Modeling Wear and Friction Regimes on Ceramic Materials with Positive and Negative Thermal Expansion
Round 1
Reviewer 1 Report
The article demonstrates the feasibility of controlling the wear and friction performance of ceramic composite materials using a negative thermal expansion coefficient approach through comparing the frictional performance of ceramic composite materials with opposite coefficients of thermal expansion.
My suggestions are as follows:
1. Academic papers should maintain objectivity and academic tone, avoiding the use of terms like "I" or "we."
2. There are too many paragraphs in the introduction section of the paper, and it should predominantly use declarative sentences, avoiding interrogative ones.
3. During the quantitative description of ceramic material friction behavior based on established principles of mechanics and thermodynamics, the descriptions of unknown variables are intricate and not easily comprehensible.
4. The continuous friction process generates high-temperature heat, so the variation in the thermal and physical properties of the model material with temperature should be more deeply considered to enhance the reliability of experimental results.
5. In the Materials section (2.2), when describing the reasons for selecting ZrO2 and Sc2W3O12 ceramics as the subjects of numerical study, change the '÷' in '1100÷1300℃' to '-'.
Author Response
We appreciate very much the reviewers’ comments to our paper and did our best to address them all and provide replies.
R1:
The article demonstrates the feasibility of controlling the wear and friction performance of ceramic composite materials using a negative thermal expansion coefficient approach through comparing the frictional performance of ceramic composite materials with opposite coefficients of thermal expansion.
My suggestions are as follows:
- Academic papers should maintain objectivity and academic tone, avoiding the use of terms like "I" or "we."
A: Corrected
- There are too many paragraphs in the introduction section of the paper, and it should predominantly use declarative sentences, avoiding interrogative ones.
A: Corrected
- During the quantitative description of ceramic material friction behavior based on established principles of mechanics and thermodynamics, the descriptions of unknown variables are intricate and not easily comprehensible.
A: Explanations provided
- The continuous friction process generates high-temperature heat, so the variation in the thermal and physical properties of the model material with temperature should be more deeply considered to enhance the reliability of experimental results.
A: This study was purely numerical based on interaction between opposite asperities with consideration of the thermal expansion effects.
- In the Materials section (2.2), when describing the reasons for selecting ZrO2 and Sc2W3O12 ceramics as the subjects of numerical study, change the '÷' in '1100÷1300℃' to '-'.
A: Corrected
Reviewer 2 Report
The author has done a lot of work to study the wear and frictional properties of ceramic composites by using components with negative thermal expansion. This work has a certain significance, but the work content needs to be further improved.
1. English is poor, this work requires careful text editing to address grammar issues.
2. The formulas on lines 115 and 118 on page 3 should be numbered as the following formula. If you derived the formula yourself, please specify. If not, please add references. Moreover, the variables in the formula need to be defined, for example, line 142.
3. Variables that do not appear in other formulas also need to be defined. For example, formula (3), (5) etc..
4. The title of chapter 2 is not reasonable, please modify. 2.1 and 2.2 cannot support the title of Chapter 2.
5. The conclusions need to be improved, the conclusions need to support the title, and then those conclusions are drawn in the course of the relevant research.
English needs improvement
Author Response
We appreciate very much the reviewers’ comments to our paper and did our best to address them all and provide replies.
Reviewer 2
The author has done a lot of work to study the wear and frictional properties of ceramic composites by using components with negative thermal expansion. This work has a certain significance, but the work content needs to be further improved.
- English is poor, this work requires careful text editing to address grammar issues.
A: Corrected
- The formulas on lines 115 and 118 on page 3 should be numbered as the following formula. If you derived the formula yourself, please specify. If not, please add references. Moreover, the variables in the formula need to be defined, for example, line 142.
A: Corrected
- Variables that do not appear in other formulas also need to be defined. For example, formula (3), (5) etc.
A: Corrected
- The title of chapter 2 is not reasonable, please modify. 2.1 and 2.2 cannot support the title of Chapter 2.
A: Corrected
- The conclusions need to beimproved, the conclusions need to support the title, and then those conclusions are drawn in the course of the relevant research.
