Characterization of Multi-Layer Rolling Contact Fatigue Defects in Railway Rails Using Sweeping Eddy Current Pulse Thermal-Tomography

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1.             Please double-check equation (1).

2.             In Table 3, you provide thermal pictures of the five coils at various excitation frequencies for the same flaw, defect 1. Please explain the influence of frequencies while utilizing a specific coil. I recommend correlating the experimental results with those gained through the simulation procedure.

3.             In Table 4, you show the thermal image of a trench-plane coil with six defects at the same excitation frequency. Please explain how to detect the defect at a specific frequency and what happens if another defect appears in practice.

4.             In the section Feature Extraction for Thermal Response, you must specify the dimensions (in pixels) of the studied domain. Is the resolution of Figure 5 500 by 600?

5.             The Skewness and TSR values reported in Table 5 are too similar to determine the defect that appears. You must explain how you will find the defect using these values.

6.             Your paper simply shows that Thermal Images comparison and quantitative analysis provide information on defects, but it does not show how to detect the presence of one of the six defects mentioned. This requires the development of an algorithm.

7.             This scientific originality should be explained, especially in the CONCLUSIONS section, which has to be improved.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper proposes a sweeping eddy current pulse thermal-tomography system for railway inspection.

The work is well organized, but some points must be better explained.

1)      What is limit of detection ion terms of penetration and sensitivity?

2)      The influence of the shape of the coil and the frequency must be better explained.

3)      The state of the art of ECPTermography must be better explored.

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Reviewer 3 Report

Comments and Suggestions for Authors

This paper is professionally written and can have its merits. 

It can be also interesting, to its specific 'audience'. 

The written style is relatively good - it is, nonetheless, clearly non-native, and a revision, with the help of a native speaker, would be extremely beneficial to the article, to make it completely up to academic standards. In particular, repetitions and redundancies, eminently at the lexical level, should be corrected and avoided. 

The paper lacks a proper literature review, which should be included, as a separate section, possibily after the Introduction and before the part with methodological contents. Works should not be 'scattered' here and there, over the article, but should have their dedicated section. More studies need to be added, also at the general level, to make the article more 'user-friendly' even to a 'non-specialized readership'. 

The methodology looks ok and very clear. However, both the methods and the figures must be double-checked by at least another Reviewer (more than one would be better) with a more direct expertise than me in the topic of the paper, for a final validation. This is something that is absolutely necessary, to clear the paper for possible publication. 

The experiment and the study in general are very well-described and easy to follow. However, also the tables need an additional validation by at least another Reviewer (more than one would be better) with direct expertise in the topic of the paper. 

The Discussion, rather than being a super-short sub-section, should be expanded considerably. Being the 'meat' of the paper, should contain a lot more analysis and comments, and even some personal observations by the Authors on possibly problematic and/or limiting aspects of their methodology and experiment. That would make the paper more complete and would definitely strengthen it. 

The Conclusion needs to be expanded considerably, by adding a summary of the research goals of the paper and the strategies implemented by the Authors to achieve them, and by stressing further on the significance of the paper itself in its field. 

I indicate 'major revision' just because I would like to re-read the paper after revision. However, the article is good and, after some enhancements and improvements will be produced and applied, I do not see any counterindication to consider it for publication. 

Thank you very much.  

Comments on the Quality of English Language

As mentioned, the written style is relatively good - it is, nonetheless, clearly non-native, and a revision, with the help of a native speaker, would be extremely beneficial to the article, to make it completely up to academic standards. In particular, repetitions and redundancies, eminently at the lexical level, should be corrected and avoided. 

Author Response

Please see the attachment.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

Changes made by authors completely fulfill the suggestions, so I believe the article can be accepted with minimal revisions.

Reviewer 3 Report

Comments and Suggestions for Authors

The paper was improved significantly and can be considered, now, for publication. 

Comments on the Quality of English Language

The English language is ok, but a further revision, before the final publication, especially at the level of written style, could help a lot. 

Round 3

Reviewer 1 Report

Comments and Suggestions for Authors I don't have comments for the author to revise