Gas hydrodynamics of metal cutting by cw laser radiation in a rare gas

Abstract

The deformation behaviour of the Bi-2223 ceramic core in an Ag/Bi-2223 composite, which is crucial for obtaining a high critical current density, has been investigated for the Ag/Bi-2223 composites where the Bi-2223 filament was located at different positions in the silver matrix. For the cores located at the mid-plane of the tape, the thickness strain and the lateral strain were large. For the cores located near the tape surface, the thickness strain and lateral strain were minimized. In a 19-filament Ag/Bi-2223 tape, the deformation state of the Bi-2223 core was less dependent on core position. It has been observed that the deformation behaviour of ceramic cores was very dependent on the core position in the silver matrix as well as the existence of the neighbouring ceramic cores.

Experimental investigation of hydrodynamics of melt layer during laser cutting of steel

“…An interesting point is that, at V = 2 m/min, the velocity of continuous flow was observed to be 3.2 m/s, whereas the velocity of humps was 0.2 m/s. It is not surprising to observe this difference, because the evolution of hump is not a mass flow but an evolution of phase as already pointed out [15,16,18].…”

“…Meanwhile, an important point firstly shown by the present observation is that there is a regime where we observe simultaneously both the stable and unstable flows, in the central and side regions, respectively. In most of the theoretical works in the past, it has been assumed that the instability in the central part naturally perturbs the flow in the side region [14][15][16][17]. This kind of assumptions should be rejected for the intermediate regime.…”

“…It has been t=0 ms t=1.5 ms t=2.5 ms t=4. already discussed that the regime of humps involves such plateaus around the humps [14][15][16][17][18].…”

“…However, it seems that the initiation of the striations at the top part of the kerf should be driven by another physical process. More promising candidate is the instability of thermal dynamics, which generates bunches of molten material (humps) sliding down the kerf front [14][15][16][17][18]. This seems to be promising to explain the initiation of striations, because it is related to the peculiarity of temperature field around the top part of the kerf.…”

Numerical investigations on high-power laser cutting of metals

“…Schulz and Becker [9] developed a numerical iterative approach, which was used to calculate the three-dimensional cutting front geometry. Makashev et al [10] proposed a quantitative physical model to investigate the evolution of a small perturbation created on a two-dimensional kerf front. It was expressed on the basis of the local drilling velocity, which depends on the local laser absorbed intensity and on the local inclination angle of the kerf front.…”