Crack-Free Joining of High-Strength AA7055 Sheets by Friction Based Self-Piercing Riveting with the Aid of Numerical Design
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsIt is an interesting paper on friction self piercing rivets, gives a good overview and good discussions - a comprehensive paper.
The weakest part is the description of the FE simulations - material properties etc.
Figures must be improved. Some language errors fixed.
I have marked some issues in the document (scanned papers are attached).
Page 1: you do not find stress concentrations in rivets, you find stresses.
Missing "and" - see scan.
Page 2: the same missing word
Pleas define difference of element erosion and "kill element"
Page 3: Figure 1 is not possible to read/see properly
Under figure: length of rivet is not given - se my comment on page
Why do you mention rivet weight - is that really relevant....must be small compared to the other parts anyway
Figure 2 i bad - size and layout. flat should be Flat. & should be and
Writing errors in page 5. Also: explain yield strength. I also miss important info on how you model hardening. Explain what you mean with friction in radial direction. Check words "as the state"
Page 6: Explain shim plates- how and where. Fig 4 is bad, text is tricky to see, explain A-S. FE plots are too small to see details.
Page 7, fig 5: photo is almost of no help....drawings to the right are bad.
describe better "old" and "new" rivet.....explain if they are commercial or specially designed/modified.
Fig 9 - define Ts or refer to table 1 - do not use new symbols for the same things
Fig 10: stress plot has limited value - and you do not stat at which load level
Page 10: what is tempering at 900h ?
Page 11: plots of stresses - at which load level?
what is the "six sides" ....?
Fig 12: stresses you could have estimated from torsional moment....comment?
Se my question to Fig 14 - solid state joining - is it?
Page 14 - Fig 16: Curves are bad - why do you need this symbols on the curves? Text does not fit in size
Page 15:
you have many references - but does not really compare your experimental findings or numerical results to findings of others. Can you do this?
See the attached file!
Good luck in the further work
Comments for author File: 
Comments.pdf
Author Response
Dear Reviewer,
Thank you so much for your input. Please see the attachment for the detailed response.
Best regards,
Authors
Author Response File: Author Response.pdf
Reviewer 2 Report
Comments and Suggestions for AuthorsThe text may be interesting. However, it has shortcomings. In its current form it is not suitable for publication. I recommend improving it to increase its quality. Some more important notes below:
1. Extend the review to include work on FEM modeling of joining aluminum sheets with various dies and rivets. In the overview you can refer to the solid rivet joining technique.
2. The exact mechanical properties of the sheet and rivet material should be provided. Flow curve: material constants and hardening factor.
3. What friction coefficient was used?
4. What type of finite elements were adopted. They should be of the appropriate class - taking into account the issue of thermo-mechanical deformation of the material.
5. What mesh reconstruction criterion was used?
6. What material separation criterion was used?
7. What does d=0 mm mean in Figure 10? Use the lock size designations already adopted in other publications in the SPR connection.
8. How were such accurate microhardness distributions obtained? The measurement is made at specific points. Was such a dense microhardness measurement performed - what approximation was used?
9. Applications need to be improved. Make a quantitative and qualitative assessment.
10. Explain what optimization was used. What equation and coefficient weights? In my opinion, this is not optimization.
Author Response
Dear Reviewer,
Thank you very much for your input. Please see the attachment for the detailed response.
Best regards,
Authors
Author Response File: Author Response.pdf
Reviewer 3 Report
Comments and Suggestions for AuthorsThe joining process of friction based self-piercing riveting is optimized by a combined 3D and 2D model. High-strength Al alloy has been joined by F-SPR effectively without cracking at the bottom of Al sheet. The modeling approach appears to be novel from the perspectives of prediction accuracy and efficiency. A few issues can be addressed to further improve the quality of presentation:
(1) Introduction. Some researchers have shown the capability of CEL model in FSW process. Please comment on the difference between current approach and literature study, and point out the uniqueness of the proposed one.
(2) The details of heat flux or temperature mapping should be described. In addition, the role of shear stress in yielding of base material needs to be discussed.
(3) Fonts in some figure is too small (e.g. Fig.1), and some are too big (e.g. Fig.2). Adjust the font size
to be consistent throughout the paper.
(4) Units of FEA results are missing in Figures 9, 10 and 13.
(5) Some symbols are defined in italic form but others are non-italic. Consider to unify the format.
(6) How do you evaluate the impact of residual stress by F-SPR on the joint strength? Does your performance model include residual stresses?
Author Response
Dear Reviewer,
Thank you very much for your input. Please see the attachment for the detailed response.
Best regards,
Authors
Author Response File: Author Response.pdf
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsThe parameter marking should be corrected: d (d to diameter) interlocking distance to here.
In Table 1, add parameter designations for all quantities.
Parameter markings should be unified in all drawings. The harmonization should be consistent with other publications.
In the axis caption on charts, add parameter labels.
Ts stands for Re or Rm. Correct all markings.
The material damage model should be described precisely. This is a very important element of the simulation. How was the fracture strain determined? According to what equation?
The friction coefficient is not the same for different temperatures!
Author Response
Dear Reviewer,
Thank you very much for your comments. Please see the attachment for the detailed response.
Best regards,
Authors
Author Response File: Author Response.pdf
