In a slab rolling operation, the maximum thickness reduction $$\left( {\Delta {h_{\max }}} \right)$$ is given by $$\Delta {h_{\max }} = {\mu ^2}R,$$ where $$R$$ is the radius of the roll and $$\mu $$ is the coefficient of friction between the roll and the sheet. If $$\mu = 0.1,$$ the maximum angle subtended by the deformation zone at the center of the roll (bit angle in degrees) is ____________

In a rolling operation using rolls of diameter $$500mm,$$ if a thick plate cannot be reduced to less than $$20mm$$ in one pass, the coefficient of friction between the roll and the plate is ____________.

A metal rod of initial length $${L_0}$$ is subjected to a drawing process. The length of the rod at any instant is given by the expression, $$L\left( t \right) = {L_0}\left( {1 + {t^2}} \right),$$ where $$t$$ is the time in minutes. The true strain rate (in $${\min ^{ - 1}}$$) at the end of one minute is _____________

A mild steel plate has to be rolled in one pass such that the final plate thickness is $$2/{3^{rd}}$$ of the initial thickness, with the entrance speed of $$10m/min$$ and roll diameter of $$500mm.$$ If the plate widens by $$2\% $$ during rolling, the exit velocity (in $$m/min$$) is ____________