Molecular Dynamics Simulation Study on the Influence of the Abrasive Flow Process on the Cutting of Iron-Carbon Alloys (α-Fe)

Round 1

Reviewer 1 Report

This paper investigates the effect of the fluid medium and cutting angle on iron-carbon alloy temperature, friction coefficient, surface morphology, and dislocation evolution by molecular dynamics simulation. The surveys in this paper are sufficient, and the topic is relatively practical. The differences and advantages compared with other research work are demonstrated enough. Comments and suggestions are listed as follows.

1. In the second paragraph of the introduction, the author cites the research on material processing through molecular dynamics simulation in recent years. Several references in recent years should be supplemented, such as:

DOI:10.1016/j.jmatprotec.2021.117106.

2. The introduction is too long and should be refined. The authors should highlight the significance of the research and propose the research content quickly. In addition to citing recent research, their common problems should also be found.

3. Many figures are not clear enough. As shown in Figure 2 and Figure 5, amplification causes distortion. Some figures are too small to see the details, as shown in Figure 9. In addition, in some figures, when cutting distance is mentioned, the coordinates should start from 0.

4. In the third point of the conclusion, the author mentioned, "As the cutting angle increases, the increase of the total dislocation length reduces the surface quality of the workpiece, thereby affecting the mechanical properties and processing performance of the material. The smaller cutting angle and the presence of the fluid medium can reduce the number of dislocations and the total dislocation length." However, from Figure 15, when θ=0° or 5°, the dislocation line length of wet cutting is longer than that of dry cutting. This part is suggested to be modified, "In the large angle cutting process, the fluid medium can reduce the number of dislocations and the total dislocation length."

Author Response

Dear editors and reviewers:

    We thank the editor and the reviewers for your positive and constructive comments and

suggestions on our manuscript. We also thank you very much for giving us an opportunity to revise our manuscript. After careful examination of manuscript, many questions proposed by reviewers and discovered by ourselves have been remedied or modified, and then highlighted by track in our revised manuscript. According to the suggestions of each reviewer and editor, we have made revision carefully and the detailed corrections are listed below point by point:

 

 

Responses to the comments of reviewer :

Question 1: In the second paragraph of the introduction, the author cites the research on material processing through molecular dynamics simulation in recent years. Several references in recent years should be supplemented, such as:

 

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Modify:

Molecular dynamics (MD) is a popular atomic-scale research tool. Many scholars have recognized the scientific validity of MD because the generation and movement of dislocations during cutting processes can be studied using atomic dynamics simulations. In recent years, the use of molecular dynamics simulations to study the material processes occurring during machining has received great attention, and parameters such as machining surface [3], machining tool shape [4] and machining direction [5] have been widely discussed. Huan Liu et al. proposed an analytical model to predict the chip thickness and ploughing width of FCC crystal in nanofabrication under arbitrary crystal orientation, concluding that crystal orientation determines chip conversion between removal and ploughing, while chip thickness and ploughing width can be predicted [6]. Yue et al. used the MD method to investigate a new nanostructured diamond abrasive for mechanical polishing of single crystal silicon. The analysis showed that the structured abrasive leads to lower polishing forces and thinner subsurface damage layers in silicon polishing [7]. Ma et al. used MD simulations to investigated the crystal structure evolution and phase transition of single-crystal germanium materials during multiple cuts. A clear understanding of the brittle fracture, ductile plasticity and structural changes in single-crystal germanium materials was obtained at the atomic scale [8].

 

3. Gou Yong-jun. Research on sub-surface damage of single crystal tungsten cutting based on molecular dynamics [D]. Dalian University of Technology, 2021. DOI: 10.26991/d.cnki.gdlu.2021.002879
4. Yang Sheng-ze; Cao Hui; Liu Yang; Yao Peng; Feng Rui-cheng. Molecular dynamics simulation of the effect of rough surface on material removal and subsurface defects during γ-TiAl processing [J]. Rare Metal Materials and Engineering, 2022,51 (09): 3236-3243
5. Du Mingyang. Fundamental study on the evolution of subsurface defects in ultra-precision-cut single-crystal copper based on molecular dynamics simulation [D]. Huaqiao University, 2022. DOI:10.27155/d.cnki.ghqiu.2022.000489.
6. Liu, H.; Guo, Y.; Li, D.; Wang, J. Material Removal Mechanism of FCC Single-Crystalline Materials at Nano-Scales: Chip Removal & Ploughing. Journal of Materials Processing Technology 2021, 294, 117106, https://doi:10.1016/j.jmatprotec.2021.117106
7. Yue Hai-xia. Study on the removal mechanism of monocrystalline silicon by three-body polishing with diamond abrasive based on molecular dynamics [D]. Guizhou University, 2022. DOI: 10.27047/d.cnki.gudu.2022.001396
8. Ma Zhen-zhong; Liang Guo-xing; Lu Ming. Molecular dynamics research on anisotropic nano-cutting of monocrystalline silicon [J]. Mechanical Design and Manufacturing 2021 (08): 99-102. DOI: 10.19356/j.cnki.1001-3997.2021.08.024

 

Question 2: The introduction is too long and should be refined. The authors should highlight the significance of the research and propose the research content quickly. In addition to citing recent research, their common problems should also be found.

