Materials

Question 1

Dutctility

Answer 1

Ease to draw into wire - Tensile or bend test

Question 2

Malleability

Answer 2

Suffer compressive deformation with fracture - Tensile or bend test

Question 3

Elasticity

Answer 3

Regain original shape after stress - Tensile or bend test

Question 4

Brittleness

Answer 4

Breaking without deformation - Charpy or Izod test

Question 5

Hardness

Answer 5

Withstand stratching or abrasion - Vickers or Brinell test

Question 6

Toughness

Answer 6

Sustain variable loads without failure - Charpy or Izod test

Question 7

Plasticity

Answer 7

Suffer permanent deformation without rupture

Question 8

Cupro nickel

Answer 8

Alloy of copper, nickel and strengthening elements such as iron and manganese.

Silver in colour, copper content varies from ~60-90%.

Highly resistant to sea water corrosion, used for piping, heat exchangers and condensers in sea water system.

Question 9

White metal

Answer 9

Alloy containing minimum 88% tin (Sn), and antimony (Sb), Copper (Cu), cadmium (Cd) and small amounts of other elements to improve fineness of grain structure and homogeneity during solidification.

These alloys consist of hard crystals embedded in a softer matrix, a structure important for machine bearings were tin gives the good embedability and sliding properties, while the antimony functions as an affective load absorber.

Question 10

Titanium

Answer 10

Titanium is a pure metallic element but it can be alloyed with 6% aluminium and 4% vanadium.

Such alloys have a very high tensile strength and toughness (even at extreme temperatures) they are light in weight have extraordinary corrosion resistance and the ability to withstand extreme temperatures. Uses include plates for heat exchanges

Question 11

Nickel aluminium bronze for cast propellers

Answer 11

Nickel aluminium bronze has exceptional resistance to cavitation damage compared to some stainless steels.

Its density is 10% less than stainless steel which reduces loading on the stern tube bearing.

It is resistant to corrosion in highly aggressive environments and has a high resistance to biofouling.

It has high fluidity making it easy to cast. Damping capacity is twice that of steel

Question 12

Stainless steel for cast propellers

Answer 12

Stainless steel has high strength to weight, higher corrosion resistance, high durability and is easily repairable. It possesses high resistance to stress corrosion cracking. Duplex stainless steel has been well known for its high resistance to corrosion and work hardening ability.

It has reasonable fluidity and is suitable for casting for propellers with separate blades (either fixed or controllable pitch)

Question 13

Chromium as an alloy

Answer 13

Increases grain size, increases hardness and resistance to erosion and corrosion. Stainless steel is steel with a chrome content of 12-18%

Question 14

Manganese as an alloy

Answer 14

Contributes to strength and surface hardness.

Question 15

Molybdenum as an alloy

Answer 15

Gives high-temperature strength, in ni-chrome steels reduces temper brittleness. Used in turbine blading.

Question 16

Nickel as an alloy

Answer 16

Gives strength and toughness. When alloyed with chrome gives ni-chrome steel; used for connecting rods and shafts.

Question 17

Vanadium as an alloy

Answer 17

Increases strength and fatigue resistance; alloyed with chrome gives high tensile strength

Question 18

Silicon as an alloy

Answer 18

Increase strength and hardness but reduces ductility. Improves fluidity in casting

Question 19

Carbon as an alloy

Answer 19

Increases hardness and strength, ductility decreases

Question 20

Spheroidal graphite cast iron

Answer 20

Good fluidity for complex casting increased strength and ductility compared to grey cast iron, used in 4 stroke cylinder heads

Question 21

Monel metal

Answer 21

Similar to cupronickel but with ~52-67% nickel.

Great corrosion and erosion resistance makes it ideal in applications such as piping systems, centrifugal pump impellers, sea water valves, and strainer baskets.

Highly susceptible to galvanic corrosion if not insulated from other metals such as steel.