Time-Resolved Absorptance and Melt Pool Dynamics during Intense Laser Irradiation of a Metal

Published: October 25, 2018


Brian J. Simonds, Jeffrey W. Sowards, Joshua A. Hadler, Erik A. Pfeif, Boris Wilthan, Jack R. Tanner, Paul A. Williams, John H. Lehman


Laser welding is a complex, dynamic process by which focused, high-intensity laser light is used to join two metallic surfaces and is being increasing deployed in a variety of industrial applications. Determining the time-dependent absorptance of the laser light by the material is important, not only for gaining a fundamental understanding of the light-matter interaction, but also for improving process design in manufacturing. Measurements of optical absorptance during this process are notoriously difficult due to the rapidly changing nature of the absorbing medium. Dynamic absorptance data is also of vital importance to weld modelers whose complex simulations rely on accurate input data, yet there is very little reliable data available. In this work, we optically measure the time-dependent scattered light during a 10 ms laser spot weld using an integrating sphere. From this, we calculate the dynamic absorptance for 1070 nm wavelength light incident to a 316L stainless steel sample. In addition, the time resolution of our experiment (< 1 µs) allows for several physical phenomena to be identified such as melt and keyhole formation. The average absorptance values determined optically were compared to calorimetrically-determined values and it was found that the calorimeter severely underestimated the absorbed energy due to measured mass loss during the spot weld. Weld nugget cross-sections are also presented in order to verify our interpretation of the optical results as well as provide experimental data for weld model validation.
Citation: Physical Review Applied
Volume: 10
Pub Type: Journals

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Laser Welding, Absorption
Created October 25, 2018, Updated September 16, 2019