Upgrade of the Universal Testing Machine for the Possibilities of Fatigue Tests in a Limited Mode

Round 1

Reviewer 1 Report

The authors present how a universal testing machine has been upgraded for possible fatigue tests. The reasoning and various possibilities for the update are presented, and then calibration and measurements are shown. The article is relatively well-written and well-structured, and the research has merit. However, the reviewer believes that some improvements must be made before publication:

1.     Although the structure of the manuscript is good, the reviewer suggests to e.g. combine sections 2 and 3. The headings are also very long and could be concentrated. This applies also to Section 7, which could just be called “Test specimens and materials”, and Section 10 and the sub-headings of Section 10.

2.     A short overview of the proposed upgrade could help section 4. It will be easier to follow the remaining paper. You can take inspiration from section 10 where all the upgrades are evaluated.

3.     It is unconventional to have a figure in the introduction, and it is suggested to move Figure 1.

4.     In section 3, many paragraphs start with “The paper [xx], or in [xx]”. This gives little information and feels repetitive. It is suggested to vary the language, but also e.g. include author names, and/or re-writing these parts.

5.     On page 4, it is written “… and a certain solution to the problem, ….” What is the problem discussed here? The problem of paper [4] or the problem in the current study?

6.     The authors vary the spelling of analog / analogue. Just choose one and stick to it. 

The language is overall good.

Author Response

Dear reviewer,

We appreciate the time and effort you have dedicated to providing valuable feedback on our manuscript. We are grateful for your comments and recommendations that improve the professional and formal level of our paper. We have successfully incorporated most of your suggestions. All changes in the revised manuscript, including changes based on other reviews, are highlighted according to the following colour scheme:

Rev#1 - red
Rev#2 - green
Rev#3 - green and cyan
Other changes - pink

Kind regards,

Authors

Response to Reviewer 1 Comments

Changes, additions and modifications according to your comments, warnings and recommendations are indicated in the manuscript and marked with red colour and have been applied in the following way:

1) a) Although the structure of the manuscript is good, the reviewer suggests to e.g. combine sections 2 and 3. b) The headings are also very long and could be concentrated. This applies also to Section 7, which could just be called “Test specimens and materials”, and Section 10 and the sub-headings of Section 10.

Reply/Answer/Solution: a) Section 2 discusses the problem of upgrading older test machines and test methods from a general point of view and perspective. Section 3 is logically separated and provides concrete examples of solutions to this problem in practice. Moreover, section 3 itself is very extensive. Therefore, with your kind permission, we would keep both of these sections in their original structure. b) Unreasonably long and detailed descriptive headings of sections and subsections were shortened according to your proposal and recommendation. The original longer headings (titles) were chosen for the reason that they allow and help the reader to more clearly and unambiguously identify and understand the issue that is discussed in the respective section or subsection.

2) A short overview of the proposed upgrade could help section 4. It will be easier to follow the remaining paper. You can take inspiration from section 10 where all the upgrades are evaluated.

Reply/Answer/Solution: The manuscript of section 4 has been changed according to your suggestion and recommendation.

3) It is unconventional to have a figure in the introduction, and it is suggested to move Figure 1.

Reply/Answer/Solution: We recognize and agree with (your) argument that in the case of Figure 1, a non-standard or less standard, unconventional solution was chosen for its placement in the introduction. However, this figure forms an integral logical part of section 1, very closely related to the corresponding problem and logically supports and illustrates the facts presented here. For it to be moved, it would be necessary to create a new section or logical whole and fundamentally change the structure of the manuscript. Therefore, I would leave this figure in its original place, with your kind permission of course.

4) In section 3, many paragraphs start with “The paper [xx], or in [xx]”. This gives little information and feels repetitive. It is suggested to vary the language, but also e.g. include author names, and/or re-writing these parts.

Reply/Answer/Solution: The manuscript of section 3 has been changed according to your suggestion and recommendation.

5) On page 4, it is written “… and a certain solution to the problem, ….” What is the problem discussed here? The problem of paper [4] or the problem in the current study?

