Experimental Analysis and Optimization to Maximize Ultimate Tensile Strength and Ultimate Elongation of Friction Stir Welded AA6082 Aluminum Alloy
Round 1
Reviewer 1 Report
The authors conducted FSW tests of AA6082-T6 sheets of thickness 2 mm, and used non-linear regression approach to get empirical formula for predicting the ultimate tensile strength and elongation of the joints.
(1) Suggest to change all the so-called "mathematical model" into "empirical formula", because the former is based on the physical phenomena & mechanism of FSW process while the later is just based on the test data. Only some common methods of data processing are used to get the prediction formula.
(2) The tool tilt angle is an important parameter which must be given out.
(3) The 1st paragraph can be condensed into one or two sentences because it is common knowledge.
(4) English expression needs further polishing. There are many inappropriate sentences like,
usually lower than 80% than the corresponding melting temperature,
The empirical tests showed as the proposed models as well as the developed optimization methods are reasonably accurate,
(5) The appendix A seems unnecessary.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
It is an original research paper dealing with “Experimental analysis and optimization to maximize ultimate tensile strength and ultimate elongation of friction stir welded AA6082 aluminum alloy”.
However, there are some issues that should definitely be taken into account:
- Written English of the manuscript must be improved. There are many grammatical errors which make the manuscript unsuitable for publication in the current form.
- Many words should be replaced, for examples, use “plunging” instead of sinking.
- Refer to ultimate tensile strength and ultimate elongation with UTS and UE, respectively, for the full manuscript.
- There are many published papers for predicting friction stir welding parameters using Response Surface Method (RSM), I cannot see a considerable novelty for this work. Recently, the integration between artificial neural networks and various metaheuristic algorithms have been used for predicting friction stir welding parameters, and mechanical properties. For example, the integration between Random Vector Functional link network (RVFL) with Marine Predators Algorithm (MPA), Gas Solubility Optimization (GSO), Harris Hawks optimizer (HHO),……….etc. Hence, It is highly suggested to improve the optimization techniques.
- Schematic of tensile sample dimension (with suitable standard) should be included in this work.
- The crosshead speed used for tensile test should be included.
- Tensile samples images should be included to support your work
- Microstructure images should be improved (use suitable etchant) to obtain clear images.
- Effect of FSW parameters on UT and UE should be discussed in detail and supported with suitable references.
- The paragraph from line No. 382 to 391 should be rewritten and moved to the introduction.
- For improved comparison between various algorithms, it is better to present data in Table 9 in a bar chart or a Figure.
- References should be updated with more recent papers
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 3 Report
The authors present a study deals with the optimization of three process parameters concerning with the friction stir welding (FSW) process of AA6082-T6 aluminum alloy. Two second order mathematical models to predict both the ultimate tensile strength (UTS) and the ultimate elongation (UE) on the basis of three process parameters (tool sinking, rotational and welding speed) were developed. These metamodels were formalized through a series of statistical methods. An additional set of experimental tests was used to validate the provided mathematical models. The empirical tests showed that they are reasonably accurate for optimizing the UTS and the UE of friction stir welded joints in AA6082-T6 aluminum alloy.
In general, the process parameters for FSW are classified into three groups: 1) tooling related parameters: shoulder and pin material, shoulder diameter, pin length, pin diameter, feature geometry, thread pitch, etc.; 2) machine related parameters: welding speed, plunge force or depth, spindle speed, tool tilt angle, etc.; and 3) other parameters: anvil material, anvil size, workpiece size, workpiece properties, etc.
Therefore, I consider this optimization performed on one specific material to be "salami slicing" of research.
I can not say, what is the novelty of the work. Two mathematical models based on three parameters and one specific material? If the authors expand their research, generalize it for a wider material category (i.e. A6XXX) and use more parameters for optimization, it will have greater potential to be published in this journal and to catch the interest of the readers. The work has a little potential and needs to be improved.
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Reviewer 4 Report
The subject of the paper is interesting and important, both experimental and different models of optimization methods were applied; the used approaches are generally up-to-date. Unfortunately, the presentation of the research work and the results is overall not unambiguous, partially redundant and wordy, significant elements and details have not been described. Consequently, the manuscript should be amended and abridged consequently.
Authors were focused during their experimental and optimization work on 6082 aluminium alloy, the title of the manuscript contains the designation of the alloy, too. However, the literature review (“Introduction” section) does not refer publications dealing with this alloy. Furthermore, data belonging to this alloy cannot be found in Table 1, which is a very important table from the point of view the whole manuscript. Please add further information and references to your manuscript, e.g. Adamowski J, Gambaro C, Lertora E, Ponte M, Szkodo M (2007) Analysis of FSW welds made of aluminium alloy AW6082-T6. Arch Mater Sci Eng 28(8):453–460; Moreira PMGP, Jesus AMP, Ribeiro AS, Castro PMST (2008) Fatigue crack growth behaviour of the friction stir welded 6082-T6 aluminium alloy. Mec Exp 16:99–106; Lukács J, Meilinger Á Pósalaky D (2018) High cycle fatigue and fatigue crack propagation design curves for 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints. Weld World 62, 737–749. https://doi.org/10.1007/s40194-018-0599-1.
