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12 pages, 3138 KiB

Open AccessArticle

Effect of Residual Stress on the Ultimate Bearing Capacity of Titanium Alloy Pressure Spherical–Cylindrical-Combined Shells

by Yuxuan Wang, Jianting Guo, Bowen Zhang, Keke Ge, Liangbi Li and Feng Lv

Metals 2024, 14(1), 123; https://doi.org/10.3390/met14010123 - 20 Jan 2024

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Abstract

Titanium alloy pressure spherical–cylindrical shells enable the effective utilization of the strength of spherical and cylindrical pressure-resistant shell components. In this study, a numerical simulation of the residual stress of a titanium alloy butt-welding plate was conducted by employing sequential coupling and a [...] Read more.

Titanium alloy pressure spherical–cylindrical shells enable the effective utilization of the strength of spherical and cylindrical pressure-resistant shell components. In this study, a numerical simulation of the residual stress of a titanium alloy butt-welding plate was conducted by employing sequential coupling and a temperature heat source model. The results of welding residual stress analysis agreed well with the experimental results reported in the literature. Subsequently, the welding residual stress of a titanium alloy pressure spherical–cylindrical shell was calculated and analyzed using the same method. Finally, the influence of residual stress on the ultimate bearing capacity of the shell was assessed. On the inner surface of the shell, the horizontal welding residual tensile stress, perpendicular to the weld path, exhibited a bimodal distribution. The longitudinal welding residual tensile stresses were higher than the horizontal welding residual stress. Near the weld on the outer shell surface, higher longitudinal welding residual tensile stresses existed, whereas the horizontal welding residual stress was compressive. Both the inner and outer shell surfaces exhibited significant longitudinal residual tensile stresses along the weld path, though residual compressive stresses existed on both surfaces. The influence of welding residual stress on the ultimate load-bearing capacity of the shell was minimal. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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13 pages, 20976 KiB

Open AccessFeature PaperArticle

Effects of Different Fouling Organisms on Corrosion Behavior of Carbon Steel in Dalian Seawater

by Wanbin Chen, Yihan Wang, Mingyu Wang, Yi Huang and Yunze Xu

Metals 2023, 13(9), 1503; https://doi.org/10.3390/met13091503 - 22 Aug 2023

Cited by 2 | Viewed by 920

Abstract

Carbon steels are widely used in ocean engineering due to their cost effectiveness, ease of manufacture, and excellent weldability. However, the attachment of macro-fouling organisms in seawater poses a serious threat to the integrity of carbon steel structures. In this experiment, carbon steel [...] Read more.

Carbon steels are widely used in ocean engineering due to their cost effectiveness, ease of manufacture, and excellent weldability. However, the attachment of macro-fouling organisms in seawater poses a serious threat to the integrity of carbon steel structures. In this experiment, carbon steel plates were immersed in the Dalian Sea area from January to October to investigate the effects of macro-fouling on corrosion propagation. The electrochemical measurement indicated that the propensity for the corrosion of Q235B is ranked as ascidians > mussels > barnacles. The characterization results indicated that various marine organisms significantly influenced the corrosion behavior of Q235B carbon steel immersed in natural seawater. The colonization of barnacles inhibited corrosion at the barnacle central area, and the presence of barnacle covering caused crevice corrosion at the edges of the barnacle due to oxygen concentration cells. The presence of ascidians resulted in general corrosion due to the locally high conductivity and ion diffusion rate. A relatively compact rust layer, which exhibited localized defects, was observed beneath the mussels. Seawater had the ability to penetrate the rust layer through these defects, leading to the formation of pitting corrosion on the metal substrate. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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23 pages, 11244 KiB

Open AccessArticle

Internal Hydroforming of Large Stainless-Steel Eggshells from Stepped Preforms

by Yinhui Tang, Jian Zhang, Ming Zhan, Huifeng Jiao, Peng Cheng and Mingqiang Dai

Metals 2023, 13(8), 1352; https://doi.org/10.3390/met13081352 - 27 Jul 2023

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Abstract

The internal hydroforming of large stainless-steel eggshells from a stepped preform is investigated in this paper. The nominal major and minor axes of the eggshell were 1537 and 1070 mm, respectively. The stepped preform was fabricated from thin-walled (1.9 mm thick) stainless-steel sheets [...] Read more.

