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  • 1.
    Abu Baker Karim, Aria
    et al.
    Örebro University, School of Science and Technology.
    Schnelzer, Anna
    Örebro University, School of Science and Technology.
    Optimering av glidlager och utveckling av dess konstruktion2012Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    We have in this project become engrossed in a plain bearing design that is located in a screw press. The screw press compact an unknown mass that is confidential. Robustus have a suggestion to over dimensioning the present plain bearing. The aim of this project was to analyze and to do an optimization on some plain bearings and compare them to the present bearing and to take the choice of material and the environment where the bearing is located into account. The analysis and the optimizations showed that the current plain bearing had the best geometry but not the optimal material selection. The project is in an early state and it needs some geometrical changes. The most important of everything is that the problem has been identified with the help of the wrecked plain bearing and with an excel model.

  • 2.
    Arén, Björn
    Örebro University, School of Science and Technology.
    Utveckling - är att se, söka och förverkliga: kursbok i produktutveckling2010 (ed. 1)Book (Other academic)
  • 3.
    Asnafi, Nader
    Örebro University, School of Science and Technology.
    Proceedings of the International Conference on Mechanical, Electric and Industrial Engineering (MEIE2018)2018Conference proceedings (editor) (Refereed)
  • 4.
    Bergman, Christian
    Örebro University, School of Science and Technology.
    How Lean is Swedish Product Development?: A study of Lean practices in large Swedish companies2010Independent thesis Advanced level (degree of Master (Two Years)), 30 credits / 45 HE creditsStudent thesis
    Abstract [en]

    This master’s thesis aims to capture the essence of Lean Product Development and to evaluate to what extent Swedish companies have implemented lean principles. Previous studies in this field exemplify how methods are used by already lean practitioners, and there is a lack ofknowledge about the extent to which lean in is used in product development in industry.

    A literature review reveals a number of principles and perspectives; 5 Lean principles, 13 Lean Product Development principles, 14 Lean Management principles and 4 critical factors for Lean (or Knowledge-based) Product Development. These principles and perspectives were the starting point in developing the survey questions.

    The survey of 26 questions was sent to 67 large Swedish companies (more than 249 employees) working with product development and design. The response rate of 39 per centwas unusually high for this type of internet survey.

    The main results of the survey are that Lean methods and tools are rather extensively used in product development, but the culturehas yet not permeated the entire company. The workload of the product developmentdepartment is too high and a structured method for organizational learning is lacking.

    Recommendations for the studied companies are to reduce the workload and increase thetime for reflection, learning and process improvement. Also, the capability to implement strategies can be improved.

  • 5.
    Flyktman, Stefan
    et al.
    Örebro University, School of Science and Technology.
    Johansson, Jan
    Örebro University, School of Science and Technology.
    Tillverkningsmetoders påverkan på en transmissions vikt och tillverkningskostnad2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Volvo Powertrain, VPT, in Köping currently manufactures transmissions for heavy-duty vehicles. For medium-duty vehicles Volvo purchase transmissions from their parts supplier ZF. Volvo wants to investigate the scenario to develop AMT - gearboxes for medium-duty vehicles. The I-shift model AT2412, which is designed for a maximum load of 2400 Nm and adapted for heavy-duty vehicles, would be able to function even in the medium-duty vehicles, but would be oversized and excessively heavy.

    In view of future development Volvo need to increase their knowledge in how the choices of manufacturing methods affect the mass and the manufacturing costs. They need to increase the understanding to make the optimal priorities with respect to mass and manufacturing costs. This study aimed to provide this understanding of how different processes affect a transmission design with respect to mass and measures from a given torque range. The aim of the study was to demonstrate the influence of the choice of production methods for individual items and how much it can affect the complete transmission's mass and manufacturing cost. The work was limited to analyzing the modified gears in the base unit.

    The first part of the work consisted of designing new gears designed for a maximum load of 1600 Nm, based on the same list of operations as the existing gears, which are found in AT2412. The second part consisted of revealing the factors for the different processes affecting the design regarding to fatigue and structural strength. For eight combinations of manufacturing processes the mass and manufacturing cost was calculated for each gear. Finally, a summary was made to show which combination of manufacturing methods that would give the optimum transmission based on minimum mass and minimum manufacturing cost.

    The results show that the choice of production methods leads to more or less reduction of mass of the gears. Generally, the calculations show that the gear that is ground, shootpeened and manganese phosphated get the lowest mass and become the most expensive to produce. On the other hand, lower manufacturing cost can be achieved by excluding certain manufacturing operations as shootpeening and manganese phosphate, but this must be compensated by increased facewidth of the gear, leading to increased mass.

    If VPT decide to develop a new variant of the I-shift in which the gears are designed for 1600Nm then the gearbox can be 6-11 kg lighter and the manufacturing costs of the gears can be reduced by about 10 percent.

  • 6.
    Hällgren, Sebastian
    Örebro University, School of Science and Technology.
    Some aspects on designing for metal Powder Bed Fusion2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Additive Manufacturing (AM) using the Powder Bed Fusion (PBF) is a relatively new manufacturing method that is capable of creating shapes that was previously practically impossible to manufacture. Many think it will revolutionize how manufacturing will be done in the future. This thesis is about some aspects of when and how to Design for Additive Manufacturing (DfAM) when using the PBF method in metal materials. Designing complex shapes is neither easy nor always needed, so when to design for AM is a question with different answers depending on industry or product. The cost versus performance is an important metric in making that selection. How to design for AM can be divided into how to improve performance and how to improve additive manufacturability where how to improve performance once depends on product, company and customer needs. Using advanced part shaping techniques like using Lattices or Topology Optimization (TO) to lower part mass may increase customer value in addition to lowering part cost due to faster part builds and less powder and energy use. Improving PBF manufacturability is then warranted for parts that reach series production, where determining an optimal build direction is key as it affects many properties of PBF parts. Complex shapes which are designed for optimal performance are usually more sensitive to defects which might reduce the expected performance of the part. Non Destructive Evaluation (NDE) might be needed to certify a part for dimensional accuracy and internal defects prior use. The licentiate thesis covers some aspects of both when to DfAM and how to DfAM of products destined for series production. It uses design by Lattices and Topology Optimization to reduce mass and looks at the effect on part cost and mass. It also shows effects on geometry translation accuracies from design to AM caused by differences in geometric definitions. Finally it shows the effect on how different NDE methods are capable of detecting defects in additively manufactured parts.

