scholarly journals High-Speed X-Ray Investigation of Pore Formation during Full Penetration Laser Beam Welding of AA6016 Aluminum Sheets Contaminated with Lubricants

2020 ◽  
Vol 10 (6) ◽  
pp. 2077 ◽  
Author(s):  
Christian Hagenlocher ◽  
Jannik Lind ◽  
Rudolf Weber ◽  
Thomas Graf
Keyword(s):  
Laser Beam ◽  
Pore Formation ◽  
High Speed ◽  
Laser Beam Welding ◽  
Welding Process ◽  
X Ray ◽  
Aluminum Sheets ◽  
Full Penetration ◽  
X Ray Imaging ◽  
The Stability

The presence of lubricants on the surface of sheets favors the formation of pores in laser welded seams. This formation process was investigated by means of high-speed X-ray imaging of the full penetration laser beam welding process of two AA6016 aluminum sheets in overlap configuration. The measurement of the growth velocity of the bubbles indicated their sudden growth once they started to form. Further analysis of the X-ray images identified the point of origin of the pores: a few millimeters behind the capillary between the two aluminum sheets. The study shows that the lubricant does not affect the stability of the capillary, which evidences that the formation of these pores is not caused by the fluctuations of the capillary. These results explain for the first time why pore formation cannot be avoided by process strategies, which stabilize the capillary, when welding uncleaned sheets.

scholarly journals Synchrotron X-Ray Analysis of the Influence of the Magnesium Content on the Absorptance during Full-Penetration Laser Welding of Aluminum

Metals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 797
Author(s):  
Jonas Wagner ◽  
Christian Hagenlocher ◽  
Marc Hummel ◽  
Alexander Olowinsky ◽  
Rudolf Weber ◽  
...  
Keyword(s):  
Aluminum Alloys ◽  
Laser Beam ◽  
Laser Beam Welding ◽  
Welding Process ◽  
High Strength ◽  
Magnesium Content ◽  
X Ray ◽  
Full Penetration ◽  
Body Production ◽  
High Strength Aluminum Alloys

Full-penetration laser beam welding is characterized by a weld seam whose depth equals the material thickness. It is associated with a stable capillary and is therefore widely used for welding of sheet metal components. The realization of lightweight concepts in car body production requires the application of high-strength aluminum alloys that contain magnesium as an alloying element, which significantly influences the evaporation temperature and pressure. This change of the evaporation processes influences the geometry of the capillary and therefore its absorptance. In order to quantify the influence of magnesium on the capillary, their geometries were captured by means of high-speed synchrotron X-ray imaging during the welding process of the aluminum alloys AA1050A (Al99.5), AA5754 (AlMg3) and AA6016 (AlSi1.2Mg0.4). The 3D-geometries of the capillaries were reconstructed from the intensity distribution in the recorded X-ray images and their absorptance of the incident laser beam was determined by the analysis of the reconstructed 3D-geometry with a raytracing algorithm. The results presented in this paper capture for the first time the influence of the magnesium content in high-strength aluminum alloys on the aspect ratio of the capillary, which explains the reduced absorptance in case of full-penetration laser beam welding of aluminum alloys with a high content of volatile elements. In order to improve the absorptance in full-penetration welding, these findings provide the information required for the deduction of new optimization approaches.

scholarly journals Analysis and optimization of the piercing process in laser beam cutting by means of high-speed X-ray imaging

2021 ◽  
Vol 69 ◽  
pp. 303-310
Author(s):  
Jannik Lind ◽  
Niklas Weckenmann ◽  
Christian Hagenlocher ◽  
Rudolf Weber ◽  
Thomas Graf
Keyword(s):  
Laser Beam ◽  
High Speed ◽  
X Ray ◽  
X Ray Imaging

scholarly journals Influence of the laser cutting front geometry on the striation formation analysed with high-speed synchrotron X-ray imaging

2021 ◽  
Vol 1135 (1) ◽  
pp. 012009
Author(s):  
Jannik Lind ◽  
Christian Hagenlocher ◽  
David Blazquez-Sanchez ◽  
Marc Hummel ◽  
A. Olowinsky ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Laser Beam ◽  
Film Thickness ◽  
High Speed ◽  
Angle Of Incidence ◽  
Time Resolved ◽  
X Ray ◽  
Cut Edge ◽  
Local Increase ◽  
X Ray Imaging

Abstract The generation of low surface roughness of the cut edge during laser beam cutting is a challenge. The striation pattern, which determines the surface roughness, can be distinguished into regular and interrupted striations, the latter resulting in an increased surface roughness. In order to analyse their formation, the space- and time-resolved cutting front geometry and melt film thickness were captured during laser beam fusion cutting of aluminium sheets with a framerate of 1000 Hz by means of high-speed synchrotron X-ray imaging. The comparison of the contours of the cutting fronts for a cut result with regular und interrupted striations shows that the contour fluctuates significantly more in case of interrupted striations. This leads to a strong fluctuation of the local angle of incidence. In addition, the average angle of incidence decreases, which results in an increase of the average absorbed irradiance. Both phenomena, local increase of absorbed irradiance and its dynamic fluctuation, result in a local increase of the melt film thickness at the cutting front which is responsible for the formation of the interrupted striations.

UFO — a scalable platform for high-speed synchrotron X-ray imaging

2016 ◽  
Author(s):  
Andreas Kopmann ◽  
Suren Chilingaryan ◽  
Matthias Vogelgesang ◽  
Timo Dritschler ◽  
Andrey Shkarin ◽  
...  
Keyword(s):  
High Speed ◽  
X Ray ◽  
X Ray Imaging

syris: a flexible and efficient framework for X-ray imaging experiments simulation

2017 ◽  
Vol 24 (6) ◽  
pp. 1283-1295 ◽  
Author(s):  
Tomáš Faragó ◽  
Petr Mikulík ◽  
Alexey Ershov ◽  
Matthias Vogelgesang ◽  
Daniel Hänschke ◽  
...  
Keyword(s):  
Motion Estimation ◽  
Data Processing ◽  
Graphics Processing Units ◽  
High Speed ◽  
Real Data ◽  
Estimation Accuracy ◽  
Processing Parameter ◽  
X Ray ◽  
X Ray Imaging ◽  
Imaging Conditions

An open-source framework for conducting a broad range of virtual X-ray imaging experiments,syris, is presented. The simulated wavefield created by a source propagates through an arbitrary number of objects until it reaches a detector. The objects in the light path and the source are time-dependent, which enables simulations of dynamic experiments,e.g.four-dimensional time-resolved tomography and laminography. The high-level interface ofsyrisis written in Python and its modularity makes the framework very flexible. The computationally demanding parts behind this interface are implemented in OpenCL, which enables fast calculations on modern graphics processing units. The combination of flexibility and speed opens new possibilities for studying novel imaging methods and systematic search of optimal combinations of measurement conditions and data processing parameters. This can help to increase the success rates and efficiency of valuable synchrotron beam time. To demonstrate the capabilities of the framework, various experiments have been simulated and compared with real data. To show the use case of measurement and data processing parameter optimization based on simulation, a virtual counterpart of a high-speed radiography experiment was created and the simulated data were used to select a suitable motion estimation algorithm; one of its parameters was optimized in order to achieve the best motion estimation accuracy when applied on the real data.syriswas also used to simulate tomographic data sets under various imaging conditions which impact the tomographic reconstruction accuracy, and it is shown how the accuracy may guide the selection of imaging conditions for particular use cases.

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