Yet Another Approach to Fatigue Crack Growth Simulation

Round 1

Reviewer 1 Report

(1) The literature review of the manuscript needs to be significantly improved by adding more research studies and publications in this regard.

(2) A paragraph is suggested to add in the introduction to more clearly describe what questions to be addressed, what methods to be used and what objectives of the study

(3)The authors are required to highlight results achieved against set objectives in the conclusion.

 

Author Response

Dear reviewer,

thank you for your comments and suggestions. In the attached file is the revised version of the manuscript with line numbers. Below are the responses to the points you raised:

1. The original introduction was indeed to short and not specific. The central was enlarged in order to position our research in the field of fatigue and fracture. (please see lines 30-53)
2. Additionally a paragraph was added to more clearly state the goals of the research. (please see lines 60-64)
3. At the end of the paper, highlights are given as a bullet list. (please see lines 343-351)

Sincerely,

Peter Zobec

Author Response File: Author Response.pdf

Reviewer 2 Report

Authors have attempted to throw new light and direction on certain grey area of age old structural materials fatigue  modeling. Overall, authors have succeeded in presenting  their thoughts well considering cohesive contact and FEM for crack nucleation and growth modeling. However, following constructive comments are made for  improvement of quality of the paper

1. Line 51 and 249  what the signs ??  meaning and should be removed to avoid confusion
2. Abstract need to be reframed as this barely reflect the research content , especially 2nd sentence to line 6th should be part of  introduction, while more research approach, objective and finding should be  included.
3. Authors should clearly spelt out the major assumptions considered for the proposed fatigue analysis framework and methodology.
4. Similarly, due to lack of validation of their results and findings, expected limitations need to be listed.
5. Authors have ignored completely the material's microstructural significance in their fatigue modeling and framework. Both nucleation site and propagation path of fatigue crack are largely controlled by the microstructural features like grain boundary, porosity, inclusions and second phase and alike. 

Author Response

Dear reviewer,

thank you for your time and comments. In the attached document you can find the revised version of the manuscript. Below I will try to discuss the raised concerns:

1. "??" signs were corrected. They were broken document links.
2. Abstract was almost completely rewritten. Please see lines 1-7. Thank you for your comment, I agree that the original abstract was to vauge.
3. The assumptions and limitations of the proposed framework are now condensed in a separate subsection. Please see lines from 299 onward.
4. I would like to believe that your fourth comment is addressed as in noted in the point 3.
5. You are absolutely correct. The "viewing glass" so to speak, on the subject is on the macro scale. Aldough we touch, or better, mention the microstructure in the first paragraph of the introduction, please see lines 10-17, and again in line 19, there is no real focus on the microstructural effect. The scope of the work is an attempt to expand now a well known fatigue approach to the scope of fracture. We believe that microstructural analysis and modeling  sets a suitable framework to describe or at least explain both fatigue and fracture. The setback, why we also did not focus on it is its lack of general application, what we believe that a practicing engineer is seeking. What we mean is that it describes a specific case  and its reach is therefore limited. Also I must be honest to say that microstructure effect is not the research area of our laboratory.

Sincerely,

Peter Zobec

Author Response File: Author Response.pdf

Reviewer 3 Report

The reviewer believes that the paper is well written and concise. The contents are interesting in materials research field and the results potentially useful. hence, the paper is accepted with minor revisions and the following comments are suggested:

1) The state of the art in the Introduction should be improved and more references should be added and cited in the text of the manuscript.

2) There is a typo at the end of Introduction section: "the results and discussion cover Sections 3 and ??" (lines 50-51). Please, check.

3) Please, check if all the equations parameters have been defined in the text.

4) legend in Figure 4 should be increased and quality improved

5) please, add more information about FEM model (mesh sensitivity, number of elements etc.).

6) what does the contour plot in Figure 4 represent? Please, provide the legend.

Author Response

Dear reviewer.

First I would like to thank you for your time and consideration. The revised manuscript is attached to this reply in order to support our discussion. Below are the responses to the raised concerns:

1. State of the art has now been greatly extended to position our research in the field of science of fatigue and fracture. The introduction now gradually builds to the focused topic of our research. Please see lines 30 - 53 that were added in the introduction.
2. The typo has been corrected.
3. The text has been rechecked. Also if the manuscript is accepted it goes through our internal check process.
4. Figure 4 has been supplemented with text and signs, hopefully to clarify the display.
5. Additional information about the FEM mesh has been given in lines 286 to 288.
6. Please see answer number 4. The graph displays a decomposition of the strain-life curve. The relation appears to be exponential if the strain is viewed as a linear combination of elastic and plastic strain. The log-log axis thus linearize  relationship.

Sincerely,

Peter Zobec

Author Response File: Author Response.pdf

Reviewer 4 Report

1 What does the question mark in line 51 mean?

2 The title of the section 2 is not suitable, not only for the introduction of materials, but also for the introduction of some theoretical foundations.

3 Figure 12 does not indicate the physical quantity, stress, strain or other?

4 How to ensure the reliability of simulation results without experimental verification?

5 The main problem of the paper is the lack of modeling process introduction, the result part of the content is too little.

Author Response

Dear reviewer.

First I would like to thank you, for your time and consideration. In the attached document is the revised manuscript with highlighted changes. Below are the answers to the raised concerns:

1. The "?" was a broken document link. It has now been fixed.
2. The title of the second paragraph was a typo. Please see line 81, for the corrected text.
3. The caption of figure 12 now states that the field variable displayed is in fact stress.
4. This is a difficult question to answer. Without some actual laboratory results  a comparison is almost impossible. We could try to find an appropriate research paper, that presents experimental data for comparison and validation, but the nature of the framework dictates a special routine of material laboratory data manipulation.  I believe that the correct path is to actually conduct the experiment and compare the results. This is the next step in the research phase of this framework and will be conducted in the near future.
5.  Yes, I agree. The results displayed are quite short. The focus of this paper was on the algorithm framework. In the methodology section we started by explaining the motivation for the algorithm based on the material observations. Topics are than added on top in order to explain the modeling tools and techniques. The idea itself is simple but the explanation of the algorithm has proven to be a challenge.  Steps are being made in the direction of code rewriting and editing for the purpose of upload to Github.

Sincerely,

Peter Zobec

Author Response File: Author Response.pdf

Round 2

Reviewer 4 Report

The author answers the questions raised last time and revises them accordingly.