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  • 1.
    Abdullah Asif, Farazee Mohammad
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Salehi, Niloufar
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Lieder, Michael
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Consumer perceptions of circular business model: a case of leasing strollers2022In: Manufacturing Driving Circular Economy: Proceedings of the 18th Global Conference on Sustainable Manufacturing, October 5-7, 2022, Berlin / [ed] Holger Kohl, Günther Seliger, Franz Dietrich, Springer Nature , 2022, p. 953-960Conference paper (Refereed)
    Abstract [en]

    Circular Economy (CE) promotes trading functions of a product as aservice instead of selling the product in conventional ways. For a product like ababy stroller, the function means ensuring mobility with infants without needingto own a stroller. This approach of acquiring functions only when needed opensup the possibility to share the same products with multiple users. For a manufacturer that has built its business on a conventional sales model over the decades,this shift may be too radical. Therefore, for the manufacturers, it is important tounderstand consumer perceptions of the service-oriented business model beforeentering this unknown territory. To develop a thorough understanding of consumerperceptions of leasing a stroller instead of buying one, a survey among 200 parentsin Stockholm is conducted. The survey brings out quantitative results such as 39%of respondents are open to leasing and identifies key influencing factors such asconvenience and environmental image that play a key role for the remaining 61%of respondents to choose leasing. This research concludes that a large numberof consumers are open to leasing if a high level of service and environmentallysustainable strollers are offered at a competitive price.

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  • 2.
    Amir, Saman
    et al.
    Department of Marketing & Strategy and Center for Sustainability Research, SSE Stockholm School of Economics, Stockholm, Sweden.
    Salehi, Niloufar
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Roci, Malvina
    KTH, School of Industrial Engineering and Management (ITM), Production engineering.
    Sweet, Susanne
    Department of Marketing & Strategy and Center for Sustainability Research, SSE Stockholm School of Economics, Stockholm, Sweden.
    Rashid, Amir
    KTH, School of Industrial Engineering and Management (ITM), Production engineering.
    Toward a Circular Economy: A Guiding Framework for Circular Supply Chain Implementation2024In: Springer Series in Supply Chain Management, Springer Nature , 2024, Vol. 23, p. 379-404Chapter in book (Refereed)
    Abstract [en]

    This chapter presents a guiding framework for circular economy implementation in supply chains. Closing the loop for resource efficiency is a well-known practice in the industry. To concretize the circular economy implementation strategies, closed-loop thinking requires innovation and adaptation. Circular supply chains (CSCs) are one of the key enablers in closing the loop by design or intention for value recovery and profit maximization. CSC is an emerging area, and the view of CSC where forward and reverse supply chain is seamlessly integrated with the overall aim to achieve system-wide circularity is missing in the academic debate. By offering a cross-functional and systemic perspective of circular supply chains, we present a guiding framework to structure and understand the underlying complexities and highlight the crucial elements of circular supply chain implementation. The framework categorizes the circular supply chain into four building blocks: systemic approach, main drivers, levels of decision making, and mechanisms to manage the full loop closure and minimize the inherent uncertainties of a complex system. We conclude the chapter by illustrating the applicability of the circular supply chain framework using two industrial cases that are transitioning toward the circular economy.

  • 3.
    Gonzalez, Monica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Peukert, Bernd
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Assessment of Fault Detection and Monitoring Techniques for Effective Digitalization2023In: 33rd European Safety and Reliability Conference: The Future of Safety in a Reconnected World / [ed] Mário P. Brito, Terje Aven, Piero Baraldi, Marko Čepin, Enrico Zio,, Research Publishing Services , 2023, p. 1705-Conference paper (Refereed)
    Abstract [en]

    As a result of digitalization, data is collected at every level of production as an enhancer for decision-making. However, including more sensors to collect additional information does not directly contribute to increasing the system reliability but instead raises challenges for optimal data utilization. This work presents an evaluation approach based on FMSA (Failure mode and symptoms analysis) combined with FMECA (Failure mode, effects and criticality analysis) prioritization methods. The different methods are applied to a feed-drive system to evaluate the suitability of the currently implemented detection and monitoring techniques. The recommendations derived from the evaluation can be utilized to maximize confidence in the monitoring and to minimize the sensors utilization and data collection. Since the FMEA family of assessment tools present shortcomings such as bias and uncertainty associated with their results, this work also aims at mitigating these effects in obtaining the monitoring priority numbers and their respective categorization and prioritization.

