The Deep Drawing of a Flanged Square Hole in Thin Stainless Steel Sheet

Round 1

Reviewer 1 Report

1. English must be improved in the whole manuscript to make readers understand fully.
2. The objective of this study is not clear. What is the shape of a final product?
3. What is the aspect ratio of the square cup desired to fabricate?
4. With the variation of the punch radius, it seems that the fabrication is not successful. What is the conclusion after the present study?
5. If the authors have a final product with certain dimensions, please show them clearly. Otherwise, what is the merit of this study?
6. In the reviewer's opinion, when the aspect ratio of the square cup is moderate or large, the fabrication process needs several progressive forming.

Author Response

Responses :

The authors appreciate reviewers’ valuable comments very much. Modifications have been made to improve the manuscript according to reviewers’ suggestions as summarized below:

• English must be improved in the whole manuscript to make readers understand fully.

Response: We have invited a natively speaker from “President Translation Service Group International (PTSGI, https://www.ptsgi.com/zhtw/certifications/ )” to revise our manuscript. Please refer the revised paper.

 

• The objective of this study is not clear. What is the shape of a final product?

Response: We have revised the Abstract and Conclusion to highlight the objective of our study and please refer the revised paper in pages 1 and 28. The shape of a final product is also provided in Figure 5 and please refer the revised paper in page 9.

 

• What is the aspect ratio of the square cup desired to fabricate?

Response: From the specification shown in Table 3, if the aspect ratio of the square cup is defined as the L/Li, L/t or Li/t, the values of aspect ratio for L/Li, L/t or Li/t analyzed in our study are 2.22, 100, 45, respectively.

Table 3. Parameters related to the dimensions of the flange material. (unit: mm)

	Model1	Model2	Model3
L	20	10	5
Li	9	4.5	2.25
R	5	2.5	1.5
Br	1.6	0.8	0.4
t	0.2	0.1	0.05
	Model1	Model2	Model3
L/Li	2.222222	2.222222	2.222222
L/t	100	100	100
Li/t	45	45	45

 

• With the variation of the punch radius, it seems that the fabrication is not successful. What is the conclusion after the present study?

Response: From the research results in our study, the variation of the punch radius causes some conclusion for the consideration of forming process as following :

1. From Figure 12 it can be seen that the punch load decreases with an increase of Rp, mainly because the sliding between the punch and the material, that occurs during the forming stroke, takes place over a greater distance. This reduces the speed of hole forming and it is clear that a larger value of Rp will reduce the load on the punch. (please refer the revised paper in page 16)
2. Figure 13 shows the relationship between the punch fillet radius and the minimum thickness of the flange. The minimum thickness increases slightly with an increase of the punch fillet radius. The average values obtained for the minimum thickness for three models were 0.148, 0.0775, 0.0374 mm. The reason for this is that while the sheet is being stretched over the larger punch fillet radius, the contact area between the plate and the corner of the punch is smaller. This results in a reduction of material flow during the downward drawing of the sheet. (please refer the revised paper in page 17)
3. Figure 14 shows the relationship between the punch fillet radius and the maximum principal stress. For Model 1, the maximum principal stress did not change very much with changes in punch fillet radius. But in the other two models, the maximum principal stress decreased with an increase in the punch fillet radius, mainly because the larger Rp value reduced the load and the stress during forming. This stress is relieved completely after the punch has retracted and the flanged sample has rebounded. (please refer the revised paper in page 17)
4. From Figure 15 it can be seen that the maximum principal strain decreases very slightly with an increase of punch fillet radius. The change of strain in Model 1 is 0.07 mm/mm and the average maximum principal strain approaches 0.575 mm/mm. The maximum principal strain in the finished product after drawing will be concentrated in the area where the sheet is in contact with the corner of the punch, but an increase of Rp reduces the duration of contact between the material and the rounded corners of the four sides of the square punch in this area, and so the amount of deformation is reduced. (please refer the revised paper in page 18)
5. From Figure 16 it can be seen that changing the punch fillet radius has no significant effect on the maximum dimension of the hole, the average value of which approaches 5.095, 2.547, and 1.273 mm for the three models respectively. Figure 17 shows the relationship between the punch fillet radius and the maximum flange height which changes very slightly as the radius of the punch fillet increases. The average flange height in the three models approaches 1.43, 0.706, and 0.353 mm. (please refer the revised paper in page 19)

 

• If the authors have a final product with certain dimensions, please show them clearly. Otherwise, what is the merit of this study?

Response: The shape of a final product is provided in Figure 5. The results in our study can be the guideline for the simulation and experiments of optimized micro square hole with a flange drawing development. Please refer the revised paper in page 9.

