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1
Content available Guided waves in ship structural health monitoring – a feasibility study
Roch Emil, Zima Beata, Woloszyk Krzysztof, Garbatov Yordan
Polish Maritime Research
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2023
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nr 2
76--84
EN
Ships and offshore structures operate in a severe corrosion degradation environment and face difficulty in providing longlasting corrosion protection. The Classification Societies recommend regular thickness measurements leading to structural component replacements, to ensure structural integrity during service life. The measurements are usually performed using ultrasonic thickness gauges and such an approach requires multiple measurements of the corroded structural components. Otherwise, the collected data are insufficient to precisely assess the corrosion degradation level. This study aims to perform numerical and experimental analyses to verify the use of guided ultrasonic waves in defining the corrosion degradation level of the corroded structural components of a ship. The study incorporates the fundamental antisymmetric Lamb mode, excited by piezoelectric transducers attached at the pre-selected points on stiffened panels, representing typical structural ship components. The specimens are exposed to accelerated marine corrosion degradation, the influence of the degree of degradation on the wave time of flight being analysed. The study indicates that guided waves are a promising approach for diagnosing corroded structural components. The signals characterised by a high signal-to-noise ratio have been captured, even for relatively long distances between the transducers. This proves that the proposed approach can be suitable for monitoring more extensive areas of ship structures by employing a single measurement.
2
Content available Ultimate compressive strength assessment of uncleaned and cleaned corroded plates with locked crack
Woloszyk Krzysztof, Garbatov Yordan
Polish Maritime Research
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2021
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nr 3
117--127
EN
The work presented here investigates the structural response of cleaned corroded plates, subjected to compressive load in the presence of a locked crack, where the change of mechanical properties as a result of corrosion development and the cleaning process is also accounted for. A Finite Element model for assessing the compressive strength, considering geometric and material nonlinearities, is developed, and the analysed plates are compared with the available experimental data. An experimental design plan is generated using the Design of Experiments techniques, which quantifies the influence of the governing variables and their interactions with respect to the plate’s ultimate compressive strength. With a limited number of observations, the most significant effects are identified. The corrosion degradation is revealed to be the most crucial effect leading to an effective strength reduction. It was found that, in the case of a corroded plate with a locked crack subjected to a compressive load, the most severe case is when the crack is transversely oriented. The strength reduction is slightly lower than when the corrosion degradation and the presence of a crack are considered to be a simple summation of these two effects but acting separately. The outcome of the analysis is the development of several empirical formulations that allow a fast estimation of the ultimate strength of a corroded plate, subjected to compressive load in the presence of a locked crack, accounting for different cleaning.
3
Content available Experimental and numerical investigations of ultimate strength of imperfect stiffened plates of different slenderness
Woloszyk Krzysztof, Garbatov Yordan, Kowalski Jakub, Samson Leszek
Polish Maritime Research
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2020
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nr 4
120--129
EN
The objective of this study is to analyse the behaviour of compressed stiffened plates of different slenderness using experimental and numerical methods. The presented results are part of a long-term project to investigate the ultimate strength of geometrically imperfect structures subjected to different degradation phenomena, including corrosion degradation and locked cracks. Several specimens were subjected to a uniaxial compressive force, and the most important quantities related to the structural behaviour were captured and analysed. A finite element model, accounting for material and geometrical nonlinearities and initial geometrical imperfections, was developed using the commercial software ANSYS. The residual welding-induced stresses were measured in the middle cross-section for two specimens. The initial imperfection was identified by employing a close-range photogrammetry approach. It was concluded that the numerical analyses, based on the finite element model, predict the ultimate strength of stiffened plates accurately, although some deviations were also observed. The detailed analysis with the indication of possible uncertainty is presented, and several conclusions are derived.
4
Content available Analysis of ultimate compressive strength of cracked plates with the use of doe techniques
Woloszyk Krzysztof, Garbatov Yordan
Polish Maritime Research
|
2020
|
nr 3
109--120
EN
The objective of this work is to investigate the structural compressive response of plates with locked cracks accounting for all relevant factors and correlation between them. The nonlinear FE model considering both geometric and material nonlinearities is employed herein, and the FE model of the structural response of intact plates is validated with the available experimental data. In the common studies, based on One Factor at a Time analysis, some of the parameters and interactions between them are excluded. In the present study, the numerical investigations are conducted with the use of the Design of Experiments techniques, where all essential parameters and their interactions are adequately considered. With a total of 32 numerical analyses, the most influential factors and their interactions are identified. As a study outcome, empirical formulations, which allow for a fast estimation of the ultimate compressive strength of intact plates, plates with locked cracks, and repaired cracked plates, are derived. The developed formulations represent a fast and practical tool for estimating the ultimate compressive strength of intact, cracked, and repaired plates, which can be easily employed in the reliability analysis.results followed by their discussion.
5
Content available Structural reliability assessment of corroded tanker ship based on experimentally estimated ultimate strength
Woloszyk Krzysztof, Garbatov Yordan
Polish Maritime Research
|
2019
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nr 2
47--54
EN
This work deals with the reliability assessment of a tanker ship hull structure subjected to a vertical bending moment and corrosion degradation. The progressive collapse and ultimate load carrying capacity are estimated based on experimentally tested scaled box-shaped-specimens. The translation of the strength estimate of the scaled specimen to the real tanker ship hull structure is performed based on the dimensional theory developing a step-wise linear stressstrain relationship. The load-carrying capacity is considered as a stochastic variable, and the uncertainties resulted from the scaled-specimen to the real-structure strength translation, and the subjected load of the real ship are also accounted for. A sensitivity analysis concerning the stochastic variables, included in the ultimate limit state function is performed. The partial safety factors, in the case of a scaled specimen and real structure, are also identified, and conclusions are derived.
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