Hull Plate Research Articles

Artificial intelligence-based ship hull plate corrosion monitoring using Convolutional Neural Network (CNN): comparison of YOLOv8 and Detectron2 architecture models

ABSTRACT Detecting and monitoring structural damage is crucial to prevent significant damage to ship structures caused by corrosion. This study aims to measure the performance of corrosion detection using Convolutional Neural Networks (CNN) by comparing YOLOv8 and Detectron2 models analyzed at various data augmentation settings. The results show that Detectron2 with the ResNet101 backbone performs better than Detectron2 ResNet50 and YOLOv8 models. The result found that applied augmentation data settings, such as vertical & horizontal flip, rotation, and increasing & decreasing colour saturation, highlight their importance in training robust corrosion detection models. These findings contribute to developing corrosion detection methods, showing that the Detectron2 model with instance segmentation can overcome the complexity and variety of corrosion shapes more effectively than YOLOv8 model. The instance segmentation model has proven to be the more effective CNN model for detecting abstract objects, such as corrosion damage in ship hulls.

A vision measurement method for ship hull plates based on multi-view stereo and image segmentation

The background denoising of point clouds is challenging for the measurement of ship hull plates. To address this issue, a vision measurement method is proposed by combining an identity cost volume network (ICV-Net) and a segment anything model (SAM). By applying the ship hull plate masks segmented by SAM to the corresponding depth maps inferred by ICV-Net, the background noise can be directly removed at the depth map level. Additionally, an edge extraction optimization algorithm complementary to SAM is proposed to eliminate the thickness-related noise. Moreover, an efficient depth map refinement algorithm is proposed by imposing the smoothness prior of ship hull plate surfaces and multi-view photometric consistency. Sub-pixel accurate depth maps of ship hull plates can be obtained by the depth map refinement. Experimental results suggest that the proposed method can automatically, accurately and efficiently remove the background noise of ship hull plates, which is crucial toward practical application.

A two-way coupled fluid–structure interaction method for predicting the slamming loads and structural responses on a stiffened wedge

Ships navigating through rough seas are subjected to slamming loads from waves, which can lead to structural damage and maritime accidents. The wedge model is commonly employed to investigate slamming loads and structural responses. While a stiffened wedge closely resembles a real ship hull plate, incorporating it into fluid–structure interaction simulations presents challenges. This paper proposes a two-way coupled fluid–structure interaction method to examine slamming loads and structural responses of a free fall non-prismatic stiffened steel wedge. Hydrodynamic loads are determined through Reynolds-averaged Navier–Stokes computations using OpenFOAM, while structural responses are predicted using the finite element analysis (FEA) software Calculix. To achieve two-way coupling between computational fluid dynamics and FEA simulations, a coupling library for partitioned multi-physics simulations, preCICE, is introduced. The computed impact pressure and stress align well with available experimental data. Various free fall heights are investigated in the numerical simulations. The results indicate that elastic deformation mitigates impact pressure, while the presence of transverse ribs enhances the rigidity of the flexible plate. The duration of pressure and the peak slamming pressure exhibit an inverse correlation. Greater free fall heights result in shorter pressure duration times, and smaller free fall heights may reduce rise time. Three-dimensional effects cause pressure to decrease along the midpoint of the plate toward both sides. Additionally, structural stress in the central area exceeds that in the areas on both sides at the same height. In conclusion, the proposed two-way coupled model proves suitable for accurately and efficiently computing hydroelastic slamming on flexible wedges.

Experimental Investigation of Ice Loads on Structures during Quasi-Static Compression Tests

In polar ship hull structural designs, methods based on regulations are considered the most authoritative; however, they tend to be conservative and often exhibit a notable degree of redundancy. This study aims to evaluate the applicability of the empirical formula for ice load assessments by conducting a series of quasi-static indentation tests on scaled hull plates under laboratory-made ice blocks of different scales. The obtained data include ice loads, structural responses, and characteristics of ice pressure distribution. A detailed comparison of various formulas is provided, along with an examination of their differences and errors in comparison to experimental results. The objective of this paper is to offer technical support for ice load forecasting and assessment.

