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BETA
Christiansson, Anna-KarinORCID iD iconorcid.org/0000-0001-5608-8636
Alternative names
Publications (10 of 62) Show all publications
Kisielewicz, A., Sadeghi, E., Sikström, F., Christiansson, A.-K., Palumbo, G. & Ancona, A. (2020). In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718. Materials & design, 186
Open this publication in new window or tab >>In-process spectroscopic detection of chromium loss during Directed Energy Deposition of alloy 718
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2020 (English)In: Materials & design, ISSN 0264-1275, E-ISSN 1873-4197, Vol. 186, p. -9Article in journal (Refereed) Epub ahead of print
Abstract [en]

In this work, a fast optical spectrometer was used to monitor the Directed Energy Deposition (DED) process, during the deposition of Alloy 718 samples with different laser power, thus different energy inputs into the material. Spectroscopic measurements revealed the presence of excited Cr I atoms in the plasma plume. The presence was more apparent for the samples characterized by higher energy input. The Cr depletion from these samples was confirmed by lower Cr content detected by Energy-Dispersive X-ray Spectroscopy (EDS) analysis. The samples were also characterized by higher oxidation and high-temperature corrosion rates in comparison to the samples produced with low energy input. These results prove the applicability of an optical emission spectroscopic system for monitoring DED to identify process conditions leading to compositional changes and variation in the quality of the built material.

Place, publisher, year, edition, pages
Elsevier, 2020
Keywords
Spectroscopic system, Additive manufacturing, Directed energy deposition, Cr depletion, High-temperature corrosion
National Category
Metallurgy and Metallic Materials
Research subject
ENGINEERING, Manufacturing and materials engineering; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14733 (URN)10.1016/j.matdes.2019.108317 (DOI)
Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2019-11-28Bibliographically approved
Nilsen, M., Sikström, F. & Christiansson, A.-K. (2019). A study on change point detection methods applied to beam offset detection in laser welding. Paper presented at 17th Nordic Laser Materials Processing Conference - (NOLAMP17), 27 –29 August 2019. Procedia Manufacturing, 36, 72-79
Open this publication in new window or tab >>A study on change point detection methods applied to beam offset detection in laser welding
2019 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 36, p. 72-79Article in journal (Refereed) Published
Abstract [en]

This paper presents an experimental study where a photodiode integrated into a laser beam welding tool is used to monitor laser beam spot deviations fromthe joint, the beam offset. The photodiode system is cost effective and typically easy to implement in an industrial system. The selected photodiode is a silicondetector sensitive in the spectral range between 340-600nm which corresponds to the spectral emissions from the plasma plume. The welding application is closed-square-butt joint welding where a laser beam offset can cause lack of fusion in the resulting weld. The photodiode signal has been evaluated by two different change point detection methods, one off-line and one on-line method, with respect to their detection performance. Off-line methods can be used to guide post weld inspection and on-line methods have the potential to enable on-line adaptive control or the possibility to stop the process for repair. The performance of the monitoring system and the change point detection methods have been evaluated from data obtained during laser beam welding experiments conducted on plates of stainless steel. The results clearly indicates the possibility to detect beam offsets by photodiode monitoring.

Keywords
Laser beam welding; monitoring; photodiode; change point detection
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-14384 (URN)10.1016/j.promfg.2019.08.011 (DOI)2-s2.0-85072523021 (Scopus ID)
Conference
17th Nordic Laser Materials Processing Conference - (NOLAMP17), 27 –29 August 2019
Funder
Vinnova, 2016-03291
Available from: 2019-09-05 Created: 2019-09-05 Last updated: 2019-12-10Bibliographically approved
Nilsen, M., Sikström, F. & Christiansson, A.-K. (2019). Adaptive control of the filler wire rate during laser beam welding of squared butt joints with varying gap width. The International Journal of Advanced Manufacturing Technology, 102(9-12), 3667-3676
Open this publication in new window or tab >>Adaptive control of the filler wire rate during laser beam welding of squared butt joints with varying gap width
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 102, no 9-12, p. 3667-3676Article in journal (Refereed) Published
Abstract [en]

Adding filler wire control to autogenous laser beam welding of squared butt joints offers a means to widen up the tight fit-up tolerances associated with this process. When the gap width varies, the filler wire rate should be controlled to assure a constant geometry of the resulting weld seam. A dual mode sensing system is proposed to estimate the joint gap width and thereby control the filler wire rate. A vision camera integrated into the welding tool together with external LED illumination and a laser line projection enables two sensing modes, one surface feature extraction mode and one laser triangulation-based mode. Data from the both modes are fused in a Kalman filter, and comparisons show that the fusing of the data gives more robust estimation than estimates from each single mode. A feed-forward control system adaptively adjusts the filler wire rate based on the estimations ofthe joint gap width in front of the keyhole. The focus is on keeping the data processing simple and affordable, and the real-time performance of the sensor and control system has been evaluated by welding experiments. It is shown that the proposed system can be used for on-line control of the filler wire rate to achieve a constant weld geometry during varying joint gap widths