The internal hydroforming of large stainless-steel eggshells from a stepped preform is investigated in this paper. The nominal major and minor axes of the eggshell were 1537 and 1070 mm, respectively. The stepped preform was fabricated from thin-walled (1.9 mm thick) stainless-steel sheets and comprised twelve conical segments inscribed inside the target eggshell. The preform was then hydroformed, and its wall thickness and shape were measured. The yield load distribution and material hardening of the hydroforming process were investigated analytically. Nonlinear finite-element analyses were employed to further investigate hydroforming behaviors and the effect of weld lines on hydroforming. The experimental, numerical, and analytical results were consistent. The results confirm that, during the hydroforming process, considerable springback occurs for large eggshells, which greatly affects forming precision. However, this effect can be reduced by accounting for the strengthening effect of weld lines. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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16 pages, 6141 KiB

Open AccessArticle

Buckling Analysis of Conical Shell Openings with Reinforced Perimeter Walls under Uniform External Pressure

by Lin Yue, Hongzhang Pan, Yongmei Zhu, Tianyi Sun and Jian Zhang

Metals 2023, 13(5), 824; https://doi.org/10.3390/met13050824 - 23 Apr 2023

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Abstract

In this paper, the effects of opening parameters and reinforcing wall parameters on the bearing capacity of conical shells with an opening were investigated. Under the condition that the conical shells with an opening were all reinforced with walls, the opening position and [...] Read more.

In this paper, the effects of opening parameters and reinforcing wall parameters on the bearing capacity of conical shells with an opening were investigated. Under the condition that the conical shells with an opening were all reinforced with walls, the opening position and the inclination angle of the reinforced wall were selected as variables to be used in the numerical analysis and hydrostatic pressure test. The nonlinear numerical buckling load and the test results were compared. The difference was within 17.8%, which verified the rationality of the finite element model. The final buckling mode obtained by numerical calculation of the measured data was in good agreement with the real collapse mode obtained by hydraulic testing of the actual model. Then the influence of the opening position and inclination angle of the reinforcing wall on the buckling load of the conical shell under different opening rates was analyzed in detail. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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25 pages, 23750 KiB

Open AccessArticle

Buckling of Bisegment Pressure Hulls Fabricated through Free Bulging

by Yun Teng, Jian Zhang and Feng Wang

Metals 2023, 13(3), 576; https://doi.org/10.3390/met13030576 - 13 Mar 2023

Viewed by 1136

Abstract

This study explored the buckling performance of bi-segment pressure hulls under external pressure. We fabricated bi-segment pressure hulls from bi-segment cylindrical preforms by using free bulging. The cylindrical preforms had a nominal thickness of 0.95 mm, nominal radius of 51 mm, and nominal [...] Read more.

This study explored the buckling performance of bi-segment pressure hulls under external pressure. We fabricated bi-segment pressure hulls from bi-segment cylindrical preforms by using free bulging. The cylindrical preforms had a nominal thickness of 0.95 mm, nominal radius of 51 mm, and nominal height of 242 mm. Six bi-segment pressure hulls were hydrostatically and externally pressurised into buckling. Experimental results revealed that the maximum buckling load of the bi-segment pressure hulls was increased by 36.75% compared with that of the bi-segment cylinders. In addition, we performed a nonlinear finite element analysis to determine the bulging and buckling modes of the hulls. We noted that the nonlinear analysis results exhibited good agreement with the experimental data. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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18 pages, 6801 KiB

Open AccessArticle

Uncertainty Analysis of Ultimate Strength for Spherical Shells Subjected to External Pressure

by Ming Zhan, Chao Ding, Jian Zhang, Lingtong Zheng and Lihui Wang

Metals 2023, 13(3), 529; https://doi.org/10.3390/met13030529 - 6 Mar 2023

Viewed by 1111

Abstract

To evaluate the stochastic characteristics of ultimate strength for spherical shells subjected to external pressure, uncertainty analysis is conducted in this study. Experimental measurements and result analysis of dimensions, as well as ultimate strength, are performed. The basic theories of the surrogate model [...] Read more.

