Why aircrafts body is riveted?

Answer 1

Air craft are mostly made from aluminum. Welding aluminum parts is very difficult to do. Conventional welding is not applicable to aluminum although some techniques to that exist.

However there are limitations to welding in general

1) Difficult to control the quality of the welds. For this purpose the welds need to go thru x-ray or ultrasound or some other quality assurance procedure.

2) Welds are prone to fatigue failure. Fatigue failure happens without much warning thus difficult to catch during inspections.

3) Welds are difficult to undo/redo for planes in service. Service or inspection may require access under the fuselage (skin) of a plane. Undo and redo the weld is dangerous to perform on the winds of a plane where fuel tanks are located.

With comparison to rivets welding also in disadvantage

1) Ductility of welds is lower. (Ductility - ability to plasticly stretch without failure) Thus if overstress occurs the weld breaks suddenly and rivet deforms to allow stress redistribution. Plastic deformation is easy to detect during inspection.