interatomic potentials readily affect the simulation results, whereas the use of rigid and non-rigid tools doesn’t show appreciable difference. Also, it was observed that the tangential and the normal cutting force components relatively increase with increase in velocity.

The atomic surface roughness evaluation is affected by the choice of the interatomic potentials used for the simulation.

Jide_Thesis_FinalDraft_October.pdf - Accepted Version
Available under License Creative Commons Attribution Non-commercial No Derivatives.

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