| 31. |
- Stark, Andreas, et al.
(författare)
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Hybrid digital manufacturing: Capturing the value of digitalization
- 2023
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Ingår i: Journal of Operations Management. - : Wiley. - 1873-1317 .- 0272-6963. ; 69:6, s. 890-910
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Tidskriftsartikel (refereegranskat)abstract
- A chasm is growing between the advanced technologies available for improving manufacturing operations and those effectively used in practice. The vision of Industry 4.0 is to mobilize industry to seek out these possibilities for improvement and to close the gap between opportunity and reality. However, when compared with more established improvement opportunities such as lean manufacturing, the digitalization of manufacturing lacks in both paradigmatic examples and an understanding of how to achieve the benefits. This lack is a complication of concern: Without an appropriate operations strategy to capture the value of digitalization, manufacturing companies will be unable to focus on technological investments and operational changes. To address this concern, operations management academics must develop new theory through active engagement in the practice of digitalization in manufacturing. This research presents a paradigmatic example, based on engaged scholarship, focused on effectively combining novel object-interactive and conventional manufacturing syntax for benefiting from digitalization in internal operations and the wider supply chain. The contribution to literature is a novel operations strategy—hybrid digital manufacturing—for capturing the value of Industry 4.0 technologies.
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| 32. |
- Stylidis, Kostas, 1978, et al.
(författare)
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Perceived Quality Evaluation with the Use of Extended Reality
- 2019
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Ingår i: Proceedings of the International Conference on Engineering Design, ICED. - : Cambridge University Press (CUP). - 2220-4334 .- 2220-4342. ; 1:1, s. 1993-2002
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Konferensbidrag (refereegranskat)abstract
- If designers want to communicate quality aspects of the product, there is a need to bring these characteristics into the measurable space of perceived quality (PQ) attributes. To illustrate the solution for designers' dilemma of the “best design choice” in this study we applied the PQ attributes importance ranking (PQAIR) method, with the example of a bread toaster. We choose for evaluation three PQ attributes which can significantly influence visual quality of a product: Gap, Flush and Parallelism. We performed the experiment measuring subjective preferences over the toaster designs of two respondent's groups - “Designers” and “Customers.” We used sequentially: (i) web-survey (still images); (ii) desktop system; and (iii) fully immersive head-mounted display system (Virtual Reality). Consequently, we conducted a post-experiment survey regarding subjective preferences, related to the PQ communication channels that have been implemented during the study. Our results indicate advantages and drawbacks for each PQ communication method that we applied in this experiment and encourage further research in the area of products' perceived quality assessment.
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| 33. |
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| 34. |
- Kumar, Mayank, 1991-
(författare)
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Friction in threaded fasteners : Influence of materials and tooling
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Threaded fasteners represent the most common type of machine element, with a unique function that facilitates ease of assembly and disassembly. This ease of disassembly allows machine parts to be reused, refurbished, and recycled. Easy as these components are to assemble, several factors must be considered to achieve the desired clamp force and to utilize the fastener to its full load capacity. The research presented in the thesis compares different tightening strategies and assembly tools to show that the clamp force and it´s scatter are influenced by the variation in the coefficient of friction (CoF) to a much larger extent than by the accuracy of an assembly tool. The research therefore focus on understanding the frictional response in a threaded fastener joint during tightening.A range of design and assembly factors are considered to identify how to increase reliability of the threaded fastener joints. These factors include tightening speed, coating, surface topography, fastener storage conditions, cutting fluid residue and joint material. A torque-controlled, two-step tightening method was mainly used in the studies as it is widely practiced across the production floor of the motor vehicle and general industries to tighten threaded fastener joints. A state-of-the-art friction test rig (FTR) was built to quantify variations in the CoF in the thread and under-head contacts during tightening. Coatings and contact surfaces are also characterized using SEM, FIB, indenters, and optical microscopes to gain an insight to find the likely reasons behind CoF variation. Fasteners with different Zn-based coatings were tightened on plates with surface topographies similar to those found in the motor vehicle industry. The samples were not cleaned before the testing but used "as-received" from the supplier. The degree of damage to the joint surface and fastener thread from the tightening depends on the hardness of the coating. The hardest coating (Zn-Ni) remained relatively unchanged but gave twice as high CoF in the under-head contact compared to the softest coating (Zn-flake). The under-head friction often dominates the tightening process and may be significantly affected by the joint surface topography and the level of cleanliness. In the automotive industry, many parts to be assembled are not thoroughly cleaned, increasing the risk of cutting fluid residue on the joint surface. Different types of cutting fluids were compared in a study with fasteners tightened against “as-received" and cleaned plates. It was shown that CoF might drastically decrease depending on the coating and cutting fluid types. An ester-based fluid performed best, providing the lowest CoF in the under-head contact due to its higher viscosity and polarity. A water-based fluid showed a significantly larger scatter. Water can also influence friction due differences in humidity and temperature. Sometimes fasteners are stored outside a factory which could lead to water diffusion in the coating in hot-humid climate or condensation of water on the fastener surface when it is brought from the outside storage at sub-zero temperatures into the production hall. Water on the coating and inside of it could lead to low CoF, with overtightening and fastener failure as a result. Four Zn-based coatings were compared and showed different response depending on the coating structure and topcoat. Another way to reduce CoF is to use variable speed tightening. It will also increase productivity, as it is faster. It will also improve operator ergonomics, as it gives much lower reaction torque. Much higher CoF was found for EPZ coating when tightened at a constant and very low speed, 5 rpm, due to cohesion that resulted in material transfer, compared to CoF during high, variable speed tightening. At the same time, speed had negligible influence on the CoF when using soft Zn-flake coating as the coating easily sheared off, acting as a solid lubricant.A soft coating is also practical when used in contact with parts made using additive manufacturing (AM). The AM parts are often rough, but a soft coating can mitigate an increase in the under-head CoF. An interesting finding was that the cheapest solution of using an uncoated fastener works very well. An anti-corrosion oil on the plain fastener helped in achieving low CoF. When the AM plate was machined, the CoF and surface damage significantly increased due to the lay of the surface topography created by machining. The findings presented in the thesis increase understanding of how various design and assembly factors govern friction in the thread and under-head contacts. The under-head contact dominates friction response. A proper selection and adjustment of these factors will help design engineers to optimize joint designs and achieve high fastener strength utilization.
