Week 10 Lecture, Joining

Week 10 Lecture, Joining

1. Methods of joining

   • Screw/Bolt types
   • Forces within a joint
   • Sheet Metal Seams
   • Rivets
     • 1- The twp pieces of plastic or aluminium are drilled to a size slightly larger than the rivet. 2- The pop rivet is passed through both holes in the sheet of plastic or aluminium.
   • Poor choice sinks he unsinkable.
     • Building the Titanic required three million rivets, and the ship builder, Harland and Wolf, may have addressed a shortage by using substandard iron rivets in the bow and the stern, scientists who reviewed company archives say Naval experts suspect that popped rivets along six seams in the hull made the ship sink quickly.

2. Welding

   • -Method of joining two similar metals, (i.e copper cannot be welded to steel). -Uses high temperatures to melt and join the metal parts. - A filler metal is often used. - When properly done, the finished weld is a strong as the surrounding metal. -If he welder applies too much heat, it can change the metals properties and weaken the weld.
   • Manual Metal arc welding
   • Arc and weld area
   • Metal Arc Gas Shielded (MAGS) welding
   • Gas Welding, oxy-acetylene welding
     • Equipment needed - Gas pressure regulator - Flash back arrestors - Rubberised Hoses - Torch - Flux
     • Oxy-acetylene Flames
       • Oxygen is turned on, flame immediatley changes into a long white inner area (Feather) surrounded by a transparent blue envelope is called Carburising flame (3000C) Addition of little more oxygen give a bright whitish cone surrounded by the transparent blue envelope is called Neutral flame (it has a balance of fuel gas and oxygen)(3200C) Used for welding steels, aluminium, copper If more oxygen is added, the cone becomes darker and more pointed, while the envelope becomes shorter and more fierce is called Oxidizing flame Has the highest temperature about 3400C Used for welding brass and brazing operation.
   • Resistance Welding (Spot welding)

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