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Material selection for an aerospace component
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, Lightweight Structures.
2015 (English)Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

In the world of today there is a drive for lighter and more effective products for various reasons e.g. reduced environmental impact, higher payload, fuel efficiency etc. There is also an expanding development of new materials for a large number of different applications. This makes it more and more difficult for engineers to make good material selections.

This has led to the development of a large amount of material selection methods that require more or less effort to select material. An effective way to do this is offered by utilisation of material selection software’s like Granta Design CES Selector [1]. A material selection tool may allow you to investigate and evaluate, unbiased, materials or material designs that meet the product requirements. This can also be used in combination with any selection method to further improve the selection of material.

The objective within this work is to propose a strategy for implementing results from material selection tools, e.g. Granta Design, into current set based design optimisation procedures at GKN. Through this new materials and their impact on an existing design may be explored in a rational way. This is then presented through materials selection in a case study.

The case is to select material for the cone at the rear of a jet engine and come up with three design proposals. Two methods are used to achive this, Ashby’s method utilized in Granta Design for finding suitable materials, and the QFD-method [] for ranking the proposed materials.

Granta design uses material property charts where material properties are presented against each other i.e. Young’s modulus versus density and then a material index is inserted in the graph to see how well different material perform against the index. The index varies depending on function of the structure i.e. a beam, on the constraints i.e. stiffness specified and on the goal i.e. minimize weight and this index is to be maximized for maximum performance. The materials are ranked against all possible material indices for the specific structure in this case the cone. Specific requirements are also possible to insert into Granta design i.e. the materials must handle at least 400°C and all materials not fulfilling the requirements or the material indices are removed. The remaining materials are presented in a list where there material performance index (MPI), how well they fulfil the material index, is presented. To rank these, since different materials have varying performance compared to different indices the QFD-method [3] is used.

The QFD-method is based on goals set up by the designer and then the material indices are weighed against these goals in a systematic way. These are then used to rank the materials MPI. The materials are then studied to find out availability, environmental issues and produceability to make the final decision. Granta design can also be used to create new materials by combining different materials i.e. sandwich. This is used to fill gaps in the materials property charts and find materials performing better than monolithic materials.

Three design proposals were retrieved and studied using FEM-software ANSYS. The first using a monolithic shell in Ti-6Al-4V titanium alloy with a weight of 51.157 kg, the second a sandwich with face material of Ti-6Al-4V and core material of Ti-6Al-4V honeycomb. This has a weight of 36.3 kg. The third design is a stiffened shell of Ti-6Al-4V with stiffeners of Stainless steel, PH 13-8Mo, H1150. Here the concept of shape factors where different materials can be shape to different slenderness and thus higher effectivity before buckling is utilized and therefore the stainless steel performs better than the titanium.

Place, publisher, year, edition, pages
2015. , p. 40
Series
TRITA-AVE, ISSN 1651-7660 ; 2015:47
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:kth:diva-198494OAI: oai:DiVA.org:kth-198494DiVA, id: diva2:1057041
Supervisors
Examiners
Available from: 2016-12-16 Created: 2016-12-16 Last updated: 2016-12-16Bibliographically approved

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