Optimizing Mandrel Dimensions for a Fixture Hardening Process of High-Strength Steel Aerospace Parts by Finite Element Simulation
Round 1
Reviewer 1 Report
This paper deals with the simulation of production process of gear parts for an aerospace application by a commercial finite element code with the user-subroutine.
The result is quite useful as an actual industrial application.
However, as an academic article, it is insufficient because the method itself is conventional and tons of parameters should be identified.
Therefore, I do not recommend this paper to the publication for Metals in the present form.
The following comments are useful for the modifications.
1. All the parameters and its identified value must be shown. Of course, I know some confidential matters. That kind of fact must be given in the text if some of them should not be available to show.
2. For pressout, the friction is not applied. The reasons why must be mentioned.
3. The results on the profile of the final product must be compared with the experimental results.
4. There are some amount of gap between the experimental results and computation in Fig.6. This gap induces some errors in actual situation.
5. In the academic paper, conventionally section entitled summary, conclusion, concluding remarks, etc. must be shown.
Author Response
Dear Reviewer,
Thank you for your time and your feedback on my paper.
Your review highlights that data values must be given in order to improve the paper. Your request is perfectly clear and I understand that any scientific paper has to describe the methods in such a manner that the described work can be reproduced and verified by the reader. Due to confidentiality issues some of the data is not available for publication. The paper now includes data and sources for the presented figures, important to reproduce the described simulation results. In case confidentiality forbids publishing, this has been mentioned.
1. All the parameters and its identified value must be shown. Of course, I know some confidential matters. That kind of fact must be given in the text if some of them should not be available to show.
Response Point 1:
Figures 1a, 1b MS and k: Carbon dependent parameters Ms and k describing the martensite transformation are included.
Figure 4a Heat transfer coefficients: Explicit values for the HTCs are now added in the figure annotations.
Figures 6a Dilatometer curves: The relevant parameters to calculate the given dilatometer curves are given in Figure 1. Details about the strain is not given due to confidentiality reasons this is mentioned in the paper.
Figures 6b Carbon profile data: Carbon profile data cannot be given due to confidentiality reasons. This is mentioned in the text now. Additionally the carburizing and hardening temperatures are given in table 2.
Figure 7b Temperature data: Explicit values for the measured temperature curves are now added in the figure annotations.
2. For press out, the friction is not applied. The reasons why must be mentioned.
Response Point 2:
Friction is an important parameter of the press out step, the current implementation of the press out is described in greater detail in the revised version of the manuscript in section 2.4, lines 185-188:
The press out step is modeled as a Boolean operation, without applied loads or friction effects. The mandrel elements are instantly deleted which leads to deformations of the part due to a re-distribution of stresses and due to the stored elastic energy. This simplified approach is chosen because of a lack of measurement data of the actual press out process.
In section 5, lines 385-393, the simplified approach and possible effects during the real press out are discussed. In short, the lack of measurement data and parameters lead to the decision to neglect these effects in the model:
Simplifications e.g. concerning the modeled process steps, the heat transfer and the chosen geometry still require validation by measurement results. Important parameters and effects during press out which are currently not modeled are the applied load and the resulting friction which leads to a transformation of mechanical energy into heat [24]. This step is time dependent and influences surface temperature and stresses and results in elastic and possibly plastic deformations. The influence and the sensitivity of these effects on the resulting displacements however cannot be measured in the real process which makes determination of modeling parameters and validation data difficult. It is planned to model the press out step more realistically with a variation of friction coefficients for lubricated steel from literature.
3. The results on the profile of the final product must be compared with the experimental results.
Response Point 3:
This comparison has been prepared by the corresponding author. The publication of these results needs approval from the industry partner, this approval process is still ongoing. Therefore it is not possible for me to add this information within the given five days starting from January 22nd. I addressed this issue in the cover letter to the editors as well.
4. There are some amount of gap between the experimental results and computation in Fig.6. This gap induces some errors in actual situation.
Response Point 4:
It is correct that the simulated dilatometer curves as well as the carbon profile yield small deviations from the experimental results. The reason for accepting these differences has been given in the original version of the paper in section 2.4. For the dilatometer curves the weighting of the fitting algorithm leads to the observed differences regarding the transformation kinetics. The thermal expansion and transformed volume fractions are reproduced precisely. For calculating the final strain correctly the volume fractions and the respective thermal expansion are the most important parameters. Therefore the displayed gaps have been accepted when conducting this study.
An industrial carburizing process usually yields variations of the resulting carbon profile. The simulated profile lies within the tolerances given in the specification for the modeled part. For the modelling work the surface carbon content is very important because it determines the start of the martensite transformation in that region which has a strong influence on the development of contact. A discussion of these points is introduced in section 4, lines.
