Vibration Assisted Nano Impact-machining By Loose Abrasives Research Articles

Damage evolution in vibration assisted nano impact machining by loose abrasives at elevated temperatures: A numerical study

In this research, a numerical study is conducted to investigate the effects of different machining parameters at elevated operating temperatures in a novel nanomachining process, Vibration Assisted Nano Impact machining by Loose Abrasives (VANILA). In this novel VANILA machining process, an atomic force microscope (AFM) is used as a platform and the nano abrasives slurry is injected between the vibrating AFM probe and the silicon workpiece. These nano abrasives are accelerated by vibration of the AFM probe and hit the workpiece and finally generate nano cavities on the top surface of workpiece. In this study, diamond particles are used as loose abrasives and the ductile mode machining is employed to describe the behavior of the brittle workpiece. The commercial finite element method (FEM) software package ABAQUS is employed to create numerical models for simulations. In addition to experimental validation, the FEM model is validated by comparing the numerical solutions against the analytic solutions to the impact problem between a semi-infinite stationary workpiece and a rigid particle at the impact speeds of 25 and 12.5 m/s. The percentage error is under 4.4%. This validated FEM model is then used to investigate the influence of the machining parameters (impact speed, impact angle, and friction coefficient between the nano particles and silicon workpiece) and the number of impact hits at elevated operating temperatures. It is found that the impact speed, impact angle, and friction coefficient between the silicon workpiece and nano particles have big influence on the damage volume and damage value (D) of the silicon workpiece at elevated temperatures. The research results show that by increasing the level of operating temperature, the machinability of silicon in the VANILA process can be improved substantially.

Effects of water molecules on material removal behavior in Vibration Assisted Nano Impact-machining by Loose Abrasives - A molecular dynamics simulation study

Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) is a novel nanomachining process that performs target specific nano abrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as a platform in this process wherein, nano abrasives, injected in slurry between the workpiece and the vibrating AFM probe, impact the workpiece and cause nanoscale material removal. Liquid medium is required in this process to confine the abrasives within the machining zone. However, the presence of liquid medium could significantly influence the abrasive dynamics as well as the substrate deformation behavior during the VANILA process. This study focuses on understanding the effect of liquid medium on the material removal behavior during the VANILA process. A Molecular Dynamics Simulation (MDS) based study is conducted under different initial conditions with and without the presence of liquid medium (water). The results obtained from the study showed that while the water absorbs some energy from the abrasive grain, it also provides a lubricating layer to the grain preventing adhesion on the workpiece surface. Visualizations of the atomic configurations of the workpiece showed that the presence of water molecules could significantly affect the material dislocations during the impact process.

A Molecular Dynamics Simulation Study of Material Removal Mechanisms in Vibration Assisted Nano Impact-Machining by Loose Abrasives

Vibration assisted nano impact-machining by loose abrasives (VANILA) is a novel nanomachining process to perform target-specific nano abrasive machining of hard and brittle materials. In this study, molecular dynamic (MD) simulations are performed to understand the nanoscale material removal mechanisms involved in the VANILA process. The simulation results revealed that the material removal for the given impact conditions happens primarily in ductile mode through three distinct mechanisms, which are nanocutting, nanoplowing, and nanocracking. It was found that domination by any of these mechanisms over the other mechanisms during the material removal process depends on the impact conditions, such as angle of impact and the initial kinetic energy of the abrasive grain. The transition zone from nanocutting to nanoplowing is observed at angle of impact of near 60 deg, while the transition from the nanocutting and nanoplowing mechanisms to nanocracking mechanism is observed for initial abrasive kinetic energies of about 600–700 eV. In addition, occasional lip formation and material pile-up are observed in the impact zone along with amorphous phase transformation. A material removal mechanism map is constructed to illustrate the effects of the impacts conditions on the material removal mechanism. Confirmatory experimentation on silicon and borosilicate glass substrates showed that all the three nanoscale mechanisms are possible, and the nanoplowing is the most common mechanism. It was also found that the material removal rate (MRR) values are found to be highest when the material is removed through nanocracking mechanism and is found to be lowest when the material removal happens through nanocutting mechanism.

Modeling of Material Removal Rate in Vibration Assisted Nano Impact-Machining by Loose Abrasives

Vibration assisted nano impact-machining by loose abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration-assisted abrasive machining, and tip-based nanomachining, to perform target specific nano abrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as a platform in this process wherein, nano abrasives, injected in slurry between the workpiece and the vibrating AFM probe, impact the workpiece and cause nanoscale material removal. The objective of this study is to develop a mathematical model to determine the material removal rate (MRR) in the VANILA process. The experimental machining results reveal that the material removal happens primarily in ductile mode due to repeated deformation which happens at near normal angles of impact. A predictive model for MRR during the VANILA process is analytically developed based on elastoplastic impact theory for normal angles of impact. The model is validated through a series of experiments performed on silicon and borosilicate glass substrates and the results confirm that the model is capable of predicting the machining results within 10% deviation.

Molecular Dynamics Simulation Study of Tool Wear in Vibration Assisted Nano-Impact-Machining by Loose Abrasives

Vibration assisted nano-impact-machining by loose abrasives (VANILA) is a novel target specific nano-abrasive machining process wherein, nano-abrasives, injected in slurry between the workpiece and the vibrating atomic force microscope probe, impact the workpiece causing nanoscale material removal. In this study, a molecular dynamics (MD) based simulation approach is used to investigate the tool wear mechanism. The simulation results reveal that the tool wear is influenced by the impact velocity of the abrasive grains and the effective tool tip radius. It is seen that based on the process conditions, the wear process could happen through distinctive mechanisms such as atom-by-atom loss, plastic deformation, and brittle fracture. Experimental results show evidences of tool wear by aforementioned mechanisms in VANILA process.

