- A useful method of doing this is by plotting them as Material Property Charts, sometimes called ‘bubble’ or ‘Ashby’ charts, with one property on one axis and another property on the other. Each material has a range of values for each property, depending on the exact composition, grade, heat.
- Material Selection Charts. In order to demonstrate the power of the material selection chart approach, a number of common property combinations have been plotted - these are listed below.If your browser is capable 1, you should see interactive chart pages which. Allow you to view the selection charts.
Using Material Selection Charts
Here is a materials selection chart for 2 common properties: Young's modulus (which describes how stiff a material is) and density.
On these charts, materials of each class (e.g. metals, polymers) form 'clusters' or 'bubbles' that are marked by the shaded regions. We can see immediately that:
- metals are the heaviest materials,
- foams are the lightest materials,
- ceramics are the stiffest materials.
Variety can destroy varietyW. Ross Ashby There are more things in heaven and earth, Horatio,Than are dreamt of in your philosophy.Hamlet (1.5.167-8) In his book An Introduction to Cybernetics, published in 1956, the English psychiatrist W. Ross Ashby proposed the Law of Requisite Variety.
Where selection charts are really useful is in showing the trade-off between 2 properties, because the charts plot combinations of properties. For instance if we want a light and stiff material we need to choose materials near the top left corner of the chart - so composites look good.
Note that the chart has logarithmic scales - each division is a multiple of 10; material properties often cover such huge ranges that log scales are essential.
There are a selection charts for many combinations of material properties, e.g. 'strength - toughness' and 'electrical resitivity - cost'. The next section shows how we cantake selection charts further.
Consider a design problem where the specification is for a component that is both light and stiff (e.g. the frame of a racing bicycle). The Young's modulus - density chart helps us to find the best materials - they lie towards the top left. The charts can be annotated to help reveal the 'best' materials, by placing a suitable selection box to show only stiff and light materials. What can we conclude?
This still leaves quite a lot of choices, so what might be considered next to narrow the choice further? |
It is unlikely that only 2 material properties matter, so what other properties are important? Let's consider strength and cost - these properties are plotted on another selection chart. So, what else does this tell us about suitable materials classes? What can we conclude?
|
Selection charts can also be used to select between members of a given class by populating it with the main materials. For instance, we can do this for metals in the stiffness-density chart. What can we conclude?
Let's summarise what we've learnt about materials selection. |
- By considering 2 (or more) charts, the properties needed to satisfy the main design requirements can be quickly assessed.
- The charts can be used to identify the best classes of materials, and then to look in more detail within these classes.
- There are many other factors still to be considered, particularly manufacturing methods. The selection made from the charts should be left quite broad to keep enough options open. A good way to approach the problem is to use the charts to eliminate materials which will definitely not be good enough, rather than to try and identify the single best material too soon in the design process.
CBEFRSFREng | |
|---|---|
| Born | Michael Farries Ashby 20 November 1935 (age 85)[1] |
| Education | Campbell College[1] |
| Alma mater | University of Cambridge (BA, MA, PhD) |
| Awards |
|
| Scientific career | |
| Fields | Materials science |
| Thesis | The metallography and mechanical properties of internally oxidised copper alloys(1961) |
| Doctoral students | Lorna Gibson[3] |
| Website | www-edc.eng.cam.ac.uk/people/mfa2.html |
Michael Farries AshbyCBEFRSFREng[2][4] (born 20 November 1935) is a Britishmetallurgical engineer.[1] He served as Royal Society Research Professor, and a Principal Investigator (PI) at the Engineering Design Centre at the University of Cambridge. He is known for his contributions in Materials Science in the field of material selection.[5][6]
In 1990, Ashby was elected as a member into the National Academy of Engineering for outstanding contributions to the understanding of mechanical behavior of materials and for development of formats useful for design.
Education[edit]
Ashby is the son of the leading botanist and educator Lord Ashby. He was educated at Campbell College in Belfast and the University of Cambridge where he studied the Natural Sciences Tripos as a student of Queens’ College, Cambridge.[1] He received his Bachelor of Arts degree in Metallurgy in 1957 (First Class Honours); his Master of Arts degree in 1959 and his PhD in 1961.[1]
Career and research[edit]
By conducting numerous studies on the active deformation mechanisms under different temperature conditions, M.F. Ashby developed a graphical approach for determining these mechanisms. He generalizes this approach to the broader field of material selection by developing the software CMS(Cambridge Materials Selector)in collaboration with David Cebon, with whom he co-founded Granta Design Limited. He also collaborated extensively with Yves Bréchet (CNRS Silver Medal). He continued to work on the software to improve its pedagogical value across Materials Education ( CES EduPack[7] – used at more than 1000 universities worldwide and value to industry (CES Selector[8]). This software is currently available from the company Granta Design, of which he is the chairman.
Ashby has revolutionized the approach to the selection of materials to take into account four aspects: feature, material, geometry, and processes; moreover, he worked with the division in classes and subclasses. In doing so he has developed a comprehensive approach that associates to the expected mechanical functions of an object a performance index that has to be optimized. These indices allow to better take into account all the properties required of a material, such as specific stiffness (ratio between the elastic modulus and density) instead of single elastic module. His approach allows one to rationally choose the most suitable materials for each application.
In practice, this approach firstly asks to identify the performance index starting from the expected function and geometry. Then it is possible to select thresholds for certain properties in order to select the most useful materials from those present in a database that has some 80,000 materials. The division into classes allows pre-selecting representative materials and therefore working only with certain classes of materials. Finally, the selected materials are shown in a 2-dimensional chart, called the Ashby diagram, in order to view those with the highest performance index. These diagrams often contain also nanostructured materials and composites.
- Materials Selection for Mechanical Design – standard text used around the world.
