Włodzimierz Zowczak

The paper describes a study on the effects of beam power and feed rate in the process of cutting fresh wood with a CO₂ laser on water contact angle on the cut surface. The study involved several broadleaved tree species (oak, birch, alder, plum, and apple tree) and one coniferous species (pine). Samples were cut with a Trumpf TLC1005 laser equipped with a TruFlow 6000 CO₂ resonator at a wavelength of 10.6 μm at three power output settings (1 kW, 2 kW, and 3 kW) and one feed rate (0.4 m∙min^− 1). Contact angle was measured by pipetting a drop of distilled water on the wood surface and recording the process with a camera. Subsequently, images of the drop were analyzed over one minute at 10 s intervals to determine changes in contact angle for each of the cases examined. It was not possible to measure the contact angle on saw-cut samples as the water was immediately absorbed, while water drops placed on laser-cut samples remained on the surface for over 60 s, with the contact angle decreasing over time for the examined species from an average of 90° to 40°. The higher beam power settings (2 or 3 kW) were found to be preferable for the hardwood species (oak, birch, alder, and apple tree). In turn, in the case of the softwood species (pine), the laser power output did not matter, as both at the low (1 kW) and high (3 kW) settings the drop did not spread over the surface quickly. Finally, the optimum beam power for plum tree wood was found to be 1 kW.

This article presents a numerical analysis of laser-welded flange pipe joints. The presented results concern the welding of low carbon S235JR and stainless 316L steels using a CO2 laser in lap and fillet joint configurations. The estimation of welding parameters was achieved using Simufact Welding software and numerical simulation, where output power, feed rate, efficiency and intensity distribution (Gaussian parameter) were analysed. In accordance with the established model, a thermo-mechanical simulation was performed. The calculated joint geometries show good agreement with experiments; therefore, the obtained results were used to study selected joint properties of both joint types. Stress-strain distribution was estimated on the basis of thermomechanical analysis. Weld bead geometry obtained from numerical simulation was compared with the results from trial joints. The numerical model established for both joint configurations shows good agreement with experimental results and were assumed to be accurate. The results of the performed analysis shown some advantages of the use of this configuration of lap joints in flange pipe joints.

While lasers are widely used across various industries, including woodworking, few studies to date have addressed the issue of cutting fresh wood. In the present investigation, wood stemming from fresh tree branches was cut at different laser powers and beam travel speeds. A fiber laser and a CO₂ laser were used for the research. The cellular structures of the cut surfaces were examined, with some of them found to be covered with a layer of compacted, charred cells. This may be a favorable phenomenon, preventing the invasion of pathogens via the wounds caused by laser beam branch cutting in nurseries, plantations, and orchards.

Artykuł Badanie właściwości mechanicznych złączy z niskowęglowych stali Cr-Mo spawanych laserowo * | Mechanik Miesięcznik Naukowo-Techniczny