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| 2. |
- Chai, Guocai, et al.
(författare)
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Mechanisms of Hydrogen Induced Stress Crack Initiation and Propagation in Super Duplex Stainless Steels
- 2009
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Ingår i: STEEL RESEARCH INTERNATIONAL. - 1611-3683. ; 80:7, s. 482-487
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Tidskriftsartikel (refereegranskat)abstract
- Austenitic and ferritic duplex stainless steels, DSS, have recently suffered from hydrogen stress induced cracking, HISC, in subsea components with a cathodic protection. This paper provides discussions on possible HISC mechanisms. HISC initiation can occur at the ferritic grain boundaries and phase boundaries at a stress lower than the yield strength, but dominantly at phase boundaries at a stress higher than the yield strength. EBSD analysis shows that HISC in DSS results from the interaction between the dynamic plasticity by creep and hydrogen diffusion. A model on the formation of microstresses in these two phases under creep conditions is proposed, which explains why HISC occurs mainly in the ferritic phase. Discontinuous two-dimensional HISC paths were observed. The austenitic phase acts as obstacles for crack propagation. The fracture covers "valleys" and "peaks" with the cleavage ferrite and the austenite with microfacets or striations due to the hydrogen-enhanced localized-plasticity.
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| 3. |
- Chen, Jian, et al.
(författare)
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AXL promotes Zika virus infection in astrocytes by antagonizing type I interferon signalling
- 2018
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Ingår i: Nature Microbiology. - : NATURE PUBLISHING GROUP. - 2058-5276. ; 3:3, s. 302-309
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Tidskriftsartikel (refereegranskat)abstract
- Zika virus (ZIKV) is associated with neonatal microcephaly and Guillain-Barre syndrome(1,2). While progress has been made in understanding the causal link between ZIKV infection and microcephaly(3-9), the life cycle and pathogenesis of ZIKV are less well understood. In particular, there are conflicting reports on the role of AXL, a TAM family kinase receptor that was initially described as the entry receptor for ZIKV(10-22). Here, we show that while genetic ablation of AXL protected primary human astrocytes and astrocytoma cell lines from ZIKV infection, AXL knockout did not block the entry of ZIKV. We found, instead, that the presence of AXL attenuated the ZIKV-induced activation of type I interferon (IFN) signalling genes, including several type I IFNs and IFN-stimulating genes. Knocking out type I IFN receptor alpha chain (IFNAR1) restored the vulnerability of AXL knockout astrocytes to ZIKV infection. Further experiments suggested that AXL regulates the expression of SOCS1, a known type I IFN signalling suppressor, in a STAT1/STAT2-dependent manner. Collectively, our results demonstrate that AXL is unlikely to function as an entry receptor for ZIKV and may instead promote ZIKV infection in human astrocytes by antagonizing type I IFN signalling.
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| 4. |
- Pant, Prabhat, et al.
(författare)
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A simplified layer-by-layer model for prediction of residual stress distribution in additively manufactured parts
- 2021
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Ingår i: Metals. - : MDPI AG. - 2075-4701. ; 11:6
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Tidskriftsartikel (refereegranskat)abstract
- With the improvement in technology, additive manufacturing using metal powder has been a go-to method to produce complex-shaped components. With complex shapes being printed, the residual stresses (RS) developed during the printing process are much more difficult to control and manage, which is one of the issues seen in the field of AM. A simplified finite element-based, layer-by-layer activation approach for the prediction of residual stress is presented and applied to L-shaped samples built in two different orientations. The model was validated with residual stress distributions measured using neutron diffraction. It has been demonstrated that this simplified model can predict the trend of the residual stress distribution well inside the parts and give insight into residual stress evolution during printing with time for any area of interest. Although the stress levels predicted are higher than the measured ones, the impact of build direction on the development of RS during the building process and the final RS distributions after removing the base plate could be exploited using the model. This is important for finalizing the print orientation for a complex geometry, as the stress distribution will be different for different print orientations. This simplified tool which does not need high computational power and time can also be useful in component design to reduce the residual stresses. © 2021 by the authors.
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| 5. |
- Peng, Ru, et al.
(författare)
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In-situ Neutron Diffraction Study of the Deformation Behaviour of two High-Manganese Austenitic Steels
- 2011
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Ingår i: Materials Science Forum. - Stafa-Zurich, Switzerland : Trans Tech Publications Inc.. - 0255-5476 .- 1662-9752. ; 681, s. 474-479
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Tidskriftsartikel (refereegranskat)abstract
- In-situ neutron diffraction experiments under tensile loading were carried out to study the micromechanical behaviour of two iron-manganese based steels, a TWIP (twinning induced plasticity) steel with 30 wt% Mn and a TRIP steel (transformation induced plasticity) with 20 wt% Mn. The former was loaded to 31.3% strain and the latter to 20% strain. The 30 wt.% Mn steel had a fully austenitic microstructure which remained stable over the loading range studied, while stress induced austenite to α´- and ε-martensite transformations occur in the 20 wt.% Mn steel which initially contained an α´-martensite in addition to the austenite. The evolution of lattice strains under tensile loading differs between the two steels, reflected their different plastic deformation mechanisms. A stronger grain-orientation dependent behaviour is observed during deformation for the 20 wt.% Mn in contrast to the 30wt.% Mn steel.
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| 6. |
- Shen, Yong-Feng, et al.
