The Experimental and FEM Studies of Friction Welding Process of Tungsten Heavy Alloy with Aluminium Alloy

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

In the manuscript, "The Experimental and FEM Studies of Friction Welding Process of Tungsten Heavy Alloy with Aluminum Alloy," authored by Radosław Winiczenko et al., the authors delve into the investigation of the CDFW (Continuous Drive Friction Welding) process involving Tungsten Heavy Alloy (THA) and aluminum alloy. Their approach combines FEM (Finite Element Method) simulations with experimental data to shed light on this process. The results presented in the manuscript are comprehensive and free from fundamental errors. However, the paper leans more towards resembling an experimental report rather than a research paper. To enhance the overall quality of the manuscript, I suggest several recommendations:

1.     Introduction: The introduction section could benefit from a discussion on why CDFW of a composite alloy with aluminum alloy holds significance. It would be valuable to explain the rationale for choosing these specific materials for the experiment and why two identical alloys were not considered.

2.     Line 111-113: The authors mention the availability and testing of both 2D and 3D simulations but ultimately opt for the 2.5D approach. It would be helpful if the authors could briefly explain why they selected the 2.5D simulation over the 2D and 3D methods, highlighting its advantages.

3.     Figure 3: In the caption for Figure 3, please add a label 'b' to indicate the relevant figure, and provide a brief explanation of the symbol 'epsilon' used in the figure.

4.     Line 162-163: The manuscript mentions "16.8 mm shortening," but this data point does not appear in Figure 6. Please rectify this inconsistency.

5.     Figure 9: Figure 9 seems to lack data for a 0 mm measurement. It would be beneficial to address this issue and clarify the reason behind the absence of this data point in the figure.

Incorporating these recommendations will not only enhance the manuscript's quality but also contribute to a more comprehensive and informative research paper. Some revisions are necessary before acceptance.

 

 

Author Response

Comment 1

Introduction: The introduction section could benefit from a discussion on why CDFW of a composite alloy with aluminum alloy holds significance. It would be valuable to explain the rationale for choosing these specific materials for the experiment and why two identical alloys were not considered.

We agree with your comment. The text has been extended. Recently, the tungsten heavy alloy projectile cores have been used as kinetic energy penetrators (KEPs) for sub-calibre bullets. These THA cores can be joined to a ballistic cap made of an aluminium alloy. This cap protects the projectile against ricochets when it hits the armour plate. These materials are often joined by threads, which require milling. This is problematic because tungsten is difficult to cut due to its relatively high hardness and strength. Therefore, the authors in papers [23, 24] have proposed the friction welding method for joining these materials. Friction welding is an effective solid-state joining method for various materials. The text has been added on p.2, l.65-72.

Comment 2

Line 111-113: The authors mention the availability and testing of both 2D and 3D simulations but ultimately opt for the 2.5D approach. It would be helpful if the authors could briefly explain why they selected the 2.5D simulation over the 2D and 3D methods, highlighting its advantages.

Thank you for this comment. A 2.5D model includes all the circumferential velocities to account for the torsional friction during welding. In the 2D axial-symmetric approach the Deform code is not able to simulate a rotational speed, the related shear deformation cannot be computed. The computed time for a 3D full simulation is very long. In this paper, the torsional friction model has a significant impact not only on heat generation but also on the deformation of the specimen as noticed in the paper [33]. This reason has been explained on p.4, l.122-127.

Comment 3

In the caption for Figure 3, please add a label 'b' to indicate the relevant figure, and provide a brief explanation of the symbol 'epsilon' used in the figure.

We agree with your comment. A label ‘b’ has been added. Figure 3 has been improved. The text has been corrected.(see p.5, l.153-156, line.167).

 Comment 4

Line 162-163: The manuscript mentions "16.8 mm shortening," but this data point does not appear in Figure 6. Please rectify this inconsistency.

Thank you for this comment. It should be ‘Figure 5’. It has been corrected. (see p.7, l.197)

Comment 5

Figure 9: Figure 9 seems to lack data for a 0 mm measurement. It would be beneficial to address this issue and clarify the reason behind the absence of this data point in the figure.

 We agree with your comment. Initially, the thermocouples were positioned close to the weld interface but they were consumed during the forging phase of the welding process. Due to the continuous ‘upset’ (axial shortening) of the specimens during welding, it is naturally difficult to place thermocouples that can record exact temperatures. Consequently, the first thermocouple was located about 20 mm away from the weld interface. This text has been added on p.8, l.224-230.

Reviewer 2 Report

Comments and Suggestions for Authors

The comments are attached herewith. It needs a major revision. The work is good and the authors have shown good results.

Comments for author File: Comments.pdf

Comments on the Quality of English Language

Author Response

Comment 1

How the friction coefficient was determined? What were the assumptions? Since there are two different materials, the friction coefficient will play a huge role. 

When the temperature is low the friction stress is calculated using the Coulomb friction law, when the temperature is high, the shear friction law is adopted. In the study, to determine an appropriate friction coefficient, preliminary simulations were carried out. It was found that using a shear friction of 0.175 gave the best results given temperatures. The text has been added on p.4, l.131-143, p.5, l.144-146.

Comment 2

Fig. 3 needs more technical discussion. Maintain a consistency in the data. Show two graphs with different strain rates and temperature (means flow stress behaviour) of these two alloys.

Thank you for this comment. These graphs (Fig.3) with different strain rates and temperatures for two alloys have been added. Additionally, the text has been modified on p.5, l.153-156, line.167.

Comment 3

Is there any evidence that the material database provided by Deform well matches with the values provided by other software such as JMaTPro?.

 

The Deform materials database is often used by researchers for FEM modelling. The Deform database corresponds to data from highly valued scientific publications.

 Comment 4

Mention the type of elements - brick, solid, shell?.

Thank you for this comment. The solid element has been considered. The text has been added.

Comment 5

How the friction coefficient was determined? What friction criteria was taken?

 We agree with your comment. In the study, to determine an appropriate friction coefficient, preliminary simulations were carried out. It was found that using a shear friction of 0.175 gave the best results given temperatures. This text has been added.(see p.4, l.131-143, p.5, l.144-146).

Comment 6

How it was ensured that the thermocouples were well embedded in the samples?

 Thanks for this comment. The thermocouple wires were stuck at the measuring specimen surfaces with high-temperature resistant glue. It has been explained on p.8, l.228-230.

 Comment 7

If these data have been taken then it is not correct to say modelled!

We agree with your comment. The word ‘modelled’ has been removed. (see p.5, l.153-154).

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

The authors have addressed all the comments.

Author Response

Reviewer #2:

Comment

Figure 3 - The strain rates presented in subfigures 3a and 3b are quite different. The authors should check these values. Besides this, the strain rate units are only displayed in subfigure 3b.

Thank you for this comment. The strain rate units in Fig.3a have been added (see. Fig.3a). To model the friction welding process, we used data available in the literature (for different strain rates) for various materials.