Modeling of Tool Wear in Vibration Assisted Nano Impact-Machining by Loose Abrasives

Vibration assisted nano impact-machining by loose abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration assisted abrasive machining and tip-based nanomachining, to perform target specific nanoabrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as a platform in this process wherein nanoabrasives, injected in slurry between the workpiece and the vibrating AFM probe which is the tool, impact the workpiece and cause nanoscale material removal. The VANILA process are conducted such that the tool tip does not directly contact the workpiece. The level of precision and quality of the machined features in a nanomachining process is contingent on the tool wear which is inevitable. Initial experimental studies have demonstrated reduced tool wear in the VANILA process as compared to indentation process in which the tool directly contacts the workpiece surface. In this study, the tool wear rate during the VANILA process is analytically modeled considering impacts of abrasive grains on the tool tip surface. Experiments are conducted using several tools in order to validate the predictions of the theoretical model. It is seen that the model is capable of accurately predicting the tool wear rate within 10% deviation.

A study on the vibration induced transport of nanoabrasives in liquid medium

Vibration Assisted Nano-Impact-machining by Loose Abrasives (VANILA) is an emerging process suitable for the target specific nanomachining of hard and brittle materials. Understanding the transport of nanodiamond powders in fluid is essential to determine the effective gap between the tool and the work surface in VANILA process. In this paper, various forces acting on the abrasive nanoparticle in aqueous slurry are analyzed. It is understood that transient cavitation force and acoustic streaming forces have the most dominating effects in causing the nanoparticle impact on the workpiece surface. A model to predict the impact velocity of the nanoabrasive grain on the workpiece surface is developed and it is found that during the machining process, an impact velocity in the order of 102m/s is achieved. molecular dynamics simulation (MDS) is used to simulate the nanoparticle transportation during the process. The MDS study reveals that the machining gap during the VANILA process needs to be maintained at less than 200nm for an abrasive grain size range of 5–20nm. The MDS results are in conformance with the theoretical modeling results.

Modeling and Experimental Verification of Nano Positioning System for Nanomanufacturing

Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration-assisted abrasive machining and tip-based nanomachining has been developed by the authors to perform target specific nano abrasive machining of hard and brittle materials. One of the critical factors in achieving nanoscale precision during the VANILA process is to maintain an optimal machining gap between the tool and the workpiece surface. Piezoelectric crystal based positioning systems is a proven method for achieving ultraprecision control, however the application of such a system for controlling the nanoscale machining gap during a machining process is not explored. In this paper, the possibility of using a piezoelectric crystal based nano positioning setup to achieve the desired gap during the VANILA process is explored. This research thus finds a new application for the nanopositioning systems in order enhance the capability of existing VANILA process. Analytical models based on piezoelectric theory are done to predict the vibrational behavior of the piezoelectric crystal in the nano-positioning setup under different machining conditions. Further experiments are conducted to validate the model and study the mass-loading effect on the piezoelectric crystal. The model developed is agreeing within 20% with the experimentally determined values and thus the model forms the basis for using the nano-positioning system for maintaining optimal gap between the tool tip and the workpiece surface.

A molecular dynamics study of the effect of impact velocity, particle size and angle of impact of abrasive grain in the Vibration Assisted Nano Impact-machining by Loose Abrasives

Vibration Assisted Nano Impact-machining by Loose Abrasives (VANILA) is a novel nanomachining process that combines the principles of vibration-assisted abrasive machining, and tip-based nanomachining, to perform target specific nanoabrasive machining of hard and brittle materials. An atomic force microscope (AFM) is used as a platform in this process wherein, nanoabrasives, injected in slurry between the workpiece and the vibrating AFM probe, impact the workpiece and cause nanoscale material removal. Molecular dynamic (MD) simulations are performed in this study to understand the effect of critical process parameters, viz. impact velocity, particle size, and the angle of impact of the abrasive grain on the material removal by the VANILA process. It was found that a higher impact velocity, larger abrasive size and higher angle of impact result in a larger amount of material removal from the workpiece. A material removal mechanism map capturing the effects of impact velocity and abrasive grain size on the occurrence and transitions between plasticity-dominated and fracture-dominated behaviors during VANILA process is made, which reveals different regimes of material removal mechanisms and their transitions. Confirmatory tests show that higher amount of material removal is observed in brittle mode machining with peak material removal occurring for high angle of impacts in the range of 60–90°. In ductile mode machining, relatively a lower amount of material removal is observed with the peak material removal occurring for low angle of impacts in the range of 15–30°.

A Feasibility Study of Vibration-Assisted Nano-Impact Machining by Loose Abrasives Using Atomic Force Microscope

Abstract Nanomachining of brittle materials is required in a wide range of applications. This paper reports on the feasibility studies of vibration-assisted nano-impact machining by loose abrasives (VANILA), a novel nanomachining process for target-specific nanomachining of hard and brittle materials. A mathematical model based on Hertzian fracture mechanics theory has been developed to evaluate the feasibility of material removal in the VANILA process, where hard abrasive grains impact the brittle workpiece surface. Experimental investigations are conducted using a commercially available atomic force microscope (AFM), to validate the feasibility of the proposed process. Several nanocavities with circular shape, having depths ranging from 6 to 64 nm and diameters ranging from 78 to 276 nm, are successfully machined. Patterns of nanocavities are machined to confirm the repeatability and controllability of the process. Observation of tool tips using a scanning electron microscope (SEM) reveals that the tool wear in the VANILA process is lesser than that observed in indentation process.