Place, publisher, year, edition, pages
Springer, 2019
Keywords
Laser beam welding, Filler wire, Squared butt joints, Varying gap width, Feature extraction, Laser triangulation, Sensor fusion
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13640 (URN)10.1007/s00170-019-03325-w (DOI)000469060700066 ()2-s2.0-85067693903 (Scopus ID)
Funder
Vinnova, 2016-03291
Available from: 2019-02-28 Created: 2019-02-28 Last updated: 2019-12-10Bibliographically approved
Elefante, A., Nilsen, M., Sikström, F., Christiansson, A.-K., Maggipinto, T. & Ancona, A. (2019). Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal. Optics and Laser Technology, 109, 178-185
Open this publication in new window or tab >>Detecting beam offsets in laser welding of closed-square-butt joints by wavelet analysis of an optical process signal
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2019 (English)In: Optics and Laser Technology, ISSN 0030-3992, E-ISSN 1879-2545, Vol. 109, p. 178-185Article in journal (Refereed) Published
Abstract [en]

Robotized laser beam welding of closed-square-butt joints is sensitive to the positioning of the laser beam with respect to the joint since even a small offset may result in a detrimental lack of sidewall fusion. An evaluation of a system using a photodiode aligned coaxial to the processing laser beam confirms the ability to detect variations of the process conditions, such as when there is an evolution of an offset between the laser beam and the joint. Welding with different robot trajectories and with the processing laser operating in both continuous and pulsed mode provided data for this evaluation. The detection method uses wavelet analysis of the photodetector signal that carries information of the process condition revealed by the plasma plume optical emissions during welding. This experimental data have been evaluated offline. The results show the potential of this detection method that is clearly beneficial for the development of a system for welding joint tracking.

Place, publisher, year, edition, pages
Elsevier, 2019
Keywords
Laser beam welding, Joint tracking, Butt joints, Photodiode, Wavelet analysis
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-12832 (URN)10.1016/j.optlastec.2018.08.006 (DOI)000446949600023 ()2-s2.0-85051138319 (Scopus ID)
Funder
Vinnova, 2016-03291
Available from: 2018-08-21 Created: 2018-08-21 Last updated: 2019-12-11Bibliographically approved
Svenman, E., Christiansson, A.-K. & Runnemalm, A. (2019). Experimental validation of an inductive probe for narrow gap measurement based on numerical modelling. Measurement, 146, 396-402
Open this publication in new window or tab >>Experimental validation of an inductive probe for narrow gap measurement based on numerical modelling
2019 (English)In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 146, p. 396-402Article in journal (Refereed) Published
Abstract [en]

Experimental validation of numeric results for an inductive probe shows that narrow gaps between two plates can be measured with accuracy suitable for laser beam welding. A two-coil inductive probe for measurement of the gap was built based on finite element modelling results. The individual coils were calibrated using a complex response method, and results from the physical coils closely match the numerical results regarding distance to gap and lift-off above the plate. The measurement of a realistic gap shows results that can be used in industrial applications for position, plate height and height alignment. © 2019

Keywords
Laser beam welding; Laser beams; Measurement; Numerical methods; Probes; Welding, Complex response; Experimental validations; Finite element modelling; Lift offs; Numerical results; Plate height; Two plates; Zero-gap, Inductive sensors
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-14459 (URN)10.1016/j.measurement.2019.06.033 (DOI)000481402800042 ()2-s2.0-85068252439 (Scopus ID)
Funder
Knowledge Foundation
Available from: 2019-10-02 Created: 2019-10-02 Last updated: 2019-12-11Bibliographically approved
Svenman, E. & Christiansson, A.-K. (2019). Investigation of effects from realistic influences on inductive gap measurement. Measurement, 143, 199-210
Open this publication in new window or tab >>Investigation of effects from realistic influences on inductive gap measurement
2019 (English)In: Measurement, ISSN 0263-2241, E-ISSN 1873-412X, Vol. 143, p. 199-210Article in journal (Refereed) Published
Abstract [en]