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  • 4.
    Gonzalez, Monica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Manufacturing and Metrology Systems.
    Peukert, Bernd
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Manufacturing and Metrology Systems.
    Theissen, Nikolas Alexander
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Manufacturing and Metrology Systems.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Experimental identification of the position-dependent dynamics of an industrial manipulator2021In: Proceedings of the 21st International Conference of the European Society for Precision Engineering and Nanotechnology, EUSPEN 2021, 2021, p. 235-238Conference paper (Refereed)
    Abstract [en]

    Industrial manipulators are desired to be commonly used for material removal applications due to their high flexibility, low cost, and large working space. However, their lower stiffness (compared to a machine tool) leads to a reduction in path accuracy. This reduction directly affects the dimensional accuracy of the machined part. Additionally, the low stiffness in the presence of dynamic process forces creates vibrations influencing the surface quality, tool life, and service life of the manipulator. Static stiffness models, optimization, and compensation techniques exist to minimize force-induced deflections. Multi-body dynamics analytical models still lack the required accuracy in predicting the position-dependent dynamics of the manipulator. Dynamics data-driven models are rising to tackle the uncertainties in modeling the robot properties. This study presents the position-dependent variation of the dynamic characteristics, namely frequency and damping, of a mid-size articulated industrial manipulator, which were determined through experimental modal analysis. The position-dependent dynamics is investigated and quantified in a low-frequency range and is discretely measured and presented in two perpendicular planes (horizontal and vertical) of the robot working space. The study concludes with a discussion on the potential to apply the dynamic information obtained experimentally for the process planning and working space optimization in contact applications. 

  • 5.
    Gonzalez, Monica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Theissen, Nikolas Alexander
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Agirre, Nora
    Research and Development, MMAEN S.L., Pol. Plazaola, Manzana E, Nave 2, 31195, Berrioplano, Spain, Pol. Plazaola, Manzana E, Nave 2.
    Larrañaga, Jon
    Faculty of Engineering, Mondragon University, Loramendi, 4, 20500, Gipuzkoa, Spain, Loramendi, 4.
    Hacala, Patxi
    Dynamics and Control Department, IDEKO Research Centre, Arriaga Kalea, 2, 20870, Elgoibar, Spain, Arriaga Kalea, 2; Robotics Department, ESTIA Institute of Technology, Technopole Izarbel, 64210, Bidart, France.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Influence of the velocity on quasi-static deflections of industrial articulated robots2023In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 125, no 3-4, p. 1429-1438Article in journal (Refereed)
    Abstract [en]

    This article presents the measurement and analysis of the influence of velocity on the quasi-static deflections of industrial manipulators of three different manufacturers. Quasi-static deflection refers to the deflection of the end effector position of articulated robots during movement at low velocity along a predefined trajectory. Based on earlier reported observations by the authors, there exists a difference in the static and quasi-static deflections considering the same points along a trajectory. This work investigates this difference to assess the applicability of robotic compliance calibration at low velocities. For this assessment, the deflections of three industrial articulated robots were measured at different speeds and loads. Considering the similarity among the robot models used in this investigation, this work also elaborates on the potential influence of the measurement procedure on the measured deflections and its implications for the compliance calibration of articulated robots. For all industrial articulated robots in this investigation, the quasi-static deflections are significantly larger than the static ones but similar in trend. Additionally, the magnitude of the quasi-static deflections presents a proportional relationship to the Cartesian velocity.

