Analyzing multispectral emission and synchrotron data to evaluate the quality of laser welds on copper

Journal of Laser Applications, vol. 36

Abstract

The validation of laser welding of metallic materials is challenging due to its highly dynamic processes and limited accessibility to the weld. The measurement of process emissions and the processing laser beam are one way to record highly dynamic process phenomena. However, these recordings always take place via the surface of the weld. Phenomena on the inside are only implicitly recognizable in the data and require further processing. To increase the validity of the diagnostic process, the multispectral emission data are synchronized with synchrotron data consisting of in situ high-speed images based on phase contrast videography. The welding process is transilluminated by synchrotron radiation and recorded during execution, providing clear contrasts between solid, liquid, and gaseous material phases. Thus, dynamics of the vapor capillary and the formation of defects such as pores can be recorded with high spatial and temporal resolution of <5 μm and >5 kHz. In this paper, laser welding of copper Cu-ETP and CuSn6 is investigated at the Deutsches Elektronen-Synchrotron (DESY). The synchronization is achieved by leveraging a three-stage deep learning approach. A preprocessing Mask-R-CNN, dimensionality reduction PCA/Autoencoders, and a final LSTM/Transformer stage provide end-to-end defect detection capabilities. Integrated gradients allow for the extraction of correlations between defects and emission data. The novel approach of correlating image and sensor data increases the informative value of the sensor data. It aims to characterize welds based on the sensor data not only according to IO/NIO but also to provide a quantitative description of the defects in the weld.

Authors 7

1. Jan Brüggenjürgen Aachen Chair for Laser Technology LLT Fraunhofer Institute for Laser Technology ILT 1

   Fraunhofer Institute for Laser Technology · RWTH Aachen University

   Affiliation as printed

   Chair for Laser Technology LLT, RWTH Aachen University 2 , Steinbachstraße 15, Aachen 52074,

   Fraunhofer Institute for Laser Technology ILT 1 , Steinbachstraße 15, Aachen 52074,

2. Christoph Spurk Aachen Chair for Laser Technology LLT

   RWTH Aachen University

   Affiliation as printed

   Chair for Laser Technology LLT, RWTH Aachen University 2 , Steinbachstraße 15, Aachen 52074,

3. Marc Hummel Aachen Chair for Laser Technology LLT

   RWTH Aachen University

   Affiliation as printed

   Chair for Laser Technology LLT, RWTH Aachen University 2 , Steinbachstraße 15, Aachen 52074,

4. André Häusler Aachen Fraunhofer Institute for Laser Technology ILT 1

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT 1 , Steinbachstraße 15, Aachen 52074,

5. Alexander M. Olowinsky Aachen Fraunhofer Institute for Laser Technology ILT 1

   Fraunhofer Institute for Laser Technology

   Affiliation as printed

   Fraunhofer Institute for Laser Technology ILT 1 , Steinbachstraße 15, Aachen 52074,

6. Felix Beckmann

   Helmholtz-Zentrum Hereon

   Affiliation as printed

   Institute of Materials Physics, Helmholtz-Zentrum Hereon 4 , Max-Planck-Str.1, Geesthacht 21502,

7. Julian P. Moosmann

   Helmholtz-Zentrum Hereon

   Affiliation as printed

   Institute of Materials Physics, Helmholtz-Zentrum Hereon 4 , Max-Planck-Str.1, Geesthacht 21502,