scholarly journals Phase transformation and subsurface damage formation in the ultrafine machining process of a diamond substrate through atomistic simulation

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Van-Thuc Nguyen ◽  
Te-Hua Fang
Keyword(s):  
Grain Size ◽  
Elastic Recovery ◽  
Vertical Direction ◽  
Substrate Material ◽  
Transformation Process ◽  
Machining Process ◽  
Machined Surface ◽  
Diamond Substrate ◽  
Force Transformation ◽  
Higher Temperature

AbstractThis report explores the effects of machining depth, velocity, temperature, multi-machining, and grain size on the tribological properties of a diamond substrate. The results show that the appearance of graphite atoms can assist the machining process as it reduces the force. Moreover, the number of graphite atoms relies on the machining speed and substrate temperature improvement caused by the friction force. Besides, machining in a machined surface for multi-time is affected by its rough, amorphous, and deformed surface. Therefore, machining in the vertical direction for multi-time leads to a higher rate of deformation but a reduction in the rate of graphite atoms generation. Increasing the grain size could produce a larger graphite cluster, a higher elastic recovery rate, and a higher temperature but a lower force and pile-up height. Because the existence of the grain boundaries hinders the force transformation process, and the reduction in the grain size can soften the diamond substrate material.

Finite Element Modeling on Dislocation Density and Grain Size Evolution in Machined Surface

2013 ◽  
Author(s):  
Liqiang Ding ◽  
Xueping Zhang ◽  
C. Richard Liu
Keyword(s):  
Grain Size ◽  
Dislocation Density ◽  
Orthogonal Cutting ◽  
Cutting Speed ◽  
Experimental Tests ◽  
Rake Angle ◽  
Machining Process ◽  
Fe Model ◽  
Machined Surface ◽  
Size Evolution

Machining process usually induces Severe Plastic Deformation (SPD) in the chip and machined surface, which will further lead to rapid increase of dislocation density and alteration of grain size in micro-scale. This paper presents a novel FE model to simulate the dislocation density and grain size evolution in the machined surface and subsurface generated from the orthogonal cutting process of Al6061-T6. A dislocation density model of microstructure evolution is implemented in the FE model as a user-defined subroutine written in FORTRAN. The model can predict the microstructure characteristic in a machined surface. The predicted chip thicknesses, cutting forces, distributions of dislocation density and grain size are verified by the experimental tests of the chip, forces, microstructure and micro-hardness. The predicted results show that the dislocation density decreases along the depths of machined surface; whereas the grain size shows an opposite tendency. Dislocation density in machined surface decreases and grain size increases when cutting speed increases. Higher cutting speeds are associated with thinner deformation layers. Dislocation density in a machined surface decreases initially and then increases with feed rates. Dislocation density increases significantly when cutting tool has a larger negative rake angle. The bigger negative rake angles further lead to the thicker deformation layers in machined surface.

Study on Nanometric Machining Process of Monocrystalline Si

2006 ◽  
Vol 315-316 ◽  
pp. 792-795 ◽  
Author(s):  
Yu Lan Tang ◽  
Ying Chun Liang ◽  
D.X. Wang ◽  
J.W. Zhao
Keyword(s):  
Phase Transformation ◽  
Surface Energy ◽  
Potential Function ◽  
Amorphous Phase ◽  
Elastic Recovery ◽  
Three Dimensional ◽  
Machining Process ◽  
Three Dimensional Model ◽  
Machined Surface ◽  
Nanometric Machining

A three-dimensional model of molecular dynamics (MD) was employed to study the nanometric machining process of Si. The model included the utilization of the Morse potential function and the Tersoff potential function to simulate the interatomic force between atoms. By analysis of snapshots and local radial distribution function (RDF) during the various stages of the cutting process, amorphous phase transformation of chip and machined surface are observed, but no phase transformation of bulk. Chip volume change is observed due to the amorphous phase transformation. Dislocations around the tool and elastic recovery of the machined surface do not appear. The effects of surface adsorption on machined surface state have been studied on the basis of surface energy and surfaces hardness. Surface energy decreases and hardness increases by adsorption. Oxygen atoms adsorbed are on the machined surface and subsurface region.

Study on Machining Single-Crystal Nickel by Molecular Dynamics Simulation

2016 ◽  
Vol 1136 ◽  
pp. 184-189
Author(s):  
Zong Xiao Zhu ◽  
Ya Dong Gong ◽  
Zi Hao Gan ◽  
Yun Guang Zhou ◽  
Guo Qiang Yin
Keyword(s):  
Molecular Dynamics ◽  
Temperature Distribution ◽  
Single Crystal ◽  
Elastic Recovery ◽  
Machining Process ◽  
Dynamics Simulation ◽  
Work Piece ◽  
Machined Surface ◽  
Nanometric Cutting ◽  
Forming Mechanism