 

Response: The expert's opinion is very accurate, we revised the original text. The specific

amendments are as follows:

 

Modify:

Many researchers are interested in the crystal orientation of BCC iron, using MD methods to simulate the effects of different crystal orientations on cutting, tensile behavior [9], impact phase transformation [10], nanoindentation and nano-scratching processes [11]. Li Xiang et al. at the same defect concentration, different types of point defects cause different degrees of α-Fe lattice distortion and thus different ease of plastic deformation [12]. Wei wei et al. studied the effect of surface lithium atoms on the plastic deformation and yield stress of ferrite by suppressing the phase transition [13]. K Alhafez and Urbassek investigated the effect of different front angle tools on single crystal iron nanocutting using MD simulations [14]. Zamzamian et al. studied the mobility of 1/2 <1 1 1> {0 -1 1} edge dislocations in low carbon α-Fe [15]. Jiao et al. studied the effect of carbon on the deformation mechanism of iron-carbon alloys [16]. However, most of the research environments used in molecular dynamics to study the cutting characteristics of α-Fe are mostly in vacuum, with a few exceptions in aqueous environment. This essay investigates the role of the liquid phase () during abrasive flow cutting in a novel way, comparing it to liquid-free machining, and simulates the effect of the liquid phase on aspects such as abrasive grain motion and workpiece surface morphology changes at the microscopic atomic scale.

This study uses MD simulations to model SiC particles cutting iron-carbon alloy (α-Fe) workpieces in a liquid medium. The effects of the presence or absence of a fluid medium ()  and cutting angle on the workpiece temperature, friction coefficient, workpiece surface morphology formation and workpiece atomic displacement mode during abrasive flow machining are investigated. This essay provides insight into the microscopic machining state and material removal phenomena in the presence of a fluid medium, which is of great academic significance and application value.

 

9. Gao Y; Urbassek HM. Evolution of plasticity in nanometric cutting of Fe single crystals. Applied Surface Science 2014; 317:6–10. https://doi.org/10.1016/j.apsusc.(2014).08.020.
10. Ma Tong, Xie Hongxian. Mechanism of formation of face-centered cubic phase in single crystal iron along [101] during crystal orientation impact[J]. Journal of Physics,2020,69(13):111-121.
11. Lian Teng-yu. Research on nano-mechanical properties and deformation mechanism of single crystal iron carbide [D]. Huaqiao University, 2022. DOI: 10.27155/d. cnki. ghqiu.2022.000543.
12. Li Xiang; Yin Yi-hui; Zhang Yuan-zhang. Point defect types and concentration pairs Molecular dynamics simulation of the effect of plastic deformation behavior of α-Fe [J]. Rare Metal Materials and Engineering 2022, 51 (08): 2881-289
13. Wei Wei; Yu Xingang. Molecular dynamics study on the effect of lithium on the tensile mechanical behavior of ferrite [J]. Journal of University of Chinese Academy of Sciences 2022, 39 (01): 13-20.
14. Alhafez IA; Urbassek HM. Influence of the Rake Angle on Nanocutting of Fe Single Crystals: A Molecular-Dynamics Study. Crystals 2020; 10:516. https://doi.org/10.3390/cryst10060516.
15. Zamzamian SM; Hossein Feghhi SA; Samadfam M. A study on the mobility of 1/2〈1 1 1〉{0 -1 1} edge dislocation in low-carbon α-Fe and its interactions with damage cascade: On picosecond time scale using molecular dynamics simulations. Journal of Nuclear Materials 2019; 527:151806. https://doi.org/10.1016/j.jnucmat.2019.151806.
16. Jiao Y; Dan W; Zhang W. The strain-induced martensitic phase transformation of Fe–C alloys considering C addition: A molecular dynamics study. J Mater Res 2020; 35:1803–16. https://doi.org/10.1557/jmr.2020.154.

 

 

Question 3: Many figures are not clear enough. As shown in Figure 2 and Figure 5, amplification causes distortion. Some figures are too small to see the details, as shown in Figure 9. In addition, in some figures, when cutting distance is mentioned, the coordinates should start from 0.

Response: Thank you very much for your advice. We recreate all of the images from scratch and improve their clarity. Because of the fluid movement, the abrasive grains are just in contact with the workpiece but no force is generated. To ensure the rigour of the simulation, we advanced the cutting distance and performed analysis to improve the accuracy of the simulation

Question 4: In the third point of the conclusion, the author mentioned, "As the cutting angle increases, the increase of the total dislocation length reduces the surface quality of the workpiece, thereby affecting the mechanical properties and processing performance of the material. The smaller cutting angle and the presence of the fluid medium can reduce the number of dislocations and the total dislocation length." However, from Figure 15, when θ=0° or 5°, the dislocation line length of wet cutting is longer than that of dry cutting. This part is suggested to be modified, "In the large angle cutting process, the fluid medium can reduce the number of dislocations and the total dislocation length."

Response: The expert's opinion is very correct. In order to make this paper more scientific, we

revised the original text. The specific amendments are as follows:

 

Modify:

During large-angle cutting, the fluid medium can reduce the number of dislocations and the total dislocation length, which in turn reduces the generation of sub-surface defect structures, resulting in better machining quality.

 

I sincerely appreciate your support of this essay. Because of the requirement for English and enhance the reader's experience, we reorganized the language and improved the image clarity. Thank you once more for your suggestions.

 

The above is the author's modification instructions, if there is something wrong, we will modify it again. Thank you for the professional review and correction of the reviewers and editors. Thank you for your professional review.

Author Response File: Author Response.docx

Reviewer 2 Report

The authors have made a significant effort to study the influence of fluid medium and impact direction on cutting iron-carbon alloy using Molecular dynamics simulation. 

