Development of SMA Spring Linear Actuator for an Autonomous Lock and Release Mechanism: Application for the Gravity-Assisted Pointing System in Moon to Earth Alignment of Directional Devices

Round 1

Reviewer 1 Report

This research proposed a shape memory alloy (SMA) lock and release mechanism. It uses the thermo-mechanical effect of the SMA to convert solar energy into mechanical energy for active control while ensuring passivity.

Yes, I think the idea is interesting and the authors have verified the potential feasibility. However, the lack of data analysis makes the article seem incomplete in structure. The authors need to properly perfect the theory on SMAs. This article could be published after correction, and the questions as follow.

1. Page 1: In Abstract, the description of the NGLR experiments can be appropriately reduced and conclusions about the effect of the SMA actuator can be added.

2. Page 5: In line 140, the friction coefficient of 3D-printing materials is not a constant value, it is strongly influenced by the roughness of the printed workpiece surface. Here the authors should cite relevant literature for additional clarification.

3. Page 5: In line 152, I guess F_att = 2.9N instead of 2,9N, which should be an input error.

4. Page 5: For easy reading, the performance parameters of the SMA spring should be summarized in a table in Section 2.2. Include the proportion of alloying elements, phase transition temperature, SMA wire diameter, spring mid diameter and number of turns, Young's modulus of the spring at the austenite phase, or stress at the end of the austenite phase transition.

5. Page 6: For the data in Figure 8, the authors should analyze the displacement-force characteristics and evaluate the effect of the hysteresis.

6. Page 7: Regarding the experimental part of Section 2.3, the authors experimentally investigated the shape memory effect (superelasticity) after the ambient temperature is greater than the end temperature of the austenite phase transformation. However, since the lunar temperature difference is huge and the shape memory effect is affected by the temperature change rate during the heating phase, which ultimately affects the spring output characteristics. So, the effect of the temperature change on the spring should be considered. Experiments should not be limited to fixed temperature conditions, which is echoed in Section 2.5.

7. Page 8: In Section 2.5, the spring emissivity should be considered concerning the internal latent heat of phase change. A discussion on this point can be found in

[1] Kato, H. Latent heat storage capacity of NiTi shape memory alloy. J Mater Sci 56, 8243–8250 (2021). https://doi.org/10.1007/s10853-021-05777-6

[2] Armattoe, K.M.; Bouby, C.; Haboussi, M.; Ben Zineb, T. Modeling of latent heat effects on phase transformation in shape memory alloy thin structures. Int J Solids Struct 2016, 88-89, 283-295, doi:10.1016/j.ijsolstr.2016.02.024.

8. Page 8: Point 5 in the Results section looks more like a follow-up discussion on the development of the SMA actuator, and I would suggest placing it in Chapter 4 (Discussion and Conclusion).

9. Finally, I suggest that the authors could analyze the relationship between the SMA spring displacement and the force from the perspective of martensitic phase transformation. This way, when the actuator structure changes, the required spring size can be quantitatively analyzed based on theory, which will help subsequent researches. This section can be found in the following articles.

 

[1] Savi, M.A.; Pacheco, P.; Garcia, M.S.; Aguiar, R.A.A.; de Souza, L.F.G.; da Hora, R.B. Nonlinear geometric influence on the mechanical behavior of shape memory alloy helical springs. Smart Mater Struct 2015, 24, doi:10.1088/0964-1726/24/3/035012.

 

[2] Ma, J.; Huang, H.; Huang, J. Characteristics Analysis and Testing of SMA Spring Actuator. Adv Mater Sci Eng 2013, 2013, 1-7, doi:10.1155/2013/823594.

 

Comments for author File: Comments.pdf

Author Response

Answer to reviewer 1

 

Dear reviewer, thanks for your valuable remarks and for the possibility to improve the manuscript. In the following a point-to-point reply has been supplied and manuscript changes highlighted.

 

1. Page 1: In Abstract, the description of the NGLR experiments can be appropriately reduced and conclusions about the effect of the SMA actuator can be added.

The abstract has been corrected accordingly to the comments

 

2. Page 5: In line 140, the friction coefficient of 3D-printing materials is not a constant value, it is strongly influenced by the roughness of the printed workpiece surface. Here the authors should cite relevant literature for additional clarification.

A reference and an extracted figure have been added as well as small text modification (lines from 156 to 164)

 

3. Page 5: In line 152, I guess Fatt = 2.9N instead of 2,9N, which should be an input error.

Corrected

 

4. Page 5: For easy reading, the performance parameters of the SMA spring should be summarized in a table in Section 2.2. Include the proportion of alloying elements, phase transition temperature, SMA wire diameter, spring mid diameter and number of turns, Young's modulus of the spring at the austenite phase, or stress at the end of the austenite phase transition.

