i. Enhance awareness of the range of engineering materials for structural environments.
ii. Introduce algorithms and charts used for materials selection. iii. Develop abilities for the analysis of materials selection engineering problems.
1. MATERIALS SELECTION - INTRODUCTION 1.1 Outline
• Materials selection without shape (Materials Performance
Index, selection charts, multiple constraints and design goals, examples).
• Materials selection – cost and environmental considerations. • Materials selection with shape (shape factors, microscopic
versus macroscopic shape, co-selecting material and shape).
• Software-based materials selection. selection • Alternatives to Ashby approach in materials selection. selection
Book: “Materials Selection in Mechanical Design”, M. F. Ashby. Copies in the library (1st, 2nd and 3rd editions – little difference). Also ???????????
1. MATERIALS SELECTION - INTRODUCTION 1.2 Materials in design
Generic properties of engineering materials:
Strength METALS CERAMICS (excl.traditional ceramics) POLYMERS COMPOSITES Usually high Low (tension) High (compression) Low Usually high Ductility Usually high Virtually zero Melting / Softening Point High Very high Shaping / Forming? Easy → difficult Usually difficult Cost Low → high Usually high
Usually high Usually low
Low Determined by matrix
Easy Easy → difficult
Usually low Usually high
There are ~ 104 – 105 different materials available to the engineer. How should you choose the most appropriate ones?
1. MATERIALS SELECTION - INTRODUCTION 1.2 Materials in design (cont’d)
It depends on the design stage. Generally, all materials may be considered in the initial design stages; but in the final design stages, you will have a shortlist of materials (perhaps several, perhaps just one). Cost will almost always be the dominant constraint on materials selection, often overriding considerations of weight, size and product life (e.g. corrosion...