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9 Dynamical Behaviors of Keyhole and Weld Pool …
design industrial vacuum chambers. This chapter mainly introduces the dynamical
behaviors of the keyhole and weld pool in vacuum laser welding, and the effect of
ambient pressure on penetration depths in laser welding.
9.2 Transient Coupling Model of Keyhole and Weld Pool
in Vacuum
In recent years, experiments have shown that ambient pressure has significant effects
on the evaporation process during laser welding. Therefore, ambient pressure must
be considered to accurately calculate the force at the evaporation interface. For that
reason, the authors have proposed a surface pressure model incorporating the factor
of ambient pressure, based on the Soviet Union scientist Anismov’s recoil pressure
model. The proposed surface pressure model can accurately describe the pressure at
the evaporation interface under variable ambient pressures, as shown in Fig. 9.1. It
can be expressed as:
p s =
⎧
⎪ ⎨
⎪ ⎩
p atm
0 ≤ T gb ≤ T L
1+β R
2
p atm exp
H v
k B T v
1 −
T v
T gb
+∞ > T gb ≥ T R
p c (T gb )
T L ≤ T gb < T R
(9.1)
Fig. 9.1 Variation of surface pressure with evaporation interface temperature