| 1. |
- Andersson, Håkan, 1970-, et al.
(författare)
-
Simulation of wear in hydraulic percussion units using a co-simulation approach
- 2023
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Ingår i: International Journal of Modelling and Simulation. - : Taylor & Francis. - 0228-6203 .- 1925-7082. ; 43:3, s. 265-281
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Tidskriftsartikel (refereegranskat)abstract
- In this study, a developed co-simulation method, which couples 1D-fluid and 3D-structural models, has been utilised to simulate wear in a hydraulic percussion unit. The effect of wear is generally detrimental on performance and lifetime for such units, but can also cause catastrophic failure and breakdown, requiring a total overhaul and replacement of core components. One experiment of standard straight impact was performed to investigate the tolerance against seizure. The percussion unit was operated at successively increasing operating pressures, and the level of wear was registered at each step, until seizure occurred. The co-simulation model was used to replicate the running conditions from the experiment to simulate the structural response to be used as input for the wear routine to calculate the wear depth. The wear pattern from the simulations corresponds well to the wear pattern from the experiment. Further, the effect of a misaligned impact on wear development was also studied, as this is a loading situation that typically occurs for hydraulic percussion units. The study demonstrates that the simulation method used has a potential for simulating wear and predicting seizure in hydraulic percussion units.
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| 2. |
- Grossmann, Igor, et al.
(författare)
-
Insights into the accuracy of social scientists' forecasts of societal change
- 2023
-
Ingår i: Nature Human Behaviour. - : Springer Nature. - 2397-3374. ; 7, s. 484-501
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Tidskriftsartikel (refereegranskat)abstract
- How well can social scientists predict societal change, and what processes underlie their predictions? To answer these questions, we ran two forecasting tournaments testing the accuracy of predictions of societal change in domains commonly studied in the social sciences: ideological preferences, political polarization, life satisfaction, sentiment on social media, and gender-career and racial bias. After we provided them with historical trend data on the relevant domain, social scientists submitted pre-registered monthly forecasts for a year (Tournament 1; N = 86 teams and 359 forecasts), with an opportunity to update forecasts on the basis of new data six months later (Tournament 2; N = 120 teams and 546 forecasts). Benchmarking forecasting accuracy revealed that social scientists' forecasts were on average no more accurate than those of simple statistical models (historical means, random walks or linear regressions) or the aggregate forecasts of a sample from the general public (N = 802). However, scientists were more accurate if they had scientific expertise in a prediction domain, were interdisciplinary, used simpler models and based predictions on prior data. How accurate are social scientists in predicting societal change, and what processes underlie their predictions? Grossmann et al. report the findings of two forecasting tournaments. Social scientists' forecasts were on average no more accurate than those of simple statistical models.
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| 3. |
- Lindström, Thomas, 1991-, et al.
(författare)
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Accounting for anisotropic, anisothermal, and inelastic effects in crack initiation lifing of additively manufactured components
- 2023
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Ingår i: Fatigue & Fracture of Engineering Materials & Structures. - : Wiley. - 8756-758X .- 1460-2695. ; 46:2, s. 396-415
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Tidskriftsartikel (refereegranskat)abstract
- The crack initiation life of a ductile additively manufactured nickel-based superalloy is studied and modeled for low-cycle fatigue and thermomechanical fatigue conditions up to 600 degrees C. Isothermal experiments were performed on smooth specimens at temperatures up to 600 degrees C with different applied strain ranges. Additionally, thermomechanical fatigue experiments at 100-450 degrees C and 100-600 degrees C were performed on smooth specimens under in-phase and out-of-phase conditions. A life prediction model accounting for the anisotropy was developed, where the temperature cycle is accounted with a Delta T$$ \Delta T $$-functionality, generating good agreements with the experiments. The model was also validated on notched specimens undergoing thermomechanical fatigue conditions at 100-500 degrees C using simplified notch correction methods.
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| 4. |
- Lindström, Thomas, et al.
