Review Reports

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

1. The abstract reports a pressure resistance of 7 MPa but fails to contextualize this against the specific engineering requirement (6.4 MPa) cited later, which is necessary to establish the significance of the results.

2. In the Introduction, citations [12-13] are incorrectly attributed to "Wen et al.," whereas the reference list identifies the first authors as Chen Yang and LIU Kefan, respectively; this attribution must be corrected.

3. The Introduction outlines general incremental forming history but fails to articulate the specific limitations of existing "paddle-type" or "single-cone" heads that necessitate the proposed "retractable double arm" design for 5A02 aluminum.

4. Several sentences in the Introduction, such as lines 47-48 ("The above problems are all that..."), are phrased awkwardly and require editing to improve the academic tone and flow.

5. Section 2.1 lists "milling the port flat" as a main process stage, contradicting Section 2.3 (lines 135-136) which states milling is unnecessary; the authors must clarify if this step is mandatory or experimental.

6. The description of the "retractable rotary drawing head" is inadequate, and Figure 3 fails to illustrate the internal expansion mechanism; a cross-sectional view or schematic is needed to explain how the double arms function.

7. Equation (1) lacks a clear derivation or citation and incorrectly assumes constant wall thickness, which contradicts the significant wall thinning (up to 18%) observed in the study; its applicability must be justified.

8. Figure 1 includes undefined force and kinematic labels; a legend or explicit textual explanation is required to interpret the diagram.

9. Section 2.3 should explicitly clarify that the three-axis CNC milling machine functions as a drive platform for the rotary forming tool, rather than performing subtractive machining.

10. The simulation methodology lacks critical details regarding boundary conditions (clamping methods) and the friction model used between the rigid head and deformable tube, which are essential for reproducibility.

11. The authors characterize an 11% discrepancy between simulated and experimental effective height as "good agreement" without discussing sources of error (e.g., machine compliance or mesh stiffness) to justify this claim.

12. The abbreviation "STH" in the Figure 9(a) contour plot legend is undefined; the authors must specify the physical variable (e.g., shell thickness) and ensure units are clear.

13. The description of the "dynamic explicit analysis" must confirm whether mass scaling was used and demonstrate that kinetic energy remained negligible compared to internal energy to validate the quasi-static approximation.

14. There is a critical error in the experimental design where the text (lines 195-196) and Table 3 transpose the definitions of Factor B (speed vs. temperature) and Factor D, rendering the analysis invalid.

15. The simulation results reporting "obvious cracks" in the cryogenic group contradict the Introduction's claim (lines 215-217) that low temperatures improve plastic deformation; this discrepancy requires theoretical analysis.

16. The reliance on Range Analysis (R-values) is insufficient to distinguish significant effects from experimental error; an Analysis of Variance (ANOVA) should be conducted to statistically validate the process parameter influence.

17. There is a major quantitative discrepancy between the simulated (28.3%) and experimental (18%) wall thinning rates that must be addressed to support the claim that the simulation model is accurate.

18. The annotation "Welding condition of the sample" in Figure 15 is misleading given the "die-less" premise; the text must clarify that welding was likely restricted to attaching test fixture end-caps.

19. The burst pressure test methodology requires additional details, specifically the pressurization medium and the rate of pressurization, to ensure the experiment is reproducible.

20. The reported pressure resistance limit is inconsistent, appearing as 7.5 MPa in the Conclusions but 7 MPa in the Abstract and Section 5; these figures must be reconciled.

21. Conclusion point (2) claims the geometric formula as a major contribution, which is problematic given that the formula lacks derivation and assumes constant wall thickness despite the study proving otherwise.

Comments on the Quality of English Language

The quality of English in the manuscript is variable; while the core technical content is generally understandable, the text suffers from awkward phrasing, grammatical redundancies, and informal expressions that detract from its scientific value. For example, the phrase "die-less rotary drawing type without mold" in the title is tautological, as "die-less" already implies the absence of a mold. Additionally, sentences such as "The above problems are all that the aerospace industry is trying to avoid" (lines 47-48) lack the necessary academic formality. There are also issues with technical precision, such as the misleading use of the label "Welding condition" in Figure 15 for a forming study and undefined abbreviations like "STH" in the simulation results. Extensive proofreading and editing by a native English speaker or a professional technical editing service are strongly recommended to ensure standard grammar, consistent terminology, and smooth logical transitions.

Author Response

Thank you for carefully reviewing my manuscript and providing your detailed and constructive suggestions. I have now completed the revisions, and the revised version is attached for your review. We look forward to a positive outcome of the review process and the eventual acceptance of our manuscript.

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

Manuscript ID : coatings-4022732
Title:

 Study on the forming process of thin-walled 5A02 aluminum 2 alloy T-tube formed by rotary drawing type without mold

This study introduces a die-less rotary drawing method to replace low-efficiency welding for forming thin-walled 5A02 aluminum alloy T-shaped tubes. Using finite element simulations and experiments, the effects of key parameters—pre-hole size, preheating temperature, feed rate, and drawing speed—on branch height and wall thinning were evaluated. The optimized process achieved over 3.5 mm branch height, ~18% wall reduction, and a pressure resistance of 7 MPa, meeting engineering requirements. It can be accepted by addressing following comments.

1. How is the synchronization between the adjustment area and the retractable double arms ensured during the rotary drawing process, and what is the tolerance for inner diameter variation?
2. Which process parameters (e.g., rotation speed, feed rate, clamping force) were varied in this study, and how were these parameters calibrated on the CNC milling machine?
3. How does the absence of a die influence surface quality or the presence of defects (e.g., thinning, wrinkling, cracking) during the die-less rotary drawing process?
4. Were there any observed limitations in rotary drawing height due to tool geometry, tube material, or the retractable arm design?
5. Does there is any change in microstructure of Al alloy after the processing? The following article can be helpful and must be cited. https://doi.org/10.1016/j.jmrt.2024.12.223.
6. In figure 15 does the authors also compared the results with traditionally welded tube. To compare the maximum pressure conditions? doi: 10.1021/acsomega.5c01732. This article is much related to this study they studied effect of rolling conditions on mechanical and corrosion properties of material. So, such comparative analysis can be added.
7. Does authors also utilized AI or Machine Learning assisted tools for design or/and properties prediction? https://doi.org/10.1016/j.actamat.2019.08.033. This article can be read and cited for better understanding or future works.

 

Author Response

Thank you for carefully reviewing my manuscript and providing your detailed and constructive suggestions. I have now completed the revisions, and the revised version is attached for your review. We look forward to a positive outcome of the review process and the eventual acceptance of our manuscript.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors have successfully addressed all points raised in the previous review, significantly improving the scientific rigor and clarity of the manuscript. I appreciate the detailed revisions, particularly the correction of the geometric derivation in Section 2.2 using the equal line length method, the inclusion of the KE/IE ratio to validate the simulation's quasi-static assumption, and the rectification of the experimental factor definitions. The added ANOVA results and the expanded explanation of the telescopic tool mechanism now provide a robust justification for the research findings, and the manuscript is now suitable for publication.