  • 6.
    Gonzalez, Monica
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering.
    Theissen, Nikolas Alexander
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production engineering.
    Experimental comparison of offline and online compliance compensation strategies for industrial articulated robots2022In: European Society for Precision Engineering and Nanotechnology, Conference Proceedings: 22nd International Conference and Exhibition, EUSPEN 2022, euspen , 2022, p. 213-216Conference paper (Refereed)
    Abstract [en]

    Industrial articulated robots appeal to high force processes such as material removal applications mainly due to their high flexibility and large working space. However, due to the articulated robot's lower stiffness, significant deformations arise in the presence of process forces which reduces the robot's positioning accuracy. To improve the positioning accuracy in tasks performed under load, offline or online compliance compensation methods are implemented. This study presents an experimental comparison of the implementation and performance of offline and online compliance compensation strategies in a high-force application, i.e., loaded circular trajectory, characterized by the presence of quasi-static forces. The performance of the two compensation strategies was evaluated by calculating the mean deformation (comparison between unloaded and loaded trajectories). The results indicate that the performance of the online compensation strategy exceeded the offline compensation strategy performance for the case study analyzed. The limitations and potentialities of the different compensation strategies are discussed in terms of implementation and applicability for contact applications.

  • 7.
    Holmberg, Jonas
    et al.
    Department of Manufacturing Processes, RISE Research Institutes of Sweden AB, Argongatan 30, Mölndal, Sweden.
    Berglund, Johan
    Department of Manufacturing Processes, RISE Research Institutes of Sweden AB, Argongatan 30, Mölndal, Sweden.
    Brohede, Ulrika
    Department of Production Technology, Swerim AB, Isafjordsgatan 28A, Kista, Sweden.
    Åkerfeldt, Pia
    Division of Material Science, Luleå University of Technology, 971 87, Luleå, Sweden.
    Sandell, Viktor
    Division of Material Science, Luleå University of Technology, 971 87, Luleå, Sweden.
    Rashid, Amir
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Zhao, Xiaoyu
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Dadbakhsh, Sasan
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Fischer, Marie
    Department of Industrial and Materials Science, Chalmers University of Technology, Hörsalsvägen 7B, Göteborg, Sweden.
    Hryha, Eduard
    Department of Industrial and Materials Science, Chalmers University of Technology, Hörsalsvägen 7B, Göteborg, Sweden.
    Wiklund, Urban
    Department of Material Science, Ångströmlaboratoriet, Uppsala University, Lägerhyddsvägen 1, Uppsala, Sweden.
    Hassila, Carl Johan Karlsson
    Department of Material Science, Ångströmlaboratoriet, Uppsala University, Lägerhyddsvägen 1, Uppsala, Sweden.
    Hosseini, Seyed
    Department of Manufacturing Processes, RISE Research Institutes of Sweden AB, Argongatan 30, Mölndal, Sweden.
    Machining of additively manufactured alloy 718 in as-built and heat-treated condition: surface integrity and cutting tool wear2023In: The International Journal of Advanced Manufacturing Technology, ISSN 0268-3768, E-ISSN 1433-3015, Vol. 130, no 3-4, p. 1823-1842Article in journal (Refereed)
    Abstract [en]

    Additive manufacturing (AM) using powder bed fusion is becoming a mature technology that offers great possibilities and design freedom for manufacturing of near net shape components. However, for many gas turbine and aerospace applications, machining is still required, which motivates further research on the machinability and work piece integrity of additive-manufactured superalloys. In this work, turning tests have been performed on components made with both Powder Bed Fusion for Laser Beam (PBF-LB) and Electron Beam (PBF-EB) in as-built and heat-treated conditions. The two AM processes and the respective heat-treatments have generated different microstructural features that have a great impact on both the tool wear and the work piece surface integrity. The results show that the PBF-EB components have relatively lower geometrical accuracy, a rough surface topography, a coarse microstructure with hard precipitates and low residual stresses after printing. Turning of the PBF-EB material results in high cutting tool wear, which induces moderate tensile surface stresses that are balanced by deep compressive stresses and a superficial deformed surface that is greater for the heat-treated material. In comparison, the PBF-LB components have a higher geometrical accuracy, a relatively smooth topography and a fine microstructure, but with high tensile stresses after printing. Machining of PBF-LB material resulted in higher tool wear for the heat-treated material, increase of 49%, and significantly higher tensile surface stresses followed by shallower compressive stresses below the surface compared to the PBF-EB materials, but with no superficially deformed surface. It is further observed an 87% higher tool wear for PBF-EB in as-built condition and 43% in the heat-treated condition compared to the PBF-LB material. These results show that the selection of cutting tools and cutting settings are critical, which requires the development of suitable machining parameters that are designed for the microstructure of the material.

