The causal relationship between melt pool geometry and energy absorption measured in real time during laser-based manufacturing

Simonds, Brian J.; Tanner, Jack; Artusio‐Glimpse, Alexandra B.; Williams, Paul; Parab, Niranjan D.; Zhao, Cang; Sun, Tao

doi:10.1016/j.apmt.2021.101049

Cited by 41 publications

(18 citation statements)

References 37 publications

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“…The core finding is the strong correlation between laser absorption and the stability of the vapor depression. Simonds et al [27] found a significant laser absorption reduction due to a change in the vapor depression aspect ratio, an event that is correlated to the formation of porosity. A 1070 nm and 1 kW Yb-doped fiber laser was used at a spot size of 49.5 µm for all the investigations.…”

Section: Introductionmentioning

confidence: 99%

“…They investigated the periodic nature of absorptance, which was traced back to protrusions of the keyhole sidewalls that either narrowed the keyhole opening or reduced the overall keyhole area. These investigations were expanded to powder bed absorption measurements and simultaneous high-speed synchrotron imaging to transfer and conduct the results to powder bed fusion of Ti6Al4V [27]. The core finding is the strong correlation between laser absorption and the stability of the vapor depression.…”

Section: Introductionmentioning

confidence: 99%

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Absorbance measurement for in situ process regime identification in laser processing

Wittemer

Grünewald

Wudy

2023

Int J Adv Manuf Technol

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Laser melting can be conducted in two different process regimes, the conduction and the keyhole mode, which exhibit significantly different characteristics, dynamics, and stability and are highly sensitive to a magnitude of process parameters. Despite these differences and the resulting high relevance of the prevailing process regime for process development, the regime is commonly deduced after specimen testing. An identification of the regime parallel to the process could speed up the process development of, for example, laser beam welding or laser-based powder bed fusion of metals. Therefore, the possibility of an in situ regime identification under process-near conditions is the aim of these investigations. For this, the absorbance is measured in situ by using an integrating sphere on an in-house-developed test rig. This test rig can mimic real production process conditions to detect the characteristic change in the degree of absorption when switching between the process regimes. These measurements were conducted during experiments in which only the laser power was varied. A significant change in absorption was detected at a threshold laser power of 100 W, which correlates with the transition between the process regimes’ conduction and keyhole regime. This threshold was proven by subsequent identification analysis of micrographic cross sections. This correlation promises the possibility of fast in situ process regime identification under near-real production process conditions with the potential of accelerating process development.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Absorbance measurement for in situ process regime identification in laser processing

Wittemer

Grünewald

Wudy

2023

Int J Adv Manuf Technol

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“…Assumptions made to develop computational models often affect their reliability, accuracy and performance in predicting and describing the process behaviour. For instance, studies suggest that melt-pool surface deformations affect power-density distribution, leading to changes in the thermal field, Marangoni flow pattern and the melt-pool shape [7][8][9]. Conversely, previous investigations [10][11][12][13] have shown a considerable influence of laser characteristics and power-density distribution on molten metal flow behaviour in laser welding and additive manufacturing.…”

Section: Introductionmentioning

confidence: 99%

The influence of laser characteristics on internal flow behaviour in laser melting of metallic substrates

Ebrahimi,

Sattari,

Bremer

et al. 2022

Preprint

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The absorptivity of a material is a major uncertainty in numerical simulations of laser welding and additive manufacturing, and its value is often calibrated through trial-and-error exercises. This adversely affects the capability of numerical simulations when predicting the process behaviour and can eventually hinder the exploitation of fully digitised manufacturing processes, which is a goal of "industry 4.0". In the present work, an enhanced absorption model that takes into account the effects of laser characteristics, incident angle, surface temperature, and material composition is utilised to predict internal heat and fluid flow in laser melting of stainless steel 316L. Employing such an absorption model is physically more realistic than assuming a constant absorptivity and can reduce the costs associated with calibrating an appropriate value. High-fidelity three-dimensional numerical simulations were performed using both variable and constant absorptivity models and the predictions compared with experimental data. The results of the present work unravel the crucial effect of absorptivity on the physics of internal flow in laser material processing. The difference between melt-pool shapes obtained using fibre and CO 2 laser sources is explained, and factors affecting the local energy absorption are discussed.

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“…A recoil pressure is thus exerted onto the melt pool, which creates a cavity (the KH) at the center of the interaction zone, in which the incident beam gets trapped. The energy coupling of the process is thus "cavity-enhanced" [1], which makes possible to weld sheets of several millimeter thick, or to ensure material continuity between subsequent layers in LPBF.…”

Section: Introductionmentioning

confidence: 99%

Physical mechanisms of conduction-to-keyhole transition in laser welding and additive manufacturing processes

Mayi

Dal

Peyre

et al. 2023

Optics & Laser Technology

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The causal relationship between melt pool geometry and energy absorption measured in real time during laser-based manufacturing

Cited by 41 publications

References 37 publications

Absorbance measurement for in situ process regime identification in laser processing

Absorbance measurement for in situ process regime identification in laser processing

The influence of laser characteristics on internal flow behaviour in laser melting of metallic substrates

Physical mechanisms of conduction-to-keyhole transition in laser welding and additive manufacturing processes

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