    List of papers
    1. Additive Manufacturing and High Speed Machining - Cost comparison of short lead time manufacturing methods
    Open this publication in new window or tab >>Additive Manufacturing and High Speed Machining - Cost comparison of short lead time manufacturing methods
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 384-389Conference paper, Published paper (Refereed)
    Abstract [en]

    Additive Manufacturing (AM) using Powder Bed Fusion (PBF) allows part with abstract shapes, that otherwise would need costly tooling, to be manufactured with short lead time. In this study AM build time simulations are used to predict series part cost for eight parts that are possible to cut from rod blanks using High Speed Machining (HSM). Results indicate that when the part shape can be cut from rod blanks, AM is more expensive than HSM even for series of one. If post processing machining is added to the printed AM blank part, the cost difference increases further. Finally, the model is used to predict part-cost in series production if print speed increases, if machine cost is reduced or if part mass is reduced as a result of redesign for AM.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, Powder Bed Fusion, High speed machining, cost, series production, AISI MR
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53931 (URN)10.1016/j.procir.2016.05.049 (DOI)000387666600064 ()2-s2.0-84986576762 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    2. (Re)Design for Additive Manufacturing
    Open this publication in new window or tab >>(Re)Design for Additive Manufacturing
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 246-251Conference paper, Published paper (Refereed)
    Abstract [en]

    3D-printing has been used to create prototypes during the development phase for more than 20 years. Now, functional parts can be printed directly in specific metal powders using similar layer-by-layer techniques. The additive method is unlike traditional mass production manufacturing methods in many ways, creating new possibilities for designers to realise new and different design ideas previously impossible to manufacture. When products are mass produced, there is a desire to improve manufacturability. This is traditionally done by a designer with knowledge about certain manufacturing methods altering design choices to make it cheaper to manufacture.

    This paper shows different design for AM (DfAM) methods where performance and part cost are both of interest. It adds to existing research by classifying design for additive manufacturing in two different classes; process-driven and designer-driven shaping of parts. A cost-prediction model for Selective Laser Melting (SLM) printed parts is suggested as an initial step to choose parts for redesign from an economical perspective. A case study of a missile launcher beam redesigned for additive manufacturing using three different approaches is presented. Differences and similarities in design methods are discussed and the redesigned parts are compared for mass and cost. It is shown that redesigning for AM can reduce mass but depending on part size and print speed, the part can become more expensive than the original design, creating a need to know the customer value of what the redesigned part provides, in this case, the value of reduced mass.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, Powder Bed Fusion, design, topology optimisation, lattices, DfAM
    National Category
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53930 (URN)10.1016/j.procir.2016.04.150 (DOI)000387666600041 ()2-s2.0-84986631521 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    3. 3D data export for Additive Manufacturing - improving geometric accuracy
    Open this publication in new window or tab >>3D data export for Additive Manufacturing - improving geometric accuracy
    2016 (English)In: 26th CIRP Design Conference, Amsterdam: Elsevier, 2016, p. 518-523Conference paper, Published paper (Refereed)
    Abstract [en]

    3D data exchange between different CAD systems and from design to manufacturing has largely moved to ISO STEP based formats. The Additive Manufacturing (AM) process today requires an approximate, planar triangle tessellated 3D model as an input. Improving accuracy in STL file exports is done differently in different CAD systems. Poor tessellation accuracy results in built parts with poor geometric accuracy because of errors in source data. In this study, results of tessellation from six different CAD systems are compared. Roundness accuracy for the different settings is calculated. Results show that tessellation effects may be visible even when roundness requirements are fulfilled. A method for 3D data exchange for AM using STEP and geometric requirements is proposed until better accuracy AM formats can be used.

    Place, publisher, year, edition, pages
    Amsterdam: Elsevier, 2016
    Series
    Procedia CIRP, ISSN 2212-8271 ; 50
    Keywords
    Additive manufacturing, 3D printing, STL, STEP, tessellation, accuracy, roundness
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-53932 (URN)10.1016/j.procir.2016.05.046 (DOI)000387666600087 ()2-s2.0-84986558119 (Scopus ID)
    Conference
    26th CIRP Design Conference, KTH Royal Institute of Technology, Stockholm, Sweden, June 15-17, 2016
    Available from: 2016-12-13 Created: 2016-12-13 Last updated: 2018-07-17Bibliographically approved
    4. Non-destructive evaluation of internal defects in additive manufactured aluminium
    Open this publication in new window or tab >>Non-destructive evaluation of internal defects in additive manufactured aluminium
    2016 (English)Conference paper, Published paper (Refereed)
    Keywords
    additive manufacturing, selective laser melting, aluminium, computed tomography, ultrasonic inspection, eddy current
    National Category
    Mechanical Engineering Materials Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-51003 (URN)
    Conference
    World PM 2016, Powder Metallurgy World Congress, Hamburg, Germany, October 9-13, 2016
    Available from: 2016-06-21 Created: 2016-06-21 Last updated: 2017-12-05Bibliographically approved
  • 7.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    More Than a Shadow: Computed Tomography Method Development and Applications Concerning Complex Material Systems2019Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    The complexity of the components fabricated in today's industry is ever increasing. This is partly due to market pressure, but it is also a result from recent progress in fabrication technologies that open up new design 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 bring benets in many areas such as; mechanical properties, weight reduction, and multifunctions. However, the increased complexity also makes inspection and dimensional control more dicult. 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, industrial computed tomography is still not a fully mature method and there are many uncertainties associated with the investigation technique. In this work, a dual-energy computed tomography tool has been developed with the aim to increase the performance of computed tomography when investigating complex geometries and material combinations. This method has been applied to various phantoms and an industrial case. Also, in this work, complex lattice structures fabricated with additive manufacturing have been investigated and analysed using computed tomography. The results show that the new DECT method improves measurement results and can be utilized to inspect multi-material components. The results also show that computed tomography can be used successfully to gain knowledge about complex lattices.

