Materials selectionMaterials selection with CES EduPack

Choosing materials for a new engineering application, or replacing those that have become obsolete, expensive, or under-performant, is a key task for engineers and designers. How do we give them the skills to do this? Granta founder Mike Ashby is well-known as a pioneer in the topic of rational materials selection, and the CES EduPack software helps to teach this approach.

A materials selection course can prepare students for wider decision-making

There are well-known methodologies for selecting materials and processes [1]. CES EduPack supports these methodologies by providing data and selection tools (you can read about those tools and the methodology in more detail elsewhere [2]). The software provides students with a 'mini textbook' on selection methodology, a guide to performance indices, and varied selection case studies (accessible via the Help menu). A series of lecture units on how to select materials and processes are also available on Granta's Education Hub. [3]

Trade-off

A diagram from one of teh CES EduPack lectures illustration a trade-off between Cost and Mass

Rational Materials Selection involves much more than just generating pretty material property charts (although CES EduPack does this beautifully!). You must decide on your selection criteria, find the data you need, prioritize different requirements, and make sure you read the 'fine print'. Students are led through this process. They decide which design requirements are constraints, and which are objectives. They learn how to derive a performance index using common engineering equations and, importantly, they learn how to handle conflicting objectives in a systematic manner [4]. Trade-offs (see figure, right) are one of life's inevitable features, and it is important that students learn how to tackle these. The results of most selection projects are a short list of potential materials. It is then important that students read the records in more detail.

There is lots of useful data in the supplementary information section in the CES EduPack data records. For example, in the Beryllium records, which show up frequently due to high strength and stiffness, it mentions that Beryllium dust is toxic (see figure, below). Reading the records can lead the student to adapt constraints, e.g., add non-toxic, or to loosen constraints as none of the candidate materials appear viable. Students can see that if they change their criteria slightly, different results show up.

CES EduPack sample record

Reading the fine print is important!

Open-ended solutions are something that undergraduates need to become comfortable with. Indeed, in industry, once a high performing material is chosen, the purchasing department may well add other criteria, such as the reliability of the supply chain, or the fact that they can bulk buy a material. These broader strategic issues for Materials Selection are something that Granta Design works on with industry. Granta has extensive experience of helping engineers and designers to apply the skills taught through CES EduPack to real industrial case studies (see the example below).

Plotting this graphically using CES Selector, the line represents points with the same value of performance index. this allowed a shortlist of materials to be quickly identified (marked red), including PS, PP-H (20%GF), ASB, and PET(35%GF).

Studying trade-offs in a project to find a replacement plastic for a metal in an air conditioning unit.
This is from a case study with the Tecumseh corporation: read the full report.

Interested in how Granta can help you to teach materials selection? Contact us for a discussion 

References

  1. Pahl, G.; Beitz, W.; Feldhusen, J.; Grote, K.-H. "Engineering Design: A Systematic Approach" Springer 3rd Ed. 2007 and Ashby, M.F. "Materials Selection in Mechanical Design" BH 4th Ed. 2010
  2. Ashby, M.F.; D. Cebon, D; Silva, A. “Paper: Teaching Engineering Materials” Granta Design Ltd 2012 www.teachingresources.grantadesign.com/Type/Papers/PAPTEMEN12
  3. Ashby, M.F. “Set of Lecture Units: Presentations” Granta Design Ltd www.teachingresources.grantadesign.com/Presentations
  4. Ashby, M.F. “Lecture Unit 8. Objectives in conflict” Granta Design Ltd www.teachingresources.grantadesign.com/Presentations/PPTOBJEN14