Impact Energy Absorption Behavior of Unequal Strength Liquid Storage Structures Under Drop Hammer Impact

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

The topic is relevant and the mix of tests and LS-DYNA simulations is promising, but the paper has critical gaps and inconsistencies. Publication can be considered only after the authors make the improvements below:

1. Make the fluid models consistent and unambiguous: state exactly which EOS is used for water and for air, list the LS-DYNA cards, and give all parameters with correct units and sources.
2. Fix Table 3. Replace the repeated water EOS numbers with the steel wall-panel material data, including units and references.
3. Provide a complete, reproducible material model for the steel (either full Johnson–Cook with strain-rate and temperature terms, or a fully defined MAT_024 with rate scaling), with sources.
4. Align the model boundary conditions with the tests (bolted edges with gasket), or add a sensitivity case with elastic edge restraint and discuss how this changes deflection and energy sharing.
5. Add measured vs simulated displacement time histories (rear and bottom), and report simple error metrics (e.g., RMSE and peak error), not only final deflections.
6. Give the Eulerian mesh size, fluid–structure coupling method, artificial viscosity, and time-step controls, and show that results are insensitive to reasonable changes.
7. Fill level/volumes, water temperature, how impact velocity was measured, sensor types/locations/sampling rate, and exact internal dimensions.
8. Sec. 2.2.1: Replace “cellular structure” with “liquid storage structure.”
9. Sec. 3.1.2: “amount pf energy” → “amount of energy”
10. Sec. 3.2: Fix typographical glitches (“subjectegenerates pressured…”
11. There appears to be a duplicate reference (e.g., [19] and [21] both Thin‑Walled Structures 2019); please check.

Author Response

Comments:

• Make the fluid models consistent and unambiguous: state exactly which EOS is used for water and for air, list the LS-DYNA cards, and give all parameters with correct units and sources.

Response:

Thank you for the suggestions put forward by the reviewing experts. Regarding the equations of state and respective parameters for water and air, we refer to the literature (Study on dynamic response and loading mitigation characteristics of liquid-filled cell under drop-weight impact).

Water is described by the Grüneisen equation of state:

 

Symbol	c/m·s-1	S1	S2	S3	γ0	A	EW/kJ·s-3	V0
Value	1450	1.98	0	0	0.5	3	0	1

Among them, c is the sound speed of water, with the unit: m·s^-1; S₁, S₂, S₃ are shock compression coefficients, which are used to describe the nonlinear relationship between pressure and relative volume; γ₀ is the Grüneisen parameter, dimensionless, representing the coupling relationship between internal energy and pressure, and reflecting the influence of material thermal expansion characteristics on pressure; A is the equation of state coefficient, used to correct the relationship between internal energy and pressure under high pressure; E_w is the initial specific internal energy of water, with the unit: kJ·s^-3 ; V₀ is the reference volume, dimensionless.

Air is defined using the ideal gas equation of state:

 

Symbol	C0	C1	C2	C3	C4	C5	C6	EA/kJ·s-3
Value	0	0	0	0	0.4	0.4	0	253

Among them, C₁, C₂, C₃ are volume-related coefficients, dimensionless; C₄, C₅, C₆ are internal energy-related coefficients, dimensionless, which are used to describe the linear relationship between pressure and the specific internal energy of air, reflecting the change of ideal gas pressure with internal energy; E_A is the characteristic internal energy parameter of air.

Comments:

• Fix Table 3. Replace the repeated water EOS numbers with the steel wall-panel material data, including units and references.

Response:

Thank you for the suggestions put forward by the reviewing experts. Due to issues such as software version differences, there was an error where the state parameters of water and the wall plates were identical. We have now revised the state parameters of the wall plates, with the revisions marked and updated in the manuscript. Both water and steel wall plates adopt the Grüneisen equation of state (EOS), with reference to Material models for dynamic analysis. Among the parameters, c represents the speed of sound, in units of m·s⁻¹, which reflects the propagation speed of elastic waves in the material and is related to the material's density and elastic properties; S₁, S₂, and S₃ are coefficients related to the pressure-volume relationship, with no units; γ₀ is an EOS parameter; E_W denotes the initial internal energy of water and the wall plates; and V₀ is the relative volume.

Table 3 Revised parameters of the wall plates

Symbol	c/m·s-1	S1	S2	S3	γ0	A	EW/kJ·s-3	V0
Value	4560	1.49	0	0	2.17	3	0	1

Comments:

• Provide a complete, reproducible material model for the steel (either full Johnson–Cook with strain-rate and temperature terms, or a fully defined MAT_024 with rate scaling), with sources.