(författare)
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Constitutive model for thermomechanical fatigue conditions of an additively manufactured combustor alloy
- 2022
-
Ingår i: Mechanics of materials. - : Elsevier. - 0167-6636 .- 1872-7743. ; 168
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Tidskriftsartikel (refereegranskat)abstract
- In this study, the mechanical response of an additively manufactured nickel-based combustor alloy, subjected to thermomechanical fatigue (TMF) loadings has been investigated and modelled. TMF tests were performed in both in-phase and out-of-phase conditions with different strain ranges and temperature ranges of 100 degrees C-450 degrees C and 100 degrees C-600 degrees C, respectively. The smooth specimens were manufactured in two different orientations to study the influence of anisotropy, and the specimens were machined to final dimensions with conventional techniques. A constitutive model with focus on describing the mid-life behaviour was developed where the total inelastic strain was divided into one plastic (rate-independent) and one creep (rate-dependent) part, to be able to describe both the rate-dependent effects from TMF conditions as well as rate-independent responses. A cycle jumping procedure was used, which enables to simulate the mid-life response of the material for TMF as well as low-cycle fatigue conditions within three simulated loading cycles.
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| 5. |
- Lindström, Thomas, et al.
(författare)
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Constitutive model of an additively manufactured combustor material at high-temperature load conditions
- 2024
-
Ingår i: Materials at High Temperature. - : TAYLOR & FRANCIS LTD. - 0960-3409 .- 1878-6413.
-
Tidskriftsartikel (refereegranskat)abstract
- In this paper, the high-temperature constitutive behaviour of an additively manufactured ductile nickel-based superalloy is investigated and modelled, with application to thermomechanical fatigue, low-cycle fatigue and creep conditions at temperatures up to 800∘800∘C. Thermomechanical fatigue tests have been performed on smooth specimens in both in-phase and out-of-phase conditions at a temperature range of 100−800∘100−800∘C, and creep tests at 625∘625∘C, 700∘700∘C, 750∘750∘C and 800∘800∘C. Additionally, low-cycle fatigue tests at different strain ranges and load ratios have been performed at 700∘700∘C, and tensile tests have been performed at 600∘600∘C, 700∘700∘C and 800∘800∘C. A clear anisotropic mechanical response is obtained in the experiments, where the anisotropic effects are larger at high stress levels in creep loadings. To capture this behaviour, a rate-dependent strain based on a double-Norton model has been adopted in the model, by which the creep and mid-life response of the thermomechanical fatigue tests can be simulated with good accuracy.
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| 6. |
- Lindström, Thomas, et al.
(författare)
-
Constitutive model of an additively manufactured ductile nickel-based superalloy undergoing cyclic plasticity
- 2020
-
Ingår i: International journal of plasticity. - : PERGAMON-ELSEVIER SCIENCE LTD. - 0749-6419 .- 1879-2154. ; 132
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a transversely isotropic elasto-plastic model based on the multilinear Ohno-Wang model was developed to simulate the cyclic behaviour of an additively manufactured ductile nickel-based superalloy. The transverse isotropy was taken into account by the incorporation of a structural tensor in the modelling framework. To calibrate the model, a number of uniaxial isothermal low-cycle fatigue tests were carried out on smooth specimens manufactured in three different orientations with respect to the building platform. The test specimens were subjected to different strain ranges and load ratios, as well as four different temperatures, namely room temperature, 400 degrees C, 500 degrees C and 600 degrees C. By using a cycle jumping procedure, where the material properties are changed from virgin parameters to mid-life parameters, the mid-life behaviour, commonly used for fatigue life predictions, of the concerned material could be simulated with good agreements to the performed experiments. To validate the results, the maximum and minimum stress, as well as the plastic strain range and hysteresis area from the simulated mid-life hysteresis loops were compared to the values obtained from the experiments.
