Calibration of the Flow Curve Up to Large Strain Range by Incremental Sheet Forming Coupled with FEM Simulation

Round 1

Reviewer 1 Report

The present work deals with the evaluation of the flow stress curve up to large strain using an inverse approach based on a numerical procedure which adopts a FEM model iteratively tuned using force data from Incremental Sheet Forming tests. In the opinion of this Reviewer the topic is worthy of investigations and the paper contains interesting both numerical and experimental results. But in the present form it is not suitable for the publication and must be improved according to the following of comments.

1. The True Stress-True Strain curves plotted in figure 1 do not match very well with the values of the Young modulus according to different orientations listed in table 1: that authors are requested to double check and, in case, comment such a (quite large) variation.
2. The friction condition in not taken into account in the FE model description: the authors should describe how such an aspect, directly related to the force level has been modelled and tuned.
3. The authors should include more details about any mass scaling technique or any inertia effect in the FE simulation.
4. More details about the need of using the subroutines VUMAT and VUHARD are requested.
5. Looking at Figure 7, the beta factor can assume a positive or negative value; but the reason why the stress should decrease (negative beta factor) in a model describing hardening should be explained by the authors.
6. The proposed approach lacks a final validation. A test in which higher level of strain are reached (for example a bulge test) or a different ISF should have been used for validation purposes.
7. The authors are requested to include comments (for example in the Conclusions) about the robustness and the generality of the proposed methodology.

Author Response

Thank you very much for your comments and suggestions.

We have provided responses to the reviewer’s comments above. Please let us know if you have any additional questions or suggestions, and we will update the manuscript accordingly to ensure that it satisfies the publishing standards of Metals. We appreciate the Editor and Reviewers' work earnestly and hope that the corrections will meet with an approval.

Author Response File: Author Response.pdf

Reviewer 2 Report

Interesting paper. The description is good, can be understand easily. The topic fit to METALS. 

May be extended a little about the use or continuation of the work. The selected method is validated only on a thin plastic aluminium foil. It would be good to validate it on another metallic material, or at least on different thickness.

Apart from the limited validation of the method I recommend the paper to publish. 

 

Author Response

Thank you very much for your review. 

Author Response File: Author Response.pdf

Reviewer 3 Report

This manuscript (metals-1567080-peer-review-v1) experimentally and numerically investigated the stress–strain curve up to a large strain range of Al5052-O sheet material by taking into account the effect of anisotropy which will facilitate the understanding of the metal forming processes. The research background was well elaborated, and the research purpose was explicit and adequately proposed. The experiment and simulation were systematic and complete, whose methodology was clearly and professionally described. The results were convincible, and had a good agreement between the experiment and the simulation. The figures and tables are eloquent and supportive for the explanation of the results, and the conclusions are concise and in close correlation with the results. Besides, the English throughout the manuscript was well expressed.

To sum up, the research has a high level of originality and quality, I have no further suggestions for making any modification of it, and therefore suggest it be accepted by the journal Metals in its current form.

Author Response

Thank you very much for your review. 

Reviewer 4 Report

The manuscript presents a nice work to give a new strategy to get stress-strain curves at large strain beyond necking point during tension. And the whole content is clear and concise. To my point of view, only minor revision is needed as follows.

1. The main advantages of the proposed method over other methods such as inverse calculation coupled with FEM simulation of the tensile test should be given more clearly and in detail;
2. On page 7, what is the purpose to give equation 4? It seems no use;
3. In Fig.6b, the index for Fz-experiment is not consistent;
4. In Fig.10b, the force prediction using the Kim-Tuan equation fitted with the tensile curves is suggested to add for better comparison;
5. In the conclusion part, the main purpose of the work is to give a new strategy  to obtain stress-strain curves at large strain, not  to verify  the feasiability of Kim-Tuan  hardening law.

Author Response

Thank you very much for your comments and suggestions.

We have provided responses to the reviewer’s comments above. Please let us know if you have any additional questions or suggestions, and we will update the manuscript accordingly to ensure that it satisfies the publishing standards of Metals. We appreciate the Editor and Reviewers' work earnestly and hope that the corrections will meet with approval.

Please check the attachment file.

Author Response File: Author Response.pdf

Reviewer 5 Report

The manuscript is clear, relevant for the field and presented in a well-structured manner. The comments are as below:

1. The subject is suitable for the journal and is relevant to current interests.
2. Please check the punctuation on line 217.
3. The dimensions of AL5052-O sheet tensile test specimens should be clarified.
4. Does the VUHARD subroutine apply to describe the stress–strain relation for this experiment?
5. Are there more options for incremental factor β? What are the trends in the results for factors above 0.1?

Comments for author File: Comments.pdf

Author Response

Thank you very much for your comments and suggestions.

We have provided responses to the reviewer’s comments above. Please let us know if you have any additional questions or suggestions, and we will update the manuscript accordingly to ensure that it satisfies the publishing standards of Metals. We appreciate the Editor and Reviewers' work earnestly and hope that the corrections will meet with approval.

Please check the attachment file.

Author Response File: Author Response.pdf