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6. What is a weak material?

  • Can be drawn into wires
  • Breaks with little stresson
  • Easily deforms
  • Shatters by crack prooagation into jagged pieces

7. Describe the structure of an oil atom

  • lipophilic head and hydrophobic tail
  • hydrophobic head and lipophilic tail

8. What material isn't a thermo plastic

  • Melamine
  • Polyethene
  • polypropelene

9. What is fracture energy?

  • 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