A: Corrected
Reviewer 3 Report
When I look at the title, I truly think this is an interesting paper. However, after reading it, I felt let down – the mathematics are a lot, but the results are not convincing. Experimental validation is definitely needed. Of course, many writing issues. So, I suggest a major revision.
1. Check English writing and do proofreading – even the title has grammar mistakes: “towards control” should be “towards controlling”, “with ensuing loss of NTE” should not have “wtih”, etc. The language is all confusing.
2. Important claims and information ALL need literature support. E.g., it is hard to believe the authors only cite one literature for the first and second paragraph in Introduction.
3. “the source α-ZrW208 transformed into β-ZrW208”: Why so?
4. “wearless dry sliding regime within some contact pressure range”: Who gave this name? And any hypothesis for why it can happen?
5. The introduction is written really bad: The authors gave all the questions at last—the correct logic should be: Review some literatures, find their missing or wrong points, and point out how you will figure it out (your paper). The introduction should be re-written.
6. When it comes to section 2.1 asperity model, etc., the authors should be aware of more recent papers and studies. Please see, learn, and discuss (do not limit to) the following ones:
[1] Multiscale analysis of friction behavior at fretting interfaces. Z Zhang, S Pan, N Yin, B Shen, J Song. Friction 9, 119-131
[2] Hu, J., Song, H., Sandfeld, S., Liu, X. and Wei, Y., 2021. Multiscale study of the dynamic friction coefficient due to asperity plowing. Friction, 9, pp.822-839.
7. Clearly, equations all need citations.
8. The authors introduce a lot for ZrW2O8, but suddenly chose Sc2W3O12??? – Why??? The logic does not flow through.
9. Based on all the results, the authors said they simulate the surface with wear – then, please show the structure and configuration for the surfaces after wear. The current results are all numbers, which are not convincing. Frankly, I do not see whether they are using analytical methods more or computational/simulation methods more…
10. Based on the current writing, I think the authors totally do not do any experiments – based on their simulation and modeling, I think at least one experiment for the optimal case should be added. E.g., the real comparison with the COF curve. Otherwise, I do not think it qualifies for a paper.
11. When looking at how they set up the models, I wonder if the situation can be achieved in reality? I suggest adding some surface tomography scanning (e.g., by confocal or VSI, very easy) for these materials, so to confirm that your modeling (and mathematics) is right.
12. After reading all the contents, I feel confused about one thing: CTE issue is more severe in metals and alloys, as they are magnitudes higher than that in ceramics. So, I suggest the authors adding a paragraph to discuss exactly how their knowledge can be transferred for real applications (e.g., in urgently needed alloy systems). I think the papers from Dr. Xiaochun Li’s group can be helpful.
Many writing issues. So, I suggest a major revision. Check English writing and do proofreading – even the title has grammar mistakes
Author Response
We appreciate very much the reviewers’ comments to our paper and did our best to address them all and provide replies.
Reviewer 3:
When I look at the title, I truly think this is an interesting paper. However, after reading it, I felt let down – the mathematics are a lot, but the results are not convincing. Experimental validation is definitely needed. Of course, many writing issues. So, I suggest a major revision.
- Check English writing and do proofreading – even the title has grammar mistakes: “towards control” should be “towards controlling”, “with ensuing loss of NTE” should not have “wtih”, etc. The language is all confusing.
A: Corrected
- Important claims and information ALL need literature support. E.g., it is hard to believe the authors only cite one literature for the first and second paragraph in Introduction.
A: Corrected
- “the source α-ZrW208 transformed into β-ZrW208”: Why so?
A: α-ZrW208 may be transformed into high temperature β-ZrW208 in heating. Friction stir processing means frictional heating.
- “wearless dry sliding regime within some contact pressure range”: Who gave this name? And any hypothesis for why it can happen?