The theme of this research meets the standard of Micromachines Journal.

The following corrections are suggested to improve the readability of this paper.

1. In the Title, "cutting iron-carbon alloy" was mentioned. I think it should be more specific like stating the machining process name, Also, write the grade of the iron-carbon alloy. 

2. State the comparative results in ABSTRACT for different cutting angles. 

3. Add the Novelty of the work in the Abstract.

4. Write the objectives of this research point-wise in the last part of the introduction.

5. In the model building section, Add the workpiece model name, mesh size, and cutting tool. 

6. In section 2.3, state the details of the machining process, tool materials, tool geometry, and cutting parameters (tool feed rate, depth of cutting, coolant flow rate, pressure, etc.) also name of coolant with their thermal properties should be added.

7. Add the values of cutting forces (Ft and Fn) with respect to different tests.

8. In section 3.2, Mention the surface roughness results as this is the main index to represent surface morphology. 

9. In the discussion part (sections 3.1, 3.2, and 3.3), the authors have not included the opinion of other published researchers. I suggest adding the agreement and disagreement of the results using previously published results.

10. Justify the following results "As the cutting progresses to 99Å, the deformed structure under the abrasive is smoothed, and some dislocations are annihilated, resulting in a decrease in the total dislocation length."

11. Conclusion should be more specific rather than a paragraph. Also, mentioned the future scope. 

12. At last, I can suggest comparing the simulation results with the experimental for a better understanding of the process. 

13. All figures are of good quality

 

Author Response

Dear editors and reviewers:

    We thank the editor and the reviewers for your positive and constructive comments and

suggestions on our manuscript. We also thank you very much for giving us an opportunity to revise our manuscript. After careful examination of manuscript, many questions proposed by reviewers and discovered by ourselves have been remedied or modified, and then highlighted by track in our revised manuscript. According to the suggestions of each reviewer and editor, we have made revision carefully and the detailed corrections are listed below point by point:

 

 

Responses to the comments of reviewer :

Question 1: In the Title, "cutting iron-carbon alloy" was mentioned. I think it should be more specific like stating the machining process name, Also, write the grade of the iron-carbon alloy. 

 

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Original:

Molecular dynamics simulation study on the influence of fluid medium and impact direction on cutting iron-carbon alloy

 

Modify:

Molecular dynamics simulation study on the influence of the abrasive flow process on the cutting of iron-carbon alloys (α-Fe)

 

Question 2: State the comparative results in ABSTRACT for different cutting angles. 

Response: Thank you very much for your advice. We revised the original text. The specific

amendments are as follows:

 

Modify:

The plastic deformation behavior and microstructural changes in workpieces during precision ultra-precision machining have piqued the interest of many researchers. In this study, a molecular dynamics simulation of nano-cutting iron-carbon alloy (α-Fe) is established to investigate the effects of fluid medium and cutting angle on workpiece temperature, friction coefficient, workpiece surface morphology, and dislocation evolution by constructing a molecular model of  as a fluid medium in the liquid phase using an innovative combined atomic approach. It is demonstrated that the presence of the fluid phase reduces the machining temperature and the friction coefficient. The cutting angle has a significant impact on the formation of the workpiece's surface profile and the manner in which the workpiece's atoms are displaced. When the cutting angle is 0°, 5°, or 10°, the workpiece's surface morphology flows to both sides in a 45° direction, and the height of atomic accumulation on the workpiece surface gradually decreases while the area of displacement changes increases. The depth of cut increases as the cutting angle increases, causing greater material damage, and the presence of a fluid medium reduces this behavior. A dislocation reaction network is formed by the presence of more single and double-branched structures within the workpiece during the cutting process. The presence of a fluid medium during large-angle cutting reduces the number of dislocations and the total dislocation length. The total length of dislocations inside the workpiece is shorter for small angles of cutting, but the effect of the fluid medium is not very pronounced. Therefore small cutting angles and the presence of fluid media reduce the formation of defective structures within the workpiece and ensure machining quality.

 

Question 3: Add the Novelty of the work in the Abstract.

Response: Thank you very much for your advice. The innovation of this essay is to study the influence of cutting angle and fluid phase on the surface of the workpiece. So we revised the original text. The specific amendments are as follows:

 

Modify:

The plastic deformation behavior and microstructural changes in workpieces during precision ultra-precision machining have piqued the interest of many researchers. In this study, a molecular dynamics simulation of nano-cutting iron-carbon alloy (α-Fe) is established to investigate the effects of fluid medium and cutting angle on workpiece temperature, friction coefficient, workpiece surface morphology, and dislocation evolution by constructing a molecular model of  as a fluid medium in the liquid phase using an innovative combined atomic approach. It is demonstrated that the presence of the fluid phase reduces the machining temperature and the friction coefficient. The cutting angle has a significant impact on the formation of the workpiece's surface profile and the manner in which the workpiece's atoms are displaced. When the cutting angle is 0°, 5°, or 10°, the workpiece's surface morphology flows to both sides in a 45° direction, and the height of atomic accumulation on the workpiece surface gradually decreases while the area of displacement changes increases. The depth of cut increases as the cutting angle increases, causing greater material damage, and the presence of a fluid medium reduces this behavior. A dislocation reaction network is formed by the presence of more single and double-branched structures within the workpiece during the cutting process. The presence of a fluid medium during large-angle cutting reduces the number of dislocations and the total dislocation length. The total length of dislocations inside the workpiece is shorter for small angles of cutting, but the effect of the fluid medium is not very pronounced. Therefore small cutting angles and the presence of fluid media reduce the formation of defective structures within the workpiece and ensure machining quality.