    List of papers
    1. Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    Open this publication in new window or tab >>Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    2016 (English)In: iCT 2016, NDT.net , 2016, p. 143-150Conference paper, Published paper (Refereed)
    Abstract [en]

    The complexity of today’s products and materials is ever increasing. There is a demand on the industry to produce lighter, stronger, and more precise products. A common practice to achieve such products is to combine different materials to enhance strengths and reduce weaknesses; multi material products. Fabricating complex parts using multi materials does, however, lead to an increased difficulty in metrological verification and material characterisation. The use of computed tomography is today widespread within the industry, providing new possibilities for internal measurements, but there are still many uncertainties associated with the method. It is well known that large variations in density of multi materials greatly affects the contrast obtained by computed tomography, resulting in difficulties to scan and acquire reliable data from certain material setups.In this work the effects on internal measurements as a consequence of differences in X-ray penetration depth have been studied with regards to multi material setups. The main interest was the ability to acquire measurements from internal features of material compositions that are commonly used in the industry. In the result, difficulties and uncertainties associated with computed tomography of multi materials are highlighted and suggestions on how to reduce problems and obtain a more reliable test method are discussed.

    Place, publisher, year, edition, pages
    NDT.net, 2016
    Keywords
    Multi-materials, computed tomography, X-ray penetration depth, dual-energy computed tomography
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47802 (URN)
    Conference
    6th Conference on Industrial Computed Tomography (iCT 2016), Wels, Austria, February 9-12, 2016
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2019-06-13Bibliographically approved
    2. A dual-energy approach for improvement of the measurement consistency in computed tomography
    Open this publication in new window or tab >>A dual-energy approach for improvement of the measurement consistency in computed tomography
    2016 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 11, article id 115013Article in journal (Refereed) Published
    Abstract [en]

    Computed tomography is increasingly adopted by industries for metrological and material evaluation. The technology enables new measurement possibilities, while also challenging old measurement methods in their established territories. There are, however, uncertainties related with the computed tomography method. Investigation of multi-material components with, in particular, varying material thickness can result in unreliable measurements. In this paper the effects of multi-materials, and differing material thickness, on computed tomography measurement consistency has been studied. The aim of the study was to identify measurement inconsistencies and attempt to correct these with a dual-energy computed tomography approach. In this pursuit, a multi-material phantom was developed, containing reliable measurement points and custom-ability with regards to material combinations. A dual-energy method was developed and implemented using sequential acquisition and pre-reconstruction fusing of projections. It was found that measurements made on the multi-material phantom with a single computed tomography scan were highly inconsistent. It was also found that the dual-energy approach was able to reduce the measurement inconsistencies. However, more work is required with the automation of the dual-energy approach presented in this paper since it is highly operator dependant.

    Place, publisher, year, edition, pages
    Bristol, United Kingdom: Institute of Physics (IOP), 2016
    Keywords
    Multi-materials, computed tomography, dual-energy, metrology, measurement consistency, varying material thickness
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-52976 (URN)10.1088/0957-0233/27/11/115013 (DOI)000385929400008 ()2-s2.0-84992365816 (Scopus ID)
    Available from: 2016-10-14 Created: 2016-10-14 Last updated: 2019-05-13Bibliographically approved
    3. Non-linear dual-energy method development and evaluation for industrial computed tomography
    Open this publication in new window or tab >>Non-linear dual-energy method development and evaluation for industrial computed tomography
    2019 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 30, no 6, article id 065006Article in journal (Refereed) Published
    Abstract [en]

    Industrial computed tomography of multi-material objects can be problematic due to difficulties in optimising the x-ray spectra of the scan. A possible solution to the problem is to use two x-ray spectra when scanning objects. The results from such scans can be fused into a single data-set that contains enhanced information. This practice is known as dual-energy computed tomography (DECT). In this work, the aim was to investigate two DECT methods ability to improve measurements in multi-material phantoms. To determine the performance of the methods three different phantoms containing precision spheres as measurement objects were investigated. To improve measurements in this work was defined as improving the measurement consistency of diameter measurements. The phantoms were also scanned with a single setting for comparison. The fusion of the data-sets was done using two methods, a linear fusion, and a novel non-linear fusion. Both of the methods relies on pre-reconstruction fusion of data-sets. The results show that both of the DECT methods improved measurement results significantly compared to the reference method. Further, the results show that the novel non-linear DECT method produces more accurate measurement results compared to the linear method.

    Place, publisher, year, edition, pages
    Institute of Physics Publishing (IOPP), 2019
    Keywords
    Industrial computed tomography, dual-energy, metrology, multi-material, measurement consistency
    National Category
    Engineering and Technology Mechanical Engineering
    Research subject
    Physics
    Identifiers
    urn:nbn:se:oru:diva-74031 (URN)10.1088/1361-6501/ab10cc (DOI)000466894300001 ()
    Available from: 2019-05-03 Created: 2019-05-03 Last updated: 2019-06-19Bibliographically approved
    4. Multi-material gap measurements using dual-energy computed tomography
    Open this publication in new window or tab >>Multi-material gap measurements using dual-energy computed tomography
    2018 (English)In: Precision engineering, ISSN 0141-6359, E-ISSN 1873-2372, Vol. 54, p. 420-426Article in journal (Refereed) Published
    Abstract [en]

    X-ray computed tomography is a highly versatile investigation method with applications in a wide range ofareas. One of the areas where the technique has seen an increased usage, and an increased interest from industry,is in dimensional metrology. X-ray computed tomography enables the measurement of features and dimensionsthat are difficult to inspect using other methods. However, there are issues with the method when it comes tomeasurements of objects that consist of several materials. In particular, it is difficult to obtain accurate computedtomography results for all materials when the attenuation of materials differs significantly. The aim of this workwas to measure small air gaps between different materials using dual-energy X-ray computed tomography. Thedual-energy method employed in this work uses two energy spectra and fuses the data in the projections spaceusing non-linear fusion. The results from this study show that the dual-energy method used in this work was ableto capture more measurements than regular absorption computed tomography in the case of specimens withhighly different attenuation, enabling, in particular, the measurement of smaller gaps. The contrast-to-noise ratiowas also increased significantly with the use of dual-energy.

