Numerical Simulation of Crack Condition in Forging Products of M50 Bearing Steel Based on Processing Map Theory
Round 1
Reviewer 1 Report
This paper deals with the experimental and numerical study of cracking in forged products, namely made out of steel. In particular, a power dissipation efficiency mapped is simulated through the use of FEM, and this is an interesting approach. However, since one of the main items of research is the study of cracking, there were no attempts made to model the cracking process nor is there a discussion of a fracture criterion. There is utility in the work, and this paper must be significantly improved before it can be accepted for publication. These are the comments to improve the paper:
Q1: In Section 4, there is no discussion on the type of constitutive theory used to model the material response. For example, what is the stress-strain law? What does the flow rule look like? Is it a simple J2 plasticity based flow rule? What is the kinetic equation for the equivalent plastic shear strain? Please list the 3D constitutive model used for the simulations. It is also not clear how is dissipation calculated, and this must be discussed in detail in Section 4.
Q2: In some of the FEM figures, the efficiency is calculated to be more than 1. Typically, most researchers are familiar with the concept of efficiency being between 0 and 1. Please explain in detail why for this case, why do we need the efficiency to be able to be larger than 1 (although this is quite clear from Equation 4 when m gets very large). Maybe it is more useful to redefine a measure of efficiency where the maximum value is 1.
Q3: Can a fracture criterion be proposed based on the total dissipation? This would seem like a natural extension of the work. Furthermore, why isn't there a discussion on how to model fracture in the material since cracking is discussed in the paper? At the very least, the authors can suggest ways to numerically-model cracking within an Abaqus framework e.g. element deletion being the easiest way to model cracking. The authors can refer to the papers of Reddy and co-workers [1,2] which uses the element deletion method in conjunction with a non-local fracture criterion to obtain mesh density independent and element type-independent deformation and fracture response within an Abaqus framework. Such works are relevant to the scope of this paper since the modeling of cracking is done within an Abaqus framework, and the extension to modeling cracking in the material can be done using the element deletion method.
References
[1] Computer Methods in Applied Mechanics and Engineering (2019) vol. 354 pp. 871-903.
[2] Mechanics of Advanced Materials and Structures (2020) vol. 27 pp. 1085-1097.
Q4: In Page 10, it is stated that the response is influenced by friction, and this is evident by the barreling of the sample. What is the coefficient of friction used in the simulations? Please list it.
If these major comments are sufficiently addressed, this paper can be accepted for publication in Metals.
The English just needs minor corrections.
Author Response
Please see the attachment.
Author Response File: 
Author Response.pdf
Reviewer 2 Report
The work paid attention to the experimental studies of processing map and its application in simulation. Some valuable conclusions have been achieved, but some questions need to be answered.
1. How to correct the curves at various temperatures and strain rates?
2. Why the flow stress increases slightly after a strain of 0.6? Is it the result of friction. Why it still increase after correction?
3. There are still some type errors. Please check it and revise very carefully.
4. Why intergranular cracks are generated under specific conditions?
5. No any other defects were identified, why? It is common that processing map can determine several microstructure defects.
There are still some type errors. Please check it and revise very carefully.
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Reviewer 3 Report
In this paper, the authors performed research involving numerical simulation of crack conditions in forging products made of M50-bearing steel based on the processing map theory. The article contains exciting experimental and numerical research results that relate to practical aspects that facilitate understanding the processes taking place during forging and can be used in the forging industry. The issue of determining the appropriate parameters of the steel forging process discussed in the article has been widely discussed and supported by a well-developed experimental part, which is the value of the publication. The authors should have avoided minor editorial errors that should have been removed before publication.
The introduction is based on the literature from many years and contains essential information necessary to determine the legitimacy of undertaking the topic of the work. In addition, in the area of research results, the authors referred to literature data on an ongoing basis. Experimental studies were well-designed, and their results were used to complete the developed computational model. The results are clearly presented and well-illustrated with graphs and pictures. Conclusions are appropriately connected with the previously carried out research part and contain relevant observations.
Suggested improvements:
1. Please check the numbering of the equations. Marking (4) is repeated in the text.
2. Line 141 Please correct the descriptions in Figure 4; it should be "Temperature".
3. Line 236 Please check the numbering of the figure to which the text refers. Please correct the colour description to "grey-coloured".
Author Response
Please see the attachment
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
The authors have significantly improved the work in the paper. In particular, the efficiency calculations are bounded between 0 and 1, and therefore it makes better reading and understanding of the work and results. Hence, this paper can now be accepted for publication.
The English language is fine and acceptable.