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| 7. |
- Nilsson, Daniel, 1982-
(författare)
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A ΔJ approach for nonlinear fatigue crack propagation : Experimental and numerical investigation of a ductile superalloy
- 2024
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation is a product of an academic-industrial collaboration between the Division of Solid Mechanics at Linköping University and Siemens Energy AB. The focus is on enhancing the design optimisation procedures for high-temperature components in industrial gas turbines (IGT). The research is centred around the behaviour of the nickelbased high-temperature superalloy Haynes 230 under service-like conditions with predominant thermal loads. The aim is to improve fatigue crack propagation life predictions for nonlinear conditions.The research findings validate the thermal ageing fatigue effects on Haynes 230 as seen in existing literature, especially on constitutive properties and crack initiation. Additionally, it was observed that thermal ageing has a minor effect on the crack growth rate up to 600 °C, which can be managed by updating the crack driving force with thermally aged properties.The project mainly focused on nonlinear crack propagation at isothermal and thermomechanical fatigue conditions. A new method for crack length description, using a modified compliance method, is introduced. This method simplifies and enhances the accuracy of crack length measurements and has become an established method for evaluating the single edge notch specimen used in the project under thermo-mechanical fatigue conditions.The nonlinear fatigue parameter ΔJ was incorporated into both Finite element method (FEM) computations and test evaluations, revealing linear trends with crack growth rates in loglog. The research highlights the crucial role of crack opening in establishing a correlation between ΔJ and crack growth rate. It was also concluded that the linear fatigue fracture parameter ΔK tends to underestimate the crack growth behaviour, resulting in non-conservative outcomes if the elasto-plastic stresses from the tests are considered.Lastly, a constitutive description of Haynes 230, based on the Ohno-Wang theory, under negligible viscoplastic effects, and an extension of the cycle jumping procedure that takes into account the significant hardening between the initial and midlife stages of the material, is presented. By this the notched geometry in 3D could be simulated with satisfying accuracy.
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| 8. |
- Adediran, Gbotemi, et al.
(författare)
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Micro and nano sized particles in leachates from agricultural soils: Phosphorus and sulfur speciation by X-ray micro-spectroscopy
- 2021
-
Ingår i: Water Research. - : Elsevier BV. - 0043-1354 .- 1879-2448. ; 189
-
Tidskriftsartikel (refereegranskat)abstract
- Colloids and nanoparticles leached from agricultural land are major carriers of potentially bioavailable nutrients with high mobility in the environment. Despite significant research efforts, accurate knowledge of macronutrients in colloids and nanoparticles is limited. We used multi-elemental synchrotron X-ray fluorescence (XRF) microscopy with multivariate spatial analysis and X-ray atomic absorption near-edge structure (XANES) spectroscopy at the P and S K-edges, to study the speciation of P and S in two fractions of leached particles, >0.45 and <0.45 mu m respectively, collected from four tile-drained agricultural sites in Sweden. P K-edge XANES showed that organic P, followed by P adsorbed to surfaces of aluminum-bearing particles were the most common forms of leached P. Iron-bound P (Fe-P) forms were generally less abundant (0-30 % of the total P). S K-edge XANES showed that S was predominantly organic, and a relatively high abundance of reduced S species suggests that redox conditions were adverse to the persistence of P bound to Fe-bearing colloids in the leachates. Acid ammonium-oxalate extractions suggested that P associated with Al and Fe (Al-P and Fe-P) in most cases could be explained by the adsorption capacity of non-crystalline (oxalate-extractable) oxides of Al and Fe. These results improve our understanding of particulate P and S speciation in the vadose zone and helps in developing effective technologies for mitigating colloidal driven eutrophication of water bodies near agricultural land. (C) 2020 The Author(s). Published by Elsevier Ltd.
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| 9. |
- Andersson, Håkan, 1970-
(författare)
-
A Co-Simulation Tool Applied to Hydraulic Percussion Units
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- In this dissertation, a co-simulation tool is presented that is meant to comprise a more comprehensive environment for modelling and simulation of hydraulic percussion units, which are used in hydraulic hammers and rock drills. These units generates the large impact forces, which are needed to demolish concrete structures in the construction industry or to fragment rock when drilling blast holes in mine drifting. This type of machinery is driven by fluid power and is by that dependent of coupled fluid-structure mechanisms for their operation. This tool consists of a 1D fluid system model, a 3D structural mechanic model and an interface to establish the fluid-structure couplings, which has in this work been applied to a hydraulic hammer. This approach will enable virtual prototyping during product development with an ambition to reduce the need for testing of physical prototypes, but also to facilitate more detailed studies of internal mechanisms. The tool has been implemented for two well-known simulation tools, and a co-simulation interface to enable communication between them has been devel-oped. The fluid system is simulated using the Hopsan simulation tool and the structural parts are simulated using the FE-simulation software LS-DYNA. The implementation of the co-simulation interface is based on the Functional Mock-up Interface standard in Hopsan and on the User Defined Feature module in LS-DYNA. The basic functions of the tool were first verified for a simple but relevant model comprising co-simulation of one component, and secondly co-simulation of two components were verified. These models were based on rigid body and linear elastic representation of the structural components. Further, it was experimentally validated using an existing hydraulic hammer product, where the responses from the experiments were compared to the corresponding simulated responses. To investigate the effects from a parameter change, the hammer was operated and simulated at four different running conditions. Dynamic simulation of the sealing gap, which is a fundamental mechanism used for controlling the percussive motion, was implemented to further enhance the simulated responses of the percussion unit. This implementation is based on a parametrisation of the deformed FE-model, where the gap height and the eccentric position are estimated from the deformed geometry in the sealing gap region, and then the parameters are sent to the fluid simulation for a more accurate calculation of the leakage flow. Wear in percussion units is an undesirable type of damage, which may cause significant reduction in performance or complete break-down, and today there are no methodology available to evaluate such damages on virtual prototypes. A method to study wear was developed using the co-simulation tool to simulate the fundamental behaviour of the percussion unit, and the wear routines in LS-DYNA were utilised for the calculation of wear.