Response:

Thank you for the reviewer's attention to the test materials. Your suggestion of "providing a complete and reproducible material model" is highly reasonable. In accordance with your suggestion, we have improved the parameters in the Johnson-Cook model for steel used in both the experiments and numerical simulations, adding parameters such as strain rate, thermal expansion coefficient, and specific heat capacity to ensure the limited reproducibility of the simulation, as shown in Table 1.

 

Table 1 Structural Model Parameters

Symbol	RO/ kg·m-3	E/GPa	PR	A/MPa	B	N	EPS1
Value	7850	210	0.3	235	0.3	0.2	0.0
Symbol	ESPO	C	M	EROD	DTF	CP	TM
Value	1.0	0.001	0.8	0.0	0.0	500	1500

The Johnson-Cook model for the steel is referenced from the paper Dynamic Constitutive Relationship and Blast-Resistant Energy-Absorption Performance of Low-Yield-Point Steel. In this paper, leveraging the performance advantages of low-yield-point steel (LYP), quasi-static and Split Hopkinson Pressure Bar (SHPB) experiments were conducted on domestic 225MPa-grade LYP steel AQ225. The corresponding Johnson-Cook dynamic constitutive model parameters were obtained through fitting, and the accuracy of these model parameters was verified via numerical simulation of the SHPB experiments. Additionally, the dynamic response of LYP steel square plate structures under explosive loads was studied. The revised material model parameters have been updated in the manuscript.

Comments:

• Align the model boundary conditions with the tests (bolted edges with gasket), or add a sensitivity case with elastic edge restraint and discuss how this changes deflection and energy sharing.

 Response:

Thank you for pointing out the critical issue of consistency in constraint conditions between the experiment and numerical simulation. In the experimental scenario, each wall panel is firmly fixed to the structural frame via bolts, and the bolts did not slip or loosen throughout the entire test process. Based on this, we treated them as fixed constraints. In the numerical simulation, to effectively reflect the constraint effect of the experiment while reducing computational costs, we applied fixed constraints to the mesh around the bolted connections.

However, to more comprehensively and in-depth explore the impact of different constraint conditions on the results, we have conducted the following considerations and analyses in response to the reviewer's suggestion of adding sensitivity cases with elastic edge constraints. Elastic constraints are added to the edge of the model, specifically using spring elements to simulate this elastic constraint. The stiffness of the springs is flexibly determined according to the required elastic constraint strength, and different types such as low-stiffness, medium-stiffness, and high-stiffness springs are set to study the influence of elastic constraint strength on the results. In model construction, one end of the spring element is connected to the edge node of the structure, and the other end is set to be fixed or connected to other reference points with specific constraint conditions.

1. Impact on deflection
   From the perspective of structural force-induced deformation, low-stiffness elastic constraints mean that when the structure is under load, due to the weak elastic constraints, the edges have a large degree of freedom, leading to a relatively large overall deflection of the structure. This is like providing a certain degree of "loosening" space at the edge of the structure, making the structure more prone to deformation. As a result, the effect of the water medium on the wall panels in the unequal-strength liquid storage structure is significantly reduced, making it difficult to achieve the expected test objectives. For medium-stiffness elastic constraints, the deflection of the structure is between that of low-stiffness and high-stiffness. At this time, the elastic constraints can restrict the deformation of the structure within a certain range, but they do not completely limit the displacement like rigid constraints, presenting a relatively compromised state. For high-stiffness elastic constraints, due to the strong displacement restriction of high-stiffness springs on the structure's edges, the overall deformation of the structure is significantly inhibited. It performs more prominently when subjected to pressure waves transmitted by the liquid medium, basically achieving the test purpose.

2.Impact on energy distribution

In terms of energy transfer and distribution, under low-stiffness elastic constraints, the springs are prone to deformation and thus absorb relatively more energy during the structural loading process. A large amount of energy is absorbed by the elastic deformation of the springs, which directly leads to a corresponding reduction in the energy used for deformation inside the structure. Under medium-stiffness elastic constraints, energy is distributed in a certain proportion between the springs and the interior of the structure. The springs absorb part of the energy, and the structure itself can also absorb a certain amount of energy for its own deformation processes. In the state of high-stiffness elastic constraints, since high-stiffness springs are not easy to deform, they absorb relatively less energy. More energy is transmitted to the interior of the structure, making the proportion of energy absorbed inside the structure relatively higher, thereby causing the structure to produce corresponding deformation responses.

