Ratcheting Assessment of Medium Carbon and Austenitic Steel Alloys at Elevated Temperatures
Round 1
Reviewer 1 Report
Comments and Suggestions for AuthorsDear Authors,
Your paper is in my opinion a very good or even an outstanding paper dealing with tracking degradation of investigated steel. Good work.
Author Response
Comments 1: Your paper is in my opinion a very good or even an outstanding paper dealing with tracking degradation of investigated steel. Good work.
Response 1: The authors would like to extend their thanks for the positive view on the manuscript.
Reviewer 2 Report
Comments and Suggestions for Authorssee the attachment
Comments for author File: 
Comments.pdf
Author Response
Comments 1: The introduction section is comprehensive but overly long and could be better focused. In addition, the research gap should be sharply defined.
Response 1: Thanks for the reviewer’s comment. The present study intends to calibrate the temperature-dependent parameters and to address the evolution of materials ratcheting over the asymmetric loading cycles. The introduction section holds a literature survey on related works, focusing on important influential factors on ratcheting of materials at elevated temperatures, including the DSA temperature domain. The last paragraph of this section focuses on the research conducted in the present study.
Comment 2: The role of the VSR model should be clearly distinguished from the A-V framework.
Response 2: Thank you for the valuable comment made by the reviewer.
The VSR equation relates the yield stress of materials to phenomenological temperature-dependent parameters. This equation has been employed along the A-V hardening framework to evaluate ratcheting at various temperatures, including the DSA temperature domain. The A-V hardening rule governed the translation of yield surfaces with loading beyond the elastic limit through increments of backstress. The VSR equation and its temperature-dependent parameters have been discussed in the manuscript (sections 2 and 3), where the isotropic hardening description and the A-V kinematic hardening models are presented.
Comment 3: The justification for using a visco-plastic formulation is weak, needs to be improved.
Response 3: The visco-plastic formulation is the irreversible deformation occurring when the material is loaded beyond the elastic limit and involves the viscous and plastic response of the materials. It is used in the calculation of the total strain accumulation of alloys that are subjected to high temperature and high strain rate loading conditions, which is conveyed in the modelling and formulation section of the manuscript. Equation (6) in the manuscript has been developed earlier in reference [20]. “Perzyna, P. The Constitutive Equation for Rate Sensitive Plastic Materials. Q. Appl. Math. 1963, 20, 321-332”. As per the reviewer’s comment, the materials strain rate-dependent coefficient , and exponent for ER9 steel samples tested at 200MPa/sec and austenitic steel tested at strain rate of 1×10-3/s have been listed in Table 1 for different temperatures.
Comment 4: The physical interpretation of DSA effects is repeatedly asserted but not rigorously connected to the model parameters in a mechanistic way. The authors need to improve the presentation of this discussion.
Response 4: Thanks for the reviewer’s comment on this topic. The physical interpretations of DSA effects are iterated to provide the readers with more insight into the mechanisms occurring at elevated temperatures, leading to an increase in materials strength. The intention is, however, to investigate the progressive plastic strain accumulation with stress cycles and to study the influence of the DSA phenomenon on the ratcheting of materials. While the connection between the two is important, the authors feel it is outside of the scope of this manuscript. The present authors aim to study the dislocation interaction with solute atoms within the domain of DSA in future studies.
Comment 5: Yield surface expansion and contraction are repeatedly presented as evidence of DSA activity. It is well documented that these trends are model-imposed outcomes, not experimentally verified phenomena, and this distinction is not acknowledged.
Response 5: Thanks for the reviewer’s insights into the yield surface evolution within the DSA domain. The isotropic hardening rule (developed by Lee-Zavrel [21]) was utilized to capture the expansion of the yield surface, and the kinematic hardening rule governed the motion of the yield surface. The isotropic-Kinematic hardening framework was employed to monitor backstress increments in the room and elevated temperatures. The observed results were that within the DSA domain, the yield surface was found to expand due to the materials hardening response, while outside the DSA domain, as the operating temperature increased, the yield surface decreased due to the materials softening. This verified that within the DSA domain, the material was strengthened, and ratcheting strain was reduced. Figure 5 shows the intercepts of yield surfaces with stress-strain curves at various temperatures.
Comment 6: The nonlinear function is treated as physically meaningful throughout the manuscript, yet its influence is only shown though improved fitting which raises concerns that acts primarily as a tuning parameter rather than a mechanistic descriptor. Authors are encouraged to expand the explanation.
