Effects of Welding Speed and Pulse Frequency on Surface Depression in Variable Polarity Gas Tungsten Arc Welding of Aluminum Alloy

Round 1

Reviewer 1 Report

The paper is well written and very significant for today's questions.

But, the assumptions leading to the model, especially a homogeneous fluid and the ellipsoidal heat-input model should be discussed thoroughly.

Reference (21) is based on another paper for the experimental justification.

Other comments:

“Effects of Welding Speed and Pulse Frequency on 2 Surface Depression in Variable Polarity GTA 3 Welding of Aluminum Alloy” review

General:

The subject addressed in present paper is most significant importance at this moment.

The English language and spelling are acceptable.

The literature review is almost complete and well done.

Special questions/remarks

From the very beginning, it is not quite clear to the reader if a homogeneous “mixture” is considered for the mushy zone or not. If not, spatial gradients of the physical constant would be needed. By reading further and, essentially, by reading reference (21) the assumption of homogeneity becomes quite clear. This should be mentioned explicitly: Equation (2) : Discuss the spatial variation of the pressure, ρ is the fluid density, is the drag coefficient K, the dynamic viscosity η, the acceleration by body force G

Equations (3) and (4) correspond to a mushy zone. Thus, the coefficients in equation (2) are not constant, if not assumed explicitly previously.

Tl and Ts are liquidus and solidus temperatures : are these temperatures constant. If, so this would correspond to an established regime. If a transient regime is considered, at least Ts will depend on very local chemical variations. Thus, this should once more pointed out as clearly and simply as possible.

Equations (7) and (8)

“where ff and fr are the frontal and rear fraction of the heat flux; af, ar, b and c are the parametric values obtained from the metallographic data and the shape of molten pool; qarc is the welding arc heat input.

"af, ar, b and c are the parametric values obtained from the metallographic data and the shape of molten pool. “Should be more explicit.

Present paper is based on reference (21). This nice paper discusses thoroughly the need and implications of an ellipsoidal shaped heat-input. Unfortunately, the experimental justification is given in Christensen et al. I could not find this paper today.

N. Christensen, L. de. V. Davies, and K. Gjermundsen: British Welding Journal, 1965, vol. 12, pp. 54-75.

To summarize, the ellipsoidal heat input model is a corner stone of present paper. Unfortunately, the experimental determination of the different parameters is not clearly given.

I suggest, to accept the paper for publication after more comments on above mentioned equations.

Comments for author File: Comments.pdf

Author Response

Dear Reviewer,

We are thankful to the valuable comments and suggestions of the academic editor. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked by Word's Track Changes feature in the revised manuscript of the paper.

Thank you.

Sincerely yours

Jun DU

State key Laboratory of Manufacturing System Engineering

Xi'an Jiaotong University

Xi’an 710049, China

Author Response File: Author Response.pdf

Reviewer 2 Report

On the whole this paper is well written and presents clear modeling results, but at the moment the modeling results appear to the reviewer to be only partly experimentally verified.

Where are the authors experimentally verifying most of their findings other than the size of the fusion zone?  It would seem to me that they have the data available to compare experimental results (and error bars representing variance) against the findings of their model.  From my understanding of Figure 12 & 14 experimental points should be able to be placed directly on these charts.

On a related note there is very little analysis of Figures 12 & 14.  Is maximum surface depression depth of the weld pool in the final solidified state or during the model while the pool is liquid?  As it is barely discussed I don’t actually know.

Another issue I found with this paper is the “calculated solidus isotherm 811K” (Pg9Ln249) in Figure 6 clearly corresponds to the melt region, but also very clearly does not correspond to 811K in both their simulations based on their own scale bars.  There seems to be relatively good agreement in 6a, but the gradient in 6b aligns much more closely with 881K than 811K.  There is clearly an error in the analysis here that needs to be addressed

More minor issues:

The caption of Figure 6 also makes no comment on “c” or “d”.  In a more minor point the scale bars should preferably be on the same relative scale with each other, if the authors performed the calculations this should be relatively easy to correct and makes the result much easier to interpret.

Pg1Ln31- “and so on”, this is casual language, authors can start with “such as” to denote a nonexclusive list, or fully elaborate.

Pg3- I’m not sure I understand the merit of Figure 1 as it currently stands as it conveys little to no information.  It should probably be removed or replaced with a detailed schematic of the welding head.

Pg4Ln130: “In present study” change to “In the present study”

Author Response

Dear Reviewer,

We are thankful to the valuable comments and suggestions of the academic editor. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made correction which we hope meet with approval. Revised portion are marked by Word's Track Changes feature in the revised manuscript of the paper.

Thank you.

Sincerely yours,

Jun DU

State key Laboratory of Manufacturing System Engineering

Xi'an Jiaotong University

Xi’an 710049, China

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The paper is now ready for publication.

Author Response

We accept the reviewer's advice and find some checked spelling errors and grammatical mistakes in this paper, we have made correction.

Reviewer 2 Report

The authors were able to address my primary concerns and the paper is ready for publication.  I will note that they really should write longer captions in the future with comments on each sub-figure, e.g. “a)”, “b)” and so forth, and that most journals have historically required this, but I see no reason this needs to go through another round of scientific revision.  For the official record I assume the issue with the temperature labeling in Figure 6 (now Figure 5) was just a labeling mistake, but I would have felt more comfortable if the authors had commented as to how the mistake happened as it’s the type of thing you might see if they were trying to force a model to fit the data.

Author Response

Dear Reviewer,

We are thankful to the valuable comments and suggestions of the academic editor. Those comments are all valuable and very helpful for revising and improving our paper, as well as the important guiding significance to our researches. We have studied comments carefully and have made an explanation for the mistake happened. Other revised portion are marked by Word's Track Changes feature in the revised manuscript of the paper.

Thank you.

Sincerely yours

Jun DU

State key Laboratory of Manufacturing System Engineering

Xi'an Jiaotong University

Xi’an 710049, China

Author Response File: Author Response.pdf