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| 10. |
- Andersson, Håkan, et al.
(författare)
-
Simulation of leakage flow through dynamic sealing gaps in hydraulic percussion units using a co-simulation approach
- 2021
-
Ingår i: Simulation (San Diego, Calif.). - : Elsevier B.V.. - 1569-190X .- 1878-1462. ; 111
-
Tidskriftsartikel (refereegranskat)abstract
- In this study, a previously developed co-simulation method has been expanded to also simulate the dynamic behaviour of sealing gap regions in hydraulic percussion units. This approach is based on a 1D system model representing the fluid components and a 3D finite element model representing the structural parts of a hydraulic hammer. The sealing gap is a fundamental feature of a percussion unit, where the reciprocating motion of the piston is generated by the valve mechanism of the sealing gap. When the gap is closed it will prevent fluid flow between regions of different pressure levels. However, a small leakage flow through the gap will always occur which size depends on the clearance and the position of the piston. The method proposed here will take the structural motion and deformation into consideration when calculating the leakage flow. The deformed state of the structure is approximated by a cylindrical surface, in a least square manner, and communicated through the co-simulation interface to the fluid simulation module, and then used when calculating the leakage flow. This method aims at a more accurate simulation of the leakage flow that will not only yield a more realistic description of the mechanism on the local level, but also a more accurate estimation of global parameters such as overall performance and efficiency. The results indicate that the simulated leakage flow will decrease when dynamic gaps are used in comparison to static gaps, which is a consequence of the deformed structure that will generate smaller clearances. The leakage flow for the dynamic gaps will even be lower than for the static perfectly concentric case, mainly due to the reduction of clearances. The results also indicate that the dynamic eccentricity does not have a major influence on the leakage flow. The outcome from this study highlights the potentials of the described co-simulation approach for analysing the dynamics of the sealing gaps in a hydraulic percussion unit (i.e. gap heights, eccentricity ratios, etc.) including the evaluation of leakage flows and its impact on the overall performance. © 2021
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| 11. |
- Azeez, Ahmed, 1991-
(författare)
-
High-Temperature Durability Prediction of Ferritic-Martensitic Steel
- 2023
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Materials used for high-temperature steam turbine sections are generally subjected to harsh environments with temperatures up to 625 °C. The superior creep resistance of 9–12 % Cr ferritic-martensitic steels makes them desirable for those critical steam turbine components. Additionally, the demand for fast and frequent steam turbine start-ups, i.e. flexible operations, causes accelerated fatigue damage in critical locations, such as grooves and notches, at the high-temperature inner steam turbine casing. A durability assessment is necessary to understand the material behaviour under such high temperatures and repeated loading, and it is essential for life prediction. An accurate and less conservative fatigue life prediction approach is achieved by going past the crack initiation stage and allowing controlled growth of cracks within safe limits. Besides, beneficial load-temperature history effects, i.e. warm pre-stressing, must be utilised to enhance the fracture resistance to cracks. This dissertation presents the high-temperature durability assessment of FB2 steel, a 9-12 % Cr ferritic-martensitic steam turbine steel.Initially, isothermal low-cycle fatigue testing was performed on FB2 steel samples. A fatigue life model based on finite element strain range partitioning was utilised to predict fatigue life within the crack initiation phase. Two fatigue damage regimes were identified, i.e. plastic- and creep-dominated damage, and the transition between them depended on temperature and applied total strain. Cyclic deformation and stress relaxation behaviour were investigated to produce an elastic-plastic and creep material model that predicts the initial and mid-life cyclic behaviour of the FB2 steel.Furthermore, the thermomechanical fatigue crack growth behaviour of FB2 steel was studied. Crack closure behaviour was observed and accounted for numerically and experimentally, where crack growth rate curves collapsed into a single curve. Interestingly, the collapsed crack growth curves coincided with isothermal crack growth tests performed at the minimum temperature of the thermomechanical crack growth tests. In addition, hold times and changes in the minimum temperature of the thermomechanical fatigue cycle did not influence crack closure behaviour.Finally, warm pre-stressing effects were explored for FB2 steel. A numerical prediction model was produced to predict the increase in the apparent fracture toughness. Warm pre-stressing effects can benefit the turbine life by enhancing fracture resistance and allowing longer fatigue cracks to grow within safe limits.