- Materials and Design – book – Aesthetic attributes as well as technical attributes of materials, making products delightful as well as functional.
- Materials Processing Science and Design- introductory textbook – trying to motivate engineers to learn about materials by starting with design.
In more recent years he has concentrated on materials and the environment and sustainability, writing award-winning textbooks and pioneering teaching methods to get this complex topic across to engineering students.He has been honored by the American Society of Engineering Education by having a teaching prize named after him.[9]
Ashby has achieved a remarkably innovative work[citation needed] in the areas of materials, design, and sustainability[10] as well as in that of pedagogy. His works on materials are comparable to those of Carrega and Colombié. His former doctoral students include Lorna Gibson.[3]
Publications[edit]
- Ashby, Michael F. 'Materials and Sustainable Development', Butterworth Heinemann, 2015 ISBN9780081001769
- Ashby, Michael F. 'Materials and the Environment: Eco-informed Material Choice', Butterworth Heinemann, 2009. 2nd Edition 2012 ISBN9780123859716
- Ashby, Michael F., Shercliff, Hugh and Cebon, David 'Materials: Engineering, Science, Processing, and Design'. Butterworth Heinemann, 2007. 3rd Edition 2013 ISBN9780080977737
- Ashby, Mike and Johnson, Kara 'Materials and Design: The Art and Science of Materials Selection in Product Design' Butterworth Heinemann, Oxford, 2002 ISBN0-7506-5554-2
- Ashby, M.F. 'How to Write a Paper', 7th Edition 2011[ISBN missing]
- Ashby, M.F. 'Materials Selection and Process in Mechanical Design', Butterworth Heinemann, Oxford, 1999 ISBN0-7506-4357-9
- Ashby, M.F. and Cebon, D. 'Case studies in Materials Selection', First Edition, Granta Design Ltd, Cambridge, 1996 ISBN9780750636049
- Ashby, M.F. and Gibson, L.J. 'Cellular Solids Structure and Properties', Cambridge University Press, Cambridge, 1997 ISBN0-521-49911-9
- Asbhy, M.F. and Jones, D.R.H. 'Engineering Materials 1, Second Edition', Butterworth Heineman, Oxford, 1996 ISBN978-0080966656
- Ashby, M.F. and Jones, D.R.H. 'Engineering Materials 2, Second Edition', Butterworth Heineman, Oxford, 1998 ISBN9780080545653
- Ashby, M.F. and Waterman, N.A. 'The Chapman and Hall Material Selector', Chapman and Hall, London, Volumes 1-3, 1996[ISBN missing]
- Ashby, M.F. and Frost H.J. 'Deformation-mechanism maps: the plasticity and creep of metals and ceramics', Pergamon, 1982 ISBN9780080293387
- Michael F. Ashby 'Materials Selection in Mechanical Design Pergamon Press 1992 (2nd edition 1999 3rd edition 2005 4th edition 2010) ISBN978-1856176637
Honours and awards[edit]
Ashby's awards and honours include:
Ashby Diagram Software Development
- elected a Fellow of the Royal Society (FRS) in 1979[2]
- received the A. A. Griffith Medal and Prize in 1981[citation needed]
- elected a member of the National Academy of Engineering in 1990
- awarded the European Materials Medal of the Federation of European Materials Societies (FEMS) in 1993 [11]
- elected a Fellow of the Royal Academy of Engineering (FREng) in 1993[citation needed]
- appointed CBE in the 1997 Birthday Honours[1]
- nominated a Foreign Honorary Member of the American Academy of Arts and Sciences in 1993[12]
- awarded the Eringen Medal in 1999[citation needed]
References[edit]
- ^ abcdefAnon (2017). 'Ashby, Prof. Michael Farries'. Who's Who. ukwhoswho.com (online Oxford University Press ed.). A & C Black, an imprint of Bloomsbury Publishing plc. doi:10.1093/ww/9780199540884.013.U5816.(subscription or UK public library membership required)(subscription required)
- ^ abcAnon (1979). 'Professor Michael Ashby CBE FREng FRS'. Royalsociety. London: Royal Society. One or more of the preceding sentences incorporates text from the royalsociety.org website where:
“All text published under the heading 'Biography' on Fellow profile pages is available under Creative Commons Attribution 4.0 International License.” --Royal Society Terms, conditions and policies at the Wayback Machine (archived 2016-11-11)
- ^ abGibson, Lorna Jane (1981). The elastic and plastic behaviour of cellular materials (PhD thesis). University of Cambridge. doi:10.17863/CAM.14049. OCLC276947761. EThOSuk.bl.ethos.257054. Retrieved 2 November 2018.
- ^'List of Fellows of the RAEng'. Raeng.org.uk. London: Royal Academy of Engineering.
- ^'Professor Michael F Ashby'. Edc.eng.cam.ac.uk. Retrieved 16 November 2018.
- ^Michael F. Ashby publications indexed by the Scopus bibliographic database. (subscription required)
- ^'CES EduPack - Granta Design'. Grantadesign.com. Retrieved 16 November 2018.
- ^'CES Selector - Granta Design'. Grantadesign.com. Retrieved 16 November 2018.
- ^'Awards » ASEE Materials'. Materials.asee.org. Retrieved 16 November 2018.
- ^'TAA announces 2016 Textbook Award winners'. Blog.taaonline.net. Retrieved 16 November 2018.
- ^'Awards | FEMS - The Federation of European Materials Societies'. www.fems.org. Retrieved 6 September 2019.
- ^'Book of Members, 1780-2010: Chapter A'(PDF). American Academy of Arts and Sciences. Retrieved 25 April 2011.
Ashby Chart Software
This article incorporates text available under the CC BY 4.0 license.