The Naval Architect: October 2018
Traditionally, the design approval of a ship by a classification society has been a paper-based process, involving the exchange of numerous large-format drawings between the shipyard and the classification society. However, Korean Register (KR), an IACS classification society, has developed a 3D model-based design approval system to manage this process more efficiently and securely, which is now being rolled out to all customers involved in this process.
It used to be the case that any plans and documents showing the details of the construction, materials, scantlings and the particulars of a ship’s hull, equipment and machinery needed to be submitted in triplicate and approved before the work was started. Now, all of the many 2D drawings are shared between the shipyards and KR using the electric drawing approval system. The drawings are transferred in compatible electronic formats such as PDF using data encryption, to pass them easily and safely between both parties.
Today, the model paradigm in ship design has shifted from 2D drawing to 3D modelling for the initial design phase in Korean major shipyards (Son et al., 2016). As a result, the model paradigm of KR’s bespoke structural assessment software SeaTrust-HullScan, which supports both the rule scantling and direct strength assessment has also moved from 2D geometry and 3D finite element modelling to 3D geometry and 3D finite element modelling to take advantage of the 3D CAD (Computer-Aided Design) model of the whole ship that has been created and used in the initial design phase (Son et al., 2017).
KR has developed the interfaces in the SeaTrust-HullScan software to include all the structural CAD (AVEVA Marine, Intergraph S3D, NAPA Steel, and TTM ISD) which are used in the initial shipbuilding structural design divisions in the Korean shipyards.
KR has been working to develop this 3D model-based design approval system since 2017, all with the aim of supporting enhanced productivity in the shipyards and providing a more accurate and intuitive review of ship structure for the classification societies.
Outline of 3D Model-based Design Approval System
The outline of 3D model-based design approval system is shown in Fig.1. It comprises two main software viewers for the 3D model of a whole ship. The functional requirements for these viewers were developed following discussions with shipyard design engineers, who were familiar with the 3D model in the initial design phase, plan approval surveyors and 3D-based engineering software developers. Their requirements were as follows:
- 3D viewer basic handling (zoom, pan, clip, rotate, selected entity)
- Dimension, area and volume measurement
- Management for approval zone/ item/ part
- Historical management for approval/ revision part
- 3D model-related comment/ annotation
- Effective SeaTrust-HullScan Interface
The viewer does not support the creation of any geometry for the ship hull structure, only providing an effective interface with the shipbuilding 3D CAD system. For this CAD interface, each 3D CAD system presents its own neutral format (XML; eXtensible Mark-up Language)-based 3D model definition for the ship structure. As a result, the neutral format containing the information necessary for the plan approval of the 3D ship model of the initial structure CAD, which is used in the shipyard, needs to be created first.
The shipyard requires a viewer that can convert and validate the 3D model into a neutral format. It is important for the shipyard to see the conversion of the model through this viewer, and the neutral format means that all information is released, with the viewer also controlling the encryption of the model and file size.
The same viewer is available to the plan approval surveyor in the classification society; it includes features that enable plan approval to be performed effectively, while supporting the calculation functions, and providing the necessary engineering software.
The encrypted 3D model file for the design approval must be registered and managed through the electronic plan approval system. The design approval system must also act as the interface for the 3D model in the viewer, allowing the verification of rule scantling and direct strength analysis using SeaTrust-HullScan.
The major features of the 3D design approval viewer
The main part of the system is the 3D model-based design approval viewer that handles the whole-ship 3D model, giving a fast response for 3D model handling. The 3D viewer supports not only the 3D geometries of the ship but also gives the properties of the structural members such as the plate and stiffeners including their thickness, size, type, and material.
The various structural member properties and associated information are presented visually with the model and also displayed in an information window. The whole ship model can be seen at a glance, and also supports various selective methods such as min-max box clipping, three plane clipping, showing only a selected object, or defining the zone that user wants to see to examine internal structures in detail or to conduct a structural review for a specific cargo hold area.