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| 12. |
- Azeez, Ahmed, 1991-
(författare)
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High-Temperature Fatigue in a Steam Turbine Steel : Modelling of Cyclic Deformation and Crack Closure
- 2021
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Existing conventional thermal power plants are retrofitted for flexible operations to assist the transition toward more renewable energies. The deployment of many renewable energy power plants is necessary to achieve a clean environment with less pollution. However, the intermittent nature of renewable energies, due to weather changes, and the lack of efficient large energy storage systems put renewables at a disadvantage. Flexible operations of power plants imply fast and frequent start-ups. Thus, retrofitted power production plants can be utilised as an energy backup to satisfy the immediate demand during peak energy times or when renewable energies are suddenly limited. Large thermal power plants generally employ steam turbines with high inlet temperature and pressure steam conditions. Materials used for components at the high-temperature turbine sections are expected to withstand harsh environments. The use of 9-12 % Cr martensitic steels is desirable due to, among other things, their superior resistance to creep for temperatures up to 625 °C. Retrofitting for flexible operations put steam turbine components under high-temperature fatigue loading conditions different from how they were designed before. The flexible operations could lead to fatigue cracking at critical locations, such as grooves and notches at the inner steam turbine casing. Thus, fatigue behaviour understanding of steam turbine materials under such loading conditions is essential for components life prediction. Accurate and less conservative fatigue life prediction approach is necessary to extend the turbine components life, which reduces waste and provides economic benefits. This can be done by extending operations past crack initiation phase and allowing controlled propagation of cracks in the components. Within the 9-12 % Cr steel class, the martensitic steam turbine steel called FB2 is studied under high-temperature fatigue. This includes investigating high-temperature fatigue life behaviour, cyclic deformation behaviour, stress relaxation behaviour, and crack propagation behaviour along with crack closure behaviour. This was achieved by experimentally testing samples made from FB2 steel under isothermal low cycle fatigue, isothermal fatigue crack propagation, and thermomechanical fatigue crack propagation.
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| 13. |
- Bogot, Alon, et al.
(författare)
-
The mutual neutralization of hydronium and hydroxide
- 2024
-
Ingår i: Science. - 0036-8075 .- 1095-9203. ; 383:6680, s. 285-289
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Tidskriftsartikel (refereegranskat)abstract
- Mutual neutralization of hydronium (H3O+) and hydroxide (OH−) ions is a very fundamental chemical reaction. Yet, there is only limited experimental evidence about the underlying reaction mechanisms. Here, we report three-dimensional imaging of coincident neutral products of mutual-neutralization reactions at low collision energies of cold and isolated ions in the cryogenic double electrostatic ion-beam storage ring (DESIREE). We identified predominant H2O + OH + H and 2OH + H2 product channels and attributed them to an electron-transfer mechanism, whereas a minor contribution of H2O + H2O with high internal excitation was attributed to proton transfer. The reported mechanism-resolved internal product excitation, as well as collision-energy and initial ion-temperature dependence, provide a benchmark for modeling charge-transfer mechanisms.
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| 14. |
- Busse, Christian, et al.
