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- Harati, Ebrahim, 1986-, et al.
(författare)
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Comparison of effect of shot-peening with HFMI treatment or use of LTT consumables on fatigue strength of 1300 MPa yield strength steel weldments
- 2020
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Ingår i: Welding in the World. - : Springer Science and Business Media LLC. - 0043-2288 .- 1878-6669. ; 64:7, s. 1237-1244
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, T-joint samples in a 1300 MPa yield strength steel were produced using conventional or low transformation temperature (LTT) type consumables. The welded samples were either subjected to high-frequency mechanical impact (HFMI) treatment or to shot-peening. Fatigue testing was performed under fully reversed, constant amplitude bending load. Shot-peening gave a significant increase in fatigue strength for more than around 50,000 cycles. Shot-peened LTT welds had the highest fatigue strength, with conventional welds being shot-peened having slightly lower fatigue strength. HFMI treatment of conventional and LTT welds improved the fatigue strength also, but to a lesser extent, keeping the slope in the SN diagram close to three, while shot-peened samples had a slope of 5–7. Significant differences in compressive residual stress were seen between the different welds, with the most compressive stress found in the shot-peened samples. This was probably one of the main reasons for the improved fatigue life of shot-peened samples. © 2020, The Author(s).
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| 2. |
- Kylén, Erik, et al.
(författare)
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Development of an Animated Video for Pre- and Postoperative Learning for Osteoarthritis Patients
- 2020
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Ingår i: Education and New Developments 2020. - Lisboa, Portugal. - 9789895481521 ; , s. 428-432
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Osteoarthritis (OA) is a condition in the joint that is developing for a long time and hit first and mainlyarticular cartilage, and it is a long-term chronic disease characterized by deterioration. In the final stage itis affected all the tissues of the joints such as bones, ligaments, arthritis, joint fluid and muscles, whichresults in bones rubbing together and creating stiffness, pain, and impaired movement. This disease canaffect the joints in the knees, hands, feet, spine and shoulder. OA is the single most common cause ofdisability in older adults worldwide. Patients need to receive detailed information about the disability,learn about their disease, its treatment and how to follow recommendations both before and after thesurgery. As hospital stays are shortening the need of information is increasing, as the patients need toprepare themselves at home before the operation, as well as take care of their rehabilitation when they arecoming home, discharged from hospital. In this paper we present a case study about the development of aweb-based animated video that was developed to support the learning for patients with OA, using adesign science research approach. DSR is an iterative process that include three iterative research cycles.The relevance cycle provided the requirements for the application from the very beginning. The relevancecycle, the rigor cycle and the design cycle were conducted iteratively, and have generated designalternatives that have been evaluated in discussions with OA surgery physicians, as representatives fromthe application domain.
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| 3. |
- Raza, Tahira, 1972-
(författare)
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Process Understanding and Weldability of Laser-Powder Bed Fusion Manufactured Alloy 718
- 2020
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Laser-powder bed fusion (L-PBF) is an additive manufacturing (AM) process that involves building components by fusing fine metal powders using laser. There is no universal set of process parameters that can yield optimum results for all the different materials, geometries, and L-PBF machines. The research performed at hand regarding the process parameters showed that laser power, scanning speed, laser exposure time, and laser point distance are the most influential process parameters to decrease the amount of lack of fusion. In contrast, gas porosities are unavoidable in the L-PBF material because they can occur either because of powder particles containing inherent gas pores from the powder atomisation process or entrapped shielding gas during the L-PBF process. To fully utilise the L-PBF technique as a commercial production process, joining of small parts to build large-sized or complex shaped components, such as structural components for jet engines, can be a solution. The as-built microstructure of L-PBF-manufactured superalloy Alloy 718, which is the material in focus in the present research, has grains mostly oriented in the building direction of the part with a very fine cellular-dendritic structure within them. The microstructure of the alloy also contains NbC, TiN and low melting Laves phase in the interdendritic regions and along the grain boundaries. The specimens in this study were subjected to different heat treatments, such as hot isostatic pressing (HIP), solution heat treatment, and solution and ageing heat treatment, prior to welding, to study the effect of these heat treatments on the microstructure of the L-PBF-718 with regard to the susceptibility towards heat-affected zone (HAZ) liquation cracking during welding. Results showed that L-PBF-718 was susceptible to HAZ cracking during welding in all material conditions. L-PBF-718 subjected to HIP was more prone to HAZ cracking while welding and revealed a lower ductility behaviour in comparison to L-PBF-718 in the as-builtixcondition and wrought Alloy 718. The welding direction with respect to the graingrowth direction in L-PBF-718 was also found to have a significant influence onhot cracking susceptibility. The extent of HAZ cracking was observed to besmaller in samples welded parallel to the elongated grain orientation than insamples where the welding was performed perpendicular to it.
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