Solids under stress Flashcards
What is a flexible material?
Large strain for little stress, so material is easy to stretch, e.g polymers
What is a stiff material?
Low strain for large stress, therefore the material is not easy to stretch, e.g metals, ceramics.
What is a crystalline material?
Crystalline - consists of crystals, a regular array of particles with long range order.
What is a polycrystalline material?
Polycrystalline - usually metals consisting of a large number of interlocking crystals (grains)
What is an amorphous material?
No long range order, e.g glass.
Why is glass amorphous?
When molten silicon dioxide is cooled, molecules dont have time to arrange themselves into a crystalline structure.
What is a ductile material?
A material that can be drawn into wires.
How can metals be strengthened?
- Introduce foreign atoms to provide a barrier to dislocations moving (alloying)
- Increase the number of dislocatons and entangle them by work hardening
- Increase the number of grain boundaries by quenching (cooling quickly)
What is a brittle material?
Brittle material has little or no plastic deformation. Material breaks at the crack tip, where the stress is concentrated, and the crack propogates.
