Fundamental investigations on the spiking mechanism by means of laser beam welding of ice

Abstract

In order to gain further understanding on the mechanism of rapid seam depth variations, the so-called spiking, in deep penetration laser beam welding, this effect is analyzed and explained using the example of laser welding of ice. Laser welding of ice provides the advantage that the temporal behavior of the vapor capillary can be analyzed by means of common imaging methods in the visible spectral range. The occurrence of spiking and its frequency is found to depend on the feed rate but is not influenced by instabilities of the rear wall of the capillary. Also, the effect of downward moving structures at the capillary front can be shown to be independent from root spiking. Spiking is found to be governed by a periodically alternating irradiation of the capillary front wall by the incident laser beam in the lower part of the capillary. This is verified by ray-tracing calculations on capillary geometries extracted from high-speed videos. These findings are further substantiated by a transient smoothed particle hydrodynamics model to simulate the melt flow and evaporation at the capillary front that was coupled to the ray-tracing calculation to determine the local absorption of the laser radiation within the capillary.

Comparison of the features of the formation of joints of aluminum alloy 7075 (Al-Zn-Mg-Cu) by laser, microplasma, and laser-microplasma welding

“…The gas forms bubbles that do not have time to surface due to small quantities of linear energy (5 J/mm) and the lifetime of the liquid metal bath (about 0.02...0.04 s). Laser radiation that does not have a free outlet forms the particle structure of the seam root described in the literature (for example, work [16]), which contributes to the occurrence of root porosity.…”

Extreme bursting events via pulse-shaped explosion in mixed Rayleigh-Lienard nonlinear oscillator

“…The abrupt emergence of fast, repetitive large-amplitude peaks (spiking or active state) alternate with the slow, steadystate like small-amplitude oscillations (quiescent or rest state) at regular or irregular time intervals are characterized as bursting. Such complex and multiple-time scale oscillatory behavior is often appeared in biological systems, especially in neuronal systems [1,2,3], but also reported in physical, chemical, mechanical, and other systems [4,5,6,7,8]. Due to the universal occurrence of this phenomenon, the concept of bursting and its emerging dynamical mechanisms has been intensively studied in mathematical models [9,10,11,12,13,14,15], and in various real-world systems [16,17,18,19,20].…”

Impact of fume particles in the keyhole vapour

“…Pointto-point calculations enabled to model keyhole geometries depending on processing parameters (e.g., [15]) or could help predict the porosity [16]. Simplified models can help to predict the keyhole depth [17], which might not fully represent the dynamic observed behavior of the keyhole (e.g., observed in ice [18] or during copper welding [19]).…”