 

Question 4: Write the objectives of this research point-wise in the last part of the introduction

 

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Modify:

This study uses MD simulations to model SiC particles cutting iron-carbon alloy (α-Fe) workpieces in a liquid medium. The effects of the presence or absence of a fluid medium  and cutting angle on the workpiece temperature, friction coefficient, workpiece surface morphology formation and workpiece atomic displacement mode during abrasive flow machining are investigated. This essay provides insight into the microscopic machining state and material removal phenomena in the presence of a fluid medium, which is of great academic significance and application value.

 

Question 5: In the model building section, Add the workpiece model name, mesh size, and cutting tool. 

Response: The expert's opinion is very accurate .In order to explain our work concisely, we revised the original text. The specific amendments are as follows:

Workpiece Modify:

It is known that Fe maintains a body-centred cubic (BCC) structure at room temperature with a lattice constant of a = 2.867 Å. The overall dimensions of the simulation model are 11.452 nm × 17.178 nm × 8.589 nm (114.52 Å × 171.78 Å × 85.89 Å), with a total of 147,773 atoms, and the x, y, and z axes correspond to the crystal directions [100], [010], [001]. We construct BCC Fe single crystal workpieces with a Newtonian layer, a thermostatic layer and a boundary layer for cutting, transfer, and stabilization.

 

cutting tool Modify:

SiC for cutting has a radius of 25Å and a grain atomic number of 6287.

 

 

Question 6: In section 2.3, state the details of the machining process, tool materials, tool geometry, and cutting parameters (tool feed rate, depth of cutting, coolant flow rate, pressure, etc.) also name of coolant with their thermal properties should be added.

 

Response: Thank you very much for your advice. we revised the original text. The specific

amendments are as follows:

 

Modify:

In the simulated processing stage of abrasive flow, the abrasive grain is set as a rigid body. According to the previous research and calculation of abrasive flow processing, the motion of the abrasive grain is set to 50m/s according to the actual processing speed, and the depth of cut is 1.25 nm. The cutting is done along the -y axis with cutting angles of 0°, 5°, and 10° to the workpiece. The cutting distance is 11nm, the cutting crystal direction is (001) [0-10], and the integral step is 1 fs. During machining, the temperature and energy in the system change continuously as the simulation proceeds, but the volume basically does not change. Therefore, the NVE system is used to balance the simulation system. In the process of solid-liquid two-phase abrasive flow, aviation kerosene or hydraulic oil is usually used as the fluid phase of the liquid phase. The fluid medium in this study is aviation kerosene. Aviation kerosene is a mixture of large molecule hydrocarbon complex hydrocarbons with complex composition, and  is an important component of aviation kerosene, so it is used as cooling fluid ( is colorless liquid with melting point -9.6℃, boiling point 216.3℃, flash point 71℃, density 0.753g/cm3, vapor pressure 0.133kPa/47.8℃, insoluble in water, with good heat dissipation).

 

Question 7: Add the values of cutting forces (Ft and Fn) with respect to different tests.

Response: The expert's opinion is very correct. In order to make this paper more scientific, we revised the original text. We provide cutting forces with respect to different tests, As can be seen in Figure 6. At the point, Ft and Fn can be calculated from Figure 6 (b) and Figure 6(c). This complements the relationship between cutting angle and cutting force in this article and makes this article more complete and rigorous. The specific amendments are as follows:

Modify:

Figure 6. Variation of cutting force with cutting distance. (a) Fx; (b) Fy; (c) Fz;

As can be seen in Figure 6 (a), the cutting forces on both sides of x cancel each other out causing the Fx values to be distributed around 0. The lattice structure on both sides is not consistent after the abrasive grain has cut through the workpiece due to the random distribution of C atoms inside the workpiece, which also contributes to the deviation of Fx up and down at a certain cutting distance. As shown in Figure 6 (b), the Fy value increases faster at the beginning of the cutting process and gradually smoothes out at a later stage. When the cutting angle is 0°, the cutting distance is approximately 50 Å. The abrasive grain has been completely cut into the workpiece at this point, and the cutting process has reached a stable cutting stage, where the Fy value has reached its peak and is stable. The Fy value gradually increases as the cutting angle increases, especially in the middle and later stages of cutting. When the cutting angle is 15° or 20°, Fy continues to rise in the late cutting stage, making it more difficult to achieve the stable cutting stage. If the cutting angle is too large, it is difficult to discharge the chips formed after the abrasive grains enter the workpiece, causing the cutting action to be hampered. As shown in Figure 5(c), Fz increases approximately linearly in the early stages of cutting, slowly after the grain has been completely submerged in the work-piece, and then gradually stabilises in the later stages. Fz allows the atoms beneath the grain to form a machined surface while also overcoming the chip's obstruction to the grain. Fz increases as the cutting angle increases at the same cutting distance. Abrasive grains with a higher cutting angle create deeper cuts in the workpiece, increasing the number of atoms contacted by the grain. To force plastic deformation of the material in the cutting area, the particles must overcome greater bonding energy and break more atomic interactions. As a result, as the cutting angle increases, the abrasive grain cutting forces increase. This is also consistent with previous research, which concluded that increasing cutting angles increases cutting forces within a certain range [31]. Therefore, smaller cutting angles and the presence of fluid improve the quality of the machined workpiece.

 

Question 8: In section 3.2, Mention the surface roughness results as this is the main index to represent surface morphology.

