New Die-Compaction Equations for Powders as a Result of Known Equations Correction: Part 1–Review and Analysis of Various Die-Compaction Equations

Round 1

Reviewer 1 Report (New Reviewer)

Dear authors,

I recommend to arrange the paper in terms of language. 

The presentation of the paper can be improved. 

The comments and explanations related to tables and figures must be added and extended. 

The comparisons must be given with the earlier works. 

Best regards

The paper needs a language editing. 

Author Response

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Reviewer 2 Report (New Reviewer)

1) The article contains many graphs with approximation dependencies, but does not say how they were constructed. It is clear that the curve was fitted to experimental data, but since the entire article is based on such examples, I would like to know this in more detail. Specifying a program is not enough.

2) On page 3, the authors write that the first person to propose the powder compaction equation was Walker, then a similar equation was proposed by M. Balshin and H. Lipson; there is no way to look at these equations for yourself and compare them within the article, since they were not given .

3) The work compares the coefficients of determination to assess the adequacy, but does not indicate what boundaries of its values should be so that we can conclude that the equation adequately describes the process. It's not obvious.

4) The logic of the penultimate paragraph before the conclusion is not very clear, but perhaps it’s just me)): “... will be made in the next article, devoted to obtaining new equations for PCP by correcting and generalizing various equations derived by M. Balshin in the framework of the “discrete” theory for describing PCP,” why did they ultimately decide to derive new equations specifically from Balshin’s equations within the framework of this theory in order to describe the powder pressing process in the next article?

5) Basically, the adequacy of the equations and applicability with respect to density are assessed; it is not indicated what other limitations in application each of the equations has, which in my opinion is important if we further derive other equations.

Author Response

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Reviewer 3 Report (New Reviewer)

This manuscript discusses the different compaction equations for the powder compaction process of rigid dies and evaluates their advantages and disadvantages. The determination of the constants in the equation is analyzed, and an improved version of the equation is presented. The logic of the manuscript is very strict, and the process of discussion is clear. I have only two suggestions for the author to address:

Comment 1: For Table 8 and Table 13, the format of the table needs to be modified.

Comment 2: The conclusion part should be more concise.

Author Response

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Reviewer 4 Report (New Reviewer)

Paper No.: powders-2701272

Title:  New die-compaction equations for powders as a result of known equations’ correction. Part 1. Review and analysis of various die-compaction equations

The subject and content of the article is interesting and deserve to be published. However, there are some raised issues that should be treated.

1-      The author has ended the literature part with an abstract-like part. Please end the literature with a clear aim of the work.

2-      In lines 26-31 the author has introduced for equations 2 and 3 without mentions these equations. Later on, in lines 104-120, he has discussed again these equations, which represent a duplication in the presentation which waste the time of the reader. Please treat it.

3-      No need for presenting the relative density against the applied pressure (in Table 1) as long as it is presenting in the graphs in Fig. 1, especially it is taken from literature. The same is applicable for Table 5 and Table 8.

4-      In Fig. 6 “(a) Fe, (b) Fe (coarse), (c) Fe (fine) as well as copper powders: (d) Cu, (e) Cu (coarse), (f) Cu (fine)”. What is the powder grain size limits for coarse and fine and the not classified powders?

5-      In Fig 7 and Fig 8, the axis of the graphs has been changed. Please keep the axis consistent in the whole work for easier comparison.

6-      Please describe in third person instead of mentioning:  I, or we. Example in line 637 “To perform the approximation, we transformed equation”.

7-      The work should end with a discussion judging the different used equations to end with the best recommended form/ or forms which describe well the powder compaction with extrapolated results up to relative density of 1.0.

8-      Some conclusions are just summary of the literature and not based on the attained results of this work: example Conclusions. No. 2, 5 and 6. Please conclude based on the achieved results.

 Minor editing of English language required

Author Response

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Round 2

Reviewer 4 Report (New Reviewer)

The authors have acceptably treated the previous comment.

This manuscript is a resubmission of an earlier submission. The following is a list of the peer review reports and author responses from that submission.