 

• In the reviewer's opinion, when the aspect ratio of the square cup is moderate or large, the fabrication process needs several progressive forming.

Response: If the aspect ratio of the square cup is defined as the L/Li, L/t or Li/t, the values of aspect ratio for L/Li, L/t or Li/t analyzed in our study are 2.22, 100, 45, respectively.

The fabrication process needs several progressive forming and in Figure 2, the punch bottom contacts the sheet metal when the stroke moves from S1 to S3, the sheet metal would gradually deviate from the punch bottom with increasing stroke until the sheet metal contacted with the punch corner bearing the drawing deformation. Please refer the revised paper page 7.

Author Response File: Author Response.pdf

Reviewer 2 Report

Please, see attached file.

Best regards.

Comments for author File: Comments.pdf

Author Response

Please refer to the attached file.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

1. The smallest width of a punch is 2.5mm, which is not a micro-forming.
   In general, a large scale sheet metal forming has a thickness of 1mm or less, but it is not called a mili-forming.
   The title needs to be changed.
2. The sign for rate terms, dot, must be placed correctly in Eq. 1, There should be a good way to express it.
3. Table 1 needs correction: there is unnecessary number below C.
4. Line 227:  Poission must be corrected to Poisson.
5. In Figure 6, 12 and 19, why the load is fluctuating? There is no reason of fluctuation.
6. In Figure 8, 14 and 21, The max. principal stresses reach to over 1 GPa, which is wrong considering the yield stress is 300+a MPa.
7. The methodology itself seems correct, but there need some corrections and improvement. Some of the contents may mislead the readers.

Author Response

Thank you for your comments and the responses are in the attached file. 

Author Response File: Author Response.pdf

Reviewer 2 Report

I want to thank the authors very much for their kind (and detailed) response. Once reading the second version of the work I want (or maybe: I must) to make the following comments to authors.

• As a general rule it is necessary (or mandatory) that all the terms used in equations should be identified in the text (like I wrote in my previous report). In this second version there are terms in equations 7 to 9 that are not described in the text (sorry if I am wrong). I know that some of these terms can be obvious, but it is necessary to identify them in the text.
• I know that the following comment is (only) my personal opinion. I believe that in this second version of the work there are some plots with a very small vertical scale (like in the previous one version). Some plots have changed in this second version of the paper, but other graphs have the same problem than in the previous version: Figs. 7, 9, 10, 23. Like I wrote in my previous report: sometimes is better to see things from afar to interpret them better (in this case “from afar” wants to mean: with a greater vertical scale).
• With relation to the “Results and discussion” point I still have the same feeling as the previous report: there are many results and very little discussion (it is my personal opinion).
• Nothing else from my part. Congratulations for the work.

Best regards!

Author Response

Responses :

The authors appreciate reviewer’s valuable comments very much. Modifications have been made to improve the manuscript according to reviewer’s suggestions as summarized below:

 

• As a general rule it is necessary (or mandatory) that all the terms used in equations should be identified in the text (like I wrote in my previous report). In this second version there are terms in equations 7 to 9 that are not described in the text (sorry if I am wrong). I know that some of these terms can be obvious, but it is necessary to identify them in the text.

Response: We have modified and added the descriptions about equations 7 to 9. Also, we added the reference [18] relative to equations 7 to 9. Please refer the revised paper in pages 4 and 29.

• I know that the following comment is (only) my personal opinion. I believe that in this second version of the work there are some plots with a very small vertical scale (like in the previous one version). Some plots have changed in this second version of the paper, but other graphs have the same problem than in the previous version: Figs. 7, 9, 10, 23. Like I wrote in my previous report: sometimes is better to see things from afar to interpret them better (in this case “from afar” wants to mean: with a greater vertical scale).

Response: Thank you very much for the valuable comments. We have checked the figures 7, 9, 10, 23 with the reviewer’s comments very detailly and redrawn those figures. Also, we have paid more attention to the range of values in the vertical axis of the graphs. Meanwhile, we also modified the corresponding texts for those figures in the revised paper. Please refer the revised paper in pages 10-11, 13-14, 25-26.

• With relation to the “Results and discussion” point I still have the same feeling as the previous report: there are many results and very little discussion (it is my personal opinion).

Response: We have revised and reorganized the section of “4. Result and Discussion” including section 4.1 to 4.3. Also, we have tried our best to highlight the important information and discussion shown in Table 8 (new added in pages 27-28) for the drawing process for stainless steel sheets. Please refer the revised paper in pages 9-28.

Author Response File: Author Response.pdf