Experimental Research of Ultrasonic Cavitation Evolution Mechanism and Model Optimization of RUREMM on Cylindrical Surface

Round 1

Reviewer 1 Report

This review is about the manuscript “Experimental Research of Ultrasonic Cavitation Evolution Mechanism and Model Optimization of RUREMM on Cylindrical Surface”. This study discusses the experimental research of ultrasonic cavitation evolution and the optimization of a model for radial ultrasonic rolling electrochemical micromachining (RUREMM) on cylindrical surfaces. It also addresses challenges in aerospace and tribology sectors by proposing a comprehensive method that adds an ultrasonic field on cylindrical surfaces. However there are few questions that need to be answered. Add proper explanation of these in the manuscript.

1. Write equation in proper format with equal size. Make sure vectors quantities are bold faced or add arrow on top.

2. Improve the visibility, quality of Figure 8, 9, 10.

3. Figures resolution are very poor. Improve the size and resolution of all figures.

4. Discuss what are the main challenges in aerospace and tribology sectors that the research aims to address?

5. How does the theoretical model created in this research help to understand the formation and collapse of bubbles in the liquid medium?

6. Add description about what parameters in RUREMM did the research analyze and how do they influence material depth/diameter ratio and roughness?

7. Explain the impact of rotation speed on the aspect ratio of micro-pits and surface roughness based on the findings in the document?

8. Describe the methodology used in the study regarding the analysis of the cavitation phenomenon and the impact of the electric field on the machining gap?

9. How was the simulation design structured in the study, particularly in relation to the electric field model and the determination of the appropriate electrode size?

10. How does the pulse frequency impact the appearance of micro pits in EMM and RUREMM processes?

Comments for author File: Comments.pdf

Author Response

List of Responses

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Processes”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

Revised portion are marked in red in the paper. The main corrections in paper and the responds to the reviewer’s comments are as flowing:

Responds to the reviewer’s comments:

Q(1): Write equation in proper format with equal size. Make sure vectors quantities are bold faced or add arrow on top.

A(1): We have revised the formula 8 in chapter 3.1 and the relevant equations according to the Reviewer’s comments.

Q(2): Improve the visibility, quality of Figure 8, 9, 10.

A(2): Thank you very much for your valuable comments. According to the reviewer’s opinion, we have Improve the visibility, quality of Figure 8, 9, 10 in chapter 5.

Q(3): Figures resolution are very poor. Improve the size and resolution of all figures. 

A(3): Thank you for your precious review, we have improved the size and resolution of all figures in this paper.

Q(4): Discuss what are the main challenges in aerospace and tribology sectors that the research aims to address?

A(4): Considering the reviewer’s suggestion, we have provided the sentence “The micro-groove structure machined on the wind propeller can reduce the load force by 10% and the array of micro-pitted surface texture machined on the cylinder liner surface of the internal combustion engine can reduce the friction force by 25%-50%” in chapter 1.

Q(5): How does the theoretical model created in this research help to understand the formation and collapse of bubbles in the liquid medium?

A(5): Thank you for your precious review, firstly, the theoretical model created in this research can not only explain the minuscule cavitation bubble nuclei within the NaNO₃ electrolyte experience a succession of growth, expansion, compression, and eventual collapse, but also explain the electrolytic products can be effectively removed due to the velocity was improved during the cavitation bubble collapse.

Q(6):Add description about what parameters in RUREMM did the research analyze and how do they influence material depth/diameter ratio and roughness?

A(6): Thank you for your precious review, the relevant sentence “That was because ultrasonic vibration can change the flow field distribution in the machining area within the gap, and can effectively discharge the insoluble products and joule heat generated during the machining process. Meanwhile, the gap high pressure generated by ultrasonic vibration can effectively discharge the gas generated during the machining process, reduce the volume fraction of gas in the flow field in the machining area, and help improve the machining precision and surface quality of the micro-texture.” was added to describe this question.

Q(7): Explain the impact of rotation speed on the aspect ratio of micro-pits and surface roughness based on the findings in the document?

A(7): We have paid attention to this issue, the sentence “This is because the voltage is unchanged, the roll erosion rate increases, the material removal is unstable, and the concentrated corrosion removal ability is weak, resulting in a decrease in the overall current density between the tool electrode and the opposite machining area. The depth of the array micro-pits is not significantly reduced. However, when the roll erosion rate increases, the electric field radiation range on the workpiece surface per unit time changes greatly, and the width of the array micro-pits changes significantly.” was added to explain this question.

Q(8): Describe the methodology used in the study regarding the analysis of the cavitation phenomenon and the impact of the electric field on the machining gap?

