| 1. |
- Hosseini, Seyed, et al.
(författare)
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Comparison of machining performance of stainless steel 316L produced by selective laser melting and electron beam melting
- 2022
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Ingår i: Procedia CIRP. - : Elsevier B.V.. - 2212-8271. ; , s. 72-77
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Konferensbidrag (refereegranskat)abstract
- Powder bed fusion processes based additively manufactured SS 316L components fall short of surface integrity requirements needed for optimal functional performance. Hence, machining is required to achieve dimensional accuracy and to enhance surface integrity characteristics. This research is focused on comparing the material removal performance of 316L produced by PBF-LB (laser) and PBF-EB (electron beam) in terms of tool wear and surface integrity. The results showed comparable surface topography and residual stress profiles. While the hardness profiles revealed work hardening at the surface where PBF-LB specimens being more susceptible to work hardening. The investigation also revealed differences in the progress of the tool wear when machining specimens produced with either PBF-LB or PBF-EB. .
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| 2. |
- Laakso, Sampsa, 1983, et al.
(författare)
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Evaluation of subcooled MQL in cBN hard turning of powder-based Cr-Mo-V tool steel using simulations and experiments
- 2022
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Ingår i: International Journal of Advanced Manufacturing Technology. - : Springer Science and Business Media LLC. - 0268-3768 .- 1433-3015. ; 118:1-2, s. 511-531
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Tidskriftsartikel (refereegranskat)abstract
- Metal cutting fluids for improved cooling and lubrication are an environmental risk and a health risk for workers. Minimizing water consumption in industry is also a goal for a more sustainable production. Therefore, metal cutting emulsions that contain hazardous additives and consume considerable amounts of water are being replaced with more sustainable metal cutting fluids and delivery systems, like vegetable oils that are delivered in small aerosol droplets, i.e., via minimum quantity lubrication (MQL). Since the volume of the cutting fluid in MQL is small, the cooling capacity of MQL is not optimal. In order to improve the cooling capacity of the MQL, the spray can be subcooled using liquid nitrogen. This paper investigates subcooled MQL with machining simulations and experiments. The simulations provide complementary information to the experiments, which would be otherwise difficult to obtain, e.g., thermal behavior in the tool-chip contact and residual strains on the workpiece surface. The cBN hard turning simulations and experiments are done for powder-based Cr-Mo-V tool steel, Uddeholm Vanadis 8 using MQL subcooled to −10 °C and regular MQL at room temperature. The cutting forces and tool wear are measured from the experiments that are used as the calibration factor for the simulations. After calibration, the simulations are used to evaluate the thermal effects of the subcooled MQL, and the surface residual strains on the workpiece. The simulations are in good agreement with the experiments in terms of chip morphology and cutting forces. The cutting experiments and simulations show that there is only a small difference between the subcooled MQL and regular MQL regarding the wear behavior, cutting forces, or process temperatures. The simulations predict substantial residual plastic strain on the workpiece surface after machining. The surface deformations are shown to have significant effect on the simulated cutting forces after the initial tool pass, an outcome that has major implications for inverse material modeling.
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| 3. |
- Malakizadi, Amir, 1983, et al.
(författare)
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Post-processing of additively manufactured metallic alloys – A review
- 2022
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Ingår i: International Journal of Machine Tools and Manufacture. - : Elsevier BV. - 0890-6955 .- 1879-2170. ; 179
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Forskningsöversikt (refereegranskat)abstract
- Additive manufacturing (AM) is characterised by several unique advantages, such as (freedom of) design, capability of fusing dissimilar materials, near-net-shape, and achieving a more sustainable production. While the increased precision of metal AM in recent years reduced the needed amount of post-processing to meet dimensional tolerance, the requirements for functional surfaces necessitate a well-understood post-processing, ranging from heat treatment to machining and finishing. The inherently rough initial (as-built) surface topography next to complex material microstructure affects the capability of post-processing/finishing operations to smooth the surface texture and obtain a favourable surface integrity. In this respect, a more fundamental understanding of the effects of material properties on post-processing/finishing is needed. Therefore, this review paper aims to establish the relationship between the characteristics of different AM technologies, microstructural properties of materials in as-built and heat-treated conditions, and the physical properties influencing the response of additively manufactured materials during post-processing/finishing operations. In particular, emphasis is placed on the physics-based understanding of how the microstructural characteristics of 316L, Ti6Al4V and Alloy 718 produced using the two principal technologies, Powder Bed Fusion (PBF) and Direct Energy Deposition (DED), influence their mechanical properties like tensile strengths, hardness and ductility. These properties are among the key factors influencing the response of material during post-processing/finishing operations involving material removal by shear deformation. This review paper also discusses the role of post-processing/finishing on fatigue performance, tribological behaviour and corrosion resistance of investigated AM materials. The paper summarises the state-of the art of post-processing/finishing operations and future research trends are highlighted.
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| 4. |
- Mallipeddi, Dinesh, 1987, et al.
(författare)
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Investigation of the surface integrity of mechano-chemically finished powder metallurgy gears
- 2022
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Ingår i: Procedia CIRP. - : Elsevier BV. - 2212-8271. ; 115, s. 142-147
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Konferensbidrag (refereegranskat)abstract
- Automotive gears are facing stringent requirements regarding weight and functional surfaces, especially in view of the electric powertrain. To achieve these demands, powder metallurgy gears need to be finished using grinding, and in certain cases, mechano-chemical treatments. With regards to the latter, five different triboconditioning strategies based on vibratory tub finishing and/or centrifugal barrel finishing were considered and their effects on the surface integrity and friction behavior were investigated. Triboconditioning improved the surface roughness after grinding and resulted in higher compressive residual stresses. Additionally, microscopic observations of the surface topography were carried out. The lowest friction coefficients were observed for triboconditioning with a doped material (tribofilm) on the finished surface.
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