5. In the academic paper, conventionally section entitled summary, conclusion, concluding remarks, etc. must be shown.
Response Point 5:
The sections summary, conclusion and concluding remarks have been introduced to the paper.
Reviewer 2 Report
This is a nice piece of work and it is worth publishing. Apart from a very small number of typos that could be corrected easily, it would be nice to include data values in the following figures: 1a, 1b, 4a, 6a, 6b, & 7b. Furthermore, since reference [15] is an old publication the K-M parameters like k, Msc, & kc should be explicitly presented. Last but not least, at least an order of magnitude explicit description for the HTC’s should be given; min/max values would be welcome by researchers in the field. Suggestions for corrections are following:
Line 86: “transformations is”, suggestion “transformations are” Line 137: “in case I.”, suggestion “in case I,” Line 267: “result in higher peak pressure and in smaller contact area”, suggestion “result in a higher pressure and a smaller contact area” Line 270: “decrases”, suggestion “decreases” Line 271: “For a further analysis pressure”, suggestion “For a further analysis, pressure” Line 303: “height 0.4 to 0.9, which is a height”, suggestion “a height of 0.4 to 0.9, which is the height” Line 305: “r_0”, suggestion “r0” Line 335: “P_Δr”, suggestion “PΔr” Line 354: “0.1 mm/μm”, suggestion “0.1 μm/mm”Author Response
Dear Reviewer,
Thank you for your time and your feedback on my paper.
Your reviews highlights that data values must be given in order to improve the paper. Your request is perfectly clear and I understand that any scienticific paper has to describe the methods in such a manner that the described work can be reproduced and verified by the reader. Due to confidentiality issues some of the data is not available for publication. The paper now includes and describes further data and sources that are already published and can be implemented in order to reproduce the described simulation results.
In detail the following data has been requested and is now added in the revised version:
Point 1: Figures 1a, 1b data values for described parameters
Response Point 1: Carbon dependent parameters Ms and k describing the martensite transformation are included.
Point 2: Figure 4a Heat transfer coefficients – (min/max values)
Response Point 2: Explicit values for the HTCs are now added in the figure annotations.
Point 3: Figures 6a Dilatometer curves – transformation parameters
Response Point 3: The relevant parameters to calculate the given dilatometer curves are given in Figure 1. Details about the strain is not given due to confidentiality reasons.
Point 4: Figures 6b Carbon profile data
Response Point 4: Carbon profile data cannot be given due to confidentiality reasons.
Point 5: Figure 7b Temperature data
Response Point 5: Explicit values for the measured temperature curves are now added in the figure annotations.
All other suggestions for corrections have have been adopted and are highlighted in red colour in the manuscript. Please note that due to the insertion of new lines of text in the document, the line numbers have changed.
Line 86: “transformations is”, suggestion “transformations are” Line 137: “in case I.”, suggestion “in case I,” Line 267: “result in higher peak pressure and in smaller contact area”, suggestion “result in a higher pressure and a smaller contact area” Line 270: “decrases”, suggestion “decreases” Line 271: “For a further analysis pressure”, suggestion “For a further analysis, pressure” Line 303: “height 0.4 to 0.9, which is a height”, suggestion “a height of 0.4 to 0.9, which is the height” Line 305: “r_0”, suggestion “r0” Line 335: “P_Δr”, suggestion “PΔr” Line 354: “0.1 mm/μm”, suggestion “0.1 μm/mm”
Best regards,
Hannes Birkhofer (corresponding author)
Author Response File: 
Author Response.pdf
Reviewer 3 Report
The authors made valuable contributions by optimizing mandrel dimensions for a fixture hardening process of high-strength-steel aerospace parts using Finite-Element simulation. The manuscript is recommended to publish with suggested comments, if it could be disclosed by the authors:
In Eqs. (3) and (6), several constants or parameters are used. Can the authors list the values which are used for the simulations? Lines 122 and 123, the authors state that thermo-physical data is partially taken from a dataset for alloy SAE 5120 (20MnCr5, 1.7147) published in [20]. Could the details about the dataset be presented here? HTC is one of most critical parameters in the thermal-mechanical-metallurgical simulation. However, no information about this is disclosed in the paper. Could an indicated range of these values (even for temperature dependent) be given? In Figure 7, only simulated temperature curves are shown. Can the temperature measurements match the simulated results? It would be also desirable that the simulated phase transformation could be presented.Author Response
Please see the attachment.
Author Response File: Author Response.pdf
Round 2
Reviewer 1 Report
Well modified. But if you get approval, figures should be appeared.