A(8): Thank you very much for your suggestion, the sentence “firstly, the analysis of the cavitation phenomenon can explain the bubble undergoes expand, compression, collapse and oscillation when the ultrasonic transducer vibrates upwards or downwards in the narrow machining gap. Then the dimensions of the micro-roll etching electrode were researched through the utilization of the COMSOL simulation software considering the effect of the electric field was added in the chapter 3.2.

Q(9): How was the simulation design structured in the study, particularly in relation to the electric field model and the determination of the appropriate electrode size?

A(9): Thank you for your precious review, based on finite element method, COMSOL multiphysics can simulate and analyze physical and chemical phenomena in reality by solving  multi-field partial differential equations, and determining the appropriate electrode size is an important step in the simulation design. Besides, consider the precision analysis of micro-electrochemical machining, the electrode sizes was chosen 50mm to 300mm.

Q(10): How does the pulse frequency impact the appearance of micro pits in EMM and RUREMM processes?

A(10): We have paid attention to this issue, “This is because the increase of the reverse current is conducive to eliminating the concentration polarization, the polarization potential distribution on the surface of the workpiece is uniform, so that the material removal is more uniform, and the replication accuracy of the micro-pits will be higher.“ is provided in chapter 5.4.

Special thanks to you for your good comments. We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence content and framework of the paper. And here we not only list the changes but also mark in red in revised paper.

We appreciate for reviewers’ warm work earnestly, and hope that the correction will meet with approval.

Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx

Reviewer 2 Report

1. An interesting numerical and experimental study of the michomachining surface technique is presented. However, the presentation is not clear in several places.

2. Page 3: “The transducer’s surface features an array of micro bulges....” - it is not clear how the “micro bulges” at the cathode are fabricated? What is the material of these “micro bulges”?

3. Page 3: From Fig. 2 it follows that the proposed RUREMM technique produces micro holes, not micro protuberances. However, from Fig. 18 it follows that microprotuberances are produced. Could the Authors explain this discrepancy between Figs. 2 and 18?

4. Page 4: In section 3 the cavitation and material removal models of RUREMM are presented, and Eqs. (1)-(10) are provided:

a) the purpose of those mathematical models are not explained - the models are not used anywhere in the rest of the paper,

b) it is not clear if Eqs. (1)-(10) are developed by the Authors or are cited from some other literature,

c) how have the Authors obtained Fig. 3 - is this figure the results of any calculations?

Due to the above problems it is recommended for the Authors to remove section 3.

5. Page 6: In section 4.1 only the geometry and the mesh of the FEM model are described. However, the physics of the model is omitted. Could the Authors explain the physics of the FEM model - what domains have been assumed with what fields, what variables have been changed as the inputs, and how they have influenced the outputs, etc.?

6. Page 7, Fig. 5:

a) what quantity/variable is presented in Fig. 5 with the color scale?

b) why in Fig. 5b) is the anode deformed in x and y directions? does the influence of the cathode deform the shape of the anode?

7. Page 8, Fig. 6: What exactly can be concluded from Fig. 6? The results presented in Figs. 6a) - 6d) are almost the same?

8. Page 12, Tab. 4: What do the Authors mean by “Short circuits”? Explain the following sentence: “However, three short circuits represent the machining environment was changed to be unstable...”

There are several minor language mistakes throughout the text. Examples are given below, yet there are more.

Page 1: “Nowdays...” -> “Nowadays...”

Page 10: “The processing experiments are mainly consists of three parts.” -> “The processing experiments mainly consist of three parts.”

Author Response

List of Responses

Dear Editors and Reviewers:

Thank you for your letter and for the reviewers’ comments concerning our manuscript entitled “Processes”. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval.

Revised portion are marked in red in the paper. The main corrections in paper and the responds to the reviewer’s comments are as flowing:

Responds to the reviewer’s comments:

Q(1): An interesting numerical and experimental study of the michomachining surface technique is presented. However, the presentation is not clear in several places.

A(1): Thank you very much for your valuable comments. According to the reviewer’s opinion, we have made detailed modifications according to the reviewers and described the article in detail in this paper.

Q(2): Page 3: “The transducer’s surface features an array of micro bulges....” - it is not clear how the “micro bulges” at the cathode are fabricated? What is the material of these “micro bulges”?

A(2): Considering the reviewer’s suggestion, “The choice of the tool electrode is 304 stainless steel material, which possesses specific stiffness and strength. Additionally, 304 stainless steel exhibits excellent bending strength, electrical conductivity, and high temperature resistance” was added in chapter 5.2 to explain the question.

Q(3): Page 3: From Fig. 2 it follows that the proposed RUREMM technique produces micro holes, not micro protuberances. However, from Fig. 18 it follows that microprotuberances are produced. Could the Authors explain this discrepancy between Figs. 2 and 18?

