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- Gu, Shijia, et al.
(författare)
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Direct indication of a higher central temperature achieved during spark plasma sintering process of a zeolite
- 2015
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Ingår i: Journal of the European Ceramic Society. - : Elsevier BV. - 0955-2219 .- 1873-619X. ; 35:5, s. 1599-1603
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Tidskriftsartikel (refereegranskat)abstract
- The transition between transparent and opaque of as-sintered zeolite samples is employed to study the temperature distribution of non-conducting samples during spark plasma sintering (SPS) process in this paper. The results show that temperature gradients exist in both radial and axial directions, which provide direct evidence of temperature distribution in the SPS process. The sample prepared at 1325 degrees C is transparent in the center and opaque in the edge, which suggests that the temperature of the center is higher than the edge and the temperature differential is about 26 degrees C by the thermal analysis model based on the experimental data in ANSYS code. The axial temperature gradient is also present in the as-sintered sample obtained at 1315 degrees C. The transparent part of the upper surface is larger than the lower surface, which illustrates that the temperature of the upper surface was higher than the lower surface and the difference is about 5 degrees C.
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- Luo, Shijian, et al.
(författare)
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RoamFab : A Design Tool for Reconfiguring Parameterized Mechanisms to 3D Models With Structural Optimization
- 2023
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Ingår i: International Journal of Human-Computer Interaction. - : Informa UK Limited. - 1044-7318 .- 1532-7590. ; 39:19, s. 3702-3716
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Tidskriftsartikel (refereegranskat)abstract
- Creating personalized 3D printing objects has become increasingly popular with the advance in end-user modeling tools and fabrication techniques. However, it remains challenging for novice makers to design and fabricate functional objects with mechanical motion such as linear or rotational. To empower users to add mechanical movements to their models for particular needs, we first investigate the commonly used 3D printable mechanisms and parameterize four mechanical primitives. We then provide a computational approach to reconfigure the mechanical primitives to user-provided 3D models, with an underlying structural optimization procedure according to a specified bending force. We further showcase a set of design examples and conduct a user study to demonstrate the potential of our approach in creating personalized functional artifacts.
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- Olsén, Jon, 1983-
(författare)
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Additive metallurgy - Thermal influences on structure and properties of stainless steel 316L
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Additive manufacturing (AM) as a manufacturing process has, in recent years, become widely accepted as capable of manufacturing parts that will be used in end products. In this thesis, stainless steel grade 316L parts are manufactured using two different powder bed fusion techniques, selective laser melting (SLM) and electron beam melting (EBM). It is recognized that parts made using these processes will have unique microstructures and mechanical properties that have not been seen in bulk parts produced with other methods. The driving force behind the formation of these structures is the fast cooling speed that induces segregation of elements, forming an inhomogeneous microstructure. How these structures react to thermal treatment is less well known and an essential aspect in many applications. Parts manufactured using SLM was treated with hot isostatic pressing (HIP) to investigate if the material retains its unique features. Two different HIP cycles were used, one with 1150 °C and one with 1040 °C. In both cases, the cellular sub-grain structure fades. The cycle utilizing the high temperature is found to coarsen the grain structure and thus lowering the mechanical properties significantly. As manufactured parts show yield strength (615±1 MPa), tensile strength (725±2 MPa) and microhardness (211±10 Hv), compared to values of yield strength (284±2 MPa), tensile strength (636±1 MPa) and microhardness (178±8 Hv) after 1150 °C HIP. Using HIP at 1040 °C, the material will retain a finer grain structure resulting in higher yield strength (417±7 MPa) compared to 1150 °C HIP temperature, while the UTS and hardness have a similar value. It is also observed that the dispersed inclusions formed during SLM are still present after HIP to increase the mechanical properties compared to a conventionally annealed bar (TS: 515 MPa, YS: 205 MPa). Samples manufactured using EBM was investigated to understand the influence of the in-situ heat treatment that is present in the EBM process. The material possesses a long-range heterogeneous structure in addition to the cellular structure, where the cellular structure is present at the top and disappears further down the sample. Samples with different geometries were produced to study the effect of heat flux, cooling speed and the elevated temperature of 800 °C that is present during the EBM process. The thickness of the cell boundaries is measured in different areas, revealing that geometry and size of manufactured parts have a significant impact on the evolving microstructure. It is also revealed that the tensile strength (562±4 MPa) and microhardness (161±11 Hv) is not affected by the change in microstructure, resulting in a very homogeneous material concerning these parameters. Heat treating the material at 800 °C show that the cellular structure becomes diffuse after several hours, but the grain morphology stays the same.
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