Round 1

Reviewer 1 Report

The manuscript presented here provides an overview of different approaches used to predict the overall, curve that relates an averaged density of the pressing sample (called also the green body) versus compaction pressure. Some of the approaches discussed in a very detailed way are very old and obsoleted by more advanced approaches. To the Reviewer’s opinion this manuscript does not contain any scientific novelty and should not be considered for publications.

The major weaknesses are listed below.

The biggest weakness is that the problem in consideration here concerns a relative density of a sample in an averaged sense. In reality this quantity changes from point to point within the greed body. It can be considered as a constant only for samples with regular and simple geometry and of very small height. Hence, the application of here considered averaged equations is of limited practical applicability as it is not “transportable” to more complex and more realistic contexts.

Indeed, there are more advanced approaches employed in modeling and simulating powder compaction that are computing the distribution of relative density over the sample. In last more than two decades there has been a number of application of phenomenological plasticity constitutive models that were developed and implemented within finite element codes that address the problem of powder compaction through numerical simulations on much more precise way that what is presented here, as they provide the prediction of distribution of relative density over the sample. These approaches were completely ignored within this manuscript. It is rather important to compere what is presented here against these approaches to critically compare pros and cons of the two approaches.  In principle these approaches should be mentioned in the paper introduction that should provide also a literature survey of current state of the art of considered problem. This, in the present manuscript is not the case as the introduction is not containing any references.

Aside of this major weakness the formatting style of the paper needs to be adequately done. As an example, quantities of the equations (like e.g. exponent m in equation (4)) in the text are typed as a normal text, not italic as in the equation. This is not the only place in the text where it is used. The whole equations were somewhere written within the text with normal text typing style instead of the one used for the equations (e.g. lines 178, 187, 203, 203, 249, 285 etc).

Quotation marks used throughout the text are not the same in the style.  

Author Response

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Reviewer 2 Report

This article verbosely reports a collections of empirical formulae reported in the literature and assessed them using some experimental data that were also reported in the literature. Albeit the collection of equations is rather comprehensive, I have the following concerns that lead me not to recommend publishing this paper:

1) the writing is not up to the publishing standard. This is not about grammatical or typographical errors, but more about technical or scientific terms: there are many odd phrases and incomprehensible technical terms. some were highlighted in the enclosed annotated PDF.

2) the manuscript is very prolix and contains a large portion of insignificant contents. it can be drastically shortened to emphasise the most significant equations as many of them are empirical and not scientifically significant.

3) The manuscript could be more logically structured.  Currently, experimental data from ref. [7-9] were introduced to evaluate the first set of equations but other experimental datasets [23], [25], [26], [32], [33] were also later introduced, no critical assessment of these key datasets used to evaluate empirical equations was given.

4) Lack of novelty. There are many book chapters reported similar set of equations to describe the compression behaviour of powders, see "Pharmaceutical Powder Compaction Technology" for example. There is little  novel contribution of this manuscript.

5) The paper title is misleading as no new equation was introduced in this paper. the conclusion is also far too long.

6) Based upon what was discussed in this paper, I don't think you are talking about "Powder Compaction", "compression" could be more appropriate term here. 

I would suggest the authors to condense the contents reported in this paper into an introduction of several pages long, highlighting the limitation of the existing equation and explain the necessity in developing new equations (i assume they are reported in other parts).   

Comments for author File: Comments.pdf

Author Response

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Reviewer 3 Report

Overall, the paper has discussed important findings related to the area of die and compaction especially involving important equations that are rarely reported in open literature. However, the authors are highly advisable to do the following changes:

1. The title of the paper is highly advisable to be modified accordingly for better understanding. The title could be written as simply as Review and analysis of various die-compaction equations. 

2. It could be highly appreciated if the authors could highlight/emphasize in the abstract and introduction the purpose of writing the current paper for example either to review previous die-compaction equations or proposing new die-compaction equations or the authors wish to present/cover both tasks.

3. The paper is highly recommended to be sent for proofreading by experts after the suggested recommendations have been made accordingly.

4. It is highly advisable to include up to date references related to the area of die and compaction to further support the justifications and review details.

Author Response

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