Analysis of the interaction between the temperature field and the weld seam morphology in laser transmission welding by using two different discrete laser wavelengths

Abstract

Laser transmission welding is a non-contact and efficient process technology for joining thermoplastic polymers. In the conventional process, laser sources in the wavelength range of 1 μm are usually used. Therefore, most of the laser radiation is transmitted through the upper joining partner and absorbed only in the lower joining partner. As a result, the possibilities to influence the temperature field especially in the upper joining partner are limited. To overcome these limitations, an additional thulium fiber-laser with a wavelength of 1.94 μm is used in this study and coaxially aligned with a diode laser. The use of an additional thulium fiber-laser leads to a significant absorption in the upper joining partner. Through this approach, it is shown that the temperature field and the weld seam geometry can be influenced by using these two different discrete laser wavelengths. Depending on the intensity distribution of both lasers, an increase of the size of the heat affected zone in the upper joining partner can be observed. In order to develop a better process understanding, a thermal finite element model is built up and verified by comparing the calculated size of the heat affected zone for different process parameters with the experimental data. The model is able to represent the influence of both laser sources on the temperature field and is used to calculate characteristics of the temperature field, such as maximum temperatures or cooling rates. The characteristics are then used to explain the weld seam morphology, such as occurrence and size of spherulitic structures in the weld seam.

Numerical Simulation of Laser Transmission Welding—A Review on Temperature Field, Stress Field, Melt Flow Field, and Thermal Degradation

“…However, it simplifies the heat source distribution law Numerical simulations allow obtaining the temperature field of multiple heat sources superimposed. Geißler [61] established a finite element model using the sum of two bulk heat source models superimposed to simulate the temperature field of a diode laser (λ = 920-1050 nm) and a fiber laser (λ = 1940 nm) used to increase the energy absorption effect of the upper partners. The study investigated the effect of the two superimposed laser sources on the temperature field and weld geometry during both contour welding and quasi-synchronous welding processes.…”

Influence of Laser Pulse Welding Power on Welding Joints of Zr‐Based Amorphous Alloys

“…[7,8] Laser welding is a common welding method for amorphous alloys. [9,10] It can ensure smaller heat input and faster DOI: 10.1002/crat.202200063 cooling [11,12] and it can effectively inhibit the crystallization of welded joints. Research on laser welding of amorphous alloys has mainly focused on reducing crystallization and the detection of crystallization composition.…”