The influence of deviations from ideal square butt joint conditions is investigated for an improved inductive gap measurement method. Varying plate thickness, chamfers, and scratches are tested on Alloy 718 at different frequencies in a working range around the gap. Results for different plate thickness show that measurements of position and gap width are affected at all frequencies tested. For a chamfered plate, position measurement is affected for all frequencies, while gap width measurement is less affected at higher frequencies. For both a narrow and a wide scratch, the position measurement at the highest frequency is affected for all scratch locations, while for gap width measurement, only the wide scratch is affecting for all locations. Errors in measurement of probe height and plate alignment are smaller than 0.04 and 0.05 mm for all situations. The results will support in selecting coil frequency and predict results in non-ideal conditions. © 2019

Place, publisher, year, edition, pages
., 2019
Keywords
Butt welding; Measurement; Position measurement, Different frequency; Gap measurements; Higher frequencies; Measurements of; Non-ideal conditions; Plate thickness; Square butt joints; Zero-gap, Inductive sensors
National Category
Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13918 (URN)10.1016/j.measurement.2019.05.020 (DOI)000470062200019 ()2-s2.0-85065701137 (Scopus ID)
Funder
Knowledge Foundation, Dnr 20140130
Available from: 2019-06-05 Created: 2019-06-05 Last updated: 2019-07-23Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2019). Robust vision-based joint tracking for laser welding of curved closed-square-butt joints. The International Journal of Advanced Manufacturing Technology, 101(5-8), 1867-1978
Open this publication in new window or tab >>Robust vision-based joint tracking for laser welding of curved closed-square-butt joints
2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 101, no 5-8, p. 1867-1978Article in journal (Refereed) Published
Abstract [en]

Robotized laser beam welding of closed-square-butt joints is sensitive to how the focused laser beam is positioned in relation to the joint, and existing joint tracking systems tend to fail in detecting the joint when the gap and misalignment between the work pieces are close to zero. A camera-based system is presented based on a high dynamic range camera operating with LED illumination at a specific wavelength and a matching optical filter. An image processing algorithm based on the Hough transform extracts the joint position from the camera images, and the joint position is then estimated using a Kalman filter. The filter handles situations, when the joint is not detectable in the image, e.g., when tack welds cover the joint. Surface scratches, which can be misinterpreted as being the joint, are handled by a joint curve prediction model based on known information about the nominal path defined by the robot program. The performance of the proposed system has been evaluated off line with image data obtained during several welding experiments.

Keywords
Laser beam welding, Joint tracking, Butt joints, Camera, Hough transform, Kalman filter
National Category
Materials Engineering Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13211 (URN)10.1007/s00170-018-3044-0 (DOI)2-s2.0-85057563235 (Scopus ID)
Projects
VINNOVA project VarGa
Funder
Vinnova, 2016-03291
Note

First Online: 27 November 2018

Funders: SWE-DEMO MOTOR ; [2015-06047]

Available from: 2018-12-18 Created: 2018-12-18 Last updated: 2019-11-25Bibliographically approved
Nilsen, M., Sikström, F., Christiansson, A.-K. & Ancona, A. (2018). In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints. Paper presented at 8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018. Procedia Manufacturing, 25, 511-516
Open this publication in new window or tab >>In-process Monitoring and Control of Robotized Laser Beam Welding of Closed Square Butt Joints
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 511-516Article in journal (Other academic) Published
Abstract [en]

In robotized laser welding of technical zero gap closed square butt joints it is critical to position the laser beam correct with regardsto the joint. Welding with an offset from the joint may cause lack of sidewall fusion, a serious defect that is hard to detect and gives a weak weld . When using machined parts with gap and misalignment between the parts that is close to zero, existing joint tracking systems will probably fail to track the joint. A camera based system using LED illumination and matching optical filters is proposed in this paper to address this issue. A high dynamic range CMOS camera and the LED illumination is integrated into the laser tool. The camera captures images of the area in front of the melt pool where the joint is visible and an algorithm based on the Hough transform and a Kalman filter estimates the offset between the laser spot and the joint position. Welding experiments, using a 6 kW fiber laser, have been conducted to evaluate the performance of the system. Promising results are obtained that can be used in the further development of a closed loop controlled joint tracking system.

