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Measurement of internal features in additive manufactured components by the use of computed tomography
Örebro University, School of Science and Technology.ORCID iD: 0000-0002-9362-8328
Örebro University, School of Science and Technology.ORCID iD: 0000-0003-1286-3420
Örebro University, School of Science and Technology.ORCID iD: 0000-0003-1408-2249
2015 (English)Conference paper, Published paper (Refereed)
Abstract [en]

Additive manufacturing (AM) is a set of manufacturing processes currently in rapid development providing designersnew freedoms in their designs. One distinct difference from other manufacturing methods is the ability to makecomplex internal features which can be of great benefit for applications in many industries. These features can bechannels, cavities, filled or not filled with powder, parts in parts etc. In order for these advantages to be industriallyapplicable there is a need for robust verification methods for these internal features. X-ray computed tomography (CT)holds the promise of being one of the few powerful tools for non-destructive imaging of internal features. In this work,selective laser sintering (SLS) has been used to manufacture parts of a complex geometry containing internal cavities.The test specimens were manufactured in two different materials; Polyamide12 and Titanium (Ti6Al4V). In order toinvestigate the limitations and controllability of the process, the dimensions of the internal cavities were determinedby a correlation of tactile measurements on external features and CT-data. The results were also compared to computeraided design (CAD) data. This work provides some insight concerning part accuracy of today’s frontier of AM systemsand the ability to measure and characterize internal features using CT.

Place, publisher, year, edition, pages
German Society for Non-Destructive Testing , 2015.
Keywords [en]
Computed tomography, additive manufacturing, internal features, selective laser melting
National Category
Mechanical Engineering
Research subject
Mechanical Engineering
Identifiers
URN: urn:nbn:se:oru:diva-47801OAI: oai:DiVA.org:oru-47801DiVA, id: diva2:898046
Conference
Digital Industrial Radiology and Computed Tomography (DIR 2015), Ghent, Belgium, June 22-25, 2015
Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2019-08-27Bibliographically approved
In thesis
1. Only a Shadow: Industrial computed tomography investigation, and method development, concerning complex material systems
Open this publication in new window or tab >>Only a Shadow: Industrial computed tomography investigation, and method development, concerning complex material systems
2016 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The complexity of components fabricated in today's industry is ever increasing. This increase is partly due to market pressure but it is also a result from progress in fabrication technologies that opens up new possibilities. The increased use of additive manufacturing and multi-material systems, especially, has driven the complexity of parts to new heights. The new complex material systems brings benefits in many areas such as; mechanical properties, weight optimisation, and sustainability. However, the increased complexity also makes material integrity investigations and dimensional control more difficult. In additive manufacturing, for example, internal features can be fabricated which cannot be seen or measured with conventional tools. There is thus a need for non-destructive inspection methods that can measure these geometries. Such a method is X-ray computed tomography. Computed tomography utilizes the X-rays ability to penetrate material to create 3D digital volumes of components. Measurements and material investigations can be performed in these volumes without any damage to the investigated component. However, computed tomography in material science is still not a fully mature method and there are many uncertainties associated with the investigation technique. In the work presented in this thesis geometries fabricated by various additive manufacturing processes have been investigated using computed tomography. Also in this work, a dual-energy computed tomography tool has been developed with the aim to increase the measurement consistency of computed tomography when investigating complex geometries and material combinations.

Place, publisher, year, edition, pages
Örebro: Örebro University, 2016. p. 61
Series
Örebro Studies in Technology, ISSN 1650-8580 ; 73
Keywords
Computed tomography, Dual-energy, Material investigation, Additive manufacturing, Measurement consistency
National Category
Other Mechanical Engineering
Research subject
Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-54880 (URN)978-91-87789-10-6 (ISBN)
Presentation
2017-01-19, HSM, Örebro universitet, Örebro, 13:15 (English)
Opponent
Supervisors
Projects
MultiMatCT
Available from: 2017-02-03 Created: 2017-01-20 Last updated: 2017-10-18Bibliographically approved
2. Application of X-ray Computed Tomography for Assessment of Additively Manufactured Products
Open this publication in new window or tab >>Application of X-ray Computed Tomography for Assessment of Additively Manufactured Products
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Additive Manufacturing (AM) is a novel method for fabricating parts from three-dimensional model data, usually by joining materials in layer upon layer fashion. The freedom of design in this method has resulted in new possibilities for fabrication of parts with complex geometries. Manufacturing nearnet- shape parts as well as geometrically complex components such as periodic cellular structures that are used in lightweight structural components, has made AM a promising manufacturing method in industry.

Despite the numerous advantages of the AM methods, the imperfections associated with the manufacturing processes has limited the application of additively manufactured parts. Porosity and surface texture of AM parts especially those fabricated using Laser Powder Bed Fusion (LPBF) methods, have been studied in this thesis. It was observed that the mentioned imperfections have a considerable impact on the mechanical performance of thin-wall structures that are the constituting units of surface-based periodic cellular structures. The quality of internal structure in components fabricated using Fused Deposition Modelling (FDM) and its effect on the strength of those components were the other issues investigated in this thesis.

In order to investigate the mechanical strength of AM parts, as the result of mentioned mesoscale imperfections, appropriate evaluation methods that are capable of quantitatively assessing these imperfections are required. X-ray Computed Tomography (CT), a non-destructive evaluation method, has shown high capabilities for providing useful and reliable geometrical information of both internal and external features of AM components. The challenges involved with the application of CT for assessment of AM component are also studied in this thesis.

Apart from the contributions of this thesis on how CT may be used in AM field, the results of this thesis has provided insight into the design process of cellular structures. This thesis has provided essential information about the strength dependency of thin-walls as the result of mesoscale fabrication defects and how these defects are dependent on the selected material and design of the structure.

Place, publisher, year, edition, pages
Örebro: Örebro University, 2019. p. 61
Series
Örebro Studies in Technology, ISSN 1650-8580 ; 85
Keywords
Additive manufacturing, X-ray computed tomography, Surface roughness
National Category
Other Mechanical Engineering
Identifiers
urn:nbn:se:oru:diva-75190 (URN)978-91-7529-296-0 (ISBN)
Public defence
2019-09-17, Örebro universitet, Långhuset, Hörsal L1, Fakultetsgatan 1, Örebro, 09:15 (English)
Opponent
Supervisors
Available from: 2019-07-22 Created: 2019-07-22 Last updated: 2019-08-30Bibliographically approved

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Jansson, AntonZekavat, Amir RezaPejryd, Lars

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