Formation Mechanism and Evolution of Plastic Damage in Billet during Reduction Pretreatment
Round 1
Reviewer 1 Report
The reviewer appreciate the extensive work for applying CDM to the hot forged steel to evaluate the mechanical property at elevated temperature.
The followings are the comments by the reviewer, which should be considered to the revision of the manuscript.
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1. Table 1.
Use mass % instead of wt. %.
2. Figure 2
The position where the reduction of 26% should be indicated accurately in (a) and (b).
Also, "Φ125" is better to be inserted in (a)
3. lines 115-116
The special variable of strain at fracture should be used. For example, εf.
4. Figure 4, Figure 7
It looks that the lines of grain boundary are added by the authors. Or the lines are real grain boundaries? It appears for the reviewer these lines is added graphically by the authors. If so, this fact should be revealed in the manuscript.
5. Figure 5
The information on temperatures of experiments should be inserted in each figure (a) - (d)
Please correct the miss spelling of necking in (a)
It will be better to use "true stress" and "true strain" for the axis labels.
6. lines 187-188
This is strange expression must be revised.
The phenomenon can be observed, but the explanation why the phenomenon occur must be based on metallurgical knowledges or research results.
7. Figure 8
It is better to add the brief explanation on the different trend in reduction in area for 900ºC and other temperatures.
8. line 226 "a typical brittle fracture along the grain boundary"
Does this fracture occurs inter-grains or intra-grain? Former is called intergranular boundary fracture, and latter is called cleavage fracture. It is better distinguish two fracture modes.
9. Figure 10(b)
What is "Spot 1"? "Spot 1" means inclusion? Please give exact explaination it in the text.
10. Equation (1)
If this equation is correct, the evolution law of DT (Eq. (3)) is different from that in reference [15]. If DN in Eq. (1) is DT, Eq. (3) is same as that in reference [15].
When the author propose the new equation on damage evolution, they should give the explanation on the modified equation (motivation, modified points and so on).
11. Equation (5)
H should be Italic style.
12. Equation (10)
E should be Italic style.
13. Table 2 and Table 4
In these tables, variables should be written in Italic style.
14. line 337, reference [20]
In the reference [20], three objective functions OF_I, OF_II and OF_III are conducted. Moreover, there is no description on genetic algorithm in reference [20].
Therefore, More accurate and detailed description should be done for the determination of the materials parameters in this manuscript.
15. Table 4 and Table 5
Unify the expression of unit; Use "/". ( ) are not necessary.
Modify the expression "e+XX" of figures to superscript like 105.
16. line 421 "The initial temperature"
Please specify the initial temperature used for the analysis definitely.
17. Table 6
Poisson's ratio is rather mechanical property. And /(-) is not necessary.
Please use the exact term on Expansion. And ( ) is not necessary.
For Density, Specific heat and Conductivity, ( ) is not necessary.
For Conductivity, use "Thermal conductivity".
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The manuscript is well written, contains informative and useful results, figures are good quality, references are enough. The authors clearly described the background. Therefore, I found this manuscript to be of high interest and originality and recommend its publication on Metals.
Minor comment:
Page 6; in Figure 5a instead of "Nicking” should be "Necking". Please correct.
In Section 4.1 in Eq. (1); What means the density. Is it the normalized dislocation density? What means the plastic strain rate? Should be the effective plastic strain rate. Please clarify.
Page 14; In Section 5.1; What means sentence: "The plastic damage model was implemented into the FEM model for reduction pre-treatment through secondary development technology in ABAQUS software". How this multi parameters damage model is implemented in ABAQUS? Please clarify.
Page 16 line 1; Sentence "The friction coefficient between contact surfaces was set to 0.3". Why it is constant for all proces temperature? Please add a comment.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
