Lecture 20 TEMPERATURE IN THE DEFORMATION ZONE

Average Temperature in the Primary Deformation Zone

When a material particle moves across the primary deformation zone, the temp. rise is given by (Boothroyd-1963)

Where,

             = Temp. rise in Primary deformation zone

            h = Fraction of primary heat which goes to the workpiece

            ρ = Density of the material

            C = Specific heat of the material

            t₁ = Uncut chip thickness

            b = Width of the cut

            Vc = Cutting speed

Where,

h is the function of the shear angle and its non-dimensional quantity

H = Thermal number

Where,

            K = Thermal conductivity of the material

 

Average Temperature in the Secondary Deformation Zone

The maximum temperature in the chip occur s where the material leaves the secondary deformation zone and is given by

θ_max = θ_o + θ_p + θ_s ………………………(4)

where

            θ_o = initial workpiece temperature

θ_p = temperature rise of the material passing through the primary deformation zone

            θ_s = temperature rise of the material passing through the secondary deformation zone

The max. temp. rise in θ_s, when the material particle passes through the secondary deformation zone along the rake face of the tool can be approximately expressed as

_{l = length of contact between tool and chip}

_{For average temp.}

_{Put Eq. (6) and (3) in eq (5)}

_also,

_{Θov = Overall temp. rise in chip tool interface}

_{Uc = Specific energy}