No. 4, 1998 - Tribology in Industry

o Y
= 10"
o Y
= 10"
oY=1
t Y
= 10"
./q'-16a
v
I - tw
b Y= 10-
A Y
= 10"
Figure 5. Ideal nrodel of the eitting process
+Y = 2A"
^T = 30"
o
{o
Since the cuttingprocess is the typical dy.namical process,
Kronenberg had, applying the D'AJembert's principle,
set the dynamic equilibrium conditions between the inertial
force and the friction force on the rake face, and by
solving the system of differential equations, he obtained
the equation for determination the average value of the
friction coefficient (Figure 6):
/\
Ini
F = trt).
l,)
- ri
\- j
oY = 50"
100 200 JUU 400 oc MN/m'
Figure 7. InJluence of llrc nonrnl prcssure on lhe vaiatiott
of the friction coefficient p on the rake face
F'' = q"''11''f'
whe.re 4'r, is the normal pressure, p' is the friction coefficient
and/ is the contact area between the clearing face
and the nrachined surface. (in determination of F2 and
F3 the. corresponding projections of the contact area are
taken into account).
Tire ratio of the friction energybetween the rake face and
the ship can be determined according to the energy
necessary for chip formatiol (Figure 8) can be determined
according to exprcssion:
/,
:'.!. .l!: . lu Ll - f(Lyl
A' ) cos(it-11
where, according to Kronenberg;
Figure 6. IYith the K'onenberg dynantical nodcl
As the experimental investigation show, the average value
of the friction coefficientpr is basically a function of
the average normal pressure on the rake face. The average
value of the friction coefficient is also affected by the
cutting speed v and the rake angle y (Figure 7).
In Merchant's model, and models similar to it, the phenomena
occurring at the contact point between the clearing
face and the machined surface are neglected.Zorev
had introduced correction in calculations of the forces,
i.e., cutting resistance, so he represented the individual
components by the sum:
Fr= R,+ F',
where the additional parts took into account phenomena
of wear on the clearing face. Thus, the correction for the
main cutting force (cutting resistance) is:
I-igure 8. Merclunt's force diagratn in orllogonal cutting
130
fribologt in ituliutrl', Volume 20, No. 4, 1998.