    Place, publisher, year, edition, pages
    Elsevier, 2018
    Keywords
    Metrology, Computed tomography, Dual-energy, Multi-material measurements
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-68991 (URN)10.1016/j.precisioneng.2018.07.012 (DOI)000452579900046 ()2-s2.0-85051065309 (Scopus ID)
    Funder
    EU, FP7, Seventh Framework Programme, 607817
    Available from: 2018-09-21 Created: 2018-09-21 Last updated: 2019-05-13Bibliographically approved
    5. Characterisation of additive manufacturing metal: carbon-fibre composite bond by dual-energy computed tomography
    Open this publication in new window or tab >>Characterisation of additive manufacturing metal: carbon-fibre composite bond by dual-energy computed tomography
    2017 (English)In: EUSPEN, Conference Proceedings, Special Interest Group: Dimensional Accuracy and Surface Finish in Additive Manufacturing, Octrober 2017, KU Leuven, Belgium: EUSPEN , 2017, p. 189-192Conference paper, Published paper (Refereed)
    Abstract [en]

    Joining of dissimilar materials is a topic of high interest for the industry. The ability to seamlessly join materials with significant differences in properties would advance the development of efficient designs and concepts within many fields. In this work, bonds between aluminium and carbon-fibre reinforced plastic have been studied. The aluminium side of the bonds were fabricated using classical methods (milling) and additive manufacturing. Two types of bonds were fabricated using additive manufacturing, one flat, relying on the rough surface for adhesion in the bond, and the other with surface features designed to hook into the carbon-fibre plies. All the bonds were fabricated using wet layup of carbon-fibre, the idea was that the aluminium parts would bond to the plastic composite in one step. The bonds were characterised using dual-energy computed tomography. The method used in this work was non-linear and based around fusing of projections acquired with different energy spectra. The mechanical strength of the bonds was also evaluated, both through tensile tests and four-point bending.It was found that the bonds including additive manufactured aluminium was stronger than the milled samples in general. In the computed tomography data, it could be seen that the adhesion in those bonds were better, most likely due to the rough surface. The strongest bonds were those with additive manufacturing surface features. However, the computed tomography data revealed that these bonds have difficulties with integration between the surface features and the carbon-fibre plies.

    Place, publisher, year, edition, pages
    KU Leuven, Belgium: EUSPEN, 2017
    Keywords
    Additive manufacturing, Dual-energy computed tomography, carbon-fibre composite, joining
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-61550 (URN)978-0-9957751-1-4 (ISBN)
    Conference
    EUSPEN, Conference Proceedings, Special Interest Group: Dimensional Accuracy and Surface Finish in Additive Manufacturing, Katholieke Universiteit Leuven, October 2017
    Available from: 2017-10-16 Created: 2017-10-16 Last updated: 2019-05-13Bibliographically approved
    6. Dual-energy computed tomography investigation of additive manufacturing aluminium: carbon-fibre composite joints
    Open this publication in new window or tab >>Dual-energy computed tomography investigation of additive manufacturing aluminium: carbon-fibre composite joints
    2019 (English)In: Heliyon, ISSN 2405-8440, Vol. 5, no 2, article id e01200Article in journal (Refereed) Published
    Abstract [en]

    In this work, aluminium–carbon-fibre reinforced plastic joints have been studied. Three types of samples were designed as double lap joints where the aluminium inserts were fabricated using both classical methods (milling) and additive manufacturing. Two versions of the joint were fabricated using additive manufacturing, one flat, and the other with small teeth designed to hook into the carbon-fibre plies. The joints were characterised using a non-linear, dual-energy computed tomography method to evaluate the bond between the composite and the metal inserts. The mechanical strength of the bonds was evaluated, both through tensile tests and four-point bending. A simple finite element model was used to discuss the joints behaviour. It was found that the joints fabricated using additive manufactured inserts were more resistant to peel stress than the milled inserts. In four-point bending tests the moment that the joint could withstand was increased by roughly 300% with the use of additive manufacturing and 400% with the use of additive manufacturing and small teeth. However, in tensile tests it was found that the teeth design reduced the maximum load capacity of the joints by roughly 30% due to porosity. Further, it was found that the additive manufactured samples did not add to the capability of withstanding shearstress. The information gained with the dual-energy computed tomography method was highly valuable as the behaviour of the joints would have been difficult to explain without the porosity information.

    Place, publisher, year, edition, pages
    Elsevier, 2019
    Keywords
    Mechanical engineering, Materials science
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-72142 (URN)10.1016/j.heliyon.2019.e01200 (DOI)000460082200023 ()30839940 (PubMedID)2-s2.0-85061013958 (Scopus ID)
    Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-06-19Bibliographically approved
    7. Surface vs Truss lattice networks, benefits and limitations
    Open this publication in new window or tab >>Surface vs Truss lattice networks, benefits and limitations
    2018 (English)In: NAFEMS nordic: Exploring the Design Freedom of Additive Manufacturing through Simulation, NAFEMS , 2018, p. 217-218Conference paper, Published paper (Refereed)
    Abstract [en]

    The use of additive manufacturing is growing rapidly among industries within many different fields of fabrication. The benefits of applying additive manufacturing can be many and an application that have received special interest is the ability to design lightweight components. Lightweight components can be fabricated with additive manufacturing with the use of lattices that have a high stiffness to weight ratio and topology optimised, complex, designs. The most commonly used lattices today are based on trusses, however, there is also the possibility to generate lattices based around continuous surfaces. In this study, the properties of the popular body-centred-cubic lattice are compared the properties of the lesser known Schwartz diamond surface lattice. The mechanical compression properties, the fabrication processes, and the possibilities of the lattices are discussed and analysed.

