IntermediateTopic 58 of 100Materials & Chemical
Materials selection
Ashby charts compare properties to choose optimal materials.
In depth
Ashby's method matches material indices to function, objectives and constraints (e.g. minimise mass of a stiff beam: maximise E^{1/2}/ρ). Screen with charts, rank, then consider processing, cost, sustainability and supply. Materials databases (Granta CES) support the process.
Key points
- Performance indices
- Property bubbles
- Trade-off surfaces
ExampleFor light stiff panels, CFRP and balsa win over steel on E^{1/3}/ρ.
What is Materials selection?
Ashby charts compare properties to choose optimal materials.
Why is it important to understand materials selection?
Materials selection matches the material to the design requirements, so the best choice meets the function at the lowest cost and weight.
What is an Ashby chart?
A plot of one material property against another, which shows the range of each material class and helps find candidates.
What is a performance index?
A combination of properties that measures how well a material suits a particular function, such as stiffness per weight for a light beam.
How is Materials selection used in practice?
Typical applications include comparing the strength to weight of several materials for a bicycle frame, choosing a material for a pressure vessel using a performance index and using an Ashby chart to find a light and stiff material for a panel.
What should I learn before Materials selection?
Study "Smart materials" first (topic 57 of 100 in Materials & Chemical). It covers the groundwork this topic builds on.
What are the key points of Materials selection?
Performance indices. Property bubbles. Trade-off surfaces.
Can you give an example of Materials selection?
For light stiff panels, CFRP and balsa win over steel on E^{1/3}/ρ.
What comes after Materials selection?
The next topic is "Failure analysis", which builds directly on this one.
How difficult is Materials selection?
It is classed as Intermediate in Materials & Chemical (topic 58 of 100). It is an intermediate topic. Work through the beginner topics in Materials & Chemical first.