Once cracked, a material's ability to withstand fracture
The energy required to fracture or break, either by compression or tension
A material's ability to withstand fracture
The level of energy at which a material will permanently deform
10. What is brittle fracture?
Fracture of a material after plastic deformation
Fracture of a material after elastic deformation
Fracture of a material without prior plastic deformation
Fracture of a material without prior elastic deformation
11. What is compression
A force that attempts to flatten a material
A force that when removed the material will return to its original shape
A material which is closely compacted
Energy stored by a material undergoing deformation
12. Describe metallic bonding
There are delocalised electrons and non-directional bonds which hold positive ions in a lattice whilst allowing slips and dislocations
Giant lattices which are hard to displace with strong directional bonds and bound electrons
Strong non-directional bonds in a lattice structure with bound electrons
13. Explain why the stress at the tip of a crack in a brittle material can be very large
Dislocations in brittle materials can't move to spread stress
A crack prevents a material from spreading stress. Stress is concentarted at the tip, a very small area. The crack deflects tensile strength and stress is concentrated below the crack.
Bonds are directional in brittle materials and can't rotate to relive stress at the crack
14. What is necking or cup and cone fracture?
Dislocations move towards grain boundaries and tangle preventing further movement
When dislocations reach a grain boundary
15. What is a stiff material?
Withstands an applied load without failure or plastic deformation
Resistant to stretching or bending
Plastically deforms without fracturing
Easily shaped
16. What is strain energy?
Energy stored by a material undergoing deformation
How much energy a material can endure
Once cracked, a material's ability to withstand fracture
Energy that allows a material to withstand stretching or bending
17. What statement about the structure of crystals is false?
Defects can occur such as vacancies and dislocations
Polycrystals are rare but large crystals are common
The structure is stable (repitition of a basic pattern)
Crystals are formed by solidification and the growth centres from which crystals grow compete for space
18. Define dense
A material that is closely compacted in its atoms
Internal structure composed of crystals
Difficult to scratch or dent
Requires a lot of stress to break
19. What equation is incorrect
Young Modulus= stress/strain
Young Modulus=strain/stress
Strain=Extension/original length
Stress=Force/Area
20. Define tough
The opposite of brittle, a material in which cracks propagate, elastically deforms without fracturing, and requires a lot of energy to break
The opposite of brittle, a material that resists crack propagation, plastically deforms without fracturing
The opposite of brittle, a material that resists crack propagation, elastically deforms without fracturing, and requires a lot of energy to break
The opposite of brittle, a material that resists crack propagation, elastically deforms without fracturing, and requires little energy to break