Finite Element Modeling of Microstructural Changes in Hard Machining of SAE 8620
Round 1
Reviewer 1 Report
This manuscript investigates the numerical prediction of hard machining of SAE 8620 using a finite element analysis with a modified Johnson-Cook material model. Overall, the paper is well written including a concise introduction and presentation of the numerical results. However, some modifications and additions are needed before publication. The questions and suggestions are listed below:
It is worth mentioning that the Johnson-Cook model is widely used for machining simulations, even for other material system such as fibre reinforced composites. As example, the following article should be added to the introduction:“X Yan, J Reiner, M Bacca, Y Altintas, R Vaziri, A study of energy dissipating mechanisms in orthogonal cutting of UD-CFRP composites, Composite Structures, Vol. 220, pp. 460-472, 2019, https://doi.org/10.1016/j.compstruct.2019.03.090”
In Section 2, it is not clear if the authors performed the experiments by themselves or if the data is extracted from literature. This also applies to the experimental results presented in Fig. 3, 7 and 9. Are these experimental results taken from literature? If yes, references need to be added to the figures. Significantly more details are required for Section 3: How was remeshing used? The contour plots in Fig. 2, 4, 5 and 8 do not indicate any remeshing. The authors should add details about i) analysis method (implicit or explicit), ii) element type (solids, shell, etc?) iii) any stabilization (hourglassing, damping, etc). The introduction of the modified J-C model needs more background and explanation Please add the original J-C equation for better understanding to indicate where modifications have taken place The hardness-based flow stress model [15] should be explained to understand further modifications on page 4 The determination/calibration of the numerical constants on page 4 is not clear. Please add a detailed description or justification for the choice of constants. It would also be helpful to add a table with all numerical constants and their values. On page 5, it is stated that it is possible to distinguish the mechanical and thermal contributions. What about their coupling? From the explanation given, it is not evident how these two effects are interacting. What element erosion/deletion used within the simulation framework? In Figure 3, it would be good to run some sensitivity analyses on the numerical constants to see the effect of parameter change to the overall prediction. The discussion of the results in Section 4 needs more experimental evidence. Often, simulation results are discussed without referring to experiments (for example line 215-217 or line 228-230)Once these questions and modifications have been addressed, the proposed manuscript provides a good contribution towards the simulation of machining.
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Reviewer 2 Report
The present study proposed a newly developed finite element model that is able to describe microstructural evolution and dynamic recrystallization during orthogonal hard machining of SAE 8620 steel. The thermo-mechanical behavior of the SAE 8620 steel is numerically represented by the new modified Johnson-Cook model. The authors concluded that the finite element strategy can be used to properly simulate the cutting process of the SAE 8620 steel. It provides satisfactory results to predict the grain refinement and the microhardness variation on the machined surface and subsurface.
This study is interesting and important for the researchers who want to discover the insight of hard machining using a numerical approach. However, the detailed information about the development of the finite element models was lack. I suggested that all the numerical inputs of the modified Johnson-Cook model and finite element model are needed to be provided. Additionally, the authors showed their findings without detailed discussions. In fact, the manuscript has no Discussion section. A major revision was recommended.
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Reviewer 3 Report
PLUS:
The structure of the article is very good - simple and legibleMINUS Literature study of such model - narrow
Be sure to expand the test on the use of the model.
In summary (conclusion), the sentence (No 284-287) is not enough.
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Round 2
Reviewer 1 Report
All the comments were addressed appropriately and the manuscript is in good shape now.
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Reviewer 2 Report
I think that the discussion of the manuscript is too rough and weak. The discussion about the study findings is still needed to be improved if possible.
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