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  • 8.
    Kokare, Samruddha
    et al.
    Mycronic AB.
    Shoaib-ul-Hasan, Sayyed
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Abdullah Asif, Farazee Mohammad
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering, Machine and Process Technology.
    Mårtensson, Gustaf
    Mycronic AB.
    Svanteson, Kristina
    Mycronic AB.
    Life Cycle Assessment of a Jet Printing and Dispensing Machine2023In: 5th International Conference on Industry 4.0 and Smart Manufacturing, 2023Conference paper (Refereed)
  • 9. Marwitz, Johann August
    et al.
    Theissen, Nikolas Alexander
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Gonzalez, Monica
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Christian, Friedrich
    Hellmich, Arvid
    Cyber-Physical Production Systems, Fraunhofer Institute for Machine Tools and Forming Technology.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production Engineering.
    Ihlenfeldt, Steffen
    Accuracy Assessment of Articulated Industrial Robots using the Extended- and the Loaded-Double-Ball-Bar2022In: Journal of Machine Engineering, ISSN 1895-7595, Vol. 22, no 2, p. 80-98Article in journal (Refereed)
    Abstract [en]

    This research paper outlines the methodology and application of geometric and static accuracy assessment of articulated industrial robots using the Extended-Double-Ball-Bar as well as the Loaded-Double-Ball-Bar. In a first experiment, the EDBB is used to assess the geometric accuracy of a Comau NJ-130 robot. Advanced measuring trajectories are investigated that regard poses, which maximize the error influences of individual robot components. The developed error-sensitive trajectories are validated in experimental studies and compared to the circular trajectories according to ISO-230-4. Next, the Loaded-Double-Ball-Bar is used to assess an ABB IRB6700 manipulator under quasi-static loads of up to 600 Newton using circular testing according to ISO-230-4 and stiffness is identified. Then, the stiffness is used to perform a reverse calculation to identify the kinematic errors on the path deviations. The concept is validated in a case study of quasi-static loaded circular testing using the Loaded-Double-Ball-Bar compared to a Leica-AT960 laser tracker.

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  • 10.
    Subasic, Mustafa
    et al.
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Olsson, Mårten
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Dadbakhsh, Sasan
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Zhao, Xiaoyu
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Krakhmalev, Pavel
    Department of Engineering and Physics, Karlstad University, 651 88 Karlstad, Sweden.
    Mansour, Rami
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics. Department of Mechanical and Production Engineering, Aarhus University, 8200 Aarhus N, Denmark; DIGIT Center, 8200 Aarhus N, Denmark.
    Fatigue strength improvement of additively manufactured 316L stainless steel with high porosity through preloading2024In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 180, article id 108077Article in journal (Refereed)
    Abstract [en]

    This work investigates the influence of a single tensile preload, applied prior to fatigue testing, on the fatigue strength of 316L stainless steel parts manufactured using laser-based powder bed fusion (PBF-LB) with a porosity of up to 4 %. The specimens were produced in both the horizontal and vertical build directions and were optionally preloaded to 85 % and 110 % of the yield strength before conducting the fatigue tests. The results indicate a clear tendency of improved fatigue life and fatigue limit with increasing overload in both cases. The fatigue limits increased by 25.8 % and 24.6 % for the horizontally and vertically built specimens, respectively. Extensive modelling and experiments confirmed that there was no significant alteration in the shape and size of the porosity before and after preloading. Therefore, the observed enhancement in fatigue performance was primarily attributed to the imposed local compressive residual stresses around the defects.