In this paper, molecular dynamics (MD) model is explored to study single-crystal nickel micro-nanomachining mechanism. Accordingly, LAMMPS would implement the simulation of nanometric cutting process, and snapshots at different steps are obtained by VMD and OVITO. On this basis, a reasonable explanation is given to the forming mechanism of chip and surface machined in the machining process of single-crystal nickel. The result of work-piece temperature distribution shows that there is a temperature gradient around the machining zone, where chip part achieved the highest temperature. Moreover, a large number of dislocations are observed. Part of dislocation atoms move forward and generate the chips, taking a lot of heat. Another part of dislocation atoms combine with the work-piece surface atoms with elastic recovery, and form the machined surface.

scholarly journals Modelling of Grain Size Evolution with Different Approaches via FEM When Hard Machining of AISI 4140

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1296
Author(s):  
Berk Tekkaya ◽  
Markus Meurer ◽  
Sebastian Münstermann
Keyword(s):  
Grain Size ◽  
Hard Turning ◽  
White Layer ◽  
High Hardness ◽  
Machining Process ◽  
Machined Surface ◽  
Size Evolution ◽  
Aisi 4140 ◽  
Fine Microstructure ◽  
Negative Effect

Thermo-mechanical loads during hard turning lead to the formation of so-called White Layers on the machined surface. Characterized by a very fine microstructure and high hardness, White Layers have a negative effect on the fatigue life of a component. The fundamental mechanism for the White Layer formation is the dynamic recrystallization (DRX). Therefore, in the current work, two different DRX models, Helmholtz free energy and Zener-Hollomon, are implemented into Abaqus/Explicit to predict the thickness of the White Layer when hard turning quenched/tempered AISI 4140 and the results are compared with each other. For the simulation of the machining process a Finite Element Method (FEM) model based on the Coupled-Eulerian-Lagrangian (CEL) method is built up. Although both DRX models achieved a very good match between predicted and measured White Layer thickness and grain size evolution on the workpiece rim zone, the Zener-Hollomon model produced more closer agreement.

Analysis of Micro-Texture and Grain Size Distributions in Machined Aluminum Alloy 7075

2014 ◽  
Vol 1052 ◽  
pp. 489-494 ◽  
Author(s):  
A. Tabei ◽  
Omar Fergani ◽  
Hamid Garmestani ◽  
Steven Y. Liang
Keyword(s):  
Grain Size ◽  
Orientation Distribution ◽  
Distribution Functions ◽  
Analytical Models ◽  
Von Mises Stress ◽  
Al Alloy ◽  
Machined Surface ◽  
Average Grain Size ◽  
Force Transformation ◽  
Von Mises

the effects of turning on the gradients of micro-texture and grain size of Al alloy 7075 processed by turning is studied. Analytical models based on Boussinesq equation and stress/force transformation, predict that the equivalent von-Mises stress penetrate almost 1 mm below the machined surface with a maximum of 1400 MPa. The induced temperature below the surface is and reaches up to 240°C. As a result of deformation below the machined surface, the grains below the surface show a preferred grain shape orientation different from the grains in the central region. The normalized population of (121) plane increases at the machined surface compared to the central part of the sample. Orientation distribution functions reveal that at the central part of the sample, the material is mostly randomly oriented and the closest texture component is the recrystallized texture. On the other hand, the strongest texture attribute at the machined surface is β-fiber torsion. The average grain size shows a 10% decreases moving away from center while below the machined surface there is a 50% increase in the average grain size. This can be due to the grain growth caused by higher temperatures right below the machining tool. The reported results provide a toolset to determine the final properties of the material after machining in addition to providing means to more accurately describing the machining mechanics.

Challenges and Issues in the Design of Micro-Machined Antennas - A Review

2020 ◽  
Vol 13 ◽  
Author(s):  
Ashish Kumar ◽  
Amar Partap Singh Pharwaha
Keyword(s):  
Patch Antenna ◽  
Ground Plane ◽  
Substrate Material ◽  
Review Article ◽  
High Index ◽  
Performance Characteristics ◽  
Machining Process ◽  
Patch Antennas ◽  
Micro Machining ◽  
The Impact

Background: Patch antennas are composed of the substrate material with patch and ground plane on the both sides of the substrate. The dimensions and performance characteristics of the antenna are highly influenced by the choice of the appropriate substrate depending upon the value of their dielectric constant. Generally, low index substrate materials are used to design the patch antenna but there are also some of the applications, which require the implementation of patch antenna design on high index substrate like silicon and gallium arsenide. Objective: The objective of this article is to review the design of antennas developed on high index substrate and the problems associated with the use of these materials as substrate. Also, main challenges and solutions have been discussed to improve the performance characteristics while using the high index substrates. Method: The review article has divided into various sections including the solution of the problems associated with the high index substrates in the form of micro-machining process. Along with this, types of micro machining and their applications have discussed in detail. Results: This review article investigates the various patch antennas designed with micro-machining technology and also discusses the impact of micro-machining process on the performance parameters of the patch antennas designed on high index substrates. Conclusion: By using the micro-machining process, the performance of patch antenna improves drastically but fabrication and tolerances at such minute structures is very tedious task for the antenna designers.

