(2) Material Selection Performance Indices Flashcards
What are the three key factors influencing a material’s performance metric (p)?
Functional requirements, geometric parameters, and material properties.
How is the stiffness-to-weight ratio for a material calculated?
It is calculated as E/ρ, where E is Young’s modulus and ρ is the material density.
What does the second moment of area (I) measure in beam bending?
The efficiency of a cross-section to resist bending.
What is the bending stiffness (S) equation in terms of force and deflection?
S = F/δ, where F is the applied force and δ is the deflection.
What is the main purpose of using performance indices in material selection?
To systematically identify materials that optimise desired properties for a specific application.
Which performance index is used for designing lightweight columns in compression?
It is calculated as E/ρ, where E is Young’s modulus and ρ is density.
What are the assumptions of Euler-Bernoulli beam theory?
Linear elastic material, symmetric cross-section, small deflections, and no plastic deformation.
What does a materials selection chart plot?
Material properties such as density and Young’s modulus, often on logarithmic scales, to compare performance.
What are typical steps in the material selection process?
- Restrict materials to suitable processing methods.
- Impose limits on essential properties.
- Use selection maps to maximise desired properties.
What factors, beyond performance, are considered in material selection?
Processability, cost, and environmental impact (lifecycle considerations).
What is the neutral axis in beam bending?
The line in the cross-section where stress changes from tension to compression and is zero.
What is a key example of a common performance index for a tensile tie?
It is calculated as σ_f/ρ, where σ_f is failure strength and ρ is density.