Ultrasonic non-destructive inspection method for glass fibre reinforcement polymer (GFRP) hull plates considering design and construction characteristics

The design and construction characteristics, including glass fibre weight fraction ( Gc), number of single-ply layers, fabric combination, and fabrication quality, of glass fibre reinforcement polymer (GFRP) hull plates affect ultrasound propagation characteristics, such as ultrasonic velocity and attenuation, thereby influencing the accuracy of ultrasonic non-destructive test results. Therefore, this study is to propose a method to decrease the ultrasonic test errors of GFRP hull plate by using statistical method. The GFRP specimens with Gc of approximately 30–50 wt%, thicknesses of approximately 5–20 mm, and different fabric combinations were prepared using the hand lay-up method, considering the general design–construction characteristics. Further, an ultrasonic velocity decision method for ultrasonic inspection was proposed considering the GFRP hull design-construction characteristics, such as Gc and number of single-ply layers of hull plate by multiple linear regression method. The results show that the proposed method can reduce the thickness measurement error from approximately 20%–30% to 1%–2%, compared to an existing ultrasonic inspection method, only considering the Gc effect on ultrasonic velocity, which indicates that the proposed test method is suitable for practical applications.

A Multipath Process-Based Inherent Strain Method for Prediction of Deformation of Hull Plate for Integrated Heating and Mechanical Rolling Forming Process

Integrated heating and mechanical rolling forming (IHMRF) has recently been introduced for manufacturing complex curvature hull plates. It fabricates the target curved plate by sequential loading along the multipath. Accurate and efficient prediction of the deformation of the plate is the basis for developing the process planning and ensuring the quality of the forming. The inherent-strain method is ideal for this purpose, but its prediction accuracy needs to be improved. This paper proposes a multipath process-based inherent-strain method (MPISM), which considers the effect of the sequential loading process of the multipath on plate deformation. First, the effect of loading paths near the plate edge was investigated, which in turn clarified the rationale for obtaining the inherent strain only in the plate center. Secondly, a strain correction strategy was established by analyzing the variation pattern of the inherent strain caused by the crossing or proximity of the previous path and the subsequent path. This allowed the effects of the loading process to be taken into account in the elastic analysis. Based on the plate-and-shell theory, the idea of an equivalent inherent strain distribution is also presented. This makes the loading of inherent strains more accurate in the elastic finite-element model. MPISM predictions and experimental results show good agreement. Compared with the thermo-elastic–plastic finite element method, the MPISM substantially improves efficiency while maintaining accuracy. Compared with the original inherent-strain method, the MPISM is more accurate in terms of deformation magnitude prediction.

Patrol Boat Strengthening Against a Collision with COLL Notation Based on Class Rules and Regulation in Indonesia – An Overview

<span lang="EN-US">Indonesian maritime security and law enforcement rely frequently on Patrol boats. However, collisions can occur during the operation, leading to potential loss of life, damage to the ship, and environmental harm. In preventing such incidents, the government needs to strengthen the patrol boats against collisions in accordance with class rules and regulations in Indonesia.</span><span lang="EN-US">The COLL notation is an additional notation for vessel collision protection, which specifies the required strength of the vessel's hull and structural components to minimize the risk of damage and reduce the consequences of a collision. This study highlights the key areas that require strengthening, including the vessel’s bow, stern, and hull, as well as the propulsion system that needs to be considered in the design stage. The addition of collision bulkheads, increasing the hull plating thickness, and reinforcing the engine mounts and shafting are also necessary to ensure the vessel's safety against collision. In conclusion, strengthening patrol boats against a collision with COLL notation based on class rules and regulations in Indonesia is one of the methods available that can be applied for the design stage to increase the level of operational safety of patrol boats.</span>

An equivalent heat source model for inducted heating forming with single-circuit inductor

