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dc.contributor.author
Wirth, Florian
dc.contributor.supervisor
Wegener, Konrad
dc.contributor.supervisor
Spoleank, Ralph
dc.date.accessioned
2019-01-09T11:16:06Z
dc.date.available
2019-01-09T09:07:31Z
dc.date.available
2019-01-09T11:16:06Z
dc.date.issued
2018
dc.identifier.isbn
978-3-906916-34-7
en_US
dc.identifier.uri
http://hdl.handle.net/20.500.11850/314396
dc.identifier.doi
10.3929/ethz-b-000314396
dc.description.abstract
Currently the additive manufacturing technologies increasingly attract attention from industry and from society due to their extended potentials compared to the conventional manufacturing technologies with regard to the producible complexity of the parts, the independence of the manufacturing costs from the batch size and the individualization options. As the additive manufacturing technologies are clearly less established than the conventional manufacturing technologies, there are still numerous challenges in the fields of computer-aided manufacturing (CAM) tools, distortion management, finding of suitable process parameters, process simulation and even the understanding of the process is still incomplete. In this work, the laser cladding process is investigated. The focus is on the improvement of the understanding of the process, especially the understanding of the melt pool dynamics, and on the development of a modular process simulation model. Based on high-speed camera recordings, an automated video analysis is developed, which tracks the particles on the melt pool surface, so that there the melt pool flow velocity field is captured. The melt pool flow turns out to be partially turbulent due to the continuous impact of powder particles, which are fed into the melt pool by a powder nozzle. Moreover, the influence of the process parameters, process gasses, powder nozzle orientation, surface geometry and powder material composition on the melt pool flow is quantified. The elaborated simulation model is constructed modularly and consists of a powder jet model, a heat source model and a melt pool model, so that each of these modules can be refined independently as needed. The simulation model is physically based in order to make predictions possible without calibration experiments and to reflect the process realistically, so that the understanding of the process can be improved. The required methods to determine the input data of the simulation model are presented, newly developed if necessary and applied. The essential data are the absorptivity values of the different surfaces and the powder particle density distribution, which can be regarded as the analog of the powder jet to the intensity distribution of the laser beam. The absorptivity of the liquid metal and the absorptivity of the solid material surfaces is calorically measured. New methods are developed for the measurement of the powder particle absorptivity and the powder particle density distribution. The attenuation is defined as the percentage of reduction in intensity on the workpiece surface due to the powder jet. The attenuation is calculated from the powder jet simulation results. Thanks to the simulation of the process gas flows in the vicinity of the powder jet, the oxidation on the melt pool surface can be explained, which depends on the process gas settings, the powder nozzle geometry and the process parameters and increases the absorptivity. The simulation model is extended in order to simulate not only single tracks, but also the several overlapping weld beads of a coating. Furthermore, the distribution of substrate material concentration in the melt pool is calculated. It is concluded from the simulation results, that the model errors can be traced back to the facts, that there is a partially turbulent melt pool flow, whereas a laminar flow is assumed in the simulation and that the wetting behavior of the liquid metal on solid substrate material surfaces is not taken into account. A simple approach to adjust the melt pool flow model is presented, which is not successful and demonstrates, that a new model for the laser cladding melt pool flow has to be developed. A particle simulation is carried out in order to investigate the behavior of pores and carbide particles inside the melt pool. According to the simulation results, the melt pool flow has only a minor influence on the movement of pores or carbide particles. The interaction time is the main factor, as it determines for a material element the time in the liquid state, which is the available time for a pore to escape from the melt pool or for a carbide particle to accumulate on the melt pool surface or on the melt pool bottom.
en_US
dc.format
application/pdf
en_US
dc.language.iso
en
en_US
dc.publisher
ETH Zurich
en_US
dc.rights.uri
http://rightsstatements.org/page/InC-NC/1.0/
dc.subject
Additive manufacturing
en_US
dc.subject
Laser cladding
en_US
dc.subject
Direct metal deposition
en_US
dc.subject
Process analysis
en_US
dc.subject
Process modeling
en_US
dc.subject
Process simulation
en_US
dc.title
Process Understanding, Modeling and Predictive Simulation of Laser Cladding
en_US
dc.type
Doctoral Thesis
dc.rights.license
In Copyright - Non-Commercial Use Permitted
ethz.size
196 p.
en_US
ethz.identifier.diss
25555
en_US
ethz.publication.place
Zurich
en_US
ethz.publication.status
published
en_US
ethz.leitzahl
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02623 - Inst. f. Werkzeugmaschinen und Fertigung / Inst. Machine Tools and Manufacturing::03641 - Wegener, Konrad / Wegener, Konrad
en_US
ethz.leitzahl.certified
ETH Zürich::00002 - ETH Zürich::00012 - Lehre und Forschung::00007 - Departemente::02130 - Dep. Maschinenbau und Verfahrenstechnik / Dep. of Mechanical and Process Eng.::02623 - Inst. f. Werkzeugmaschinen und Fertigung / Inst. Machine Tools and Manufacturing::03641 - Wegener, Konrad / Wegener, Konrad
en_US
ethz.date.deposited
2019-01-09T09:07:40Z
ethz.source
FORM
ethz.eth
yes
en_US
ethz.availability
Open access
en_US
ethz.rosetta.installDate
2019-01-09T11:16:30Z
ethz.rosetta.lastUpdated
2019-01-09T11:16:30Z
ethz.rosetta.exportRequired
true
ethz.rosetta.versionExported
true
ethz.COinS
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