Engineering science makes ships lighter and more environmentally friendly

With innovative structures and materials, we can reduce cruise ship’s hull weight by 20%.

Cruise ship

My research group focuses on advanced marine structures. We study large global challenges within engineering sciences, i.e. how to build and maintain large-scale structures that are safe, sustainable, and energy efficient.

To tackle these challenges, we apply science-based structural design by combining material science, solid mechanics, and structural engineering. We work within the marine technology framework, but we share several fundamental research questions with the design of other large structures. Therefore, the same principles can be utilised, for example, in the design of steel bridges and skyscrapers.

Cruise ships are Finland’s largest individual export product

Maritime industry is among the most important export sectors in Finland. Cruise ships are, in fact, Finland’s largest individual export product. One cruise ship costs over one billion euros and total sales equals around 1.5% of Finland’s annual exports. The size of cruise ships has gradually increased since the 1970s, but currently the goal is a lighter ship with lower emissions. The objective is to produce ships with a 20% lower steel weight.

In our research group, we examine three strategic issues of ship design: use of high-strength materials, new structural solutions, and efficient design methods. In science-based structural design, these three areas are combined using theoretical modelling, experimental research, and modern digital technologies.

Although high-strength materials are already available, their excellent properties are lost in the manufacturing process. While the cruise ships are hundreds of meters in length, the strength of the material and the structure is defined in millimetre and micrometre scale. Therefore, the key challenge is the different length scales involved. In addition, ships operate in extreme conditions, facing around one hundred million load cycles during their lifetime, and climate change makes the prediction of these extreme conditions exceptionally difficult.

Materials matter in bringing new ship concepts into reality

Using theoretical modelling and experimental research that covers different length scales we can discover, for example, how the properties of the materials affect the strength of the structure, and what kind of materials and manufacturing processes are needed to bring new ship concepts into reality. Besides, we can use digital measurement technologies to specify the geometry and the material properties of the structure. A good example of this is thin deck structures, where the strength is increased but plate thickness is reduced from six to only four millimetres. What at first glance seems to be small number, actually has a huge impact on the ship’s weight.

Design rules for ships do not yet allow utilisation of high-strength steels in ship structures because there is not sufficient knowledge of their behaviour in large welded structures. Our research addresses this gap in scientific knowledge, and has shown, for instance, that a ship’s side structure constructed from high-strength steel can withstand significantly higher loads compared to traditional steel. The use of high-strength steels combined with thinner decks would make it possible to decrease hull weight by 15 to 20 percent. This means that an extra deck, i.e. hundreds of passenger cabins, could be added to the cruise ship.

Alternatively, the ship’s hull shape could be designed to be more streamlined, reducing energy consumption. The new structures also allow for new kinds of cabin designs as demonstrated by our students, who have developed a two-storey cabin module which has caught the interest of shipbuilders around the world.

Increasing knowledge and innovations create the need for more experts

Innovations utilised in the industrial sector require breakthroughs in engineering science. For this reason, cross-disciplinary basic research is the foundation for impact maximisation. At the same time, producing more knowledge and innovations creates the need for more experts who can put this research into practical use.

For these reasons, in marine technology we focus on educating Masters of Science, Doctors of Science, and post-doctoral researchers. Our research group is continuously educating new marine technology experts that have had an excellent success rate in finding employment in different parts of the world both as industrial specialists and academic professors – to continue research in our field and training new experts.

Heikki Remes
Professor of Marine Technology, Aalto University

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