(författare)
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Criteria evaluation for the transition of cracking modes in a single-crystal nickel-base superalloy
- 2020
-
Ingår i: Theoretical and applied fracture mechanics (Print). - : ELSEVIER. - 0167-8442 .- 1872-7638. ; 106
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Tidskriftsartikel (refereegranskat)abstract
- Single-crystal nickel-base superalloys frequently experience two distinct fatigue crack growth modes. It has been observed that, under certain conditions, cracks transition from a path perpendicular to the loading direction to a crystallographic slip plane. As crystallographic cracking is associated with an increased fatigue crack growth rate, it is important to be able to predict when this transition occurs. In this work three different criteria for crystallographic cracking based on resolved anisotropic stress intensity factors are evaluated in a three-dimensional finite element context. The criteria were calibrated and evaluated using isothermal fatigue experiments on two different specimen geometries. It is suggested by the results, that a threshold value of a resolved shear stress intensity factor can act as a conservative criterion indicating cracking mode transition. Further, a trend hinting towards a loading frequency dependency could be observed.
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| 15. |
- Eklund, Gustav, 1990-
(författare)
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Experiments on mutual neutralization using storage rings with merged ion beams
- 2020
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This thesis presents work on merged-beams experiments using the DESIREE facility, which consists of two electrostatic ion-storage rings operated at cryogenic temperatures of about 13 K. The two storage rings have a common straight section, where oppositely charged ions can interact at sub-eV collision energies. The work consists of development of the experimental method, tools for data analysis, and simulations for interpretation of the experimental results. This development has led to the first results from merged-beams experiments at DESIREE. The experiments are performed on mutual neutralization, a collision process where an electron is transferred from a negatively charged ion to a positively charged ion, resulting in two neutral products. This reaction is investigated for three systems: Li+ with D−, Na+ with D−, and Mg+ with D−. The reactions studied are of astrophysical interest, in particular for modeling of stellar atmospheres. The detection of the reaction products is done by using a position- and time-sensitive detector, and from this information it is possible to determine the quantum states involved in the reaction. The branching fractions of the reaction channels are measured and compared to theoretical modeling.
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| 16. |
- Ekqvist, David, et al.
(författare)
-
Safety and pharmacokinetics-pharmacodynamics of a shorter tuberculosis treatment with high-dose pyrazinamide and rifampicin : a study protocol of a phase II clinical trial (HighShort-RP)
- 2022
-
Ingår i: BMJ Open. - : BMJ Publishing Group Ltd. - 2044-6055. ; 12:3
-
Tidskriftsartikel (refereegranskat)abstract
- Introduction: Increased dosing of rifampicin and pyrazinamide seems a viable strategy to shorten treatment and prevent relapse of drug-susceptible tuberculosis (TB), but safety and efficacy remains to be confirmed. This clinical trial aims to explore safety and pharmacokinetics-pharmacodynamics of a high-dose pyrazinamide-rifampicin regimen.Methods and analysis: Adult patients with pulmonary TB admitted to six hospitals in Sweden and subjected to receive first-line treatment are included. Patients are randomised (1:3) to either 6-month standardised TB treatment or a 4-month regimen based on high-dose pyrazinamide (40 mg/kg) and rifampicin (35 mg/kg) along with standard doses of isoniazid and ethambutol. Plasma samples for measurement of drug exposure determined by liquid chromatography tandem-mass spectrometry are obtained at 0, 1, 2, 4, 6, 8, 12 and 24 hours, at day 1 and 14. Maximal drug concentration (C-max) and area under the concentration-time curve (AUC(0-24h)) are estimated by non-compartmental analysis. Conditions for early model-informed precision dosing of high-dose pyrazinamide-rifampicin are pharmacometrically explored. Adverse drug effects are monitored throughout the study and graded according to Common Terminology Criteria for Adverse Events V.5.0. Early bactericidal activity is assessed by time to positivity in BACTEC MGIT 960 of induced sputum collected at day 0, 5, 8, 15 and week 8. Minimum inhibitory concentrations of first-line drugs are determined using broth microdilution. Disease severity is assessed with X-ray grading and a validated clinical scoring tool (TBscore II). Clinical outcome is registered according to WHO definitions (2020) in addition to occurrence of relapse after end of treatment. Primary endpoint is pyrazinamide AUC(0-24h) and main secondary endpoint is safety.Ethics and dissemination: The study is approved by the Swedish Ethical Review Authority and the Swedish Medical Products Agency. Informed written consent is collected before study enrolment. The study results will be submitted to a peer-reviewed journal.