Response 6: Thanks for the reviewer’s comment on the nonlinear function . This nonlinear function (equation (12)) was developed through the original work of Chaboche cited in reference [25] and utilized within the dynamic recovery term of the kinematic hardening rule to accurately capture temperature and plastic strain effects. This function varies between zero and unity. For temperatures other than the DSA range, becomes unity and it drops to lower than unity within the DSA temperature domain.
Comment 7: Mean stress and stress amplitude effects are shown graphically, yet the discussion does not convincingly explain how the hardening framework captures the asymmetry driven accumulation of plastic strain.
Response 7: Thanks for the reviewer’s comment on mean stress and stress amplitude effects on ratcheting behaviour. While Figure 8 showed how influential the effect of applied stress levels on the ratcheting response of materials is, the present manuscript focused primarily on studying the ratcheting response of steel samples within the DSA temperature domain.
Comment 8: The absence of microstructural characterization weakens physical interpretation
Response 8: Thanks for the comments made by the reviewer. The present manuscript briefly discusses the interaction of solute atoms with dislocations within the DSA temperature domain. This was discussed to briefly address how the materials strength was improved at this domain. The present study intends to investigate the ratcheting of the steel samples at elevated temperatures and discuss how the hardening framework can accurately predict the ratcheting of steel samples involving temperature-dependent parameters. The authors concur with the reviewer that microstructural features are highly influential on the DSA response and ratcheting progress in materials, and the authors intend to investigate these important features in future studies.
Comment 9: The quality of all figures needs to be improved.
Response 9: Please find that the figures have been updated to be of higher quality.
Comment 10: The English of the manuscript is acceptable but occasionally verbose and repetitive, authors need to improve readability
Response 10: Thanks for the comment regarding the readability of the manuscript. The manuscript is checked for its technical writing as suggested by the reviewer.
Reviewer 3 Report
Comments and Suggestions for AuthorsRatcheting of a ER9 whell medium carbon steel was studied through cyclic loading at high temperatures. Various models were evaluated. The authors should address the following issues before considering for publication.
1. Please provide additional details on the cyclic loading procedure
2. How did the authors to measure mechanical properties
3. Why use the Voyiadjis-Song-Rusinek model?
4. What are the purity degrees of the casting materials?
5. Please increase the image resolution. Some fonts are barely visible. For example, the insets in Figure 4 are too small.
6. Are the results transferable to other systems?
7. Please provide a careful list of the limitations of the current work.
Author Response
Comment 1: Please provide additional details on the cyclic loading procedure
Response 1: Additional details have been included in the manuscript to support the test procedures within the original texts. Data regarding the test specimens used in cyclic loading have been provided for ER9 samples, and the use of extensometers for recording strain deformation has been included for austenitic samples.
Comment 2: How did the authors to measure mechanical properties
Response 2: Tensile stress-strain curves were extracted from references [6] and [28] for steel samples and tests conducted at the various operating temperatures and loading conditions. The details of materials and tests are given in Section 3.
Comment 3: Why use the Voyiadjis-Song-Rusinek model?
Response 3: The VSR model was employed to calibrate the yield stress of steel samples tested at various operating temperatures. The model introduces temperature-dependent parameters to capture the yield strength of the materials within the DSA temperature regime.
Comment 4: What are the purity degrees of the casting materials?
Response 4: Thanks to the reviewer for the comment. The original studies referenced [6] and [28] show no details on the purity degrees of the casting materials and only provides the chemical compositions, which have been already included in the materials section of the present manuscript.
Comment 5: Please increase the image resolution. Some fonts are barely visible. For example, the inserts in Figure 4 are too small.
Response 5: Based on comments made by the reviewer, figures were made with higher resolution in the manuscript.
Comment 6: Are the results transferable to other systems?
Response 6: The A-V hardening rule utilizes coefficients and parameters unique to the model and can be applied to the A-V hardening rule. Other models, such as the Ohno-Wang or Armstrong-Fredrick should utilize different materials parameters that would need to be extracted/calculated for ratcheting analysis at room and elevated temperatures
Comment 7: Please provide a careful list of the limitations of the current work
Response 7: Thanks for the comment made by the reviewer. The last paragraph in the results/discussion section has addressed the future works, and limitations of the current work.
Round 2
Reviewer 2 Report
Comments and Suggestions for AuthorsAccepted.
Reviewer 3 Report
Comments and Suggestions for AuthorsThe authors have addressed all of my questions