    Place, publisher, year, edition, pages
    NAFEMS, 2018
    National Category
    Engineering and Technology Composite Science and Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-70704 (URN)
    Conference
    NAFEMS Nordic 2018, Göteborg, Sweden, 24-25 April, 2018
    Available from: 2018-12-12 Created: 2018-12-12 Last updated: 2019-06-13Bibliographically approved
    8. In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices
    Open this publication in new window or tab >>In-situ computed tomography investigation of the compression behaviour of strut, and periodic surface lattices
    2019 (English)In: iCT 2019 / [ed] Rolf Diederichs, NDT.net , 2019, p. 221-227Conference paper, Published paper (Refereed)
    Abstract [en]

    In this work the effects of fabrication errors in the Body Centered Cubic strut lattice, and the periodic surface lattice Schwarz Diamond has been investigated. The lattices were both fabricated as-is and with induced errors to evaluate the lattices response to fabrication errors. The behaviour of the lattices were studied using compression test and in-situ computed tomography investigation. The results show that the Schwarz Diamond lattices in general are stronger than the Body Centered Cubic lattices in all of the measured aspects. Often up to five times stronger. It was also found that the elastic behaviour of the Schwarz Diamond lattices were mainly unaffected by fabrication errors while the Body Centered Cubic lattices experienced severe losses in performance. The behaviour of the lattices under compression could be followed using computed tomography which aided in the understanding of their behaviour.

    Place, publisher, year, edition, pages
    NDT.net, 2019
    Keywords
    Additive manufacturing, computed tomography, periodic surface lattices, in-situ compression, fabrication error
    National Category
    Engineering and Technology Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-72514 (URN)
    Conference
    9th Conference on Industrial Computed Tomography (iCT) 2019, 13-15 Feb, 2019, Padova, Italy
    Available from: 2019-02-18 Created: 2019-02-18 Last updated: 2019-06-13
  • 8.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Only a Shadow: Industrial computed tomography investigation, and method development, concerning complex material systems2016Licentiate 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.

    List of papers
    1. Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering
    Open this publication in new window or tab >>Characterisation of carbon fibre-reinforced polyamide manufactured by selective laser sintering
    2016 (English)In: Additive Manufacturing, ISSN 2214-8604, Vol. 9, p. 7-13Article in journal (Refereed) Published
    Abstract [en]

    Polymers and reinforced plastics are employed in various load-bearing applications, from household objects to aerospace products. These materials are light, strong, and relatively cheap but can be difficult to form into complex geometries. However, the development of additive manufacturing processes has made it easier to manufacture reinforced plastics in complex shapes. The aim of this work was to study the internal features and mechanical properties of carbon fibre-reinforced polyamide (CF/PA12) fabricated with the additive manufacturing technique of selective laser sintering. The test specimens were studied using computed tomography to analyse the internal geometry, and the material proved to be highly porous. Moreover, the test specimens revealed an internal layered structure, which was found to have a great effect on the tensile properties of the material. The results highlight that there is room for further optimisation of the manufacturing parameters for CF/PA12, because the layered structure makes it challenging to design end user parts with acceptable mechanical properties.

    Place, publisher, year, edition, pages
    Amsterdam, Netherlands: Elsevier, 2016
    Keywords
    Computed tomography, carbon fibre–reinforced polymer, selective laser sintering, additive manufacturing
    National Category
    Materials Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47800 (URN)10.1016/j.addma.2015.12.003 (DOI)000435752300002 ()2-s2.0-84952789063 (Scopus ID)
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2018-11-27Bibliographically approved
    2. Measurement of internal features in additive manufactured components by the use of computed tomography
    Open this publication in new window or tab >>Measurement of internal features in additive manufactured components by the use of computed tomography
    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
    Computed tomography, additive manufacturing, internal features, selective laser melting
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47801 (URN)
    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
    3. Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    Open this publication in new window or tab >>Effects of X-ray Penetration Depth on Multi Material Computed Tomography Measurements
    2016 (English)In: iCT 2016, NDT.net , 2016, p. 143-150Conference paper, Published paper (Refereed)
    Abstract [en]

    The complexity of today’s products and materials is ever increasing. There is a demand on the industry to produce lighter, stronger, and more precise products. A common practice to achieve such products is to combine different materials to enhance strengths and reduce weaknesses; multi material products. Fabricating complex parts using multi materials does, however, lead to an increased difficulty in metrological verification and material characterisation. The use of computed tomography is today widespread within the industry, providing new possibilities for internal measurements, but there are still many uncertainties associated with the method. It is well known that large variations in density of multi materials greatly affects the contrast obtained by computed tomography, resulting in difficulties to scan and acquire reliable data from certain material setups.In this work the effects on internal measurements as a consequence of differences in X-ray penetration depth have been studied with regards to multi material setups. The main interest was the ability to acquire measurements from internal features of material compositions that are commonly used in the industry. In the result, difficulties and uncertainties associated with computed tomography of multi materials are highlighted and suggestions on how to reduce problems and obtain a more reliable test method are discussed.

    Place, publisher, year, edition, pages
    NDT.net, 2016
    Keywords
    Multi-materials, computed tomography, X-ray penetration depth, dual-energy computed tomography
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47802 (URN)
    Conference
    6th Conference on Industrial Computed Tomography (iCT 2016), Wels, Austria, February 9-12, 2016
    Available from: 2016-01-27 Created: 2016-01-27 Last updated: 2019-06-13Bibliographically approved
    4. A dual-energy approach for improvement of the measurement consistency in computed tomography
    Open this publication in new window or tab >>A dual-energy approach for improvement of the measurement consistency in computed tomography
    2016 (English)In: Measurement science and technology, ISSN 0957-0233, E-ISSN 1361-6501, Vol. 27, no 11, article id 115013Article in journal (Refereed) Published
    Abstract [en]

    Computed tomography is increasingly adopted by industries for metrological and material evaluation. The technology enables new measurement possibilities, while also challenging old measurement methods in their established territories. There are, however, uncertainties related with the computed tomography method. Investigation of multi-material components with, in particular, varying material thickness can result in unreliable measurements. In this paper the effects of multi-materials, and differing material thickness, on computed tomography measurement consistency has been studied. The aim of the study was to identify measurement inconsistencies and attempt to correct these with a dual-energy computed tomography approach. In this pursuit, a multi-material phantom was developed, containing reliable measurement points and custom-ability with regards to material combinations. A dual-energy method was developed and implemented using sequential acquisition and pre-reconstruction fusing of projections. It was found that measurements made on the multi-material phantom with a single computed tomography scan were highly inconsistent. It was also found that the dual-energy approach was able to reduce the measurement inconsistencies. However, more work is required with the automation of the dual-energy approach presented in this paper since it is highly operator dependant.

