Fatigue Behavior of Conventional and Stationary Shoulder Friction Stir Welded EN AW-5754 Aluminum Alloy Using Load Increase Method

Round 1

Reviewer 1 Report

The concept of the  publication  is  interesting and important for future applications of such FSW joints in  aeronautical and automotive constructions , from the point of view of their specific conditions of exploitation, including fatigue.

   To present the results e FSW proces using relatively new  tool with stationary shoulder in comparison to conventional one, it will be better to improve some figures  showing important details  ( e.g. fracture fig.10, Fig. 11 ).

Preparation of enlarged Figures 6,7, 8 will allow  for better  identification of detailes of presented relationships. 

Captions under the drawings  should reflect their contence exactly.  E.g. Fig.6 Quasi-static tensile test results OF WHAT ?

There is to much references to position of lit, [7 ] on page 2. 

You should avoid self-citations - references [7], [8], [9] and change text of this part of the work. 

The effect of fatigue behaviour should be better support by microscopic analysis of FSW joints after demonstrated fatigue tests ( LIT, CAT ).   

Author Response

The authord would like to thank for the reviewer comments. Attached you can find the answer point by point

Author Response File: Author Response.pdf

Reviewer 2 Report

In this paper, the authors comparatively investigated the fatigue properties of aluminum structures elaborated using conventional and stationary shoulder FSW. Many characterization/measurement techniques were used and the work is interesting. However there are some points to improve before that the paper could be considered for publication:

-          In the paper (line 252), the authors speak of “bending test”. However, if I well understand (also from the test set-up), the fatigue tests were performed under uniaxial tension-tension with a load ratio R=0.1.

-           The stepwise material response observed under cyclic loading is due to rather the PLC effect than the cyclic creep phenomenon. At least, what the authors said in Conclusions about this point is not accurate.

-          For the results of fatigue tests with constant stress amplitudes, the two fitted S-N curves tend to join each other as the stress amplitude decreases. It means that the advantages shown by stationary shoulder also disappear when the imposed stress level is low. For this phenomenon, the authors did not really explain why. In my opinion, it is interesting to give some explanations about this phenomenon.

-          There are many linguistic errors in the paper, and some of them are inacceptable. Several examples are given as follows:

·         line 35: Subsequent the tool moves…

·         line 35: Meanwhile the continuous plasticizing, …

·         line 44: …a increased surface roughness

·         line 46: … the probe is the only rotating part in the FSW tool and generate…

·         line 72: Even though, …

·         line 157: … the influence of the conventional …. were

·         line 254 : …the manufacturing of…requires a detailed …of the areas favors the crack initiation (it is difficult to understand because there are two verbs in this sentence).

·         And other errors that I do not cite. The authors should check the paper thoroughly.

-          Fig. 9a: The values given on the abscissa represent already the real numbers of cycles. Thus it does not need to add 10^4 to amplify the values.

Author Response

The authors would like to thank for the reviewer comments. Attached you can find the answers point by point.

Author Response File: Author Response.pdf