投稿历程（7.3-8.3）（Langmuir一审结束）

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投稿历程（7.3-8.3）（Langmuir一审结束🤔）

刚好一个月的一审，结果还不算太糟糕，有望中刊！

目前在回复审稿人意见，后续见刊后，会将论文所涉及到的代码以及后处理的脚本全部上传到git仓库中，也会单独写一份详细的模仿文档，提供初学者建模、动力学、后处理一个完整的练习过程。

请持续关注~

Langmuir一审

编辑👴：require significant consideration and revision of the manuscript

The reviews for your manuscript are enclosed with this letter. Please consider the reviewers’ comments. They have raised points that require significant consideration and revision of the manuscript before it is suitable for publication. However, with adequate response and revision, the manuscript may be acceptable for publication in Langmuir. We would like to receive your revision as soon as possible, by 24-Aug-2020 at the latest.

Reviewer1🗣：Major revisions needed as noted.

Comments:

In this work, the authors performed coarse-grained molecular dynamics (MD) simulations to study the interfacial friction heating mechanism of amorphous polyethene (PE) in both the Single Sliding Friction (SSF) and Reciprocating Sliding Friction (RSF) modes. They found that the RSF process led to a better heat generation performance that SSF even though there was no apparent plastic deformation. This is different from the traditional view that the plastic deformation is the primary source of heat generation. They attributed the interfacial friction heating enhancement in RSF to the concentrated high-frequency chain motion related to molecular rearrangement.

I have the following concerns over the present study:

1. For PE, the yield stress is about 20-30 MPa, which is much high than the loading pressure, which is about 0.2, 0.4 and 0.8 MPa. The authors need to explain what they mean plastic deformation here.

2. For real PE, the melting temperature is 388-408 K and the glass transition temperature is 195 K. But the predicted glass transition temperature here is 300 K. Do the authors really model PE?

3. The authors discussed chain diffusion and entanglements of PE. Can the authors specify what kinds of PE they simulated, for example chain length, degree of entanglement and gyration radius?

4. The simulation cell size is too small. The authors need to assess/examine the size effects.

5. In calculating the temperature (Eq. (3)-(8)), the authors used the number of atoms. Do they mean the number of beads? How is the calculated temperature converted to the real physical temperature?

6. The sliding speed (50 m/s) is too fast and unrealistic, compared to real experiments. The authors need to discuss the effect of the unrealistic large speed.

7. Previous studies (for example, Dai, et al. ACS Appl. Mater Interfaces 8, 8765 (2016)) have shown that chemical bond breaking and remaking can change the friction and wear mechanisms. In the current consideration, bond breaking was not allowed. Therefore, there were no chemical breaking and remaking processes. How does this assumption affect the conclusions of the present work?

8. Due to the above issues, there are some uncertainties over the simulation results and conclusions. There is strong need for the authors to provide certain validations (either experimental and theoretical works). However, the authors did not present any comparisons and validation for their results. This is a significant concern.

9. A surface temperature of a sliding couple over a wide range of load and sliding velocity was studied before (see Ashby et al. Tribology Tran. 34(4), 577 (1991)). Some discussions and comparisons with this work might be insightful.

Additional Questions:

Significance: High (suitable for Langmuir)

Originality: Moderate (not suitable for Langmuir)

Broad Interest: High (suitable for Langmuir)

Technical Quality: Moderate (not suitable for Langmuir)

Is the manuscript appropriate for Langmuir?: In Part

Are the conclusions adequately supported by the data?: No

Are the references appropriate and correct?: In Part

Is the English adequate?: Yes

Is the quality of the figures sufficient?: Yes

Are the data statistically significant with appropriate controls included?: In Part

Reviewer2🗣：Major revisions needed as noted.

Comments:

The manuscript titled “Progressive Molecular Rearrangement and Heat Generation of Amorphous Polyethene Under Sliding Friction: Insight from the United-Atom Molecular Dynamics Simulations” mainly studied the interfacial friction heating mechanisms of PE under the Single Sliding Friction (SSF) and Reciprocating Sliding Friction (RSF) by molecular dynamics (MD) simulations, respectively. The results showed that the RSF process exhibited a better heat generation performance than SSF process, which was tightly related to the molecular motion. Generally, the work is interesting and well written, contains interesting results for the theoretical and experimental science community. However, some issues listed below should be addressed before consideration of publication.

1. There are some grammatical errors in the manuscript. For instance, in Introduction section, Paragraph 2, line 8, “what factor mainly influence” should be rewritten as “what factor mainly influences”?

2. Some variables are not in italics, like the number of atoms k and n. “Ebond” in the left side of Eq. 1 should be “Etotal”. The center-of-mass kinetic energy below Eq. 3 should be (Ek)cm, not (Ek)total. The authors should proof-read the manuscript to minimize grammatical errors.

3. The authors give the information of the model and simulation process, however, some details like the equilibrium process and model generation should be provided for others to follow their work. In addition, the author did not give the density of the amorphous PE after equilibrium. Is it comparable with that in experiment?

4. The authors used “PE block” as “PE bulk” in the manuscript. Maybe the authors should unify them for clarity.

5. There are many fitting curves in the manuscript. However, the color of the fitting curves should better be same as that of the corresponding simulation data. For example, in Figure 3B, the color of the fitting curve under a pressure of 0.8 MPa is same as that the simulation data under a pressure of 0.2 MPa. This might make the readers confused.

6. In Heat Generation section, line 16, what’s the meaning of “friction temp”?

7. The velocity of the simulations is extremely high. Actually, the loading rate of MD simulation in other researches is also extremely high indeed. I am just curious about it.

8. In Figure 11, the authors analyzed the distribution of bond length in different times. However, the change of the bond length is not obvious in Figure 11A.

Additional Questions:

Significance: Moderate (not suitable for Langmuir)

Originality: High (suitable for Langmuir)

Broad Interest: High (suitable for Langmuir)

Technical Quality: High (suitable for Langmuir)

Is the manuscript appropriate for Langmuir?: Yes

Are the conclusions adequately supported by the data?: Yes

Are the references appropriate and correct?: Yes

Is the English adequate?: In Part

Is the quality of the figures sufficient?: Yes

Are the data statistically significant with appropriate controls included?: Yes

感觉审稿人1比较偏实验，要求也比较高，指出论文还是缺发实验论证，审稿人2更多的是提出了一些格式上的问题。

如果各位看到审稿人意见，有啥好的建议，例如如何回复模拟参数和实验相差较大、尺度效应如何考虑等模拟的共性问题，也可以给我留言，万分感谢！

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