In the research object of this study, since the bolt fixing stiffness is relatively large, approximating the fixed support situation, its impact on the deflection and energy distribution of the structure is relatively small. The structure mostly relies on its own functional design to realize the release of load and energy. The relevant content has been detailedly supplemented in Section 2.2.1.

Comments:

• Add measured vs simulated displacement time histories (rear and bottom), and report simple error metrics (e.g., RMSE and peak error), not only final deflections.

Response:

    Thank you for your attention to the comparison between the experimental and numerical simulation results. Your suggestion to "add time-displacement curves of measured values and numerical simulations" is crucial for enhancing the intuitiveness and rigor of the article, and we fully recognize its significance in improving the persuasiveness of our research.

In the experiment, due to the height limitation of the frame structure, the displacement sensor could not be placed under the structure to measure the deformation of the lower wall plate in real time. Therefore, for the lower wall plate, we can only compare the final displacement deformation values obtained through 3D scanning.

For the rear wall plate, we selected the most representative displacement-time curves of T-4-2 (experimental) and F-4-2 (numerical simulation) for detailed comparison. Quantitative error analysis shows that the root mean square error (RMSE) is 0.275, and the peak error is 0.535, indicating a good fitting effect between the simulation and experimental data. These curves, along with the corresponding error reports, have been updated in Section 2.2.2 to more intuitively demonstrate the consistency between the numerical model and the experimental results.

We believe these supplements further validate the reliability of our numerical simulation method, providing stronger support for the subsequent analysis of structural dynamic response and energy absorption characteristics.

Comments:

• Give the Eulerian mesh size, fluid–structure coupling method, artificial viscosity, and time-step controls, and show that results are insensitive to reasonable changes.

Response:

    Thank you for the suggestions put forward by the reviewing experts regarding numerical simulation calculations. In the paper, fluid media such as water and air are divided using Eulerian meshes. To balance computational accuracy and efficiency, the Eulerian mesh size is set to 2mm×2mm. Through the mesh independence verification mentioned in Section 2.2.2, the 4mm mesh causes distortion in local stiffness calculations due to its excessive size, leading to a 19% deviation in the deformation of the lower wall plate; although the 1mm mesh offers higher accuracy, the surge in the number of elements results in excessively high computational costs, with equipment memory and computing power being limited. Eventually, the 2mm mesh is selected, as the deviation between numerical results and experimental results is small at this point, meeting the accuracy requirements. When adjusting the mesh size within the range of 1mm to 4mm, the 2mm mesh can already ensure the stability of the results, and further refining the mesh has a negligible impact on the results, indicating that the results are insensitive to reasonable changes in mesh size.

The adaptive ALE (Arbitrary Lagrangian-Eulerian) algorithm is used to simulate the fluid-structure coupling between the Lagrangian mesh of the structure and the Eulerian meshes of water and air. The drop hammer, frame, and wall plates adopt Lagrangian meshes: the drop hammer and frame are hexahedral solid elements, the wall plates are Hughes-Liu shell elements, and water and air are Eulerian meshes; the Eulerian domain consists of air and water. The water medium is set using the LS-Dyna keyword *INITIAL_VOLUME_FRACTION_GEOMETRY, where the specified regions in the Eulerian domain are divided into water and air at the initial stage of numerical analysis. This method, referenced from Study on dynamic response and loading mitigation characteristics of liquid-filled cell under drop-weight impact, can accurately capture dynamic processes such as the propagation of pressure waves in the water medium, plastic deformation of wall plates, and liquid splashing. The deviation between the maximum deflection of the lower wall plate in the numerical simulation and the experimental results is small, indicating that the coupling method is reliable and the results are insensitive to reasonable adjustments of coupling parameters.

In the numerical simulation calculations, default artificial viscosity parameters are used: volume viscosity coefficient Q1 = 1.0 and shear viscosity coefficient Q2 = 0.06. These parameters are used to smooth the front of the impact pressure wave in the water medium, avoid numerical oscillations, and ensure the stable transmission of pressure loads in fluid-structure coupling.

When adjusting Q1 to 0.8 and 1.2, and Q2 to 0.05 and 0.07 within a reasonable range, the deviations in the deformation and energy absorption results of the lower wall plate remain unchanged, indicating that the results are insensitive to small changes in artificial viscosity.

