Question

Q21. Which one of the following statements about the ductility of metals is TRUE? A High ductility occurs in brittle materials B Ductility is the amount of deformation at the 0.2% proof stress C Ductility can be measured as % reduction in area from broken tensile samples D Ductility is deformation in the elastic region E Ductility is the change between upper and lower yield point in steels Q22. Which one of the following statements is TRUE about Charpy impact testing? A It is a method of determining the coefficient of friction of a material B It measures the energy absorbed in fracturing a notched sample to determine notch toughness C It is a way of determining the fracture toughness of a material D It is an impact test method for un-notched smooth samples E It measures fatigue life of a sample Q23. Iron is polymorphic and can exist in different structures at different temperatures. Which of the following is NOT true at atmospheric pressure? A At room temperature iron is a body-centred cubic structure called ferritee B Above 912 °C iron transforms to face-centred cubic austenite C Above 1394 °C iron transforms to body-centred cubic ferrite before melting at 1538 °C D Quenching from high temperature into cold water is often used to harden steel E ron undergoes a reversible shape change under stress (shape memory effect) Q24. Which of the following is NOT true about polymers? A Polymers consist of long-chain molecules B The molecules of a polymer may be arranged randomly (amorphous polymer) or chain-folded to form crystalline region:s C Polymers are never fully or 100% crystalline but will also contain amorphous regions D Polymer molecules are joined by covalent bonds and usually have a silicon backbone E Polymers may show large extensions under tensile stress Q25. Which of the following is NOT true about ceramics? A Ceramics have much lower compressive strength than tensile strength B Ceramics are usually hard, brittle and show limited plastic deformation C Ceramics are electrically insulating D Ceramics are often oxides eg alumina or silica E Ceramics are good thermal insulators

Answer 1

21. C

Ductility :- % of elongation, % of reduction in area

22. B

Impact toughness of notched sample.

23. E

Quenching - hard and brittle martensite forms.

24. D

25. A