A: When modeling the behavior of NTE materials in sliding it was shown that the asperities shrink when being heated by friction and therefore are not subjected to plastic deformation or fracture, i.e. wear. This regime is therefore was called “wearless” what in no case means that there is no real wear at all, for example, by adhesion. The term has been replaced to read “wear-free|”
- The introduction is written really bad: The authors gave all the questions at last—the correct logic should be: Review some literatures, find their missing or wrong points, and point out how you will figure it out (your paper). The introduction should be re-written.
A: Thank you. This section has been totally rewritten. The main point is that we could not find references that analyze the effect of CTE on friction and wear not to say about the NTE materials. The major part of works is dedicated to studying thermal expansion of material when filled with the NTE components.
- When it comes to section 2.1 asperity model, etc., the authors should be aware of more recent papers and studies. Please see, learn, and discuss (do not limit to) the following ones:
[1] Multiscale analysis of friction behavior at fretting interfaces. Z Zhang, S Pan, N Yin, B Shen, J Song. Friction 9, 119-131
[2] Hu, J., Song, H., Sandfeld, S., Liu, X. and Wei, Y., 2021. Multiscale study of the dynamic friction coefficient due to asperity plowing. Friction, 9, pp.822-839.
A: Thank you. These references were very helpful.
- Clearly, equations all need citations.
A: Corresponding citations have been provided
- The authors introduce a lot for ZrW2O8, but suddenly chose Sc2W3O12??? – Why??? The logic does not flow through.
A: All these materials are NTE ones and we study only the effect of NTE on formation of worn surfaces. In connection with this, the most important issue was to look for an NTE material with maximum thermal contraction effect and without transformations. The majority of references, however, are dedicated to ZrW2O8, and we can not ignore them
- Based on all the results, the authors said they simulate the surface with wear – then, please show the structure and configuration for the surfaces after wear. The current results are all numbers, which are not convincing. Frankly, I do not see whether they are using analytical methods more or computational/simulation methods more.
A: This is purely numerical study since it was not possible to carry out experimental work at this stage of the work. All the surfaces were simulated by a set of asperities represented by roughness. The roughness changed after sliding as shown in this paper and according to CTE.
- Based on the current writing, I think the authors totally do not do any experiments – based on their simulation and modeling, I think at least one experiment for the optimal case should be added. E.g., the real comparison with the COF curve. Otherwise, I do not think it qualifies for a paper.
A: Our intention was to simulate the behavior of NTE materials at the microscale level. It was hardly possible to do that experimentally, even if using an atomic force microscope. There is no a tribometer now that could be used to study the asperity physical behavior under frictional heating and that microscale expansion/contraction. The attempts are now done to obtain the NTE material in the form of a coating. In such a case some experimenting would be feasible. Earlier we admixed the NTE with aluminum alloy using friction stir processing and studied tribological characteristics of such a material, which, as expected were determined by behavior of metallic matrix.
- When looking at how they set up the models, I wonder if the situation can be achieved in reality? I suggest adding some surface tomography scanning (e.g., by confocal or VSI, very easy) for these materials, so to confirm that your modeling (and mathematics) is right.
A: This work was focused on studying fundamental physical behavior of NTE materials, which are very brittle and can not be used now for fabricating any real components. The attempts are now done to obtain the NTE material in the form of a coating. In such a case some experimenting would be feasible. Earlier we admixed the NTE with aluminum alloy using friction stir processing and studied tribological characteristics of such a material, which, as expected were determined by behavior of metallic matrix.
- After reading all the contents, I feel confused about one thing: CTE issue is more severe in metals and alloys, as they are magnitudes higher than that in ceramics. So, I suggest the authors adding a paragraph to discuss exactly how their knowledge can be transferred for real applications (e.g., in urgently needed alloy systems). I think the papers from Dr. Xiaochun Li’s group can be helpful.
A: The asperities on the surface of metallic materials are easily deformed in sliding contact so that nanocrystalline subsurface layer is usually generated that determines the further behavior of the materials in sliding. Therefore, thermal expansion/contraction is of negligible meaning in comparison with asperity height reduction by deformation.
Round 2
Reviewer 2 Report
The revised version is acceptable.
Reviewer 3 Report
No more comments
