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Mechanism study on the effects of power modulation on energy coupling efficiency in infrared laser welding of highly-reflective materials
摘要： High-reflectivity of materials, such as magnesium, copper and aluminum, results in low thermal efficiency of their infrared laser welding processes. AZ31 magnesium alloy was selected to study the effects of power modulation on energy coupling efficiency in laser welding of highly-reflective materials. A model for the relationship between energy coupling efficiency and modulation parameters was obtained. The energy coupling efficiency in optimized modulated-power laser welding was about 1.58 times that in constant-power welding. The mechanism was explored by analyzing keyhole evolution and the resulted pressure distribution along keyhole wall during welding. The keyhole evolutions in laser continuous welding of common material (Q345 steel, reflectivity of 65%) and highly-reflective material (AZ31, reflectivity of 85%) were observed through high-speed imaging by utilizing a half sandwich method. The results indicated that the secret of improving energy coupling efficiency of laser welding process of highly-reflective materials through power modulation was the formation of a deep keyhole and its long life. When instantaneous power decreased from the peak, there was still enough recoil pressure at the bottom of keyhole to resist surface tension and hydrostatic pressure of liquid metal, which was the fundamental reason for the long time existence of keyhole with a large depth.
关键词： laser welding,magnesium alloy,recoil pressure,keyhole,highly-reflective materials,power modulation
更新于2025-11-28 14:24:20
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Processing of Keyhole Depth Measurement Data during Laser Beam Micro Welding
摘要： Analysing the quality of weld seams is still a challenging task. An optical inspection of the surface is giving limited information about the shape and depth of the weld seam. An application for laser beam welding with high demands regarding the weld depth consistency is the electrical contacting of battery cells. The batteries themselves have a limited terminal or case thickness that must not be penetrated during the welding process to avoid leakage or damage to the cell. That leads to a minimum weld depth to ensure the electrical functionality, and a maximum weld depth indicated by the case thickness. In such applications, a destructive analysis is not suitable which leads to the demand for a non-destructive measurement during the process. Using a coaxial, interferometric measurement setup, the keyhole depth during the deep penetration welding is measureable. For a keyhole with a depth of a couple of millimetres, such a system is commercially available. In micro scale, however, these systems are facing several challenges such as scanning systems, small spot diameters of a few tens of micrometres and narrow keyholes. This study contains an investigation of an interferometric measurement of the keyhole depth and the suitability for laser micro welding. Therefore, the data processing of the achieved measurements is investigated, and the results are compared with the depth measurement of metallographic analysed samples. Stainless steel is used to investigate the behaviour and the stability of developed data processing strategy and the resulting depth values.
关键词： Laser welding,battery,copper,spatial power modulation,aluminium,keyhole depth measurement
更新于2025-09-23 15:21:01
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Power modulated fiber-optic loop sensor: theoretical and experimental investigation
摘要： The present work is focused on discussing a power modulation based sensor created using a single mode optical fiber. The sensing principle allows making displacement measurements with high accuracy and in a large measurement range due to the presence of resonance peaks in the transmitted intensity. A theoretical model is developed for the Fiber-Optic Loop Sensor (FOLS) and is validated with experimental data. The results show close matching between theoretical predictions and experimental results, allowing the use of the sensor for displacement measurement.
关键词： experimental validation,Fiber optic loop sensor,deformation,theoretical model,power modulation
更新于2025-09-23 15:21:01
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Overlap joining of aluminium and copper using laser micro welding with spatial power modulation
摘要： The rising demand for high power battery systems for the electric mobility requires the connection of a large number of cells. Due to the functionality of the cell chemistry, a combination of copper and aluminium is necessary. The differing material properties like thermal conductivity as well as the formation of intermetallic phases are challenging for welding processes. This study contains the results for overlap joints of copper and aluminium using a laser beam welding process with spatial power modulation. With a parameter variation, the cross-sectional shape of the weld seams and therefore, the ratio of depth to width can be adjusted. With additional longitudinal cross sections and an energy-dispersive X-ray spectroscopy analysis, the different mixing behaviour of the dissimilar material depending on the top layer is investigated.
关键词： Laser welding,Spatial power modulation,Micro joining,Battery,Aluminium,Copper
更新于2025-09-19 17:13:59