A(3): Thank you for your effective review, Figure. 18(a) and (b) show the micro-dimple arrays with good performance were generated by the optimized parameters. Furthermore, 3D morphology of micro pits and cross-sectional profile curve were obtained through optical profiling shown in Figure 18(c), which is not micro protuberances, the same with Figure 2.

Q(4): Page 4: In section 3 the cavitation and material removal models of RUREMM are presented, and Eqs. (1)-(10) are provided:

1. a) the purpose of those mathematical models are not explained - the models are not used anywhere in the rest of the paper,
2. b) it is not clear if Eqs. (1)-(10) are developed by the Authors or are cited from some other literature,
3. c) how have the Authors obtained Fig. 3 - is this figure the results of any calculations?

A(4): a) Considering the reviewer’s suggestion, the sentence “In order to analyze the change of cavitation bubble collapse in electrochemical machining state in the machining gap more precisely under the alternating ultrasonic pressure during the RUREMM process,” was added in section 3.

3. b) Thank you very much for your valuable comments, the relevant conference [43] and [44] were added to provethe reliability of the formula in chapter 3.1.
4. c)Considering the reviewer’s suggestion, differential equation can effectively describe a variety of current mathematical problems by solving the differential equation to get the best solution, but in practical application process, sometimes only need to ask for one of the appropriate solutions can be without calculating too many steps. Therefore, the MATLAB analysis module that can analyze a variety of differential equation functions is not suitable for the calculation of formula 1-6. It is recommended to use Runge-Kutta equation with higher calculation accuracy to solve this equation, which not only solves faster, but also has higher efficiency.

Q(5): Page 6: In section 4.1 only the geometry and the mesh of the FEM model are described. However, the physics of the model is omitted. Could the Authors explain the physics of the FEM model - what domains have been assumed with what fields, what variables have been changed as the inputs, and how they have influenced the outputs, etc.?

A(5): Thank you for your precious review, the relevant sentence “The upper surface of the model is the tool cathode surface, whose initial potential is 0 V, and the lower surface is the workpiece anode surface, the potential of the raised end face is the voltage potential, and the other faces are 0 potential surfaces.” was provided to explain the physics of the FEM model.

Q(6):Page 7, Fig. 5:

1. a) what quantity/variable is presented in Fig. 5 with the color scale?
2. b) why in Fig. 5b) is the anode deformed in x and y directions? does the influence of the cathode deform the shape of the anode?

A(6): a) Thank you for your effective review, the quantity/variable is presented in Fig. 5 with the color scale is the displacement scale from anode surface in the right position, and the maximum depth is 0.07mm.

1. b) Considering the reviewer’s suggestion,COMSOL Multiphysics can simulate and analyze physical and chemical phenomena in reality by solving single-field and multi-field partial differential equations. In electrochemical processes, the current distribution may be uneven, resulting in higher current density in some regions of the anode. These regions are subjected to greater electrochemical corrosion or electrolysis, resulting in dissolution and deformation of the anode material.

Q(7): Page 8, Fig. 6: What exactly can be concluded from Fig. 6? The results presented in Figs. 6a) - 6d) are almost the same?

A(7): We have paid attention to this issue, the sentence “From the above 3D simulated cloud image, under certain simulation parameters, the surface of the workpiece can be fitted with square pits of relatively uniform size, and the consistency is good. In the small spacing of 400μm and 600μm, the electric field line interferes obviously, forming a disturbing electric field distribution, which ultimately affects the size and accuracy of the formed micro-pits.” is represented in chapter 4.2.

Q(8): Page 12, Tab. 4: What do the Authors mean by “Short circuits”? Explain the following sentence: “However, three short circuits represent the machining environment was changed to be unstable...”

A(8): Thank you very much for your suggestion, In the electrochemical micro machining, short circuits is mainly caused by the spacing between the workpiece and the electrode, the blockage caused by impurities in the electrolyte, and the excessive roughness of the workpiece surface. Furthermore, the more short circuits represent the machining environment was changed to be more unstable.

Q(9): There are several minor language mistakes throughout the text. Examples are given below, yet there are more.

Page 1: “Nowdays...” -> “Nowadays...”

Page 10: “The processing experiments are mainly consists of three parts.” -> “The processing experiments mainly consist of three parts.”

A(9): Thank you for your precious review, the relevant sentence “Nowdays...” was changed to “Nowadays...”, and the “The processing experiments are mainly consists of three parts.” was changed to be ““The processing experiments mainly consists of three parts.”

Special thanks to you for your good comments. We tried our best to improve the manuscript and made some changes in the manuscript. These changes will not influence content and framework of the paper. And here we not only list the changes but also mark in red in revised paper.

We appreciate for reviewers’ warm work earnestly, and hope that the correction will meet with approval.

Once again, thank you very much for your comments and suggestions.

Author Response File: Author Response.docx