Determination of the Plastic Stress–Strain Relationship of a Rupture Disc Material with Quasi-Static and Dynamic Pneumatic Bulge Processes

Round 1

Reviewer 1 Report

The authors present a very interesting experimental study for industry. A simple but well-conceived experimental campaign is carried out, which allows the linking of two widely used measurement methods in the measurement of stresses with steel discs. The work is considered optimal for publication in the journal.

 

Attached are some minor comments in case they might be helpful:

 

Line 88, correct the sentence: "There are two difficult problems in this work...", I understand that the authors are referring to the challenges or goals posed by the research.

Line 218 indicate the unit of measurement used to define the discs.

It would be useful to describe the characteristics of the steel used in more detail.

Use the same number of significant figures in the results when discussing them.

The bibliography is not in format and several sections of the template have been omitted: authors' contributions, conflicts of interest...

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Reviewer 2 Report

An interesting, well written and comprehensible paper. The aim of the paper is to deliver a method to determine a reliable stress-strain relationship for metallic rupture disc materials in a biaxial stress state. It is explained in the introduction that the stress-strain data from uniaxial tests may not be adequate for numerical simulations.

Major remarks are that the stress determination appears to be inappropriate wihtout further explanations or validation and that the resulting stress-strain relationship is not assessed in comparison with the uniaxial stress-strain relationship of the tested material.

Comments:

Line 132 f: The conclusion is not lcear, why strain at the top can be extrapolated from other locations. Please explain in more detail.

line 145: rather "incompressebility hypothesis"

line 158: guess t should be ti (CURRENT thickness)

line 162: Eq (5) is valid only for an isotropic material. Otherwise different stresses in the different directions would appear.

line 164: "bulge" instead of "bule"

line 169: Eq (6) is also only valid for an isotropic material. Otherwise sig_ei would be unequal to sig_theta and sig_phi.

line 184: Eq (8): Why does time t starts with t0 while pressure P starts with P1? Better align the numbering for ease of understanding.

line 200: How was the sacrificial rupture dics designed before the tests as the tests intend to provide the basis for a relaible design of rupture discs?

line 219: Is this the effective stress at the top of the dome? If so, please mention it. And if so: Is it really appropriate to determine the stress at the top with the radii near the bottom? Fig 3 indicates that the radii along the curvature can vary. In membrane theory, stress is consequently dependend on the radius of curvature, thus it is important to compute the stress at a specific location with the radius at the same location.

line 221: It is mentioned that the measurement is different from the pre-set. But how much? Give numbers. Assess the difference. Is it insignificant?

Figure 11: It was said that the initial thickness of the samples was 0.05 mm. The first recorded thickness in Figure 11 is approx. 0,045 mm. This is already a big drop down. What could be the reason for that?

line 314, line 361: Give a reference to the "Hollomon hardening model" and explain it. Provide a comparison between your result and this model. Otherwise the "good agreement" cannot be assessed.

Figure 12: Provide a comparison between your results and the stress-strain relationship resulting from a uniaxial test. It is important to assess the results from the bulge process and to estimate the mentioned inadequacy of uniaxual test results of this specific material.

 

Author Response

Please see the attachment.

Author Response File: Author Response.docx

Round 2

Reviewer 2 Report

Al ast comment: Line 430: [26] shoul read [23]

Author Response

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Author Response File: Author Response.docx