A table, according to the referee’s suggestions, has been added in Section 2.2.

 

5. Page 6: For the data in Figure 8, the authors should analyze the displacement-force characteristics and evaluate the effect of the hysteresis.

Comments have been implemented in lines 205-211

 

6. Page 7: Regarding the experimental part of Section 2.3, the authors experimentally investigated the shape memory effect (superelasticity) after the ambient temperature is greater than the end temperature of the austenite phase transformation. However, since the lunar temperature difference is huge and the shape memory effect is affected by the temperature change rate during the heating phase, which ultimately affects the spring output characteristics. So, the effect of the temperature change on the spring should be considered. Experiments should not be limited to fixed temperature conditions, which is echoed in Section 2.5.

At the present development stage it is considered the shape memory spring to be self-activated during heating. Should a deepest investigation evidence a lower temperature, a power activated activation system could be added.

 

7. Page 8: In Section 2.5, the spring emissivity should be considered concerning the internal latent heat of phase change. A discussion on this point can be found in [1] Kato, H. Latent heat storage capacity of NiTi shape memory alloy. J Mater Sci 56, 8243–8250 (2021). https://doi.org/10.1007/s10853-021-05777-6 [2] Armattoe, K.M.; Bouby, C.; Haboussi, M.; Ben Zineb, T. Modeling of latent heat effects on phase transformation in shape memory alloy thin structures. Int J Solids Struct 2016, 88-89, 283-295, doi:10.1016/j.ijsolstr.2016.02.024.

Discussion has been considered in line 246-247, and references updated accordingly

 

8. Page 8: Point 5 in the Results section looks more like a follow-up discussion on the development of the SMA actuator, and I would suggest placing it in Chapter 4 (Discussion and Conclusion).

Point 5 has been moved in line 282

 

9. Finally, I suggest that the authors could analyze the relationship between the SMA spring displacement and the force from the perspective of martensitic phase transformation. This way, when the actuator structure changes, the required spring size can be quantitatively analyzed based on theory, which will help subsequent researches. This section can be found in the following articles. [1] Savi, M.A.; Pacheco, P.; Garcia, M.S.; Aguiar, R.A.A.; de Souza, L.F.G.; da Hora, R.B. Nonlinear geometric influence on the mechanical behavior of shape memory alloy helical springs. Smart Mater Struct 2015, 24, doi:10.1088/0964-1726/24/3/035012. [2] Ma, J.; Huang, H.; Huang, J. Characteristics Analysis and Testing of SMA Spring Actuator. Adv Mater Sci Eng 2013, 2013, 1-7, doi:10.1155/2013/823594.

Comments have been implemented in line 173-181 and references updated accordingly

 

I hope this answer satisfying your comments.

Should you need further clarifications please do not hesitate to ask.

Best regards.

 

Giovanni Delle Monache

Reviewer 2 Report

1 The authors should tell more about the design of the SMA spring. 

2 The authors should give the composition of the SMA material. Moreover, the phase transformation temperatures, recoverable strain, actuation stress should be introduced.

3 The pin needs to resist the dynamic load environment of the launch and landing phases. So, detailed analysis should be carried out to determine the force that the SMA actuator needs to generate.

4 The pin and the other structures should be made from metals in the future. So, isolation of the SMA spring should be considerate in the EM model.

5 The stiffness of the steel spring looks very weak, which may result in a low 1st model frequency, probably within 50Hz.  How to solve the problem of resonance during the launch stage?

Author Response

Dear reviewer, thanks for your valuable remarks and for the possibility to improve the manuscript. In the following a point-to-point reply has been supplied and manuscript changes highlighted.

 

1. The authors should tell more about the design of the SMA spring. 

The actuator is a Breadbord so in this proof-of-concept stage a try and error approach has been adopted, leading to the definition of an appropriate working springon the second attempt. Nonetheless an analytical method has been mentioned in the paper as consequence of reviewer comments in line 173-181 and references updated accordingly

2. The authors should give the composition of the SMA material. Moreover, the phase transformation temperatures, recoverable strain, actuation stress should be introduced.

Composition, activation temperature and recoverable strain have been added in Table 1

3. The pin needs to resist the dynamic load environment of the launch and landing phases. So, detailed analysis should be carried out to determine the force that the SMA actuator needs to generate.

This is correct. At present the dynamic load environment has not yet been defined, so the analysis will be postponed

4. The pin and the other structures should be made from metals in the future. So, isolation of the SMA spring should be considerate in the EM model.

