proceedings of the fourth us water jet conference - Waterjet ...

MODEL EMPLOYMENT
Three materials were used to conduct linear cutting tests: aluminum, titanium and
Inconel. Hydraulic, abrasive, mixing and cutting parameters were varied to generate a
data matrix on the effects of these materials on depth of cut. The main objectives of
generating this data matrix are to:
• Use data to verify a prediction model.
• Use the prediction model, if adequate, to forecast a machining strategy.
• Observe the geometrical quality of cuts.
- Roughness of produced surface
- Variation of depth of cut along the direction of traverse
The following is a discussion of this effort:
Review of Model
Cutting with abrasive-waterjets has been found to consist of two modes (6,7): the
cutting wear mode occurs by the impact of particles at shallow angles (8), and the
deformation wear mode occurs by impacts at large angles (9,10). The first mode results in
a steady-state cutting interface, while the second is unsteady. The relative contribution of
each mode to the total depth of cut depends on the traverse rate. Above a critical traverse
rate, the cutting will be due only to the deformation wear mode. The total depth of cut (h)
can be expressed with a simplified model as
2 ( )v
h = m av2 8 u + 2ma 1 − c
u d j
where V is the jet velocity, σ is the flow stress, ε is the material specific energy, d j
is the abrasivewaterjet diameter and c is a constant. The term on the left is due to cutting
wear, while that on the right is due to deformation wear. The critical traverse rate at
which cutting wear terminates is (7)
uc = m 2
av 2
20 d j
In the above equation, the effect of depth on particle velocity is neglected. When
considering the decay of particle velocity with depth as a result of kerf wall interference,
the following expression results (11) if the cutting wear mode is ignored (high traverse
rates):
where
3
(2)
(1)
2
h ( 1−
N1)
= (3)
d N 2 N
j 3
( ) + C f ( 1−
N1)
1−
c
N
1
Vc
=
V