  • 11.
    Söderberg, Vilhelm
    et al.
    Volvo Group Trucks Operations, Gropegårdsgatan 2,405 08 Gothenburg, Sweden.
    Tomkowski, Robert
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Chen, Danfang
    Volvo Group Trucks Operations, Gropegårdsgatan 2,405 08 Gothenburg, Sweden.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    The effect of technology development on components machined in the current production system used by the OEMs in the truck industry2023In: 56th CIRP International Conference on Manufacturing Systems, CIRP CMS 2023, Elsevier B.V. , 2023, p. 1588-1593Conference paper (Refereed)
    Abstract [en]

    The transport sector is growing and so is the awareness of the environmental impact from fossil fuels. This calls for changes in how road transport is powered, driven by both rules and regulations and from customer and societal expectations. There are several technical solutions to reduce and finally replace the use of fossil fuels currently discussed both in academia and industry and those solutions are at different maturity levels. The aim of this research is to investigate how the introduction of new technologies effects the evolvement of the components in the powertrain. This knowledge will be valuable for the truck industry OEMs to support the transition of the production system to match future needs. This is done in two parts. First, a semi-structured interview with experts from the automotive industry was conducted, then a literature study. The research shows that several powertrain technologies will exist, optimized for different markets and applications. On a component level, effort will be made to reduce the losses in the powertrain and the strive for efficiency will lead to higher requirements on geometrical quality, tighter tolerances, and surface requirements.

  • 12.
    Theissen, Nikolas Alexander
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Gonzalez, Monica
    KTH, School of Industrial Engineering and Management (ITM), Production engineering.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Working vs. operating space kinematic calibration of articulated industrial manipulators2022In: European Society for Precision Engineering and Nanotechnology, Conference Proceedings: 22nd International Conference and Exhibition, EUSPEN 2022, euspen , 2022, p. 205-208Conference paper (Refereed)
    Abstract [en]

    Kinematic calibration improves the positioning accuracy of articulated industrial manipulators. Industrial manipulators with kinematic calibration are more likely to be successfully offline programmed. Almost all manufacturers offer this calibration service. The calibration provided by the robot manufacturer is a working space calibration, which means that it guarantees a positioning accuracy for all possible configurations. This approach seems reasonable for an unknown target operation and if only a single set of model parameters can be stored in the robot controller. However, nowadays robot controllers can store more than one set of model parameters to reflect the significantly different orientations in which industrial manipulators can be mounted, e.g., floor-, wall, or ceiling-mounted. Thus, this work investigates the variability of the mean and maximum positioning accuracy of industrial manipulators in four different operating space calibrations and compares them with the working space calibration provided by the robot manufacturer. The article concludes with a discussion about potential improvements of existing kinematic calibration procedures.

  • 13.
    Tomkowski, Robert
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Zhao, Xiaoyu
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Leiro, A.
    Materials Technology YTMN, Scania CV AB, Granparksvägen 10, Södertälje, 151 87, Sweden.
    Archenti, Andreas
    KTH, School of Industrial Engineering and Management (ITM), Sustainable production development.
    Areal topography evaluation of a Ni-based alloy printed by electron beam melting (EBM) process2022In: European Society for Precision Engineering and Nanotechnology, Conference Proceedings: 22nd International Conference and Exhibition, EUSPEN 2022, euspen , 2022, p. 433-436Conference paper (Refereed)
    Abstract [en]

    Electron beam melting (EBM) is a powder bed fusion (PBF) additive manufacturing (AM) process for metal powder printing with wide applications in key industrial sectors, including automotive, healthcare, aerospace, etc. The high-temperature processing of this technique extensively sinters the powders on the surfaces and creates a poor and coarse surface finish. Differences between the surfaces from EBM in comparison with other AM processes make it difficult to answer which measurement method, with what measurement settings, and which evaluation parameters should be used for surface characterization. In this work, the performance of various optical methods for the measurement of areal topography of rough EBM-made metal surfaces was investigated. A specially prepared artefact allowing for the generation of different angles was designed and produced from a nickel-based alloy using EBM without any supporting structure for down-facing surfaces. The as-built up-facing and down-facing surfaces from the artefacts were measured in orthogonal to the build direction. Measurement system capability for as-EBM surfaces is presented along with areal surface texture analysis.