In addition to the basic functions for handling the 3D model, the system also supports the specific functions for the 3D model design approval viewer. Tag information linked to objects in each model can be added and modified and annotation can be created, modified and managed. In addition, the measurement function allows users to see the distance and angle between each structural member.
The advanced section view functionality has been developed for surveyors from the classification society who are not familiar with 3D model. It presents the conventional 2D drawing style view using the 3D model, allowing the user to check specific details, as shown in Fig. 3. The user can view the longitudinal direction of the whole ship model, changing the desired position freely and whenever he/she presses the calculation button to check the cross section, a 2D drawing-style view is generated in real time for that position.
The generated information is expressed in text, giving the major locations of the main structure members, the spacing between each member, and the size of the stiffeners. These objects can be moved and arranged to any working space position, allowing the screen-captured view to be used as a rough drawing.
The benefits of the 3D model can be found in the right-hand side of Fig. 3.
Providing the 2D drawing style view alongside the relevant 3D models gives an easy understanding of the continuous and corresponding structural members related to the specific frame position.
Unlike the 2D drawing, this model can then be viewed by rotating, magnifying, selecting objects, with the optional graphical representations for various member properties.
Further developments
In August 2018, KR developed a 3D model-based design approval viewer which supports multiple platforms such as PC (MS Windows, linux) or mobile devices such as tablet or smartphone (Android, iOS). This means that same 3D model and corresponding comments from the plan approval surveyor can now be accessed on the mobile devices of the field surveyors in the shipyard. In addition, the 3D model, its associated information and engineering data can now be managed through the ship’s lifecycle as the digital twin. A web browser-based 3D model viewer is now under development, which will allow the 3D model to be shared without requiring a file transfer, thereby protecting the customer’s intellectual property.
Different types of vessels in different types of database for engineering and design (CAE; Computer-Aided Engineering, CAD) have been tested in the viewer as shown in Fig. 5, including an 180,000dwt LNG Carrier with CAE model (Coarse-mesh, fine-mesh, fatigue-mesh with their CAE results), a 13,000 TEU Container Carrier with CAE model (Girder-sized mesh with yield assessment result), a PCTC with CAE model (longi. sized coarse mesh model with yield assessment result), and various naval vessels with CAE models and results.
The viewer supports the CAE result review functionality, giving the design engineer access to more comprehensive engineering data (Son et al., 2018). KR’s engineers have also developed an Aframax tanker and various naval vessels as 3D models, using the actual 2D structure drawings and initial structure 3D CAD system to test the viewer in the development stages.
In addition, the lightweight whole ship 3D model can be used to review the design using a VR (virtual reality) environment applying stereographic output, and some touch-up such as texturing and lightening for the VR rendering, the model also can be transferred for further analysis using the VR simulation ship model.
Conclusion and future work
Today, 3D modelling is being applied and used at all stages of shipbuilding design, resulting in improved processes and more efficient task completion.
KR has widely researched new 3D-model-centric engineering software, resulting in the development of the 3D model-based design approval system. The 3D model should be applied to all parts of the design phase, with the whole ship 3D model offering real-time quick response handling. This article introduces the 3D model-based design approval viewer that satisfies these functional requirements, delivering for the first time a digital twin of a ship.
Using the 3D model-based viewer, KR plans to develop further user-friendly functions for design approval in the future, focused on shortening design approval time, providing more detail and comprehensive reviews of the hull structure members to enhance safety. It is expected that this technology will in time, make the digital twin of a ship commonplace across the maritime industry.
Acknowledgements
This research was performed as a part of the research project below and supported by the organizations indicated. We acknowledge and appreciate the support provided.
‘In shipbuilding design, 3D Development and commercialization of safety education, training VR contents of sailor using virtual reality technology” project funded by Ministry of Science and ICT of Korea (No. S0602-17-1016).