ABSTRACT Induction line heating is a suitable method for plate bending in shipbuilding, and the rapid prediction of this forming process is required. However, the existing coupled magnetic-thermal prediction method is time-consuming and requires complicated modelling operation, which makes it difficult to rapidly estimate the thermal conduction of large-size ship hull plate bending. This paper proposes an equivalent heat source (EHS) model for a single-circuit inductor and establishes its quantitative relationship with heating parameters. First, based on a local yet accurate magnetic-thermal coupling model, an EHS model was constructed with three governing parameters. Second, the results with the EHS model were consistent with the experiments, while the thermal analysis was accelerated eight times over current magnetic-thermal coupling analysis. Finally, the effects of heating parameters - current, frequency, air gap and plate thickness on the three governing parameters were investigated, and the relationship between the heating parameters and the EHS model was identified with dimensional analysis.

Equivalent load model for the numerical simulation of integrated induction heating and mechanical rolling forming of curved hull plates

Equivalent load model for the numerical simulation of integrated induction heating and mechanical rolling forming of curved hull plates

Deflection Intelligent Prediction for High-Strength Steel Saddle Plate Forming Applicable to Reducing Ship Weight.

The application of high-strength steel plates can reduce ship weight, and the saddle plate is one of the most common types of double-curved hull plates. To fill the research gap regarding high-strength steel saddle plates, two prediction models are established here to predict deformation in saddle plate forming. Deflection is a key parameter reflecting the overall deformation of a curved plate. Therefore, first of all, the influencing factors of the line heating of high-strength steel saddle plates were analyzed. The influence of plate geometric parameters and forming parameters on deflection was researched. Second, a multiple linear regression model between deflection and the geometric parameters and forming parameters of high-strength steel saddle plates was established. Finally, to solve the problem of a large error in the multivariate regression model for extrapolation, an intelligent prediction program for deflection based on a support vector machine (SVM) was developed using the Python language. The results show that the error of the multiple regression model was less than 5% for data interpolation. The error of the intelligent prediction model for deflection was less than 5% for data extrapolation. This research can provide data support for the automatic forming of marine saddle plates.

Application of IT2Fs-AHP and TOPSIS modeling for performance analysis of tank coatings in chemical tankers

There are a wide range of chemical cargoes carried in chemical tankers. The chemical tankers are carrying hazardous chemical cargoes in their cargo tanks. When carrying hazardous chemicals in cargo tanks, the coating is required which is to provide safety barrier between the hull plate and the cargo. Therefore, capabilities of cargo tanks are of paramount importance for safe and efficient transport. Tank coatings to be applied to chemical tankers are epoxy coatings, zinc silicate coating, stainless steel coating, and marine line coating. This paper aims at conducting a numerical performance analysis of tank coatings in chemical tankers to contribute decision-making process of shipowner and safety professionals. To achieve this purpose, a multi-criterion decision-making (MCDM) tool is adopted: An Analytical Hierarchy Process (AHP) and Technique for Order Preference by Similarity to an Ideal Solution (TOPSIS) under interval type-2 fuzzy set (IT2Fs) environment. The outcomes of the numerical performance analysis showed that stainless steel type tank coating has the best performance since result of closeness coefficient value c( xj) is found 0.55. The findings of the research will contribute chemical tanker ship owners, safety inspectors, naval architects, and safety professionals during decision-making process of ideal cargo tank coating.

Binocular vision measurement for large-scale weakly textured ship hull plates using feature points encoding method

The accurate forming measurement for curved hull plates is vital to ensure the quality of shipbuilding. However, the weak texture, large scale and complex shapes of curved hull plates present challenges for shape inspections. To enrich the texture of plates, checkerboard patterns are combined with the binocular vision system. Moreover, calculating the sub-pixel coordinates of corner points enhances reconstruction accuracy. A novel encoding method for the feature points on the complex shaped plates with repeatable texture is proposed to match the homologous points correctly. Finally, three dimensional coordinates are obtained by triangulation. Experimental results show that the dimensional accuracy is 300 ± 0.636 mm and the average accuracy is ±0.219 mm by registration. Inspection processes are completed within 1 min. This method is more automatic and convenient than contact measurement. Moreover, the efficiency is improved by about 2 times than multi-vision measuring method, enhancing the accuracy and efficiency of measurement for curved hull plates.

