A Comprehensive Review of Fatigue Strength in Pure Copper Metals (DHP, OF, ETP)

Round 1

Reviewer 1 Report

In the manuscript titled “A comprehensive review of fatigue strength in pure copper metals (DHP, OF, ETP),” the authors examined the most relevant aspects of mechanical fatigue in Cu-DHP, ETP, OFE and OF. They analyzed the impact of many factors on fatigue strength, including the frequency, temperature, chemical environment, grain size, metallurgical condition, and load type. However, the reviewer believes that the current version is not suitable for publication in this journal. The following suggestions are available for reference:

1.     The current manuscript needs to be polished by a native English speaker or a professional language editing service.

2.     In the introduction section, the authors need to provide detailed information on the current progress in the fatigue of copper alloys, and emphasize their relevance in industrial applications.

3.     What is the methodology employed in this review article? Additional descriptions of the search criteria, selection process, and possibly the data analysis techniques used are needed to fully understand the approach taken in compiling this review.

4.     Are there limitations in the available data, and how have the authors addressed them?

5.     Organize the discussion on factors affecting fatigue strength into subheadings to improve readability.

6.     Please provide more information in the paper about the development and implications of Stress-Life (S-N) curves and Strain-Life (ε-N) curves. Explain the significance of these curves in practical applications. It would help non-expert readers understand them better.

7.     The authors primarily illustrate the mathematical relationship between different factors and fatigue strength through figures, with little mention of the impact mechanisms by which these factors affect fatigue strength. Please summarize and add relevant content from the literature.

8.     Figure 10 and figure 12 are a bit blurry. Please consider replacing them with clearer ones.

9.     The significance of this paper is not sufficiently expounded. The authors need to highlight the innovative contributions of this paper.

The current manuscript needs to be polished by a native English speaker or a professional language editing service.

Author Response

Dear Reviewer
Thank you very much for your comments to review our work. In the attached document we have answered the questions you have raised to improve the article.
Best regards
Carlos Berlanga 

Author Response File: Author Response.pdf

Reviewer 2 Report

This article presents a summary of some literature data about the low-cycle and high-cycle fatigue strength of pure copper. The topic is interesting, but the article has ground for improvements.

First of all, the article structure is not very effective. Collecting all results in only one long section (Section 2), separated in many subsections, does not help the reader grasp the various topics addressed (e.g. loading, environment, temperature, ect). Please use sections more effectively so that the different topics are best emphasised.

In several parts (see for example L110-118, L128-135, L154-158, L210-217) the article is merely a summary of conclusions from other articles, without any in-depth discussion. The reader is forced to go back to the cited references to have the necessary details, so decreasing the value of the present paper. The absence of an in-depth discussion does not comply very much with an article meant to be a “comprehensive review”.

It is often not clear whether the S-N curves reported in the articles are estimated by the present authors, or they are taken from literature articles. Moreover, the information on the probability of survival associated to a S-N curve is often missing, although it represents an important information. For example, in Figure 1 it is not clear whether the curves refer to a Ps=50% (regression lines) or higher. On the other hand, please note that Figure 1 is redundant since its data is also reported in Figure 2.

In most figures (e.g. Figure 6, 7, 8, 9, etc), the regression lines are extrapolated outside the regions where experimental data is not present. This approach is not recommended, since in regions where tests were not performed, the uncertainty about S-N is very large.

P4 it seems that the article makes some confusion between the effect of frequency (in high-cycle fatigue) and the so-called “giga-cycle fatigue”, for which testing frequencies are of the order of kHz. Moreover, please note that if giga-cycle fatigue region is also considered, the S-N curve is not simply a straight line in log-log plot, but has a different shape.

L195 and Eq (1) etc: it is not clear how the coefficients 0.75 and 0.68 have been established. Where are they taken from?

L245: the sentence “a new different relationship” is not appropriate if it refers to the well-known Manson-Coffin equation.

In most figures (e.g. Figure 3, 4, 5, etc) the y-axis extends far beyond the maximum stress amplitude, creating an unnecessary white region in the graph.

Two topics that could also be included in the article are: i) the cyclic behaviour of copper alloys in low-cycle fatigue regime, and ii) some examples of failure analysis (fracture surface) for different environmental conditions.

Last, but not least, the article relies heavily on colours, which makes the interpretation of figures impossible in a black/white hardcopy, as that in my hands.

Author Response

Dear Reviewer
Thank you very much for your comments to review our work. In the attached document we have answered the questions you have raised to improve the article.
Best regards
Carlos Berlanga 

Author Response File: Author Response.pdf

Reviewer 3 Report

Authors present a review of articles concerning influence of different factors on fatigue strength of three copper metals. Those investigated factors include the loading/stress type, temperature, chemical environment (atmosphere), grain size, metallurgical conditions. This review is presented in both the chronological and logical manner, with conclusions drawn on influence of each of the considered factors.

The valuable contribution is the presented nomenclature of abbreviations and variables used in the text.

The presentation is clear, with relatively high level of English language and grammar.

- Reference [11] is practically used as the skeleton of this review, being cited 12 times, with third of the figures used from that particular reference. One gets the impression that all the other cited articles are used just to be compared to that reference. That slightly reduces the generality of the review, and makes the article as being a discussion on this reference’s results.

 There are a few points on the style of presentation.

- There is no need to put the number of the equation/expression, just before it is written. See lines 240, 253.

- When citing an article in the text it suffices to give the last name of the first author followed by the phrase “et al.”; it is not usual to put the full first name(s). See lines 250 to 253.

- The “References” section is not written according to the Journal’s template.

The scanned pages of the manuscript with marked errors and suggested corrections are enclosed.

Comments for author File: Comments.PDF

Quality of English language is quite good.

Do not start a sentence with "Also". The proper phrase is "In addition".

Author Response

Dear Reviewer
Thank you very much for your comments to review our work. In the attached document we have answered the questions you have raised to improve the article.
Best regards
Carlos Berlanga 

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

it could be accepted as-received.

it could be accepted as-received.

Reviewer 2 Report

The article is fine.