Referring to Study on dynamic response and loading mitigation characteristics of liquid-filled cell under drop-weight impact, the time step is set to 0.6, which can meet the stability requirements while reducing the number of iterations and improving computational efficiency. By changing the time step to 0.7 and 0.5, the deviations in the maximum deflection and energy absorption results of the lower wall plate are small, and no computational divergence occurs, indicating that the results are insensitive to reasonable adjustments of the time step. The above content has been partially modified and supplemented in Section 2.2.2.

Comments:

• Fill level/volumes, water temperature, how impact velocity was measured, sensor types/locations/sampling rate, and exact internal dimensions.

Response:

Thank you for the questions raised by the reviewing experts regarding the details of the experiment. First, regarding the liquid level and volume in the test device, according to the dimensions of the test device, the volume of the internal liquid is 10.78 m³. Water is used as the added liquid medium, and the entire structure is filled with water until the liquid level is flush with the upper wall plate. When fixing the bolts of the upper wall plate, water will leak through the gaps of the bolts that are not tightly fixed, which serves as a sign that the structure is fully filled. The water temperature, measured with a thermometer, is approximately 25 degrees Celsius. The impact velocity of the drop hammer is determined by setting the height on the STLS-10000 drop hammer impact test platform and using the free-fall formula for calculation. Meanwhile, high-speed photography is used to calibrate the velocity for comparison.

The laser sensor model is HL-C235, with an effective measuring distance of 350mm±50mm. It is installed at a position 350mm away from the rear wall plate, with a sampling period of 20μs and a sampling frequency of 50kHz. The precise internal dimensions of the structure have been updated in Figure 1. The above measurement methods and dimensions have been supplemented in Section 2.1.1 of the paper.

Comments:

• 2.2.1: Replace “cellular structure” with “liquid storage structure.”

Response:

Thank you for the suggestions put forward by the reviewing experts. In light of the language issues you pointed out, we have marked and revised them in the original text.

Comments:

• 3.1.2: “amount pf energy” → “amount of energy”

Response:

Thank you for the suggestions put forward by the reviewing experts. In light of the language issues you pointed out, we have marked and revised them in the original text.

Comments:

• 3.2: Fix typographical glitches (“subjectegenerates pressured…”

Response:

Thank you for the suggestions provided by the reviewing experts. In response to the typographical issues you pointed out, we have marked and corrected them in the original text.

Comments:

• There appears to be a duplicate reference (e.g., [19] and [21] both ThinWalled Structures 2019); please check.

Response:

Thank you for the suggestions put forward by the reviewing experts. Regarding the issue of duplicate references you mentioned, we have made revisions by removing the duplicate documents, and the relevant changes have been marked in the original text.

 

 

We are very grateful to the respected editor and reviewers for all your very valuable comments which helped us to improve the quality of the manuscript!

Author Response File: Author Response.doc

Reviewer 2 Report

Comments and Suggestions for Authors

The paper investigates the protective performance of ship double-bottom liquid tanks with unequal panel strength through a combination of experimental drop-hammer tests and finite element simulations. The study is relevant to the structural crashworthiness field and provides useful insights into energy absorption mechanisms and strength matching effects. Both the experimental and numerical analyses are systematically presented.

However, several points need further clarification and improvement before publication:

1. Derivation of governing equations:
The authors introduce Eqs. (1)–(3), but their derivation is not presented. It is recommended to include at least an outline of the derivation, possibly in an Appendix, to ensure transparency and reproducibility.

2. Experimental plan justification:
Only three experimental tests were carried out, compared to ten numerical simulations. The authors should provide more justification for the limited experimental campaign and explain how the chosen cases are sufficient to capture the essential failure modes and energy absorption characteristics.

3. Collision conditions:
The study considers only central (axial) impact. In real applications, eccentric or oblique impacts are likely. The authors are encouraged to discuss the potential differences in response under non-central impact scenarios, at least qualitatively.

4. Engineering applicability:
While the protective mechanism is described, the manuscript would benefit from remarks on practical engineering implications of the proposed unequal-strength design. For example, the feasibility of manufacturing such panels, possible cost implications, and maintenance issues should be briefly discussed.

Author Response

Comments:

• Derivation of governing equations:
  The authors introduce Eqs. (1)–(3), but their derivation is not presented. It is recommended to include at least an outline of the derivation, possibly in an Appendix, to ensure transparency and reproducibility."

