by Sthéfano Lande Andrade and Thiago Gabriel Monteiro – MSc Students in Ship Design / Høgskolen i Ålesund
Henrique M. Gaspar – Associate Professor Aalesund University College / Ulstein International SA
(firstname.lastname@example.org, email@example.com), v1, Dec 2014.
The objective of this work is to present a simplified modularization process appllied to Ship Design. In short, given a module library, we are able to combine all the modules within and generate a fair amount of different, but viable designs. The connection process and setup viability is controlled by a set of rules and the final designs are evaluated to determine their final characteristics. The following picture summarizes the Modularization Process.
Figure 1 – Representation of the Modularization Process.
The database is composed by libraries of each module. In this case they are cataloged in an excel file, which contains all the information specific to each module and assigns an identification number to them. The number refers to the module type and the characteristics of each different modules. This composition can be visualized bellow:
Figure 2 – PSV Systems Breakdown. The third tier is composed by the modules used in this work.
In this first approach, a PSV will be described as a combination of 4 modules: Crane, Bow, Cargo Section and Propulsion. The characteristics of each of them are:
It will be composed of 3 modules defined by lifting capacity, height and arm length:
- 150 TM (height: 5 m; arm: 6 m);
- 300 TM (height: 6 m; arm: 8 m);
- 450 TM (height: 7 m; arm: 10 m).
It will be composed of 4 modules defined by type and beam.
- Conventional type and 18 m beam;
- X-Bow type and 18 m Beam;
- Conventional type and 20 m beam;
- X-Bow type and 20 m beam.
Besides, all have 10 m in length and depth of 12 m.
Cargo Section Library
Composed of 4 modules, which are defined by length and beam:
- 60 m length and 18 m beam;
- 80 m length and 20 m beam;
- 60 m length and 18 m beam;
- 80 m length and 20 m beam.
They also have a height of 12m
Propulsion Section Library
4 modules, defined by power, length and beam:
- 100% Power,4 m length and 18 m beam;
- 150% Power,7 m length and 18 m beam;
- 100% Power,4 m length and 20 m beam;
- 150% Power,7 m length and 20 m beam.
And all have height of 12 m.
Also, it’s necessary to note the database should also include information about the CAD File location and Cost for each module.
Figure 3 – The modules library
The described modules were also drawn using the NX-Siemens program.
Figure 4 – The designed modules for a first approach and how they are will be connected
The library contains all the modules related to the design and in this simple case, 11 different parts were created and have attributed values. Their combination alone would result in 192 different results. Fortunately, this case can be lowered when some connection rules are in place. They are defined by the client requirements, classification society norms and the ability of modules to connect between them.
If we consider but the connections restrictions, in this case bow, cargo and propulsion section must have the same beam, we end up with 48 different designs. The rules applied to the combination where defined using excel functions and evaluate the possible designs as feasible/unfeasible.
Figure 5 – The rules applied to the combinations.
After the combinations are evaluated, it is possible to create the assembled design. Using the pre-made modules and the CAD software, we are able to visualize the PSV as a whole. Furthermore, each module has it’s own properties, as defined previously, which will be used to define the vessel’s properties, as final length, power, height, beam, deck area, cargo area and lifting capacity.
For a exemplification purpose two feasible designs were assembled and can be seen in the following picture, also with some of their final characteristics.
Figure 6 – Design no.1 (right) and Design no.39 (left) CAD assemblies and main features.
To decide which are the best solutions, we need to define a set of performance indicators. For this case, the following indicators were considered: Cost, Operability, Deck, Cargo Tank and Structural Analysis, which were considered as comparative factors and graded from n to 100, were 100 is the biggest value in the assemblies. Cost is deducted from the final score. For the Operability, the X-Bow and 150% Power options are considered better than Conventional and 100% Power. Deck was divided in 2 components: Deck Area (0.4*L*B) and Crane, then graded.Cargo Tank was calculated (0.4*L*B*D).
Finally, after the solutions are graded, only the ones that satisfy the client’s requirements are chosen to the next phase, which consists in a Structural Analysis using Finite Elements Method. The evaluation method for this example was an analysis of the stress caused by a cargo of 5 tons lifted by the crane, which was placed on the deck of the cargo section module.
Figure 7 – Structural Analysis.
To this stage, only a few examples were assembled using CAD software, NX-Siemens, and have been analysed structurally. To further this case study and display the advantages of the process, we are going to further the study by working with more examples. These will be created within a context, with client requirements and the final viable assemblies being evaluated structurally.
Reuse Parts Library
Reuse Parts Library is an easy and fast way to deal with standard designs, which need to be reused several times. It is possible to define these designs with different dimension, according to the user’s needs. The use of this tool is explained in the link.
Making a technical drawing
The NX-Siemens software offers a tool that makes possible to draw a 2D technical drawing from your 3D model. This link will teach how to do it.