16
1 Laser Welding Basics
Fig. 1.5 Diagram of energy conservation in deep penetration laser welding process
(1) Establishment of a mathematical model of volume heat source in deep
penetration laser welding;
(2) Applying basic equations of fluid dynamics to establish a three-dimensional
mathematical model for melting and solidification of weld pool in deep penetration laser welding under action of a moving heat source to simulate the shape
of the keyhole formed by the titanium alloy under different welding heat input;
(3) Based on software FLUENT, applying the finite volume method to study
temperature distribution and velocity distribution characteristics of weld
pool in deep penetration laser welding and verifying the correctness of the
mathematical model through deep penetration laser welding experiment;
(4) Simulating the effective position and size of the velocity field and protected
area under the interaction of the auxiliary side airflow and the keyhole jet near
the keyhole and the weld pool.
Figure 1.6 shows the main contents and their relationship in three aspects of
fluid dynamics research on deep penetration laser welding. The study concludes as
follows:
(1) It is suitable to employ a combined heat source model consisting of the rotating
Gauss heat source and double-ellipsoid heat source to simulate the formation
of the keyhole in deep penetration laser welding of titanium alloy and the flow
velocity field of the weld pool. The body heat source model can reflect the
basic physical process in deep penetration laser welding, and also embodies
the simulation characteristics of the control volume method.
(2) In the process the deep penetration laser welding with full penetration, the
diameter of the keyhole is not very sensitive to the laser power, but the inclined