 

Response: Thank you very much for your comments. In the molecular dynamics study report, we felt that the roughness values were not accurate enough to reflect the surface finish of the workpiece. Because roughness quantification at the atomic scale of the small size model is less accurate, we do not quantify roughness values and instead obtain trends in surface roughness as variables are changed by looking at the height of the surface pile up, as shown in Figure 7 and Figure 8. Thank you once more for your insightful comments.

 

Question 9: In the discussion part (sections 3.1, 3.2, and 3.3), the authors have not included the opinion of other published researchers. I suggest adding the agreement and disagreement of the results using previously published results.

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Modify:

1. Cutting fluid to reduce cutting temperature:

According to previous research, the presence of cutting fluid in the mechanical cutting process can better reduce the cutting temperature of the conclusion [26,27]. This study is an important resource for explaining the reasons under a microscopic perspective.

26. Cao Hongwei; Zhang Tianrong; Chen Yajun. Research on the method of cutting fluid cooling[J]. Equipment Management and Maintenance,2021 (05):144-145. DOI:10.16621/j.cnki.issn1001-0599.2021.03.70.
27. Yang Yi. Study on the characteristics of coolant temperature field change during high speed cutting [D]. Yanshan University,2018.

 

2. Cutting fluid can lubricates:

This is also consistent with previous research, which concluded that Cutting forces and frictional wear are better reduced when cutting fluid is present [29,30]. This essay pro-vides a more detailed explanation of the causes of this.

• Pan Chuanyi; Wang Chengyong; Li Weiqiu; Wang Yong; Yuan Yaohui; Wu Huayi. Development and practical testing of a special micro-lubrication cutting fluid for titanium alloy [J]. Mould manufacturing, 2022, 22(11):70-75.
• Yang Yongfeng. Research on the application of micro-lubrication technology of green nano cutting fluid[D]. Hangzhou University of Electronic Science and Technology, 2020. DOI:10.27075/d.cnki.ghzdc.2020.000926.

3. The cutting force increases with the increase of cutting angle:

This is also consistent with previous research, which concluded that increasing cutting angles increases cutting forces within a certain range [31].

• Wang Haitao. Cutting numerical simulation and cutter roller optimization design of drum chipper [D]. Northeast Forestry University, 2019. DOI: 10.27009/d.cnki.gdblu.2019.000291.

 

• the absence of twinning structure during the cutting process:

The absence of Böhler vectors of 1/3<111>, 1/,6<111> and 1/12<111> during the cutting process, indicating the absence of twinning structure. This is consistent with the findings of Katzarov Ivaylo Hristov et al [33].

33. Katzarov Ivaylo Hristov; Drenchev Ljudmil Borisov. "Unveiling the Mechanisms of High-Temperature 1/2[111] Screw Dislocation Glide in Iron–Carbon Alloys." Crystals 12.4(2022). doi:10.3390/CRYST12040518.

 

Question 10: Justify the following results "As the cutting progresses to 99Å, the deformed structure under the abrasive is smoothed, and some dislocations are annihilated, resulting in a decrease in the total dislocation length."

Response: Thank you very much for your advice. we revised the original text. The specific

amendments are as follows:

 

Modify:

As the cut reaches 99 Å, the deformed structure beneath the grain is smoothed out and some of the dislocations are obliterated resulting in a decrease in the total dislocation length. This is consistent with the findings of Li Shang-Jie et al [34].

 

34. Li Shang-Jie, Chen Zheng, Yun Jiang-Juan, Zhang Jing. Phase-field crystal method investigated the dislocation annihilation and grain boundary migration in grain shrink process. Acta Phys. Sin., 2014, 63(12): 128101. doi: 10.7498/aps.63.128101.

 

Question 11: Conclusion should be more specific rather than a paragraph. Also, mentioned the future scope. 

Response: The experts' opinions are very constructive, we revised the original text. References to the future in the conclusion have been removed. The specific amendments are as follows:

 

Modify:

1. In comparison to machining without a fluid medium, machining using a fluid medium () lowers the machining temperature and the coefficient of friction.
2. Temperature and coefficient of friction increase with increasing cutting angle during abrasive flow machining.
3. The cutting angle has a greater influence on the formation of the workpiece's surface profile and the manner in which the workpiece atoms are displaced, whereas the fluid medium has a lesser influence. When the cutting angle is 0°, 5° and 10° respectively, the workpiece's surface profile flows at 45° to both sides. The height of atomic accumulation on the workpiece's surface gradually decreases, but at the same time the area where displacement changes occur becomes larger. As the cutting angle increases, so does the depth of cut, resulting in more material damage.
4. The area of displacement gradually expands towards the interior of the workpiece as the cutting angle increases. The number of atoms displaced to the workpiece's surface decreases and remains within the workpiece. The atoms that accumulate inside the workpiece squeeze the uncut area, causing a bulge in the workpiece's surface, which degrades the workpiece's quality but is beneficial for the removal of large burrs.
5. During the cutting process, a large number of dislocations were discovered at b=1/2111> and b=100>. The b=1/2111> dislocations dominate, with b=100> connecting the dislocations in different areas. The dislocation reaction network is formed by the presence of a large number of single and double-branched structures within the workpiece. During large-angle cutting, the fluid medium reduces the number of dislocations and the total dislocation length, which in turn reduces the generation of sub-surface defect structures, resulting in better machining quality.

 

Question 12: At last, I can suggest comparing the simulation results with the experimental for a better understanding of the process. 