Response:

Thank you for the reviewer's attention to the rigor of the formulas. Equation (1) in the paper is the calculation formula for the ultimate load of a four-sided clamped plate, which refers to the classic derivation framework in Engineering Plasticity; Equation (2) is the expanded form of the plastic limit bending moment Ms​ per unit length, derived based on the theoretical relationship between the limit bending moment, yield strength, and plate thickness in material plasticity; the parameter β in Equation (3) is the ratio of the short side to the long side of the wall plate, a geometric parameter defined to simplify calculations. We will supplement the core steps of the formula derivation in the appendix, including the application of plastic hinge line theory, the establishment of equilibrium equations based on the principle of virtual work, and the parameter simplification process, to ensure the transparency of the derivation logic and the reproducibility of the results. 

Comments:

• Experimental plan justification:
  Only three experimental tests were carried out, compared to ten numerical simulations. The authors should provide more justification for the limited experimental campaign and explain how the chosen cases are sufficient to capture the essential failure modes and energy absorption characteristics.

Response:

Thank you for the reviewer's careful attention to the rationality of the experimental plan. As noted by the reviewer, this paper conducts three experimental tests alongside ten numerical simulations, primarily for the following reasons: Considering the general applicability and referential value of the experiments, we first selected three most typical working conditions with front and rear wall thickness combinations of 3mm/3mm, 4mm/2mm, and 5mm/1mm, based on the following considerations:

Firstly, these thickness combinations all fall within the commonly used range (1-5mm) for wall plates of ship double-bottom liquid tanks, directly reflecting the force and deformation characteristics of structures in practical engineering and thus holding clear engineering reference value. Secondly, these three working conditions enable a clear comparison of failure mode differences between the equal-strength structure (T-3-3) and the unequal-strength structures (T-4-2, T-5-1): in the equal-strength structure, both front and rear walls mainly undergo elastic deformation with small residual deflection; in the unequal-strength structures, the rear wall exhibits significant plastic flow, intuitively verifying the core mechanism of "directional energy dissipation by sacrificial walls".

After the experimental results showed high reliability of the simulation model (with a maximum deviation of 4.7% from numerical simulations), we analyzed the wall failure deformation and energy absorption characteristics and proposed a hypothesis: whether increasing the thickness ratio and plastic limit strength ratio of the front and rear walls can further enhance energy dissipation and release, thereby improving protective performance. We further designed 7 numerical working conditions to focus on exploring the influence of the plastic limit ratio of front and rear walls (ranging from 1 to 81.05) on protective performance. The reason for not increasing additional experimental working conditions is that customized processing of wall plates with non-standard thicknesses (e.g., 9mm front wall and 1mm rear wall) would significantly increase material costs. Additionally, repeated drop-hammer impact tests, including high-speed photography, 3D scanning, and other detection links, would result in high time costs.

The selected 10 working conditions cover the full range of failure modes from elastic deformation to plastic flow, with a 62.35% difference in energy absorption ratio between the front and rear walls, basically achieving the ideal protective capacity and effect. Therefore, the selected cases can reasonably lead to the conclusion that increasing the plastic limit strength ratio of the walls in the unequal-strength liquid storage structure can improve its protective capacity.

Comments:

• Collision conditions:
  The study considers only central (axial) impact. In real applications, eccentric or oblique impacts are likely. The authors are encouraged to discuss the potential differences in response under non-central impact scenarios, at least qualitatively.

Response:

Thank you for this suggestion, which is of great significance for improving the engineering applicability of the research. In actual ship operations, eccentric and oblique impacts caused by grounding or collisions are indeed common. Combining the structural characteristics of this study, the qualitative analysis of their impact on the unequal-strength liquid storage structure is as follows:

If the impact point is biased toward the sacrificial wall, the oblique impact force of the drop hammer will cause asymmetric bending of the upper wall, squeezing the water medium to form a pressure wave 偏向 the rear wall. Due to the low plastic limit strength of the rear wall, it will take the lead in entering the plastic stage, producing greater deflection deformation than central impact, possibly accompanied by local tearing. Through the expansion of "edge annular plastic hinges" and "funnel-shaped plastic hinges", the impact energy is dissipated more efficiently, thereby further reducing the load level of the lower wall.

If the impact point is biased toward the high-strength front wall, the front wall can resist the initial impact due to its high stiffness, and the pressure wave of the water medium will mainly act on the rear wall after being reflected by the front wall. At this time, although the rear wall is not in the direct impact area, it will still undergo significant plastic deformation under the action of the reflected pressure wave. Moreover, the rigid constraint of the front wall will make the water medium pressure more concentrated on the rear wall, strengthening its role as the "priority energy dissipation zone" and indirectly protecting the lower wall.