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| 17. |
- Lindström, Thomas, 1991-
(författare)
-
Fatigue life prediction of additively manufactured ductile nickel-based superalloys : Constitutive and crack initiation modelling
- 2022
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- This dissertation was produced at the Division of Solid Mechanics at Linköping University, and is the final result of a project that included mechanical testing and modelling of an additively manufactured ductile nickel-based superalloy.The main objective of the work presented in this thesis was to investigate and model the cyclic behaviour and the fatigue life behaviour of an additively manufactured ductile nickel-based superalloy, with emphasis on modelling the stabilised material behaviour, by which fatigue life predictions can be based upon. The mechanical and fatigue behaviour of additively manufactured alloys have shown to often depend on how the components are manufactured in the 3D-printing machine, meaning that the material is anisotropic. This anisotropic effect is important to account for when predicting the life of components. Therefore, in this work models to predict the mechanical response and the fatigue life of such components have been established. Monotonic tensile tests, creep tests and cyclic fatigue tests at constant temperatures, as well as anisothermal cyclic tests, have been performed to investigate the mechanical and the fatigue behaviour of the material, where specimens built in different orientations have been used to also study the anisotropic behaviour of the material. With the tests as a basis, a constitutive model has progressively been developed and implemented in a finite element context that accounts for the anisotropic behaviour under both elastic and inelastic deformations. In addition, a fatigue crack initiation life model has been developed for the tested low-cycle fatigue and thermomechanical fatigue conditions, which account for both material anisotropy and temperature effects.
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| 18. |
- Loureiro-Homs, Jordi, 1985-
(författare)
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Modelling of TMF Crack Growth in Polycrystalline Gas Turbine Alloys : Accounting for Crack Closure Effects
- 2020
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The main objective of the work presented in this Licentiate of Engineering thesis is to investigate and model the fatigue crack propagation behaviour of the nickel-based superalloy Inconel 792, with special attention to the industrial lifing of high-temperature components. In-phase (IP) crack propagation tests have been performed at different temperatures and loading regimes, including extended hold times. The observations from these tests have been the basis for establishing several hypotheses to describe the crack growth behaviour, which progressively have been verified experimentally and numerically. Most prominently, it has been observed that crack closure has a substantial impact on crack growth and can explain, to a large degree, the crack growth behaviour for this material under the conditions studied. This phenomenon has been observed experimentally and modelled numerically to extend further the precision of the methodology.
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| 19. |
- Loureiro, Jordi, et al.
(författare)
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Accounting for crack closure effects in out-of-phase TMF crack growth with extended hold times
- 2022
-
Ingår i: International Journal of Fatigue. - : Elsevier Science Ltd. - 0142-1123 .- 1879-3452. ; 158
-
Tidskriftsartikel (refereegranskat)abstract
- The crack growth behaviour of the alloy CM 247 LC is investigated for out-of-phase TMF and isothermal tests at the same temperature as the minimum temperature in the TMF tests. The results suggest that it is possible to characterise crack growth behaviour if experimental corrections for crack closure are accounted for. The repli -cation of these experimental tests using a numerical FE-solver results in similar crack growth behaviour, sug-gesting that the main mechanism in place is plasticity-induced crack closure. A pragmatic analytical model to characterise crack closure including hold time effects is proposed. The comparison of the response from this model with the experimental and numerical results suggests that the proposed analytical model is capable to approximate crack closure effects for cases where substantial creep deformation is to be expected.
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| 20. |
- Loureiro, Jordi, 1985-, et al.
(författare)
-
Accounting for crack closure effects in TMF crack growth tests with extended hold times in gas turbine blade alloys
- 2021
-
Ingår i: International Journal of Fatigue. - : Elsevier. - 0142-1123 .- 1879-3452. ; 142
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Tidskriftsartikel (refereegranskat)abstract
- Crack closure effects are known to have a large impact on crack growth behaviour. In this work, tests were performed on Inconel 792 specimens under TMF loading conditions at 100–850 °C with extended hold times at tensile stress. The effective stress-intensity range was estimated experimentally using a compliance-based method leading to the conclusion that crack closure appears to have a primary impact on the crack growth behaviour for this material under the conditions studied. The crack closure behaviour for the tests was successfully modelled using numerical simulations, including creep.