Response: The experts' opinions are very constructive, we revised the original text. The specific amendments are as follows:

In addition, the elastic constants of α-Fe using this EAM potential were  These values were very close to the elastic constants  And calculated by density functional theory (DFT) for iron-carbon alloy[26].The above two tests show that the EAM potential function can correctly express the physical properties of α-Fe.

Question 13: All figures are of good quality

Response: Thank you very much for your approval of this article in order to improve the reader's experience. We reorganized the language and improved the ima

Dear editors and reviewers:

    We thank the editor and the reviewers for your positive and constructive comments and

suggestions on our manuscript. We also thank you very much for giving us an opportunity to revise our manuscript. After careful examination of manuscript, many questions proposed by reviewers and discovered by ourselves have been remedied or modified, and then highlighted by track in our revised manuscript. According to the suggestions of each reviewer and editor, we have made revision carefully and the detailed corrections are listed below point by point:

 

 

Responses to the comments of reviewer :

Question 1: In the Title, "cutting iron-carbon alloy" was mentioned. I think it should be more specific like stating the machining process name, Also, write the grade of the iron-carbon alloy. 

 

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Original:

Molecular dynamics simulation study on the influence of fluid medium and impact direction on cutting iron-carbon alloy

 

Modify:

Molecular dynamics simulation study on the influence of the abrasive flow process on the cutting of iron-carbon alloys (α-Fe)

 

Question 2: State the comparative results in ABSTRACT for different cutting angles. 

Response: Thank you very much for your advice. We revised the original text. The specific

amendments are as follows:

 

Modify:

The plastic deformation behavior and microstructural changes in workpieces during precision ultra-precision machining have piqued the interest of many researchers. In this study, a molecular dynamics simulation of nano-cutting iron-carbon alloy (α-Fe) is established to investigate the effects of fluid medium and cutting angle on workpiece temperature, friction coefficient, workpiece surface morphology, and dislocation evolution by constructing a molecular model of  as a fluid medium in the liquid phase using an innovative combined atomic approach. It is demonstrated that the presence of the fluid phase reduces the machining temperature and the friction coefficient. The cutting angle has a significant impact on the formation of the workpiece's surface profile and the manner in which the workpiece's atoms are displaced. When the cutting angle is 0°, 5°, or 10°, the workpiece's surface morphology flows to both sides in a 45° direction, and the height of atomic accumulation on the workpiece surface gradually decreases while the area of displacement changes increases. The depth of cut increases as the cutting angle increases, causing greater material damage, and the presence of a fluid medium reduces this behavior. A dislocation reaction network is formed by the presence of more single and double-branched structures within the workpiece during the cutting process. The presence of a fluid medium during large-angle cutting reduces the number of dislocations and the total dislocation length. The total length of dislocations inside the workpiece is shorter for small angles of cutting, but the effect of the fluid medium is not very pronounced. Therefore small cutting angles and the presence of fluid media reduce the formation of defective structures within the workpiece and ensure machining quality.

 

Question 3: Add the Novelty of the work in the Abstract.

Response: Thank you very much for your advice. The innovation of this essay is to study the influence of cutting angle and fluid phase on the surface of the workpiece. So we revised the original text. The specific amendments are as follows:

 

Modify:

The plastic deformation behavior and microstructural changes in workpieces during precision ultra-precision machining have piqued the interest of many researchers. In this study, a molecular dynamics simulation of nano-cutting iron-carbon alloy (α-Fe) is established to investigate the effects of fluid medium and cutting angle on workpiece temperature, friction coefficient, workpiece surface morphology, and dislocation evolution by constructing a molecular model of  as a fluid medium in the liquid phase using an innovative combined atomic approach. It is demonstrated that the presence of the fluid phase reduces the machining temperature and the friction coefficient. The cutting angle has a significant impact on the formation of the workpiece's surface profile and the manner in which the workpiece's atoms are displaced. When the cutting angle is 0°, 5°, or 10°, the workpiece's surface morphology flows to both sides in a 45° direction, and the height of atomic accumulation on the workpiece surface gradually decreases while the area of displacement changes increases. The depth of cut increases as the cutting angle increases, causing greater material damage, and the presence of a fluid medium reduces this behavior. A dislocation reaction network is formed by the presence of more single and double-branched structures within the workpiece during the cutting process. The presence of a fluid medium during large-angle cutting reduces the number of dislocations and the total dislocation length. The total length of dislocations inside the workpiece is shorter for small angles of cutting, but the effect of the fluid medium is not very pronounced. Therefore small cutting angles and the presence of fluid media reduce the formation of defective structures within the workpiece and ensure machining quality.

 

Question 4: Write the objectives of this research point-wise in the last part of the introduction

 

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Modify:

This study uses MD simulations to model SiC particles cutting iron-carbon alloy (α-Fe) workpieces in a liquid medium. The effects of the presence or absence of a fluid medium  and cutting angle on the workpiece temperature, friction coefficient, workpiece surface morphology formation and workpiece atomic displacement mode during abrasive flow machining are investigated. This essay provides insight into the microscopic machining state and material removal phenomena in the presence of a fluid medium, which is of great academic significance and application value.

 

Question 5: In the model building section, Add the workpiece model name, mesh size, and cutting tool. 

