Match the product in Group 1 and the main manufacturing process in Group 2.

Group 1	Group 2
P. Cement kilns	1. Rolling and welding
Q. Gas pipelines	2. Casting and welding
R. Cycle rims	3. Forging and welding
S. Seamless pipe	4. Extrusion and welding
	5. Forging and extrusion

In a tensile test of ductile material, necking starts at

A metallic sheet 1 m wide and 10 mm thick is to be rolled under a front tension force of 100 KN. A specimen from the sheet, tested under tension, shows a yield stress of 100 MPa. Assume plain strain condition during rolling and ignore the friction. If yielding is assumed to start at a roll pressure of σ3 MPa, then the stress in the width direction (where strain is zero) is

Match the forming methods in Group 1 with the defects in Group 2.

Group 1	Group 2
P. Extrusion	1. Flash cracking
Q. Closed die forging	2. Fir-tree cracking
R. Rolling	3. Alligatoring
	4. Earing

The maximum axial compression stress during cold upsetting of a cylindrical rod of radius, 'r', occurs at