Study of Alloy Hot Flow and Hardening Behavior Using a New Correction Method for Hot Uniaxial Tests
Round 1
Reviewer 1 Report
The publication describes a current engineering issue. The content of the paper does not raise any objections. The work can be published in its current form, since it contains only minor editing shortcomings that do not affect the overall evaluation of the work.
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Reviewer 2 Report
1. Abstract:
The results have shown a 7% overestimation of the ductility, 5~8%, 7~8% and 4~8% overestimation of the strain hardening component (i.e. n), strain rate hardening component (i.e. m) and uniform strain value (i.e. ??), respectively, compared to conventional 28
method.
Please, avoid numbers in abstract, rewrite sentence.
2. Explain why are i.e. 800°C and 900°C as temperatures were chosen and there are some impact of the chosen temperatures on the presented method.
3. Figure 7. Prediction of angle equation
At the specimen figure it is given for the 800°C there are two sets of data, for 0,1/s and 0,01/ s, and for 900°C only 0,1/s. Please explain
4. Fig.9. Both curves are very similar till true strain above 0,35. Do you have some explanation.
5. At the Figure 9. Experimental stress-strain curves with and without correction. The temperature is 800 °C and 260 the strain rate is 1/s. is given. ,figure 10 is representation of obtained results. Please give some comments, as for Fig.9, what is difference of results compered to the previous model ( no correction). Is similar trend observed for other results given at Fig.10?
Author Response
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Reviewer 3 Report
The thermomechanical simulator Gleeble has a large number of advantages for the investigation of hot deformation behaviour of the metallic materials such as wide range of the temperatures and strain rates, large accuracy of the deformation rate due to hydraulic system, etc. However, Gleeble a has disadvantage for tension test as non-uniform temperature distribution, and as s result non-uniform strain. The authors of the paper “Study of the alloy hot flow and hardening behavior using a new correction method for hot uniaxial tests” have tried to create a method for correction of the primary force vs stroke data to obtain the true stress – true strain curves for samples with non-uniform temperature distribution. Unfortunately, I cannon recommend the publication of the paper due to some methodological errors and the absence of the approving developed correction method by the comparison with the results of other scholars. The manuscript should be significantly improved before publication accordingly following comments:
- In my opinion, the main error in the developed correction method is that the authors used a 2D model for the description of the strain localization. It may be accepted for the cylindrical samples with axial symmetry. However, the authors have tested the samples made from titanium sheets. In that, case localization should significantly differ in two directions due to differences in the size: the thickness of the sheet (initial size is 1.5 mm) and the width of the sample (initial size is 12 mm). It is not possible to correct using a C-gauge extensometer because it does not measure the change in the thickness of the sample. The authors should add to their model the influence of the strain localization in the thickness direction.
- The authors should compare obtained results with the stress-strain curves obtained in the usual testing machines (not Gleeble) where the samples are heated by the furnace and have no temperature gradient in the deformation zone.
- The stress-strain curves presented by the authors in Figures 9 and 10 are hard to be true stress – true strain curves. True stress cannot decrease during the deformation to such values even due to dynamic recrystallization. The decreasing of the stress is because of the strain localization. The authors should change the name of the axis to “engineering stress” or leave the only part with uniform deformation on the curve.
- Minor correction:
- Lines 129-130: What do the authors mean by the phrase “the specimen was soaked at the target temperature for the 60s to guarantee a uniform temperature” if it is not possible in the Gleeble system due to “cold” specimen’s holders?
Author Response
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Round 2
Reviewer 2 Report
All requirements and corrections given by reviewers are given, as well answers to the questions. In present form the paper could be is accepted for publication.
Reviewer 3 Report
The authors have answered previous comments. The paper may be accepted for publication.