Keywords
Laser welding, Butt joints, Joint tracking, Camera
National Category
Production Engineering, Human Work Science and Ergonomics Manufacturing, Surface and Joining Technology
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-12828 (URN)10.1016/j.promfg.2018.06.123 (DOI)
Conference
8th Swedish Production Symposium (SPS 2018), Stockholm, Sweden, May 16-18, 2018
Projects
VINNOVA project VarGa (2016-03291)MoRE program project Hy-Las - Hybrid sensing for understanding of laser welding technology for process control, no 608473
Funder
Vinnova, 2016-03291EU, European Research Council, FP7/2007-2013
Note

Del av specialnumret Proceedings of the 8th Swedish Production Symposium (SPS 2018) Redaktörer: M. Onori, L. Wang, X. V. Wang och W. Ji

Available from: 2018-08-28 Created: 2018-08-28 Last updated: 2019-06-05Bibliographically approved
Kisielewicz, A., Sikström, F., Christiansson, A.-K. & Ancona, A. (2018). Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718. Paper presented at 8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018. Procedia Manufacturing, 25, 418-425
Open this publication in new window or tab >>Spectroscopic monitoring of laser blown powder directed energy deposition of Alloy 718
2018 (English)In: Procedia Manufacturing, E-ISSN 2351-9789, Vol. 25, p. 418-425Article in journal (Refereed) Published
Abstract [en]

Experimental explorations of a spectrometer system used for in-process monitoring of the laser blown powder directed energy deposition of Alloy 718 is presented. Additive manufacturing of metals using this laser process experiences repeated heating and cooling cycles which will influence the final microstructure and chemical composition at every given point in the built. The spectrometer system disclosed, under certain process conditions, spectral lines that indicate vaporisation of chromium. Post process scanning electron microscope energy dispersive spectroscopy analysis of the deposited beads confirmed a reduction of chromium. Since the chromium concentration in Alloy 718 is correlated to corrosion resistance, this result encourages to further investigations including corrosion tests.

National Category
Metallurgy and Metallic Materials Production Engineering, Human Work Science and Ergonomics
Research subject
ENGINEERING, Manufacturing and materials engineering; Production Technology
Identifiers
urn:nbn:se:hv:diva-13303 (URN)10.1016/j.promfg.2018.06.112 (DOI)2-s2.0-85065640848 (Scopus ID)
Conference
8th Swedish Production Symposium, SPS 2018, Stockholm, Sweden, 16-18 May, 2018
Note

Del av specialnumret Proceedings of the 8th Swedish Production Symposium (SPS 2018) Redaktörer: M. Onori, L. Wang, X. V. Wang och W. J

Funders: SUMANnext ; DigiAM

Available from: 2018-12-20 Created: 2018-12-20 Last updated: 2019-10-18Bibliographically approved
Ericsson, M., Zhang, X. & Christiansson, A.-K. (2018). Virtual Commissioning of Machine Vision Applications in Aero Engine Manufacturing. In: Proceedings of The 15th International Conference on Control,Automation, Robotics and Vision, November 18-21, 2018: . Paper presented at 2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) Marina Bay Sands Expo and Convention Centre, Singapore, November 18-21, 2018 (pp. 1947-1952). , Article ID 0293.
Open this publication in new window or tab >>Virtual Commissioning of Machine Vision Applications in Aero Engine Manufacturing
2018 (English)In: Proceedings of The 15th International Conference on Control,Automation, Robotics and Vision, November 18-21, 2018, 2018, p. 1947-1952, article id 0293Conference paper, Published paper (Refereed)
Abstract [en]

New aero engine design puts new demands on the manufacturing methods with increased automation level. Therefore, the use of vision sensors for control and guiding of industrial robots is being increasingly used. In such system, it is need to customise the machine vision system with real components in the real environment which is normally done close to the start-up of the production. This paper addresses a new concept for designing, programming, analysing, testing and verifying a machine vision application early in the design phase, called Virtual Machine Vision. It is based on a robot simulation software where the real machine vision application is simulated before the implementation in the production line. To verify the Virtual Machine Vision concept an advanced stereo vision application was used. Using two captured images from the robot simulated environment, camera calibration, image analysis and stereo vision algorithms are applied to determine a desired welding joint. The information of the weld joint, i.e. robot position and orientation for the weld path, are sent from the machine vision system to the robot control system in the simulation environment and the weld path is updated. The validation of the Virtual Machine Vision concept using the stereo vision application is promising for industrial use, and it is emphasised that the same programs are used in the virtual and real word.

Keywords
Vision for robots, Image-based modeling, Modeling and identification
National Category
Manufacturing, Surface and Joining Technology
Research subject
Production Technology; ENGINEERING, Manufacturing and materials engineering
Identifiers
urn:nbn:se:hv:diva-13390 (URN)978-1-5386-9581-4 (ISBN)
Conference
2018 15th International Conference on Control, Automation, Robotics and Vision (ICARCV) Marina Bay Sands Expo and Convention Centre, Singapore, November 18-21, 2018
Available from: 2019-01-09 Created: 2019-01-09 Last updated: 2019-01-09Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-5608-8636

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