To evaluate the stochastic characteristics of ultimate strength for spherical shells subjected to external pressure, uncertainty analysis is conducted in this study. Experimental measurements and result analysis of dimensions, as well as ultimate strength, are performed. The basic theories of the surrogate model and probability-box method for ultimate strength are introduced briefly. Uncertainty analysis of ultimate strength is completed utilizing double-nested random sampling based on the established Gaussian process model with high precision, and the results are compared with the experimental findings. The results show that the experimental empirical cumulative distribution function is contained in the probability-box obtained while considering the influence of welding, and the absolute errors of the mean value, as well as those of the standard deviation, are much smaller. The study verified that the influence of welding cannot be ignored, and the prediction of ultimate strength, considering uncertainties, can eliminate the occasionalities of simulations and experimental tests. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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21 pages, 74409 KiB

Open AccessArticle

Numerical and Experimental Buckling and Post-Buckling Analyses of Sphere-Segmented Toroidal Shell Subject to External Pressure

by Chenyang Di, Jian Zhang, Fang Wang and Yu Zhang

Metals 2023, 13(1), 64; https://doi.org/10.3390/met13010064 - 26 Dec 2022

Viewed by 1192

Abstract

This study determined the buckling characteristics of sphere-segmented toroidal shells subjected to external pressure. The proposed toroidal vessel comprises six spheres and six rings. Two laboratory models with the same nominal dimensions were manufactured, measured, tested, and evaluated. To investigate whether sphere-segmented toroidal [...] Read more.

This study determined the buckling characteristics of sphere-segmented toroidal shells subjected to external pressure. The proposed toroidal vessel comprises six spheres and six rings. Two laboratory models with the same nominal dimensions were manufactured, measured, tested, and evaluated. To investigate whether sphere-segmented toroidal shells are imperfection-sensitive structures with closely spaced eigenvalues, the subspace algorithm was applied to evaluate the first 50 eigenmodes, and the modified Riks algorithm was used to obtain post-buckling characteristics. The results indicated that the deviation between the results of the experimental and numerical analyses was within a reasonable range. The proposed sphere-segmented toroidal shells were highly imperfection-sensitive structures with closely spaced eigenvalues. Subsequently, imperfection sensitivity analysis confirmed this conclusion. In numerical analyses, the first eigenmode could be considered as the worst eigenmode of sphere-segmented toroidal shells. The trend of the equilibrium path of sphere-segmented toroidal shells was consistent with spherical shells, revealing instability. In addition, ellipticity and completeness exerted a negligible effect on the buckling load of sphere-segmented toroidal shells. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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12 pages, 2597 KiB

Open AccessArticle

Mutual Interactions of Lamb Waves in Nonlinear Elastic Plates

by Shuyi Ma, Guixian Zhang, Hongfeng Hou and Lidong Wang

Metals 2022, 12(12), 2175; https://doi.org/10.3390/met12122175 - 16 Dec 2022

Viewed by 1002

Abstract

The mutual interactions of Lamb waves in nonlinear elastic plates are studied in this article. Many researchers have investigated the interactions of Lamb wave modes at nonlinear higher harmonics. However, little is known about nonlinearity-driven Lamb modulations from two primary modes with different [...] Read more.

The mutual interactions of Lamb waves in nonlinear elastic plates are studied in this article. Many researchers have investigated the interactions of Lamb wave modes at nonlinear higher harmonics. However, little is known about nonlinearity-driven Lamb modulations from two primary modes with different frequencies. In this study, the existence of symmetric or antisymmetric mode due to Lamb wave mutual interactions is firstly theoretically formulated. Then, an approach is proposed to evaluate the intensity of phase velocity matching for selecting primary modes. Finally, the characteristics of the modulated wave generation are investigated and demonstrated. The generation of modulated waves in an aluminum plate and fatigue crack can be detected by mutual interactions of Lamb waves. The main contribution of this work is the proposed mutual interaction theory of Lamb waves in fatigue plates, which can guide fatigue detection in the metal plate. Full article

(This article belongs to the Special Issue Mechanical Failure and Metal Degradation of Ships and Marine Structures (Volume II))

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