(författare)
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Deformation mechanisms of a 20Mn TWIP steel investigated by in situ neutron diffraction and TEM
- 2013
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Ingår i: Acta Materialia. - : Elsevier. - 1359-6454 .- 1873-2453. ; 61:16, s. 6093-6106
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Tidskriftsartikel (refereegranskat)abstract
- The deformation mechanisms and associated microstructure changes during tensile loading of an annealed twinning-induced plasticity steel with chemical composition Fe-20Mn-3Si-3Al-0.045C (wt.%) were systematically investigated using in situ time-of-flight neutron diffraction in combination with post mortem transmission electron microscopy (TEM). The initial microstructure of the investigated alloy consists of equiaxed gamma grains with the initial alpha'-phase of similar to 7% in volume. In addition to dislocation slip, twinning and two types of martensitic transformations from the austenite to alpha'- and epsilon-martensites were observed as the main deformation modes during the tensile deformation. In situ neutron diffraction provides a powerful tool for establishing the deformation mode map for elucidating the role of different deformation modes in different strain regions. The critical stress is 520 MPa for the martensitic transformation from austenite to alpha'-martensite, whereas a higher stress (>600 MPa) is required for actuating the deformation twin and/or the martensitic transformation from austenite to epsilon-martensite. Both epsilon- and alpha'-martensites act as hard phases, whereas mechanical twinning contributes to both the strength and the ductility of the studied steel. TEM observations confirmed that the twinning process was facilitated by the parent grains oriented with < 1 1 1 > or < 1 1 0 > parallel to the loading direction. The nucleation and growth of twins are attributed to the pole and self-generation formation mechanisms, as well as the stair-rod cross-slip mechanism.
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| 7. |
- Afshari, Davood, et al.
(författare)
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An approach in prediction of failure in resistance spot welded aluminum 6061-T6 under quasi-static tensile test
- 2012
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Ingår i: Proceedings of the Institution of mechanical engineers. Part B, journal of engineering manufacture. - : SAGE Publications. - 0954-4054 .- 2041-2975. ; 226:B6, s. 1026-1032
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Tidskriftsartikel (refereegranskat)abstract
- The aim of this article is to predict the failure load in resistance spot welded aluminum 6061-T6 sheets with 2mm thickness under quasi-static tensile test. Various welding parameters, e. g. welding current, welding time and electrode force are selected to produce welded joints with different quality. The results show that for all the samples in this study only interfacial failure mode was observed in tensile-shear test and no pull-out mode was observed. According to the failure mode, an empirical equation was used for the prediction of failure load based on nugget size and hardness of failure line. Microstructure study has been carried out to investigate microstructural changes in the welded joints. For determination of the minimum hardness, microhardness tests have been carried out to find hardness profiles. The minimum hardness value was observed for a thin layer around the nugget with large and coarse grains. The results show that by using the presented empirical equation, the failure can be predicted with a good agreement only by measuring nugget size.
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| 8. |
- Agmell, M., et al.
(författare)
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Modeling subsurface deformation induced by machining of Inconel 718
- 2017
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Ingår i: Machining Science and Technology. - : Informa UK Limited. - 1091-0344 .- 1532-2483. ; 21:1, s. 103-120
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Tidskriftsartikel (refereegranskat)abstract
- Traditionally, the development and optimization of the machining process with regards to the subsurface deformation are done through experimental method which is often expensive and time consuming. This article presents the development of a finite element model based on an updated Lagrangian formulation. The numerical model is able to predict the depth of subsurface deformation induced in the high- speed machining of Inconel 718 by use of a whisker-reinforced ceramic tool. The effect that the different cutting parameters and tool microgeometries has on subsurface deformation will be investigated both numerically and experimentally. This research article also addresses the temperature distribution in the workpiece and the connection it could have on the wear of the cutting tool. The correlation of the numerical and experimental investigations for the subsurface deformation has been measured by the use of the coefficient of determination, R2. This confirms that the finite element model developed here is able to simulate this type of machining process with sufficient accuracy.
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| 9. |
- Ahmad, Maqsood, et al.
(författare)
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Bending Fatigue Behavior of Blast Cleaned Grey Cast Iron
- 2017
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Ingår i: Residual Stresses 2016: ICRS-10, Materials Research Proceedings 2 (2016). - : Materials Research Forum LLC. - 9781945291166 ; , s. 193-198
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Konferensbidrag (refereegranskat)abstract
- This paper presents a detailed study on the effect of an industrial blast cleaning process on the fatigue behavior of a grey cast iron with regard to the residual stresses and microstructural changes induced by the process. A comparison was also made to the effect of a machining operation which removed the casting skin layer. The blast cleaning process was found to greatly improve the fatigue resistance in both the low and high cycle regimes with a 75% increase in the fatigue limit. Xray diffraction measurements and scanning electron microscopic analyses showed that the improvement was mainly attributed to compressive residual stresses in a surface layer up to 800 μm in thickness in the blast cleaned specimens. The machining also gave better fatigue performance with a 30% increase in the fatigue limit, which was ascribed to the removal of the weaker casting skin layer.
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| 10. |
- Albacete, Javier L., et al.
(författare)
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Predictions for p + Pb Collisions at sN N = √5 TeV : Comparison with Data
- 2016
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Ingår i: International Journal of Modern Physics E. - 0218-3013. ; 25:9
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Forskningsöversikt (refereegranskat)abstract
- Predictions made in Albacete et al. [Int. J. Mod. Phys. E 22 (2013) 1330007] prior to the LHC p+Pb run at sNN = 5 TeV are compared to currently available data. Some predictions shown here have been updated by including the same experimental cuts as the data. Some additional predictions are also presented, especially for quarkonia, that were provided to the experiments before the data were made public but were too late for the original publication.
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