Important information are missing about the chemical composition and the basic mechanical properties of the investigated alloy; please, add these information to the relevant part (subsection “Overview of the experimental campaign”) of the manuscript.
Both the shape and the dimensions of the investigated tensile specimens and the rupture locations of the specimens are missing. Please, add these information to the subsection “Experimental design matrix”; my suggestions are a new figure (the former) and a new column in Table 1 (the latter). In my opinion, the locations of the rupture of the specimens contain important information.
For the verifying the accuracy of the proposed metamodels, five randomly selected additional experiments were applied (subsection “Validation of the metamodels”). Please, add further information about these investigations.
Authors have written in rows 280-281: “The interaction effects of any two process parameters on the ultimate tensile strength are shown by both contour plots and surface plots, as reported in Figure 6 [48].” It is necessary to specify this sentence: does Figure 6 contain reference [48] or not? If yes, please add further interpretation, because reference [48] deals with magnesium alloy. If not, please modify the statement. Please, consider this remark in connection with Figure 9, too.
I have suggestions for the improving of the understandability of the manuscript:
- please, consider adding a list of symbols and abbreviations (e.g. redundancies are avoidable);
- please, consider using Tm instead of Tm;
- “MPa” should be used instead of “Mpa” in Figure 4;
- “3 x 3 x 3” or “33” should be used instead of “33” in row 172;
- “AA” should be used instead “Aa” under the reference [17].
Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 3 Report
The revision of the manuscript was not sufficient enough because there was no significant addition to the research by the authors, as I stated in the first review. My opinion is that the manuscript does not meet the criteria of novelty and complexity of results. There are many published papers for predicting friction stir welding parameters using sofisticated algorithms and methods. I cannot see a considerable novelty in the current form of this manuscript.
In the cover letter authors claim, that future developments of this research aim at expanding the number of welding parameters used as independent variables for the development of methodologies and algorithms for the optimization of the mechanical performances of welded joints. Furthermore, the authors intend to generalize their research by also considering other aluminum alloys. I consider this an appropriate extension of the manuscript. Once completed, the manuscript would have publishing potential for the Metals journal.
Author Response
We would thank again the Reviewer for the valuable comments aiming at improving the quality of the manuscript. We are aware that increasing the number of process variables and the types of aluminum alloys to be tested would represent a remarkable added-valued for the proposed research. However, it is worth pointing out that extending the present research according to the Referee’s requests would imply a time-consuming activity, which results not compatible with the dead-line to submit the revised manuscript (5 days) and with the access limitation to laboratories due to the pandemic contingency. As declared in the manuscript, we would consider the Reviewer’s suggestions as leading steps of a future research on FSW.
As for the missing “criteria of novelty and complexity” invoked by the Reviewer, we regret to assert that the research we propose in the manuscript ID metals-1039773, in our opinion, presents several elements of originality, which distinguish our paper from most researches presented by literature on the same topic, as follows.
1) We present an extended review of the literature, which converge on a comprehensive Table indicating the main attributes (e.g., process parameters, performance measure, modeling methods etc..) for analyzing the state-of-the-art on the single objective optimization of FSW process.
2) We propose a full factorial DOE (instead of a fractional/partial DOE) for generating the metamodels of the process related to UTS and UE performance measures. Then, we use a set of additional experimental tests to strengthen the validation phase of both metamodels.
3) We optimize the FSW process for AA6082-T6 aluminum alloy that, to the best of our knowledge, never has been investigated by literature so far.
4) We introduce a process parameter, namely the tool plunging, whose influence on FSW never has been studied so far.
5) We arrange a large comparison analysis among three different optimization methods (i.e., metaheuristic algorithms), while most papers in the literature present a single method for selecting the most performing process parameters for improving UTS and UE performance measures.
Motivated by the aforementioned remarks we decided to keep unchanged the main structure of the research.
Reviewer 4 Report
Thanks to the Authors for the valuable amendments, the added information and the corrections of more details; the modifications were precisely highlighted in the manuscript and were explained in the authors response file. The manuscript has been undergone a significant transformation.
The “Introduction” section has been amended, important information have been added to the section. Both the chemical composition of the investigated alloy (Table 2) and its mechanical properties (Table 5) have been added.
The shape and the dimensions of the investigated tensile specimens have been inserted too (Figure 3). Unfortunately, the rupture locations of the specimens have not been added, Authors have been accounted their decision in the authors response file. I can accept their second reason, and I hope that the difference of the rupture location (which is probable) does not significant influence on the results of the research.
I have suggested several modifications for the improving of the understandability of the manuscript, Thanks to the Authors for the achieved changes, especially for the Appendix A.
Author Response
The authors would like to thank the reviewer for his appreciation.
Best wishes for the upcoming holidays!