Response: The expert's opinion is very accurate .In order to explain our work concisely, we revised the original text. The specific amendments are as follows:

Workpiece Modify:

It is known that Fe maintains a body-centred cubic (BCC) structure at room temperature with a lattice constant of a = 2.867 Å. The overall dimensions of the simulation model are 11.452 nm × 17.178 nm × 8.589 nm (114.52 Å × 171.78 Å × 85.89 Å), with a total of 147,773 atoms, and the x, y, and z axes correspond to the crystal directions [100], [010], [001]. We construct BCC Fe single crystal workpieces with a Newtonian layer, a thermostatic layer and a boundary layer for cutting, transfer, and stabilization.

 

cutting tool Modify:

SiC for cutting has a radius of 25Å and a grain atomic number of 6287.

 

 

Question 6: In section 2.3, state the details of the machining process, tool materials, tool geometry, and cutting parameters (tool feed rate, depth of cutting, coolant flow rate, pressure, etc.) also name of coolant with their thermal properties should be added.

 

Response: Thank you very much for your advice. we revised the original text. The specific

amendments are as follows:

 

Modify:

In the simulated processing stage of abrasive flow, the abrasive grain is set as a rigid body. According to the previous research and calculation of abrasive flow processing, the motion of the abrasive grain is set to 50m/s according to the actual processing speed, and the depth of cut is 1.25 nm. The cutting is done along the -y axis with cutting angles of 0°, 5°, and 10° to the workpiece. The cutting distance is 11nm, the cutting crystal direction is (001) [0-10], and the integral step is 1 fs. During machining, the temperature and energy in the system change continuously as the simulation proceeds, but the volume basically does not change. Therefore, the NVE system is used to balance the simulation system. In the process of solid-liquid two-phase abrasive flow, aviation kerosene or hydraulic oil is usually used as the fluid phase of the liquid phase. The fluid medium in this study is aviation kerosene. Aviation kerosene is a mixture of large molecule hydrocarbon complex hydrocarbons with complex composition, and  is an important component of aviation kerosene, so it is used as cooling fluid ( is colorless liquid with melting point -9.6℃, boiling point 216.3℃, flash point 71℃, density 0.753g/cm3, vapor pressure 0.133kPa/47.8℃, insoluble in water, with good heat dissipation).

 

Question 7: Add the values of cutting forces (Ft and Fn) with respect to different tests.

Response: The expert's opinion is very correct. In order to make this paper more scientific, we revised the original text. We provide cutting forces with respect to different tests, As can be seen in Figure 6. At the point, Ft and Fn can be calculated from Figure 6 (b) and Figure 6(c). This complements the relationship between cutting angle and cutting force in this article and makes this article more complete and rigorous. The specific amendments are as follows:

Modify:

Figure 6. Variation of cutting force with cutting distance. (a) Fx; (b) Fy; (c) Fz;

As can be seen in Figure 6 (a), the cutting forces on both sides of x cancel each other out causing the Fx values to be distributed around 0. The lattice structure on both sides is not consistent after the abrasive grain has cut through the workpiece due to the random distribution of C atoms inside the workpiece, which also contributes to the deviation of Fx up and down at a certain cutting distance. As shown in Figure 6 (b), the Fy value increases faster at the beginning of the cutting process and gradually smoothes out at a later stage. When the cutting angle is 0°, the cutting distance is approximately 50 Å. The abrasive grain has been completely cut into the workpiece at this point, and the cutting process has reached a stable cutting stage, where the Fy value has reached its peak and is stable. The Fy value gradually increases as the cutting angle increases, especially in the middle and later stages of cutting. When the cutting angle is 15° or 20°, Fy continues to rise in the late cutting stage, making it more difficult to achieve the stable cutting stage. If the cutting angle is too large, it is difficult to discharge the chips formed after the abrasive grains enter the workpiece, causing the cutting action to be hampered. As shown in Figure 5(c), Fz increases approximately linearly in the early stages of cutting, slowly after the grain has been completely submerged in the work-piece, and then gradually stabilises in the later stages. Fz allows the atoms beneath the grain to form a machined surface while also overcoming the chip's obstruction to the grain. Fz increases as the cutting angle increases at the same cutting distance. Abrasive grains with a higher cutting angle create deeper cuts in the workpiece, increasing the number of atoms contacted by the grain. To force plastic deformation of the material in the cutting area, the particles must overcome greater bonding energy and break more atomic interactions. As a result, as the cutting angle increases, the abrasive grain cutting forces increase. This is also consistent with previous research, which concluded that increasing cutting angles increases cutting forces within a certain range [31]. Therefore, smaller cutting angles and the presence of fluid improve the quality of the machined workpiece.

 

Question 8: In section 3.2, Mention the surface roughness results as this is the main index to represent surface morphology.

 

Response: Thank you very much for your comments. In the molecular dynamics study report, we felt that the roughness values were not accurate enough to reflect the surface finish of the workpiece. Because roughness quantification at the atomic scale of the small size model is less accurate, we do not quantify roughness values and instead obtain trends in surface roughness as variables are changed by looking at the height of the surface pile up, as shown in Figure 7 and Figure 8. Thank you once more for your insightful comments.

 

Question 9: In the discussion part (sections 3.1, 3.2, and 3.3), the authors have not included the opinion of other published researchers. I suggest adding the agreement and disagreement of the results using previously published results.

Response: The experts' opinions are very constructive, we revised the original text. The specific

amendments are as follows:

 

Modify:

1. Cutting fluid to reduce cutting temperature:

According to previous research, the presence of cutting fluid in the mechanical cutting process can better reduce the cutting temperature of the conclusion [26,27]. This study is an important resource for explaining the reasons under a microscopic perspective.