Reply/Answer/Solution: In this case, a problem was discussed, which was presented in the post [4]. In this sense, the manuscript was also changed and clarified.

6) The authors vary the spelling of analog / analogue. Just choose one and stick to it.

Reply/Answer/Solution: The uniform form "analogue" (as standard in British English) was chosen and applied, instead of "analog" as standard in American English. The manuscript has been changed according to your suggestion and recommendation.

Author Response File: Author Response.pdf

Reviewer 2 Report

The Authors in this paper entitled “Upgrade of the Universal Testing Machine for the Possibilities of Fatigue Tests in a Limited Mode” report a detailed description of an upgrade of an old analog-based testing machine designed for tensile testing. For this aim a low-cost and adaptable jig was designed for rotational bending fatigue tests of structural elements, for educational or less demanding commercial applications. 

However, I have some comments reported below that I would recommend the authors to consider carefully:

-Pag. 4, paragraph 3., line 131. What are the multiple customization options? Explain it. 

 - Pag. 6, paragraph 4., line 232. The Author should provide more information about the older HECKERT FPZ 100/1. What is it the maximum frequency to perform a fatigue test? 

-Pag. 8, paragraph 7., lines 327-328. The material characteristic such as yield strength is usually reported as “Sy”. What do you mean with Rm? 

-Pag. 8, paragraph 7, Figure 5. Why did you use two specimens with different shapes for calibration and fatigue tests? Explain it.

- Pag. 10, paragraph 8.1, lines 386-387. I think is better is more correct write “…Maximum pressure of 1 N”.

Minor editing of English language required

Author Response

Dear reviewer,

We appreciate the time and effort you have dedicated to providing valuable feedback on our manuscript. We are grateful for your comments and recommendations that improve the professional and formal level of our paper. We have successfully incorporated most of your suggestions. All changes in the revised manuscript, including changes based on other reviews, are highlighted according to the following colour scheme:

Rev#1 - red
Rev#2 - green
Rev#3 - green and cyan
Other changes - pink

Kind regards,

Authors

Response to Reviewer 2 Comments

Changes, additions and modifications according to your comments, warnings and recommendations have been applied in the following way:

1) Did the author compare the fatigue test with commercial standard testing machine such as Instron? How is the result performing? The reviewer doesn’t see it in this work.

Reply/Answer/Solution: Sorry, we did not have the Instron series testing machine and the fatigue tests performed by it available. Therefore, we could not compare such results with the results obtained by our test machine after its upgrade.

2) What is the limitation of this modified universal testing machine, like the speed limit, and cycle numbers? And what are the potential ways to overcome these limitations?

Reply/Answer/Solution: Due to the obvious moral obsolescence of the FPZ 100 testing machine, the possibilities of its further possible upgrade from a practical and economic point of view are already very ineffective or even impossible. The fundamental obstacles are mainly the basic concept. In the case of FPZ 100/1 device, it is not a pulsator with an electro-hydraulic drive, directly designed for fatigue tests, but a universal testing machine on an electro-mechanical basis. Therefore, it is preferably intended for static tensile or compression tests and thus for obtaining strength and deformation characteristics. The possibilities of the pulsation function as a pulsator, i.e. for cyclic loading, is only supplementary, with limited possibilities. These are mainly related to the possibility of loading either only in tension or only in compression mode, i.e. without the possibility of simultaneous alternating tension and compression loading for an alternately symmetrical or asymmetrical cycle. There are 2 separate working spaces for tension and compression tests. Another limiting factor for the functionality of the pulsator is the loading frequency. This is listed in the datasheet of the device as the so-called switchable frequency, continuously variable up to the maximum value at the level of only 0.1 Hz. The speed of movement of the clamping jaws is given in the range of 0.00035 to 10 mm/s. No information is available on the total possible adjustable number of load cycles. But considering the highest possible switchable frequency of 0.1 Hz, fatigue tests in the order of e.g. 10⁵ cycles and more, i.e. for the area of high-cycle fatigue, they took a disproportionately long time. We are talking about weeks or even months here (per one test specimen). And in addition, the actual adjustable frequencies will be lower. Well, it is precisely these limitations that are difficult or even impossible to overcome without a fundamental redesign of the device. Therefore, we think that with the described upgrade we have already reached the limit of the equipment's capabilities, redesigned for less demanding fatigue tests in the area of rather only low-cycle fatigue.