    Place, publisher, year, edition, pages
    Bristol, United Kingdom: Institute of Physics (IOP), 2016
    Keywords
    Multi-materials, computed tomography, dual-energy, metrology, measurement consistency, varying material thickness
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-52976 (URN)10.1088/0957-0233/27/11/115013 (DOI)000385929400008 ()2-s2.0-84992365816 (Scopus ID)
    Available from: 2016-10-14 Created: 2016-10-14 Last updated: 2019-05-13Bibliographically approved
  • 9.
    Liljeros, Patrik
    Örebro University, School of Science and Technology.
    IDENTIFIERING AV BÄSTA PLATS OCH MÄTMETOD FÖR TEMPERATURMÄTNING EFTER VÄRMEVÄXLARE2013Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The main goal with this report has been to investigate a suspected temperature measurement error after a heat exchanger. Previous reports concerning this heat exchanger leads to a suspicion that the temperature is measured incorrectly. One reason to why it might be incorrect could be the placement of the sensor, which is located quite close to the heat exchanger.

    The first part of this task has been a literature study with the goal to increase my knowledge about different measurement techniques, and how to apply them in practice. This segment also contained gathering of information from previous reports. The second and largest part of the task has been to measure the temperature in two places after the heat exchanger using thermocouples. The data that has been collected was analyzed with the goal to determine whether the temperature is measured correctly or not.

    The measurements indicated inhomogeneous temperatures directly after the heat exchanger, and a difference of 0,5˚C between the original sensor and the thermocouples. My recommendation from this study will be to move the temperature sensor further away from the heat exchanger.

  • 10.
    Lundh, Robert
    et al.
    Örebro University, Department of Technology.
    Karlsson, Lars
    Örebro University, Department of Technology.
    Saffiotti, Alessandro
    Örebro University, Department of Technology.
    An algorithm for generating configurations of groups of robots2007Report (Other academic)
    Abstract [en]

    This work is about the use of artificial intelligence (AI) planning techniques to automatically configure cooperation among robots. We consider groups of autonomous robots in which robots can help each other by offering information producing resources and functionalities. A configuration in this context, is a way to allocate and connect functionalities among robots. In general, different configurations can be used to solve the same task, depending on the current situation. Configuration generation is the problem of automatically generating a configuration for some specific purpose given a set of robotic devices possessing dfferent functionalities. In this paper, we consider an existing configuration planner both from a theoretical point of view (soundness, completeness, and optimality), and an empirical point of view (scalability). We also present a technique to improve the scalability of the configuration planner.

  • 11.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Evaluation of internal defects in additive manufactured metallic network structures by Computed Tomography2018Conference paper (Refereed)
    Abstract [en]

    The ability to manufacture complex internal features is one of the distinct differentiators of Additive Manufacturing (AM) as compared to other manufacturing methods for metal components. This manufacturing process provide designers with new opportunities in the design, such as e.g. networks and curved and non round cooling channels. To fully take advantage of metal AM in industrial use, robust methods for the detection of potential internal defects is however needed. A method that holds the promise of being one of the few tools for non-destructive evaluation (NDE) of internal features and defects is X-ray computed tomography (CT). The applicability and limitations of CT, especially for defect determination in products with complex internal structures is however not fully understood. In this work, parts with different sizes of controlled internal defects in the form of slots of varying width, 0,1 – 0,4 mm was manufactured by AM, using Selective Laser melting (SLM). The parts were produced in both titanium and aluminium alloys and both with internal networks and as solid pieces. For both of the designed types of samples, containing the pre designed defects, the ability to detect the defects by industrial computed tomography (CT) was evaluated. The evaluation of defects using CT data can be done by a trained operator. For solid components this can be done with some assistance of analysis modes that are available in comersial software. For components with complex internal structures, the result is more operator dependant and more work is needed to develop methods for CT inspection that can enable automation of the inspection process and/or to assist a trained operator.

  • 12.
    Rahayem, Mohamed
    et al.
    Örebro University, School of Science and Technology.
    Werghi, Naoufel
    Electrical and Computer Engineering Department, Khalifa University, Sharjah, United Arab Emirates.
    Kjellander, Johan
    Örebro University, School of Science and Technology.
    Best ellipse and cylinder parameters estimation from laser profile scan sections2012In: Optics and lasers in engineering, ISSN 0143-8166, E-ISSN 1873-0302, Vol. 50, no 9, p. 1242-1259Article in journal (Refereed)
    Abstract [en]

    Industrial applications like robot-aided welding, automated inspection, and 3D measurements require 3D points to be captured from the surfaces of objects and processed to calculate the information-of-interest. The lack of research focused on fitting ellipses to 3D laser profile data, and the intrinsic features that distinguish it from 2D digital images, motivated us to conduct a comparative study involving the most popular ellipse-fitting methods. After describing our laser profile scanning system, and a survey of ellipse-fitting methods, we compare, using extensive experiments performed with synthetic and real data, the fitting algorithms in terms of stability and accuracy with respect to a variety of factors. The estimate obtained with the best method is used to initialize a robust non-linear iterative ellipse fitting method. Finally, we describe a novel method for the construction of cylindrical surfaces from estimated elliptical sections.

  • 13.
    Reed, Sean
    et al.
    Resilience Engineering Research Group, Faculty of Engineering, University of Nottingham, Nottingham, UK.
    Löfstrand, Magnus
    Örebro University, School of Science and Technology.
    Andrews, John
    Resilience Engineering Research Group, Faculty of Engineering, University of Nottingham, Nottingham, UK.
    An efficient algorithm for computing exact system and survival signatures of K-terminal network reliability2019In: Reliability Engineering & System Safety, ISSN 0951-8320, E-ISSN 1879-0836, Vol. 185, p. 429-439Article in journal (Refereed)
    Abstract [en]

    An efficient algorithm is presented for computing exact system and survival signatures of K-terminal reliability in undirected networks with unreliable edges. K-terminal reliability is defined as the probability that a subset K of the network nodes can communicate with each other. Signatures have several advantages over direct reliability calculation such as enabling certain stochastic comparisons of reliability between competing network topology designs, extremely fast repeat computation of network reliability for different edge reliabilities and computation of network reliability when failures of edges are exchangeable but not independent. Existing methods for computation of signatures for K-terminal network reliability require derivation of cut-sets or path-sets which is only feasible for small networks due to the computational expense. The new algorithm utilises binary decision diagrams, boundary set partition sets and simple array operations to efficiently compute signatures through a factorisation of the network edges. The performance and advantages of the algorithm are demonstrated through application to a set of benchmark networks and a sensor network from an underground mine.

