Materials Selection in Mechanical Design by M'F'Ashby

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Materials Selection in Mechanical Design by
M.F.Ashby

• MLZ430
• Emrah Dolekcekic

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Mechanical Design

• Mechanical components
• - have mass
• - carry loads
• - conduct heat and electricity
• - exposed to wear and corrosion
• - are made of materials
• - have a shape
• - must be manufactured

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Inter- relations
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Evolution of Engineering Materials
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The Design Process

• To develop a methodology for selecting materials
  and processes which is design led, i.e. the
  design uses as inputs the functional requirements
  of the design.

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The design process
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A technical system
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A systems approach
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Types of design

• Original design
• Adaptive or development design
• Variant design

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Design Methodology
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Function analysis
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How to open a corked bottle ?
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Working principles
Axial force
Internal pressure
Shear force
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Function structure and working principles of cork
removers
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Realisation
Lever
Straight force
Spring
Spindle
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Conclusion

• Design is an iterative process
• It starts with a need statement
• The a concept is devised
• An embodiment is envisaged and detailed
• The embodiment is refined on the basis of ever
  more refined data

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Engineering materials and their properties

• Classes of materials
• Intrinsic or atom related material properties
• Tailored or microstructure related properties
• Non-mechanical properties, such as cost

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Engineering material families
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Definition of properties in units

• Density (kg/m3)
• Elastic moduli (GPa)
• Fracture strength (MPa)
• Resilience (J/m3)
• Hardness (GPa)
• Toughness (MPa.m1/2)
• Loss coefficient (-)
• Thermal conductivity (W/mK)

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Shapes of stress strain curves
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Material properties (continued)

• Thermal diffusivity (m2/s)
• Specific heat (J/kg.K)
• CTE (K-1)
• Thermal Shock resistance
• Creep resistance
• Wear constant (Archard W/A.P)
• Corrosion rate

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MATERIAL SELECTION CHARTS (bar chart)
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MATERIAL SELECTION CHART (Bubble chart)
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Material Property Charts