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Publications

13th CIRP Conference on Photonic Technologies  08/2024

Acoustic process monitoring during the structuring of diffusion media for fuel cells with Ultrashort Laser Pulses

Authors:

Christian Geigera, Pawel Garkushaa, Christian Bernauera, Simon Mehrla, Pascal A. Schirmerb, Michael F. Zaeha

Contents:
  •          Diffusion media in fuel cells can be optimized through laser structuring to improve their performance characteristics.
  •          An optical microphone was used to monitor the process during laser structuring.
  •          This paper demonstrated that acoustic data can be used to monitor the laser focus position as well as material transitions in the diffusion media during structuring.

Link

Wood Materal Science & Engineering  10/2024

Predicting wood moisture classes by sound frequency spectra and Explainable Machine Learning during milling

Authors:

Mehieddine Derbas, Timothy Mark Young, Stephan Frömel-Frybort, Hans- Christian Möhring & Martin Riegler

Contents:
  •          The moisture content in wood has a strong impact on the optimal process parameters during milling.
  •          In this work, wood milling was monitored by a novel optical microphone to distinguish between moisture classes (dried, conditioned, wet and frozen).
  •          Machine learning was applied to the selected spectral data to determine both the moisture classes and milling speed. The best model achieved an accuracy of 97.2%. 

Link

Journal of Laser Applications  03/2025

Layer detection in ultrashort pulsed multilayer laser ablation by analyzing ultrasonic process emission

Authors:

Christian Lutz, Cemal Esen, Ralf Hellmann

Contents:
  • Laser ablation is used for processing electronic applications (e.g. PCB)
  • This paper presents the detection of material transitions during laser ablation by analyzing acoustic data captured with an optical microphone.
  • The focus of this work was on the material transition between polyimide and copper. Due to the higher removal rate in polyimide compared to copper, a    significant increase in acoustic energy was detected at the material transition.
  •  In addition to detecting material transitions, a correlation between the emitted acoustic energy and layer thickness was observed.

Link

17th CIRP Conference on Intelligent Computation in Manufacturing Engineering (CIRP ICME ‘23)  08/2024

In-situ acoustic signals correlation of process parameters in laser powder bed fusion

Authors:

Levent Subasi, Soner Oren, Gokhan Dursun, Cagdas Sen, Akin Orhangul

Contents:
  • Laser powder bed fusion (LPBF) is a metal additive manufacturing technique in which repeatability is a major concern in quality results.
  •          An optical microphone was used to monitor the acoustic emission during the LPBF process.
  •          The analysis showed a strong correlation between the acoustic signals and the process parameters.
  •         This methodology allows for the evaluation of process flaws and overall quality.
Link

Springer 03/2025

Handbook of Nondestructive Evaluation 4.0

Authors:

Norbert Meyendorf, Nathan Ida, et.al.

Contents:
  • This handbook is a comprehensive overview of advanced NDE technologies for use in many different industrial applications
  • XARION is represented with a chapter on its innovative automated spot-weld inspection technology
Link

Applied Sciences 10/2024

Acoustic Emission and Digital Image Correlation-Based Study for Early Damage Identification in Sandwich Structures

Authors:

Aitor García de la Yedra, Igor Erro, et al.

Contents:
  • Monitoring the quality of complex sandwich structures is difficult with common testing techniques for accessibility reasons
  • A novel approach to solve this issue is enabled by acoustic monitoring in the ultrasound regime with the Optical Microphone
  • The results from acoustic monitoring were compared to findings obtained with digital image correlation
  • It could be shown that early identification of structural damage is possible with the Optical Microphone
Link

Additive Manufacturing 01/2024

Healing of keyhole porosity by means of defocused laser beam remelting: Operando observation by X-ray imaging and acoustic emission-based detection

Authors:

Charlotte de Formanoir, Milad Hamidi Nasab, et al.

Contents:
  • In Laser Powder-Bed Fusion (LPBF) the unpredictable formation of defects such as pores can lead to compromised mechanical properties
  • Using XARION’s optical microphone a strategy for monitoring in-situ healing of pores through laser remelting was implemented
  • Acoustic signals acquired during laser remelting are temporally synchronized and analyzed with X-ray images to identify acoustic signatures of the pore healing event
  • The approach presented in this paper enables precise monitoring of defect healing during the LPBF process without the use of elaborate machine learning algorithms
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SPIE. Photonics West 01/2024

Towards process control by detecting acoustic emissions during ultrashort pulsed laser ablation of multilayer materials

Authors:

C. Lutz, R. Sommerhuber, M. Kettner, C. Esen, R. Hellmann

Contents:
  • Ultra-short-pulsed laser ablation of thin multilayer materials can be monitored using XARION’s Eta450 Ultra optical microphone
  • It is possible to monitor the material transition between polymer and copper during laser ablation by observing a broad acoustic frequency spectrum between 100 kHz and 2 MHz in air, and by detecting a sudden change in acoustic energy
  • A direct correlation was found between increased detected acoustic energy and higher ablation rate
Link

Nature Communications 12/2023

Harmonizing sound and light: X-ray imaging unveils acoustic signatures of stochastic inter-regime instabilities during laser melting

Authors:

Milad Hamidi Nasab, Giulio Masinelli, et al.

Contents:
  • Laser Powder Bed Fusion Additive Manufacturing (LPBF AM) is a metal additive manufacturing process capable of directly producing intricate three-dimensional metallic components from CAD models
  • The present work deploys high-speed synchrotron X-ray imaging to scrutinize keyhole melting instabilities in LPBF and correlates these with the process’ acoustic emission (AE)
  • XARION’s optical microphone was used to measure airborne AE from the interaction zone between laser and material
  • The transition between conduction, stable keyhole, and unstable keyhole regimes, which leads to porosity formation and other instabilities, can successfully be discerned using the AE data
PDF

Nature Communications 11/2023

Ultrasonic barrier-through imaging by Fabry-Perot resonance-tailoring panel

Authors:

Chung Il Park, Seungah Choe, et al.

Contents:
  • Ultrasonic imaging through nearly impenetrable metal barriers or the human skull remains an unresolved challenge
  • Applying a Fabry-Perot resonance approach and resonance tailoring panels the authors show that ultrasonic transmission through otherwise impenetrable barriers can be achieved
  • XARION's optical hydrophone (Eta100L Ultra) was employed to capture ultrasonic signals in the experiments
  • The newly developed method enables almost equivalent image quality as without barriers and has the potential to improve ultrasonic imaging
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