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| 35. |
- Somhorst, Joop, 1965
(författare)
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Thermal insulation of the combustion chamber in a light duty diesel engine
- 2024
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Reduction of heat loss from the combustion chamber in an engine has great potential to decrease fuel consumption and CO2 emissions. Research on thermal barrier coatings (TBC) has been performed since the early eighties to address this potential. However, reported results for engine efficiency improvements with insulation show a large spread and there is no consensus on the actual benefits of TBCs. The purpose of this PhD project was to make an accurate assessment of state-of-the-art TBCs and establish what coating properties are required to improve indicated engine efficiency. Cylinder pressure data and measured heat losses to the piston cooling oil in a light duty single cylinder engine formed the basis for the experimental research. A robust and automated measurement method was developed and combined with statistical modeling of the data. Plasma sprayed yttria stabilized zirconia and anodized alumina were selected to establish the effectiveness of state-of-the-art TBCs. These coatings, applied on the piston top, did not improve indicated efficiency. The high surface roughness of the coatings was an important contributor to the poor performance. Experiments with a novel coating technology: suspension plasma spraying and a new material gadolinium-zirconate, led to a slightly improved indicated efficiency. Details in the heat release analysis indicated that the high open porosity in this coating might lead to increased heat losses and fuel entrainment. An investigation of possible charge entrainment effects in a standard plasma sprayed zirconia thermal barrier coating was performed, using a combination of engine experiments, CFD simulations and a 0D crevice model. The crevice model predicted the observed deviations of the apparent rate of heat release surprisingly well, which is strong evidence for the existance and significance of this crevice effect. To significantly increase engine efficiency with thermal insulation, materials with further reduced thermal conductivity and volumetric heat capacity are needed, while negative effects such as high surface roughness and crevice effects from permeable porosity should be minimized.
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| 36. |
- Alonso Fernandez, Iñigo, 1985, et al.
(författare)
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Identification of Technology Integration Challenges at Two Global Automotive OEMs
- 2020
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Ingår i: Proceedings of the Design Society: DESIGN Conference. - : Cambridge University Press (CUP). - 2633-7762. ; 1, s. 2245-2254
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Konferensbidrag (refereegranskat)abstract
- Platform design has been firmly established in the automotive industry as a strategy to provide wider product variety while maintaining cost effective production. But this strategy can struggle to keep up with the pace and nature of emerging technologies. This paper reviews the existing approaches to modelling product platforms, and showcases the challenges at OEMs introducing new technological innovations in their platforms. A gap is identified in the methods to assess the ability of existing platforms to integrate new technologies whenever they become available.
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| 37. |
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| 38. |
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| 39. |
- Lämkull, Dan, 1966, et al.
(författare)
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Consistency in figure posturing results within and between simulation engineers
- 2006
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Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191 .- 2688-3627.
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Konferensbidrag (refereegranskat)abstract
- This paper presents the results of an effort to compare figure posturing results within and between simulation engineers. The simulation engineers simulated four manual tasks. Alternately they used a posture prediction tool, and alternately they were only allowed to apply manual adjustments of the body angles. The simulation engineers repeated each task six times and always with at least six days between each occasion, to minimize the subject's rememberance of how she/he carried out the cases. Results show that the use of a posture prediction tool, in such complex tasks as the study includes, neither reduces needed time to fulfill a simulation, nor differences within or between simulation engineers. Differences in simulation results often originate from the different assumptions the simulation engineers have of the task when positioning the manikins. The differences could be minimized by a more careful orderer description and by such activities as simulation engineering days at assembly plants and by bringing the people working with human simulation tools together in the organization. Copyright © 2006 SAE International.
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| 40. |
- Radovan, Drazumeric, et al.
(författare)
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Truing of diamond wheels - Geometry, kinematics and removal mechanisms
- 2018
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Ingår i: CIRP Annals - Manufacturing Technology. - : Elsevier BV. - 1726-0604 .- 0007-8506. ; 67:1, s. 345-348
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Tidskriftsartikel (refereegranskat)abstract
- An investigation is made into traverse truing of diamond grinding wheels using various truing grit types, grit sizes and truing parameters. Geometry and kinematics of the truing contact are modeled. Specific energies are found to depend on truing-grit size but not on truing parameters, indicating little to no size effect. Removal mechanisms are analyzed via SEM examination of diamond- and truing-wheel swarf. A fundamental relationship is established relating the truing compliance number to the truing efficiency, which encompasses truing parameters and truing- and diamond-grit sizes. Recommendations are made for optimum conditions to minimize force-constrained truing time.
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