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Structural analysis of introducing high strength steel in light craft design

Christoffer Ahlström ; Lisa Kilsmark
Göteborg : Chalmers tekniska högskola, 2015. 85 s. Report. X - Department of Shipping and Marine Technology, Chalmers University of Technology, Göteborg, Sweden, 2015.
[Examensarbete på avancerad nivå]

Light crafts are traditionally built in aluminium since this material has a high strength in relation to its weight. However, the industry is constantly searching for alternatives that could reduce weight. The use of composites is developing but it has proven to be challenging. Another alternative for a light construction is high strength steel, which is the focus of this thesis. The analysis consists of three cases. The first and main case is to evaluate two smaller light crafts, one passenger ferry and one high speed vessel, with respect to the DNV light craft rules. The vessels are chosen due to their differences regarding speed and operating conditions. The comparison is made between aluminium NV5083 and high strength steel Weldox 700 E Offshore. The second case is a comparison between aluminium NV5083 and high strength steel Weldox 700 E Offshore when introducing an ice-reinforcement to a light craft passenger vessel. This ice-reinforcement is based on the Finnish-Swedish ice class IC and applied to one of the vessels in the first case. The third and last case regards larger vessels and is a simplified study comparing the high strength steel Weldox 700 E Offshore with a commonly used steel with a yield strength of 360 MPa. The purpose of this study is to give an indication if weight can be reduced using high strength steel, therefore it only includes bottom plating. The results from the first case show that a light craft built in high strength steel is heavier than the same vessel built in aluminium. The second case shows that the ice-reinforcement is heavier for a vessel built in high strength steel. For larger vessels, the third case, the results indicate that weight can be reduced by using high strength steel compared to the commonly used steel. The main conclusion from the study of the first case is that high strength steel is not an alternative to aluminium in terms of weight when using the DNV light craft rules as they are today. Due to uncertainties discovered during the work further investigations needs to be conducted before high strength steel is disregarded as an alternative to aluminium for light craft designs. The conclusion from the second case is that the ice class rules are not applicable to aluminium and therefore the weight estimation is not reliable. The conclusion from the study of the third case is that the weight can probably be reduced and a more holistic analysis needs to be conducted before a solid conclusion can be drawn.

Nyckelord: aluminium, high strength steel, ice-reinforcement, light craft, weight reduction



Publikationen registrerades 2015-07-09. Den ändrades senast 2015-07-09

CPL ID: 219626

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