Chip Morphology and Chip Formation Mechanisms During Machining of ECAE-Processed Titanium

2017 ◽  
Vol 140 (3) ◽  
Author(s):  
Brian Davis ◽  
David Dabrow ◽  
Ryan Newell ◽  
Andrew Miller ◽  
John K. Schueller ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Chip Formation ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Shear Localization ◽  
Coarse Grained ◽  
Cyclic Shear ◽  
Uniform Shear ◽  
Chip Formation Mechanism ◽  
Speed Regime

Severe plastic deformation (SPD) processing such as equal channel angular extrusion (ECAE) has been pioneered to produce ultrafine grained (UFG) metals for improved mechanical and physical properties. However, understanding the machining of SPD-processed metals is still limited. This study aims to investigate the differences in chip morphology when machining ECAE-processed UFG and coarse-grained (CG) titanium (Ti) and understand the chip formation mechanism using metallographic analysis, digital imaging correlation (DIC), and nano-indentation. The chip morphology is classified as aperiodic saw-tooth, continuous, or periodic saw-tooth, and changes with the cutting speed. The chip formation mechanism of the ECAE-processed Ti transitions from cyclic shear localization within the low cutting speed regime (such as 0.1 m/s or higher) to uniform shear localization within the moderately high cutting speed regime (such as from 0.5 to 1.0 m/s) and to cyclic shear localization (1.0 m/s). The shear band spacing increases with the cutting speed and is always lower than that of the CG counterpart. If the shear strain rate distribution contains a shift in the chip flow direction, the chip morphology appears saw-tooth, and cyclic shear localization is the chip formation mechanism. If no such shift occurs, the chip formation is considered continuous, and uniform shear localization is the chip formation mechanism. Hardness measurements show that cyclic shear localization is the chip formation mechanism when localized hardness peaks occur, whereas uniform shear localization is operative when the hardness is relatively constant.

Study of Chip Morphology and Chip Formation Mechanism During Machining of Magnesium-Based Metal Matrix Composites

2017 ◽  
Author(s):  
Brian Davis ◽  
David Dabrow ◽  
Licheng Ju ◽  
Anhai Li ◽  
Chengying Xu ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Formation Mechanism ◽  
Chip Formation ◽  
Metal Matrix ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Matrix Composites ◽  
Particle Type ◽  
Chip Formation Mechanism ◽  
Cutting Speeds

Magnesium (Mg) and its alloys are among the lightest metallic structural materials, making them very attractive for use in the aerospace and automotive industries. Recently, Mg has been used in metal matrix composites (MMCs), demonstrating significant improvements in mechanical performance. However, the machinability of Mg-based MMCs is still largely elusive. In this study, Mg-based MMCs are machined using a wide range of cutting speeds in order to elucidate both the chip morphology and chip formation mechanism. Cutting speed is found to have the most significant influence on both the chip morphology and chip formation mechanism, with the propensity of discontinuous, particle-type chip formation increasing as the cutting speed increases. Saw-tooth chips are found to be the primary chip morphology at low cutting speeds (lower than 0.5 m/s), while discontinuous, particle-type chips prevail at high cutting speeds (higher than 1.0 m/s). Using in situ high speed imaging, the formation of the saw-tooth chip morphology is found to be due to crack initiation at the free surface. However, as the cutting speed (and strain rate) increases, the formation of the discontinuous, particle-type chip morphology is found to be due to crack initiation at the tool tip. In addition, the influences of tool rake angle, particle size, and particle volume fracture are investigated and found to have little effect on the chip morphology and chip formation mechanism.

Study of Chip Morphology and Chip Formation Mechanism During Machining of Magnesium-Based Metal Matrix Composites

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Brian Davis ◽  
David Dabrow ◽  
Licheng Ju ◽  
Anhai Li ◽  
Chengying Xu ◽  
...  
Keyword(s):  
Crack Initiation ◽  
Formation Mechanism ◽  
Chip Formation ◽  
Metal Matrix ◽  
Cutting Speed ◽  
Chip Morphology ◽  
Matrix Composites ◽  
Particle Type ◽  
Chip Formation Mechanism ◽  
Cutting Speeds

Magnesium (Mg) and its alloys are among the lightest metallic structural materials, making them very attractive for use in the aerospace and automotive industries. Recently, Mg has been used in metal matrix composites (MMCs), demonstrating significant improvements in mechanical performance. However, the machinability of Mg-based MMCs is still largely elusive. In this study, Mg-based MMCs are machined using a wide range of cutting speeds in order to elucidate both the chip morphology and chip formation mechanism. Cutting speed is found to have the most significant influence on both the chip morphology and chip formation mechanism, with the propensity of discontinuous, particle-type chip formation increasing as the cutting speed increases. Saw-tooth chips are found to be the primary chip morphology at low cutting speeds (lower than 0.5 m/s), while discontinuous, particle-type chips prevail at high cutting speeds (higher than 1.0 m/s). Using in situ high-speed imaging, the formation of the saw-tooth chip morphology is found to be due to crack initiation at the free surface. However, as the cutting speed (and strain rate) increases, the formation of the discontinuous, particle-type chip morphology is found to be due to crack initiation at the tool tip. In addition, the influences of tool rake angle, particle size, and particle volume fracture are investigated and found to have little effect on the chip morphology and chip formation mechanism.