  • 14.
    Viberg, Mikael
    Örebro University, School of Science and Technology.
    Koncept för ny Monteringsmaskin2011Independent thesis Advanced level (degree of Master (One Year)), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The purpose of this thesis is to develop a new concept for an assembly machine that assembles drive motors to the ICARUS parachute rocket at Nammo LIAB AB in Lindesberg. The current assembly machine is old, difficult to clean, has a high loudness level and is a full time job to run.The primary objective of this study is to have the new concept meet the company objectives regarding capacity, noise, human resources, ergonomics, cleaning, and pay of time.

    The project resulted in a concept that facilitates cleaning, reduces staffing requirements with a full time job and exceeds the current production capacity. Proposals are given on how noise can be reduced and how ergonomics can be improved. The cost of the new assembly machine is about 920000kr with a pay of time of about two years. The robot cell is not streamlined due to time constraints and ongoing changes. A number of methods and tools adapted to develop new concepts are used in the thesis. Further work is required to construct a working machine. The project to develop the new assembly machine should be started immediately.

  • 15.
    Zekavat, Amir Reza
    Örebro University, School of Science and Technology.
    Application of X-ray Computed Tomography for Assessment of Additively Manufactured Products2019Doctoral 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.

    List of papers
    1. Measurement of internal features in additive manufactured components by the use of computed tomography
    Open this publication in new window or tab >>Measurement of internal features in additive manufactured components by the use of computed tomography
    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
    Computed tomography, additive manufacturing, internal features, selective laser melting
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-47801 (URN)
    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
    2. Investigating the effect of fabrication temperature on mechanical properties of fused deposition modelling parts using X-ray computed tomography
    Open this publication in new window or tab >>Investigating the effect of fabrication temperature on mechanical properties of fused deposition modelling parts using X-ray computed tomography
    2019 (English)In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, no 1-4, p. 287-296Article in journal (Refereed) Published
    Abstract [en]

    Fused deposition modeling (FDM) is one of the most common additive manufacturing (AM) techniques for fabricating prototypes as well as functional parts. In this technique, several parameters may influence the part quality and consequently mechanical properties of fabricated components. In this paper, an experimental investigation on effects of fabrication temperature as one of the influential parameters on mechanical properties of manufactured parts is presented. A series of specimens fabricated at temperatures ranging from 180 to 260 C were used for this investigation. X-ray computed tomography (CT) was used in order to non-destructively analyze the internal geometry of the specimens especially the bond between extruded filaments. Finally, the specimens were subjected to a uniaxial tensile load for evaluation of mechanical properties. The results showed that the specimens fabricated at lower temperatures have relatively lower tensile strength despite their considerably higher strain at break. In addition, the specimens fabricated at higher temperature range had significantly higher tensile strength because of the better bond between extruded filaments. The different mechanical responses were highly related to the internal geometry of the specimens and not necessarily the porosity. CT showed great potential as a non-destructive tool for investigation and development of FDM process.

    Place, publisher, year, edition, pages
    Springer London, 2019
    Keywords
    Fused deposition modeling, Computed tomography, Polylactic acid, Additive manufacturing
    National Category
    Other Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-69110 (URN)10.1007/s00170-018-2664-8 (DOI)000455946000025 ()2-s2.0-85053832455 (Scopus ID)
    Available from: 2018-09-28 Created: 2018-09-28 Last updated: 2019-08-27Bibliographically approved
    3. Effect of X-ray Computed Tomography Magnification on Surface Morphology Investigation of Additive Manufacturing Surfaces
    Open this publication in new window or tab >>Effect of X-ray Computed Tomography Magnification on Surface Morphology Investigation of Additive Manufacturing Surfaces
    2018 (English)In: 8th Conference on Industrial Computed Tomography, 2018Conference paper, Published paper (Refereed)
    Abstract [en]

    Additive manufacturing (AM) in the last decade has become a widespread manufacturing process. The possibilities that such technologies have provided for manufacturing of complex geometries compared to conventional manufacturing processes has made them popular in many branches of industry. Despite the advantages of these methods, there are limiting issues which needs to be thoroughly investigated. A limiting factor, especially for powder bed AM parts is their undesired surface finish. AM surfaces can be investigated using various methods such as optical or tactile methods, however for complex AM surfaces they are incapable of capturing all details such as deep valleys at surface level. X-ray computed tomography (CT), can provide 3D information of complex AM surfaces and does not have limitations that line of sight and tactile methods have. There are several parameters in CT investigation, which can potentially alter the obtained results. Depending on the CT magnification at which the data is acquired the result specifically surface level detail might be affected. The aim of this study is to investigate the effect of different CT magnifications on surface texture measurement of additively manufactured surfaces. Surface features, including highest peaks and deepest valleys contributing to maximum and minimum thickness of specimen from different magnifications were compared with each other. The result shows that, the lower magnification scans underestimate both peak and valley measurements in comparison to the highest magnification scan. Measurement of valleys and re-entrant features were underestimated at more considerable level. The results from this study provide some understanding regarding surface morphology assessment of AM parts and the level of detail which can be expected depending on the CT magnification.