  • 14.
    Zhao, Xiaoyu
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Wei, Yuan
    Northwestern Polytech Univ, Xian Inst Flexible Elect IFE, Xian Inst Biomed Mat & Engn, Frontiers Sci Ctr Flexible Elect, Xian 710072, Peoples R China..
    Mansour, Rami
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Vehicle Engineering and Solid Mechanics, Solid Mechanics.
    Dadbakhsh, Sasan
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Rashid, Amir
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Effect of Scanning Strategy on Thermal Stresses and Strains during Electron Beam Melting of Inconel 625: Experiment and Simulation2023In: Materials, E-ISSN 1996-1944, Vol. 16, no 1, article id 443Article in journal (Refereed)
    Abstract [en]

    This paper develops a hybrid experimental/simulation method for the first time to assess the thermal stresses generated during electron beam melting (EBM) at high temperatures. The bending and rupture of trusses supporting Inconel 625 alloy panels at similar to 1050 degrees C are experimentally measured for various scanning strategies. The generated thermal stresses and strains are thereafter simulated using the Finite-Element Method (FEM). It is shown that the thermal stresses on the trusses may reach the material UTS without causing failure. Failure is only reached after the part experiences a certain magnitude of plastic strain (similar to 0.33 +/- 0.01 here). As the most influential factor, the plastic strain increases with the scanning length. In addition, it is shown that continuous scanning is necessary since the interrupted chessboard strategy induces cracking at the overlapping regions. Therefore, the associated thermal deformation is to be minimized using a proper layer rotation according to the part length. Although this is similar to the literature reported for selective laser melting (SLM), the effect of scanning pattern is found to differ, as no significant difference in thermal stresses/strains is observed between bidirectional and unidirectional patterns from EBM.

  • 15.
    Łukasz, Bohdal
    et al.
    Department of Mechanical Engineering, Koszalin University of Technology, Koszalin, Poland.
    Leon, Kukiełka
    Department of Mechanical Engineering, Koszalin University of Technology, Koszalin, Poland.
    Mateusz, Miksza
    Department of Mechanical Engineering, Koszalin University of Technology, Koszalin, Poland.
    Katarzyna, Kośka
    Department of Mechanical Engineering, Koszalin University of Technology, Koszalin, Poland.
    Tomkowski, Robert
    KTH, School of Industrial Engineering and Management (ITM), Production engineering, Manufacturing and Metrology Systems.
    Influence of tool geometry on residual stresses and strains in fine blanking process of electrical steel2023Conference paper (Refereed)
    Abstract [en]

    The fine blanking process is often used in plastic working to produce both simple details and those with complex shapes. This process consists in separating the material with the use of a tool that causes pressure on the shaped material, creating an appropriate state of deformation in the cross-section of the sheet and the cutting zone. The main challenge in the production lines is to obtain high-quality products with the optimal shape of the cut edge. Electrical steels are usually supplied as very thin sheets ready to be cut and blanked for use in the construction of stators and rotors for the cores of electric motors or as laminates for shielding and winding transformers. The presence of high silicon content in electrical steels together with their low thickness makes them susceptible to the formation of serious cut edge defects, such as: concentration of excessive deformations and stresses in the vicinity of the cut edge, excessive burrs, edge cracks. This condition results in a reduction of the magnetic efficiency in the final products.  A new approach to the design of the fine blanking process was proposed by optimizing the geometry of the punch, allowing for the reduction of contact pressures in the cutting zone and cut edge defects of electrical steel. By using the optimal blanking clearance, it is also possible to reduce the deformation zone concentrated near the cut edge. The proposed approach allows for extending the work cycles of the punches. FEM combined with the updated Lagrange description was used to describe the phenomena at a typical incremental step. The states of strain and strain rate are described by non-linear relationships without linearization. The description of the nonlinearity of the material was made with an incremental model taking into account the influence of the history of strain and the strain rate. The condition of the material after the previous treatments was also taken into account by introducing the initial states: displacements, stresses, strains and their velocities. An optimization process was carried out to determine the process conditions that would ensure the highest quality of the cut edge and the greatest durability of the cutting tools. The research results may be useful for the design of modern blanking tools used in the processing of electrical materials.

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    Influence of tool geometry on residual stresses and strains in fine blanking process of electrical steel
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