[Influence of slide-blown on plasma characterization of laser dressing for bronze-bonded diamond wheel by a fiber laser].

The effects of assistant side-blown operating parameters on the behavior of plasma characteristics and plasma geometry were studied with the aid of high-speed camera in laser dressing of bronze-bonded diamond grinding wheel. The results showed that: high pressure argon plasma reduces swelling height, and as the pressure increases, argon blowing side of the plasma effect is more obvious. Plasma emission spectrum was studied on the grinding wheel radial maximum value with the change in argon gas pressure through the acquisition of plasma emission spectroscopy using spectrometer, and according to the Boltzmann slash and Stark broadening method, the maximal values of plasma electron temperature and electron density in the wheel radial were calculated. It was found that the plasma spectral line intensity first increased and then decreased as gas pressure reached the peak at 0. 2 MPa, Larger argon pressure can significantly reduce the temperature and density of plasmas. With optical 3D scanner the wheel surface topography before and after adding side-blown gas was compared. The results indicated that: the topography of grinding wheel with 0. 5 MPa side-blown argon is better than that without adding side-blown gas.

Direct observation of keyhole characteristics in deep penetration laser welding with a 10 kW fiber laser.

Keyhole formation is a prerequisite for deep penetration laser welding. Understanding of the keyhole dynamics is essential to improve the stability of the keyhole. Direct observation of the keyhole during deep penetration laser welding of a modified "sandwich" specimen with a 10 kW fiber laser is presented. A distinct keyhole wall and liquid motion along the wall are observed directly for the first time. The moving liquid "shelf" on the front keyhole wall and the accompanying hydrodynamic and vapor phenomena are observed simultaneously. Micro-droplets torn off the keyhole wall and the resultant bursts of vapor are also visualized. The hydrodynamics on the keyhole wall has a dominant effect on the weld defects. The emission spectrum inside the keyhole is captured accurately using a spectrometer to calculate the characteristics of the keyhole plasma plume.