    Keywords
    Computed tomography, Additive manufacturing, Surface texture
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-65426 (URN)
    Conference
    iCT conference 2018, Wels, Austria, 7 February, 2018
    Available from: 2018-03-02 Created: 2018-03-02 Last updated: 2019-08-27Bibliographically approved
    4. Effect of X-Ray Computed Tomography Magnification on Porosity Analysis of Additively Manufactured Parts
    Open this publication in new window or tab >>Effect of X-Ray Computed Tomography Magnification on Porosity Analysis of Additively Manufactured Parts
    2018 (English)In: World PM2018 Congress Proceedings, 2018Conference paper, Published paper (Refereed)
    Abstract [en]

    X-ray computed tomography has been widely used for inspection of parts manufactured using additive manufacturing (AM) and powder metallurgy (PM). The ability of this method to non-destructively evaluate the porosity content of parts fabricated using AM and PM has made it a reliable method for such inspection. The results obtained from this method are highly dependent on CT acquisition parameters such as the magnification (resolution) at which the part has been scanned. Depending on the size of the parts the scan might need to be performed at lower magnifications which results in loss of information for porosity analysis. Therefore the effect of changing CT magnification on the obtained porosity of an additively manufactured specimen made of AlSi10Mg is investigated in this study. The specimen was scanned at various magnifications resulting in data sets with different resolutions. The porosity content was measured for each data set and the results showed that the porosity measurement using CT is highly dependent on the magnification (resolution) at which the data sets are acquired. The results from this study provided essential information about the porosity content which should be expected depending on the CT magnification.

    Keywords
    Porosity, X-ray computed tomography (CT), Additive manufacturing (AM)
    National Category
    Mechanical Engineering
    Research subject
    Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-69047 (URN)
    Conference
    2018 World Congress on Powder Metallurgy (WORLDPM2018), Beijing, China, September 16-20, 2018
    Available from: 2018-09-25 Created: 2018-09-25 Last updated: 2019-08-28Bibliographically approved
    5. An experimental approach to investigatethe influential parameters on mechanical strength of AlSi10Mgthin-wall structures manufactured by selective laser melting
    Open this publication in new window or tab >>An experimental approach to investigatethe influential parameters on mechanical strength of AlSi10Mgthin-wall structures manufactured by selective laser melting
    Show others...
    (English)Manuscript (preprint) (Other academic)
    National Category
    Other Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-75923 (URN)
    Available from: 2019-08-27 Created: 2019-08-27 Last updated: 2019-08-27Bibliographically approved
    6. Surface Characterization of Additively Manufactured AlSi10Mg andTi6Al4V thin-wall Structures using X-Ray Computed Tomography
    Open this publication in new window or tab >>Surface Characterization of Additively Manufactured AlSi10Mg andTi6Al4V thin-wall Structures using X-Ray Computed Tomography
    (English)Manuscript (preprint) (Other academic)
    National Category
    Other Mechanical Engineering
    Identifiers
    urn:nbn:se:oru:diva-75922 (URN)
    Available from: 2019-08-27 Created: 2019-08-27 Last updated: 2019-08-27Bibliographically approved
  • 16.
    Zekavat, Amir Reza
    Örebro University, School of Science and Technology.
    Surface Characterization of Additively Manufactured AlSi10Mg andTi6Al4V thin-wall Structures using X-Ray Computed TomographyManuscript (preprint) (Other academic)
  • 17.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Adibi, Pooya Tahib Zadeh
    RISE, Borås, Sweden.
    Johannesson, Pär
    RISE, Borås, Sweden.
    Karlsson, Patrik
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Sjögren, Torsten
    RISE, Borås, Sweden.
    An experimental approach to investigatethe influential parameters on mechanical strength of AlSi10Mgthin-wall structures manufactured by selective laser meltingManuscript (preprint) (Other academic)
  • 18.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Jansson, Anton
    Örebro University, School of Science and Technology.
    Larsson, Joakim
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Investigating the effect of fabrication temperature on mechanical properties of fused deposition modelling parts using X-ray computed tomography2019In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 100, no 1-4, p. 287-296Article in journal (Refereed)
    Abstract [en]

    Fused deposition modeling (FDM) is one of the most common additive manufacturing (AM) techniques for fabricating prototypes as well as functional parts. In this technique, several parameters may influence the part quality and consequently mechanical properties of fabricated components. In this paper, an experimental investigation on effects of fabrication temperature as one of the influential parameters on mechanical properties of manufactured parts is presented. A series of specimens fabricated at temperatures ranging from 180 to 260 C were used for this investigation. X-ray computed tomography (CT) was used in order to non-destructively analyze the internal geometry of the specimens especially the bond between extruded filaments. Finally, the specimens were subjected to a uniaxial tensile load for evaluation of mechanical properties. The results showed that the specimens fabricated at lower temperatures have relatively lower tensile strength despite their considerably higher strain at break. In addition, the specimens fabricated at higher temperature range had significantly higher tensile strength because of the better bond between extruded filaments. The different mechanical responses were highly related to the internal geometry of the specimens and not necessarily the porosity. CT showed great potential as a non-destructive tool for investigation and development of FDM process.

  • 19.
    Zekavat, Amir Reza
    et al.
    Örebro University, School of Science and Technology.
    Pejryd, Lars
    Örebro University, School of Science and Technology.
    Ekengren, Jens
    Örebro University, School of Science and Technology.
    Tracking the shape deformation of voids from tensile loading by the use of computed tomography2015In: Digital Industrial Radiology and Computed Tomography (DIR 2015), 2015, article id 18034Conference paper (Refereed)
    Abstract [en]

    The understanding of interaction between voids such as pores or holes in additive manufactured open structures is of importance in understanding the strength of components. Behavior in three dimensions is of particular interest. X-ray tomography is one of the few techniques that has the possibility to nondestructively aid in analyzing issues such as shape deformation. In this work, X-ray computed tomography was applied as a nondestructive tool for tracking the shape deformation of voids.

    A simplified model representing three dimensional voids is used to investigate the effect of influential parameters like void size, their distance from each other and orientation of voids in respect to the uniaxial tensile load. A set of ex-situ X-ray micro tomography tensile test is performed on flat aluminum (6082-T6) tensile bars with drilled through holes representing different configuration of voids. Digital image correlation was used to measure the strain localization in the adjacent area of the holes. Corresponding Finite Element (FE) analysis is performed to predict the shape deformation and by this validate the model. This modelling may give a better insight of pores interaction under more complex loading scenarios and leads to better controllability of internal structure design of additive manufactured (AM) parts.

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