Effect of Void Content on the Mechanical Properties of GFRP for Ship Design

Defects such as voids in composite materials often degrade the mechanical properties of laminates. Even if these materials are manufactured based on the design requirements, there is a possibility of instability occurring in these composite structures. In this study, several prototypes were developed based on changes in composite ship design conditions (glass fiber weight fraction and fabric combination type) using a hand lay-up approach. The fabrication quality was quantitatively defined using the burn-off test, and statistical analysis was performed. A combination of chopped strand mat and woven roving material laminates possessed relatively less void content in the entire glass content (Gc) region (30–70 wt%) compared to a chopped strand mat single-material laminate. The effect was more pronounced in the high-Gc region (50–70 wt%) than that in the normal-Gc region (30–50 wt%). The composite hull plate can be designed seamlessly according to changes in fabrication quality. To ensure safety, the thickness of the laminate must be greater than that specified in the ISO standards, regardless of the combination type in the normal-Gc region. As a result of the void content considered, the flexural strength in the single laminate decreased by 15.02%. Furthermore, 3.33% of the flexural strength calculation decreased in the combined laminate compared to that in the ISO rules. Thus, a single CSM material can be designed to be thicker than a combined-material laminate with the same Gc, while considering the void content on the mechanical properties.

Forming Difficulty Evaluation for Curved Hull Plates Based on Grey Relational Analysis

To solve the problem that the lack of reference for hull plate division leads to the difficulty and low efficiency of curved plate forming, the forming difficulty evaluation of complex curved hull plates is researched. Considering the characteristics in curved plate forming process, the forming difficulty evaluation model of complex curved hull plates based on grey relational analysis is established. The evaluation process of forming difficulty for curved plates is designed. The influence law of parameters and forming parameters on the forming difficulty of curved plates are revealed. The weight coefficients of different influencing factors on the forming difficulty of curved plates are quantified. Taking the real hull plate of a container ship as an example, the evaluation results for the forming difficulty of curved plates are calculated based on the evaluation model. The rationality of the evaluation model is verified by comparing the evaluation results of curved plate forming and the process time data. The research can provide a reference for the reasonable division of hull plates and reduce the forming difficulty of curved plates.

Advanced empirical formulae for the ultimate strength assessment of continuous hull plate under combined biaxial compression and lateral pressure

This paper focuses on developing empirical formulae for the hull structural design and safety estimation. An equivalent sequential loading method for biaxial compression is verified and adopted to realize decoupling the conventional implicit strength relationship of plates expressed by elliptic function. In total, 2737 and 1944 scenarios regarding the combinations of slenderness ratio, aspect ratio and applied loads are selected to perform non-linear finite element analysis for longitudinal and transverse ultimate strength, respectively. Influences of considered parameters on the ultimate limit state behaviours are documented and clarified aiming to provide some useful insights for the load-carrying capacity assessment. Based on the outcomes of numerical investigation, two empirical formulae with the same general explicit shape, which can be utilized in various load scenarios including not only combined biaxial compression and lateral pressure but also other load combinations, are proposed through response surface method. According to the statistical analysis, the equations show good agreement with the ABAQUS simulation results (R = 0.993 and 0.996), confirming they can be used as a practical design technology in the ultimate strength assessment.

Effect Of Sea Moisture Content On Corrosion Hull Of A Warship Made By PT Pal Indonesia

Seawater temperature ranges from -2 0 c to 300 c. Low temperatures are usually found in seawater around the poles and on the deep seabed. Meanwhile, high seawater temperatures are found in the sea in the Arid area. The Red Sea and Bab El Mandeb have temperatures of about 290 c to 300. Corrosion is a subject matter that concerns various disciplines, or in other words, it connects elements of physics, chemistry, metallurgy, electronics and engineering. This study uses the literature review study method to collect, identify, evaluate the effect of seawater content on the corrosion of the hulls of warships made by PT Pal Indonesia. An effective corrosion control strategy should be selected with the selection of suitable coatings for the marine environment. Hull plating with paint has a special function to protect the construction of the hull, especially those located below the waterline and the construction of the ship above the waterline.