26. Cao Hongwei; Zhang Tianrong; Chen Yajun. Research on the method of cutting fluid cooling[J]. Equipment Management and Maintenance,2021 (05):144-145. DOI:10.16621/j.cnki.issn1001-0599.2021.03.70.
27. Yang Yi. Study on the characteristics of coolant temperature field change during high speed cutting [D]. Yanshan University,2018.

 

2. Cutting fluid can lubricates:

This is also consistent with previous research, which concluded that Cutting forces and frictional wear are better reduced when cutting fluid is present [29,30]. This essay pro-vides a more detailed explanation of the causes of this.

• Pan Chuanyi; Wang Chengyong; Li Weiqiu; Wang Yong; Yuan Yaohui; Wu Huayi. Development and practical testing of a special micro-lubrication cutting fluid for titanium alloy [J]. Mould manufacturing, 2022, 22(11):70-75.
• Yang Yongfeng. Research on the application of micro-lubrication technology of green nano cutting fluid[D]. Hangzhou University of Electronic Science and Technology, 2020. DOI:10.27075/d.cnki.ghzdc.2020.000926.

3. The cutting force increases with the increase of cutting angle:

This is also consistent with previous research, which concluded that increasing cutting angles increases cutting forces within a certain range [31].

• Wang Haitao. Cutting numerical simulation and cutter roller optimization design of drum chipper [D]. Northeast Forestry University, 2019. DOI: 10.27009/d.cnki.gdblu.2019.000291.

 

• the absence of twinning structure during the cutting process:

The absence of Böhler vectors of 1/3<111>, 1/,6<111> and 1/12<111> during the cutting process, indicating the absence of twinning structure. This is consistent with the findings of Katzarov Ivaylo Hristov et al [33].

33. Katzarov Ivaylo Hristov; Drenchev Ljudmil Borisov. "Unveiling the Mechanisms of High-Temperature 1/2[111] Screw Dislocation Glide in Iron–Carbon Alloys." Crystals 12.4(2022). doi:10.3390/CRYST12040518.

 

Question 10: Justify the following results "As the cutting progresses to 99Å, the deformed structure under the abrasive is smoothed, and some dislocations are annihilated, resulting in a decrease in the total dislocation length."

Response: Thank you very much for your advice. we revised the original text. The specific

amendments are as follows:

 

Modify:

As the cut reaches 99 Å, the deformed structure beneath the grain is smoothed out and some of the dislocations are obliterated resulting in a decrease in the total dislocation length. This is consistent with the findings of Li Shang-Jie et al [34].

 

34. Li Shang-Jie, Chen Zheng, Yun Jiang-Juan, Zhang Jing. Phase-field crystal method investigated the dislocation annihilation and grain boundary migration in grain shrink process. Acta Phys. Sin., 2014, 63(12): 128101. doi: 10.7498/aps.63.128101.

 

Question 11: Conclusion should be more specific rather than a paragraph. Also, mentioned the future scope. 

Response: The experts' opinions are very constructive, we revised the original text. References to the future in the conclusion have been removed. The specific amendments are as follows:

 

Modify:

1. In comparison to machining without a fluid medium, machining using a fluid medium () lowers the machining temperature and the coefficient of friction.
2. Temperature and coefficient of friction increase with increasing cutting angle during abrasive flow machining.
3. The cutting angle has a greater influence on the formation of the workpiece's surface profile and the manner in which the workpiece atoms are displaced, whereas the fluid medium has a lesser influence. When the cutting angle is 0°, 5° and 10° respectively, the workpiece's surface profile flows at 45° to both sides. The height of atomic accumulation on the workpiece's surface gradually decreases, but at the same time the area where displacement changes occur becomes larger. As the cutting angle increases, so does the depth of cut, resulting in more material damage.
4. The area of displacement gradually expands towards the interior of the workpiece as the cutting angle increases. The number of atoms displaced to the workpiece's surface decreases and remains within the workpiece. The atoms that accumulate inside the workpiece squeeze the uncut area, causing a bulge in the workpiece's surface, which degrades the workpiece's quality but is beneficial for the removal of large burrs.
5. During the cutting process, a large number of dislocations were discovered at b=1/2111> and b=100>. The b=1/2111> dislocations dominate, with b=100> connecting the dislocations in different areas. The dislocation reaction network is formed by the presence of a large number of single and double-branched structures within the workpiece. During large-angle cutting, the fluid medium reduces the number of dislocations and the total dislocation length, which in turn reduces the generation of sub-surface defect structures, resulting in better machining quality.

 

Question 12: At last, I can suggest comparing the simulation results with the experimental for a better understanding of the process. 

Response: The experts' opinions are very constructive, we revised the original text. The specific amendments are as follows:

In addition, the elastic constants of α-Fe using this EAM potential were  These values were very close to the elastic constants  And calculated by density functional theory (DFT) for iron-carbon alloy[26].The above two tests show that the EAM potential function can correctly express the physical properties of α-Fe.

Question 13: All figures are of good quality

Response: Thank you very much for your approval of this article in order to improve the reader's experience. We reorganized the language and improved the image clarity. Thank you once more for your suggestions.

The above is the author's modification instructions, if there is something wrong, we will modify it again. Thank you for the professional review and correction of the reviewers and editors. Thank you for your professional review.

 

ge clarity. Thank you once more for your suggestions.

The above is the author's modification instructions, if there is something wrong, we will modify it again. Thank you for the professional review and correction of the reviewers and editors. Thank you for your professional review.

 

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Accepted.