Biomedical Engineering Reference
In-Depth Information
where V
s
is calculated to be 9.5 m/s. V
s
can also be found from:
V
s
VSin
(19)
.
Again, the two results are in agreement with each other. The strain rate
is given by:
VCos
(20)
yCos
(
)
.
is found to be 8333 x 10
3
s
-1
. The
feed rate is 1mm/min under experimental conditions and the feed per tooth δ is
given by,
where Δy is the shear plane spacing and
F
r
(21)
N
where N is the number of teeth. Therefore, Δ is 6.67 μm and the scallop height
is found by using the following:
(22)
h
4
T
8
N
td
Therefore h is calculated to be 1.59x10
-11
m under the experimental
conditions of machining. These conditions assume that the tool is rotating
concentrically about a fixed point, but this is not usually the case with such
small tools machining at high speeds. This means that the modeling of chip
curl during the initial stages of machining is difficult and one approach is to
consider a situation where the bending of the cutting tool produces a multiple
number of shear planes rather than a single unified shear plane. This idea is
generally suited to machining at the microscale and is considered as a
modification of the early assumption made by Ernst and Merchant that a single
shear plane model exists during the machining of materials. Also, because
compact bones are composed of laminates of porous tissue, the orientation of