Numerical investigation on the ultimate strength behaviour and assessment of continuous hull plate under combined biaxial cyclic loads and lateral pressure

The ultimate strength of continuous hull plate under combined biaxial cyclic loads and lateral pressure is investigated in the present paper by using nonlinear finite element method. Geometric nonlinearity due to large deflection and material nonlinearity induced by kinematic hardening and isotropic hardening are both accounted for. A parametric study is designed and completed to examine the longitudinal ultimate compressive strength behaviours in the cycles on the basis of a large number of load-shortening curves. Effects of series of parameters especially the plate slenderness ratio, transverse cyclic compression, lateral pressure and cycle number are analyzed with details. It is found that the strength characteristic and collapse mode are highly affected by the coupling influence of the mentioned factors as well material behaviours. A dimensionless unified formulation as a function of the decisive factors is empirically proposed to accurately assess the ultimate strength of continuous hull plate in various cycles.

Ice impact response and energy dissipation characteristics of PVC foam core sandwich plates: Experimental and numerical study

In this paper, the dynamic responses and energy dissipation characteristics of polyvinyl chloride (PVC) foam core sandwich plates under ice impact are investigated. The ice impact tests of PVC foam core sandwich plates were conducted by employing the horizontal impact experimental apparatus. The finite element simulations were conducted to analyze the dynamic response of PVC foam core sandwich plates based on soil and concrete material model for ice impactor. It was demonstrated that numerical results were in good agreement with experimental results. The deformation modes of the top facesheets were coupling of local indentation with global bending deformation, while the deformation modes of bottom facesheets were overall bending deformation. The permanent deformation of face sheets show that the impact resistance of sandwich plate is better than that of equivalent weight hull plate (EWHP). In addition, based on the actual navigation environment of ship, the effect of impact angle and ice floe shape on dynamic response and energy dissipation are analyzed.

Prediction of line heating deformation on sheet metal based on an ISSA–ELM model

A prediction method based on an improved salp swarm algorithm (ISSA) and extreme learning machine (ELM) was proposed to improve line heating and forming. First, a three-dimensional transient numerical simulation of line heating and forming was carried out by applying a finite element simulation, and the influence of machining parameters on deformation was studied. Second, a prediction model for the ELM network was established based on simulation data, and the deformation of hull plate was predicted by the training network. Additionally, swarm intelligence optimization, particle swarm optimization (PSO), the seagull optimization algorithm (SOA), and the salp swarm algorithm (SSA) were studied while considering the shortcomings of the ELM, and the ISSA was proposed. Input weights and hidden layer biases of the ELM model were optimized to increase the stability of prediction results from the PSO, SOA, SSA and ISSA approaches. Finally, it was shown that the prediction effect of the ISSA–ELM model was superior by comparing and analyzing the prediction effect of each prediction model for line heating and forming.

Drawing deviation assessment of ship plate marking lines using progressive target extraction

In the construction of large marine structures such as ships, the precise assembly of parts is imperative for ensuring the overall structure's strength and functionality. Currently, construction workers still use marking lines to assist with ship part assembly tasks, and conventional measuring tools are used to draw marking lines throughout the whole assembly process. Unfortunately, there is not yet a method for accurately assessing marking line errors. Hence, this article proposes a method for evaluating the marking line accuracy of a hull part. A progressive sampling method is applied to extract the edge point set and marking lines. An optimised marking evaluation can be obtained while preserving the details of the as-built model. In the proposed method, geometric features are used to extract edge elements from the as-built model and then register it with its as-designed counterpart instead of using the overall data for registration. In addition, the marking lines are extracted in HSV colour space instead of RGB colour space. Using the most common panels in a ship hull structure, we evaluated the accuracy of the marking lines for each hull plate and demonstrated the effectiveness of the proposed method. The proposed method has the potential to reduce the need for rework and increase the speed of ship fabrication.