Comments have been implemented in lines 265-266

5. The stiffness of the steel spring looks very weak, which may result in a low 1st model frequency, probably within 50Hz.  How to solve the problem of resonance during the launch stage?

This is an important comment. Towards the development of the EM, the layout will be modified by considering a compression spring (instead of a traction one), whose buckling will be prevented by coaxially mounting it around the pin itself.

 

I hope this answer satisfies your comments.

Should you need further clarifications please do not hesitate to ask.

Best regards.

 

Reviewer 3 Report

This paper proposed a lock and release mechanism using SMA spring linear actuator. The mechanism is used for The Next Generation Lunar Reflector experiment, so the SMA actuator only needs to actuate once. The paper provides very interesting data. However, I think that there are a few improvements that should be made before publication. I have the following comments and questions.

You mistake that the paragraph numbers of paper. 2.2 SMA spring… is wrong, 2.3 SMA spring… is correct. 

You explain SMA actuator releasing scheme as shown in Fig.5. I do not understand that when should the actuator be operated. 

On line 189, you indicate the maximum force of SMA spring is about 13N, and it represents a SF greater than 4. I was wondering that it's a wrong. Because the SF should be calculated based on the force at the length of the actuator at the end of its movement.

I think that the paper has shortages of the information about EBB model test. Where did you heat the SMA actuator with a heat gun? What are the specifications of the heat gun. (how many degrees of hot air?) In this test, I would like you to clarify the driving conditions of the SMA actuator. (how many millimeters should you move it?)

On the Chapter 3. Results, the pulling force needed to remove the sealing pin of Fig.4 has been measured and correlated with the analytical calculation. I did not find the correlation with the analytical calculation. Please let us know more detail about it.

Finally, if you are assuming that the SMA spring actuator is activated by the radiation of the solar or lunar regolith, you should provide evidence that it can be moved by it. I don't know why SMA, which transforms at 65 degree, would be sufficient.

Author Response

Dear reviewer, thanks for your valuable remarks and for the possibility to improve the manuscript. In the following a point-to-point reply has been supplied and manuscript changes highlighted.

 

• You mistake that the paragraph numbers of paper. 2.2 SMA spring… is wrong, 2.3 SMA spring… is correct. 

Paragraph numbers have been changed.

• You explain SMA actuator releasing scheme as shown in Fig.5. I do not understand that when should the actuator be operated. 

The complete release scheme is detailed in Fig. 2 (structural resistance of the CCR package), Fig. 3 (detail of the actuator) and Fig. 4 (cross section view).

 

• On line 189, you indicate the maximum force of SMA spring is about 13N, and it represents a SF greater than 4. I was wondering that it's a wrong. Because the SF should be calculated based on the force at the length of the actuator at the end of its movement.

Comment has been implemented in lines 221 227

• I think that the paper has shortages of the information about EBB model test. Where did you heat the SMA actuator with a heat gun? What are the specifications of the heat gun. (how many degrees of hot air?) In this test, I would like you to clarify the driving conditions of the SMA actuator. (how many millimeters should you move it?)

Comment has been implemented in lines 232 233 and 237-238

• On the Chapter 3. Results, the pulling force needed to remove the sealing pin of Fig.4 has been measured and correlated with the analytical calculation. I did not find the correlation with the analytical calculation. Please let us know more detail about it.

The correlation statement has been removed. It is a trivial calculation but we are not organized to produce an explication drawing shortly, and does not add much to the paper

• Finally, if you are assuming that the SMA spring actuator is activated by the radiation of the solar or lunar regolith, you should provide evidence that it can be moved by it. I don't know why SMA, which transforms at 65 degree, would be sufficient.

At the present development stage it is considered the shape memory spring to be self-activated during heating. Should a deepest investigation evidence a lower temperature, a power activated activation system could be added.

I hope this answer satisfies your comments.

Should you need further clarifications please do not hesitate to ask.

Best regards.

Giovanni Delle Monache

Round 2

Reviewer 2 Report

G（T）is the shear moulus of SMA, the author should give the values of G under different temperatures.

Author Response

Dear reviewer, thanks for your valuable remarks and for the possibility to improve the manuscript. 

With reference to your last comment please refer to integration in the manuscript in lines 178-179 and table 2.

Best regards.

Giovanni Delle Monache

Reviewer 3 Report

The manuscript has been improved and is in a nice condition now.

Author Response

Dear reviewer, thanks for your valuable remarks and for the possibility to improve the manuscript. 

I hope I understand correctly in assuming that you do not ask for additional modifications to the manuscript.

Best regards.

Giovanni Delle Monache