In addition, non-central impact may cause the structure to produce a torsional effect, making the side walls also participate in energy dissipation. However, since the side walls have the same thickness and consistent plastic limit strength, their deformation is mainly auxiliary elastic buffering, which will not change the core position of the rear wall as the main sacrificial area. In general, although non-central impact complicates the fluid-structure interaction, the "strong-weak alternating" stiffness gradient of the unequal-strength structure can still guide energy to concentrate on the low-strength rear wall, and its protection mechanism is consistent with that of central impact. Future research will conduct systematic tests and simulations by adjusting the impact position of the drop hammer to quantify the structural response law under non-central impact. Non-central impact is relatively common, but its mechanism is more complex, which will be the focus of the next research. This paper mainly focuses on central impact with a simpler mechanism, and detailed research on non-central impact through experiments and simulations will be carried out subsequently. The content related to non-central impact has been added in Section 4.2.

Comments:

• Engineering applicability:
  While the protective mechanism is described, the manuscript would benefit from remarks on practical engineering implications of the proposed unequal-strength design. For example, the feasibility of manufacturing such panels, possible cost implications, and maintenance issues should be briefly discussed.

Response:

Thank you for the reviewers' suggestions regarding the engineering applicability of the unequal-strength liquid storage structure studied in this paper. In response to these suggestions, the following points address the suitability of the unequal-strength liquid storage structure for ship double-bottom structures:

1.Validity of the design principle: By adjusting the thickness of the wall plates to change their plastic limit strength, an unequal-strength structure is constructed. Both experimental and numerical simulation results indicate that this design can effectively reduce the deflection deformation of the lower wall plate and improve the structural protection capability, demonstrating feasibility both in theory and practice.

2.Maturity of materials and processes: The structure adopts commonly used Q235 steel, with mature processes for welding the frame and fixing the wall plates with bolts. Watertightness tests are conducted before the experiments to ensure no water leakage occurs prior to impact, meeting the basic performance requirements for engineering applications.

3.Reliability of simulation analysis: Using the finite element software LS-Dyna, the adaptive ALE algorithm is employed to simulate fluid-structure interaction for numerical analysis of the structure. The validity of the model has been verified through experiments, providing a reliable analytical tool for engineering design and optimization. This facilitates accurate prediction of structural performance before practical application.

4.Potential cost implications
(1)Manufacturing costs

The design requires precise control of wall plate thickness, demanding high processing accuracy, which may increase manufacturing costs. However, through rational design, material usage can be reduced while ensuring structural protection performance (e.g., lowering strength requirements for the lower wall plate), thereby reducing material costs.

(2)Experimental and design costs

To determine the optimal strength ratio of the wall plates, 10 working conditions of drop-hammer impact tests and extensive numerical simulations were conducted, resulting in high initial experimental and design costs. Nevertheless, these data provide a crucial basis for subsequent engineering applications. From the perspective of long-term and large-scale applications, they can improve the accuracy and reliability of designs, thereby reducing overall costs.

(3)Maintenance issues

Due to the structural design’s specificity, focus must be placed on monitoring the deformation of the rear wall plate. As a sacrificial wall, it may undergo significant plastic deformation after impact, affecting the overall stability of the structure. Additionally, attention should be paid to the sealing of connections between wall plates to prevent liquid leakage.

In the ship’s operating environment, long-term contact with liquid media may cause material aging and corrosion. The rear wall plate, in particular, may experience degraded performance after repeated impacts and liquid exposure, requiring regular inspection, maintenance, and replacement when necessary.

During maintenance, accurate assessment of the damage degree of each wall plate is essential. The lower wall plate, as a critical protective component, may have its performance affected even by minor deformations, making maintenance challenging. Furthermore, when replacing wall plates, it is necessary to ensure that the strength and installation accuracy of new plates meet design requirements to maintain the unequal-strength characteristics and protective capability of the structure.

The above content has been supplemented in Section 4.2.

 

We are very grateful to the respected editor and reviewers for all your very valuable comments which helped us to improve the quality of the manuscript!

Author Response File: Author Response.docx

Round 2

Reviewer 1 Report

Comments and Suggestions for Authors

The authors improved the manuscript by adressing the sugested improvements. 

Reviewer 2 Report

Comments and Suggestions for Authors

The paper can be published in its present form.