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| 21. |
- Loureiro, Jordi, et al.
(författare)
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Accounting for initial plastic deformation for fatigue crack growth predictions under TMF loading condition
- 2020
-
Ingår i: International Journal of Fatigue. - : ELSEVIER SCI LTD. - 0142-1123 .- 1879-3452. ; 136
-
Tidskriftsartikel (refereegranskat)abstract
- Crack propagation rates from isothermal and in-phase high temperature thermomechanical fatigue crack propagation tests for Inconel 792 resulted in a rather large scatter band when plotted against the linear-elastic stress intensity function Delta K. Previous observations indicated that the residual strains generated during the first few cycles in the uncracked specimen can explain, to a large extent, the differences between the tests. An effective Delta K-eff was calculated for each test based on non-linear FE simulations. When the crack propagation rates for each test were plotted against the calculated Delta K-eff, the curves collapsed to a smaller scatter band.
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| 22. |
- Nasr, Patrik, et al.
(författare)
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A rapid, non-invasive, clinical surveillance for CachExia, sarcopenia, portal hypertension, and hepatocellular carcinoma in end-stage liver disease : the ACCESS-ESLD study protocol
- 2023
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Ingår i: BMC Gastroenterology. - : BioMed Central (BMC). - 1471-230X. ; 23:1
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Liver cirrhosis, the advanced stage of many chronic liver diseases, is associated with escalated risks of liver-related complications like decompensation and hepatocellular carcinoma (HCC). Morbidity and mortality in cirrhosis patients are linked to portal hypertension, sarcopenia, and hepatocellular carcinoma. Although conventional cirrhosis management centered on treating complications, contemporary approaches prioritize preemptive measures. This study aims to formulate novel blood- and imaging-centric methodologies for monitoring liver cirrhosis patients.METHODS: In this prospective study, 150 liver cirrhosis patients will be enrolled from three Swedish liver clinics. Their conditions will be assessed through extensive blood-based markers and magnetic resonance imaging (MRI). The MRI protocol encompasses body composition profile with Muscle Assement Score, portal flow assessment, magnet resonance elastography, and a abbreviated MRI for HCC screening. Evaluation of lifestyle, muscular strength, physical performance, body composition, and quality of life will be conducted. Additionally, DNA, serum, and plasma biobanking will facilitate future investigations.DISCUSSION: The anticipated outcomes involve the identification and validation of non-invasive blood- and imaging-oriented biomarkers, enhancing the care paradigm for liver cirrhosis patients. Notably, the temporal evolution of these biomarkers will be crucial for understanding dynamic changes.TRIAL REGISTRATION: Clinicaltrials.gov, registration identifier NCT05502198. Registered on 16 August 2022. Link: https://classic. CLINICALTRIALS: gov/ct2/show/NCT05502198 .
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| 23. |
- Nyman, Elin, et al.
(författare)
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Mechanisms of a sustained anti-inflammatory drug response in alveolar macrophages unraveled with mathematical modeling
- 2020
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Ingår i: CPT. - : John Wiley & Sons. - 2163-8306. ; 9:12, s. 707-717
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Tidskriftsartikel (refereegranskat)abstract
- Both initiation and suppression of inflammation are hallmarks of the immune response. If not balanced, the inflammation may cause extensive tissue damage, which is associated with common diseases, e.g. asthma and atherosclerosis. Anti-inflammatory drugs come with side-effects which may be aggravated by high and fluctuating drug concentrations. To remedy this, an anti-inflammatory drug should have an appropriate pharmacokinetic half-life or better still: a sustained anti-inflammatory drug response. However, we still lack a quantitative mechanistic understanding of such sustained effects. Here, we study the anti-inflammatory response to a common glucocorticoid drug, Dexamethasone. We find a sustained response 22 hours after drug removal. With hypothesis testing using mathematical modeling, we unravel the underlying mechanism - a slow release of Dexamethasone from the receptor-drug complex. The developed model is in agreement with time-resolved training and testing data, and is used to simulate hypothetical treatment schemes. This work opens up for a more knowledge-driven drug development, to find sustained anti-inflammatory responses and fewer side effects.
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