Assertion (A) : Cold working of metals result in increase of strength and hardness.
Reason (R) : Cold working reduces the total number of dislocations per unit volume of the material.

The true stress-true strain curve is given by $$\sigma = 1400\,{\varepsilon ^{0.33}},$$ where the stress $$\sigma $$ is in $$MPa.$$ The true stress at maximum load (in $$MPa$$) is

A level having $${90^0}$$ bend is to be produced by drop forging using mild steel bar as raw material. The various operations to be performed on it during forging are:
$$P$$ - Cutting;
$$Q$$ - Bending;
$$R$$ - Fullering;
$$S$$ - Blocking cum finishing;
$$T$$ - Edgering

The correct sequence for performing the operations is:

A round billet made of brass is to be extruded (extrusion constant $$=250$$ $$MPa$$ ) at $${700^ \circ }C.$$ The billet diameter is $$100$$ $$mm$$ and the diameter of the extrusion is $$50$$ $$mm.$$ The extrusion force required (in $$MN$$) is