Surface Roughness and Cutting Force Components Evaluation in Hard Turning by Differently Shaped Cutting Tools

2016 ◽  
Vol 862 ◽  
pp. 26-32 ◽  
Author(s):  
Michaela Samardžiová
Keyword(s):  
Surface Roughness ◽  
Cutting Force ◽  
Hard Turning ◽  
Cutting Tool ◽  
Single Point ◽  
Machining Process ◽  
Tool Geometry ◽  
Machined Surface ◽  
Cutting Force Components ◽  
Force Components

There is a difference in machining by the cutting tool with defined geometry and undefined geometry. That is one of the reasons of implementation of hard turning into the machining process. In current manufacturing processes is hard turning many times used as a fine finish operation. It has many advantages – machining by single point cutting tool, high productivity, flexibility, ability to produce parts with complex shapes at one clamping. Very important is to solve machined surface quality. There is a possibility to use wiper geometry in hard turning process to achieve 3 – 4 times lower surface roughness values. Cutting parameters influence cutting process as well as cutting tool geometry. It is necessary to take into consideration cutting force components as well. Issue of the use of wiper geometry has been still insufficiently researched.

scholarly journals The Comparative Study on Cutting Performance of Different-Structure Milling Cutters in Machining CFRP

2018 ◽  
Vol 8 (8) ◽  
pp. 1353
Author(s):  
Tao Chen ◽  
Fei Gao ◽  
Suyan Li ◽  
Xianli Liu
Keyword(s):  
Carbon Fiber ◽  
Cutting Force ◽  
Surface Quality ◽  
Cutting Edge ◽  
Cutting Performance ◽  
Machining Process ◽  
Carbon Fiber Composites ◽  
Machined Surface ◽  
Milling Cutter ◽  
Machined Surface Quality

Carbon fiber reinforced plastic (CFRP) is typically hard to process, because it is easy for it to generate processing damage such as burrs, tears, delamination, and so on in the machining process. Consequently, this restricts its wide spread application. This paper conducted a comparative experiment on the cutting performance of the two different-structure milling cutters, with a helical staggered edge and a rhombic edge, in milling carbon fiber composites; analyzed the wear morphologies of the two cutting tools; and thus acquired the effect of the tool structure on the machined surface quality and cutting force. The results indicated that in the whole cutting, the rhombic milling cutter with a segmented cutting edge showed better wear resistance and a more stable machined surface quality. It was not until a large area of coating shedding occurred, along with chip clogging, that the surface quality decreased significantly. At the stage of coating wear, the helical staggered milling cutter with an alternately arranged continuous cutting edge showed better machined surface quality, but when the coating fell off, its machined surface quality began to reveal damage such as groove, tear, and fiber pullout. Meanwhile, burrs occurred at the edge and the cutting force obviously increased. By contrast, for the rhombic milling cutter, both the surface roughness and cutting force increased relatively slowly.

Research on Grinding Force of Zirconia Internal Grinding with Resin Bond Diamond Wheel

2016 ◽  
Vol 1136 ◽  
pp. 30-35
Author(s):  
He Wang ◽  
Ke Zhang ◽  
Yu Hou Wu ◽  
Hong Song
Keyword(s):  
Grain Size ◽  
Surface Quality ◽  
Diamond Wheel ◽  
Grinding Force ◽  
Wheel Speed ◽  
Zirconia Ceramic ◽  
Machined Surface ◽  
Research Results ◽  
Internal Grinding ◽  
Machined Surface Quality

The zirconia parts are limited by machined surface quality. The grinding force is one of the most important parameters of grinding and has effects on surface quality. The MK2710 grinder and resin bond diamond wheels were used in zirconia grinding. The grinding force was obtained by Kistler dynamometer. The paper focused on wheel speed and grain size on grinding force, and examined the surface by SEM. The research results indicated that decreasing the grain size, the grinding force increased and the surface quality improved, and increasing wheel speed could decrease grinding force to improve grinding surface quality. The results can improve zirconia ceramic parts surface quality and promote application.

Evaluation of Surface Integrity in Electrochemical Micromachining of A286 Super alloy

2021 ◽  
Author(s):  
Rajkeerthi E ◽  
Hariharan P
Keyword(s):  
Surface Roughness ◽  
Surface Quality ◽  
Surface Integrity ◽  
Research Work ◽  
Machining Process ◽  
Electrochemical Micromachining ◽  
Dissolution Mechanism ◽  
Machined Surface ◽  
Micro Holes ◽  
Super Alloy

Abstract Surface integrity of micro components is a major concern particularly in manufacturing industries as most geometry of the products must meet out necessary surface quality requirements. Advanced machining process like electrochemical micro machining possess the capabilities to machine micro parts with best surface properties exempting them from secondary operations. In this research work, different electrolytes have been employed for producing micro holes in A286 super alloy material to achieve the best surface quality and the measurement of surface roughness and surface integrity to evaluate the machined surface is carried out. The machined micro hole provides detailed information on the geometrical features. A study of parametric analysis meant for controlling surface roughness and improvement of surface integrity has been made to find out the suitable parameters for machining. The suitability of various electrolytes with their dissolution mechanism and the influence of various electrolytes have been thoroughly studied. Among the utilized electrolytes, EG + NaNO3 electrolyte provided the best results in terms of overcut and average surface roughness.

Sign in / Sign up

Export Citation Format

Share Document