Research on Chip Formation Mechanism of Laser-Assisted Machining of Fused Silica Based on Variable Laser Angle

2020 ◽  
Author(s):  
Pengfei Pan ◽  
Huawei Song ◽  
Junfeng Xiao ◽  
Zuohui Yang ◽  
Guoqi Ren ◽  
...  
Keyword(s):  
Formation Mechanism ◽  
Chip Formation ◽  
Incident Angle ◽  
Chip Morphology ◽  
Fused Silica ◽  
Machining Process ◽  
Laser Assisted Machining ◽  
Chip Formation Mechanism ◽  
On Chip ◽  
Cutting Model

Abstract Laser-assisted machining (LAM) is a promising technology for improving the machinability of hard-to-cut materials. In this study, based on the finite element method (FEM), a cutting model of thermally coupled non-uniform temperature field is established. The chip formation mechanism of fused silica during the laser-assisted machining process is explored from the aspects of laser power and laser incident angle. The results show that as the laser incident angle increases, the continuity of the chip increases gradually. An annular tool holder that can adjust the angle between the laser beam and the tool was designed. And the similar chip morphology obtained by variable-angle cutting experiments verified the effectiveness of the cutting model. Moreover, fracture chips and continuous banded chips are found in both simulation and experiment, which implies that the cutting mechanism works under a hybrid mode of brittle fracture and plastic deformation in the LAM process.

Experimental Analysis of Ti6Al4V Orthogonal Cutting

2015 ◽  
Vol 665 ◽  
pp. 17-20 ◽  
Author(s):  
Apostolos Korlos ◽  
Orestis Friderikos ◽  
Dimitrios Sagris ◽  
Constantine David ◽  
Gabriel Mansour
Keyword(s):  
Formation Mechanism ◽  
Chip Formation ◽  
Orthogonal Cutting ◽  
Chip Morphology ◽  
Serrated Chip ◽  
Wide Range ◽  
Chip Formation Mechanism ◽  
Serrated Chip Formation ◽  
Chip Geometry ◽  
Cutting Speeds

The chip formation mechanism in orthogonal cutting is a phenomenon that attracts the attention of many researchers. This paper investigates experimentally the orthogonal cutting of Ti6Al4V at different cutting conditions aiming at the understanding of the chip formation mechanism. Serrated chip formation is obtained during orthogonal cutting of Ti6Al4V in a wide range of cutting speeds. The results are analyzed in order to extract useful indices relevant to chip geometry, as the adiabatic zone angle and other dimensions that describe the serrated chip. The cutting forces and the acoustic emission are measured. Finally, by the aid of 3D Computed Tomography (CT) the chip morphology is analyzed to better understand the segmentation process.

Investigation of Interatomic Potential on Chip Formation Mechanism in Nanometric Cutting Using MD Simulation

2011 ◽  
Vol 312-315 ◽  
pp. 983-988
Author(s):  
Seyed Vahid Hosseini ◽  
Mehrdad Vahdati ◽  
Ali Shokuhfar
Keyword(s):  
Single Crystal ◽  
Formation Mechanism ◽  
Chip Formation ◽  
Morse Potential ◽  
Md Simulation ◽  
Atomic Displacement ◽  
Cutting Process ◽  
Machining Process ◽  
Chip Formation Mechanism ◽  
Eam Potential

Nowadays, the nano-machining process is used to produce high quality finished surfaces with precise form accuracy. To understand and analyze the chip formation mechanism of nano-machining process on an atomistic scale, since the experimentation is not an easy task, numerical simulation such as molecular dynamic (MD) simulation is a very useful method. In this paper, MD simulation of the nano-metric cutting of single-crystal copper was performed with a single crystal diamond tool. The model was solved with both pair wise Morse potential function and embedded atom method (EAM) potential to simulate the inter-atomic force between the work-piece and a rigid tool. The chip formation mechanism, dislocation generation, tool forces and generated temperature were investigated. Results show that the Morse potential cannot perform an appropriate defect formation and plastic deformation in nano-metric cutting of metals. Also, tool forces in Morse potential are more than the forces in EAM potential. Furthermore, the fluctuations of resultant forces in Morse potential are greater than that of EAM. In addition, using many-body interaction potentials like EAM can lead to substantial changes in surface energies, elastic-plastic properties and atomic displacement, compared with the pair-wise potentials like Morse. Finally, the atomic displacement investigation shows that in EAM potential study, only the atoms in a local region near the cutting process are displaced, but in Morse potential a large portion of atoms has affected during cutting process. Subsequently, the chip temperature in EAM potential is more than that of Morse potential.

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