Changes and additions based on your comments from point 2 are marked in green in section 5 and cyan in subsection 10.4 in the manuscript.

The English has been checked and slightly edited and corrected.

Author Response File: Author Response.pdf

Reviewer 3 Report

This paper presented upgrade of older analog-based universal testing machine, which can be used for the fatigue tests in a limited mode while maintaining low cost. The upgrade of the equipment includes the processes of calibration, creation of related calibration jigs, creation of transformation dependencies and digitization, creation or completion of missing parts of chain signal conditioning modules, A/D converters, special jigs, etc. as elements of the experimental hardware. This work seems very useful in customizing the mechanical testing machine, and the reviewer has just minor comments.

1, Did the author compare the fatigue test with commercial standard testing machine such as Instron? How is the result performing? The reviewer doesn’t see it in this work

2, what is the limitation of this modified universal testing machine, like the speed limit, and cycle numbers? And what are the potential ways to overcome these limitations?

Author Response

Dear reviewer,

We appreciate the time and effort you have dedicated to providing valuable feedback on our manuscript. We are grateful for your comments and recommendations that improve the professional and formal level of our paper. We have successfully incorporated most of your suggestions. All changes in the revised manuscript, including changes based on other reviews, are highlighted according to the following colour scheme:

Rev#1 - red
Rev#2 - green
Rev#3 - green and cyan
Other changes - pink

Kind regards,

Authors

Response to Reviewer 3 Comments

Changes, additions and modifications according to your comments, warnings and recommendations are indicated in the manuscript and marked with green colour and have been applied in the following way:

1) -Pag. 4, paragraph 3., line 131. What are the multiple customization options? Explain it.

Reply/Answer/Solution: The multiple customization options (among others) consist in the ability to choose the method of fatigue loading of the beam in the mode of three-point or four-point bending, with the choice of the level of minimum (compressive) and maximum (tensile) loading force and loading speed. This information has been added to the manuscript.

2) -Pag. 6, paragraph 4., line 232. The Author should provide more information about the older HECKERT FPZ 100/1. What is it the maximum frequency to perform a fatigue test?

Reply/Answer/Solution: The entire section 5 is devoted to the technical description of the FPZ 100/1 device and related information. The relevant reference was inserted in section 4, line 232. Based on your recommendation, information regarding the maximum frequency for performing fatigue tests has been added and inserted to section 5.

3) -Pag. 8, paragraph 7., lines 327-328. The material characteristic such as yield strength is usually reported as “Sy”. What do you mean with Rm?

Reply/Answer/Solution: Symbol R_e stands for yield strength and symbol R_m stands for (ultimate) strength. Such symbols are used in the standards of some countries (Czech Republic, Slovak Republic, ...). They were subsequently changed according to your recommendation - so now in the manuscript: symbol s_y stands for yield strength and symbol s_u stands for ultimate strength, or f_y and f_u according to the Eurocode 3 standard.

4) -Pag. 8, paragraph 7, Figure 5. Why did you use two specimens with different shapes for calibration and fatigue tests? Explain it.

Reply/Answer/Solution: A certain limited time range was available to solve the problem and carry out a large number of time-consuming measurements. The use of test specimens of several shape, size, material modifications and structural states was related precisely to their different physical availability or unavailability during these measurements. This information has been added to the manuscript.

5) -Pag. 10, paragraph 8.1, lines 386-387. I think is better is more correct write “…Maximum pressure of 1 N”.

Reply/Answer/Solution: The text has been changed according to your suggestion and recommendation.

Author Response File: Author Response.pdf

Round 2

Reviewer 1 Report

The authors have taken all the reviewer's comments into account and the manuscript is now ready for publication.