| 1. |
- Östmans, Rebecca, et al.
(författare)
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Solidified water at room temperature hosting tailored fluidic channels by using highly anisotropic cellulose nanofibrils
- 2024
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Ingår i: Materials Today Nano. - : Elsevier BV. - 2588-8420. ; 26
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Tidskriftsartikel (refereegranskat)abstract
- Highly anisotropic cellulose nanofibrils can solidify liquid water, creating self-supporting structures by incorporating a tiny number of fibrils. These fibrillar hydrogels can contain as much as 99.99 wt% water. The structure and mechanical properties of fibrillar networks have so far not been completely understood, nor how they solidify the bulk water at such low particle concentrations. In this work, the mechanical properties of cellulose fibrillar hydrogels in the dilute regime from a wt% perspective have been studied, and an elastoplastic model describing the network structure and its mechanics is presented. A significant insight from this work is that the ability of the fibrils to solidify water is very dependent on particle stiffness and the number of contact points it can form in the network structure. The comparison between the experimental results and the theoretical model shows that the fibrillar networks in the dilute regime form via a non-stochastic process since the fibrils have the time and freedom to find contact points during network formation by translational and rotational diffusion. The formed, dilute fibrillar network deforms by sliding fibril contacts upon straining the network beyond its elastic limit. Our results also show that before macroscopic failure, the fibril contacts are restored once the load is released. The exceptional properties of this solidified water are exploited to host fluidic channels, allowing directed fluid transportation in water. Finally, the microfluidic channels formed in the hydrogels are tailored by the layer-by-layer technique to be interactive against external stimuli, a characteristic envisioned to be useful in biomedical applications.
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| 2. |
- Koptioug, Andrei, 1956-, et al.
(författare)
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3D-printing: a future “magic wand” for global manufacturing. How can we benefit from it today for sports and health care?
- 2017
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Ingår i: Proceedings of the 5th International Congress on Sport Sciences Research and Technology Support, icSPORTS<em></em>. - : INSTICC Press. - 9789897582691
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Konferensbidrag (refereegranskat)abstract
- 3D-printing, or as it is also known, additive manufacturing (AM), is promising to be one of the determining manufacturing technologies of the present century. It is not a single technology but a family of rather different ones common in the way components are made, adding materials layer by layer. Additive manufacturing is already quite competitive to existing and well established technologies, but it also can provide unprecedented flexibility and complexity of shapes making components from the materials as different as cheese, chocolate and cream, live cells, concrete, polymers and metal. Many more materials we were not even thinking about few years ago are also becoming available in additive manufacturing, making it really believable that “only the sky is the limit”. During the time available for the keynote lecture, we will analyze the present position of AM in relation to other technologies, the features that make it so promising and its influence upon the part of our life we call sports and health, using the examples relevant to the Congress areas from computer systems to sports performance. Out of all enormities of materials available for different representatives of this manufacturing family we will concentrate at polymers and metals. AM technologies working with these two material families are already providing some unique solutions within the application areas relevant to the Congress' scope. We will also talk about some limitations inherent to the AM in polymers and metals to have the awareness that though the limit is somewhere “high in the sky”, it still exists.
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| 3. |
- Laptev, Roman, et al.
(författare)
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Influence of beam current on microstructure of electron beam melted Ti-6Al-4V alloy
- 2019
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Ingår i: Progress in Natural Science. - : Elsevier BV. - 1002-0071 .- 1745-5391. ; 29:4, s. 440-446
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Tidskriftsartikel (refereegranskat)abstract
- The defect microstructure of the samples manufactured from Ti-6Al-4V powder was studied using electron beam melting (EBM) in the beam current range of 17 - 13 mA. The hybrid digital complex combined positron lifetime spectroscopy and coincidence Doppler broadening spectroscopy was used to characterize the defect structure of the materials. The microstructure and defects were also analyzed by transmission electron microscopy. It has been established that the main type of the defects in the EBM manufactured samples is dislocations. According to the conducted measurements and calculations, the dislocation density in the EBM manufactured samples exceeds by two orders the similar value for the cast Ti-6Al-4Valloy. Formation of Ti-Ti-Al nanoscale clusters has been found in the EBM manufactured samples.
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| 4. |
- Norman, Peter, et al.
(författare)
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A sophisticated platform for characterization, monitoring and control of machining
- 2006
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Ingår i: Measurement science and technology. - BRISTOL, ENGLAND : IOP Publishing. - 0957-0233 .- 1361-6501. ; 17:4, s. 847-854
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Tidskriftsartikel (refereegranskat)abstract
- The potential for improving the performance of machine tools is considerable. However, for this to be achieved without tool failure or product damage, the process must be sufficiently well understood to enable real-time monitoring and control to be applied. A unique sophisticated measurement platform has been developed and applied to two different machining centres, particularly for high-speed machining up to 24 000 rpm. Characterization and on-line monitoring of the dynamic behaviour of the machining processes has been carried out using both contact-based methods (accelerometer, force sensor) and non-contact methods (laser Doppler vibrometry and magnetic shaker) and numerical simulation (finite element based modal analysis). The platform was applied both pre-process and on-line for studying an aluminium testpiece based on a thin-walled aerospace component. Stability lobe diagrams for this specific machine/component combination were generated allowing selection of optimal process parameters giving stable cutting and metal removal rates some 8-10 times higher than those possible in unstable machining. Based on dynamic characterization and monitoring, a concept for an adaptive control with constraints based machine tool controller has been developed. The developed platform can be applied in manifold machining situations. It offers a reliable way of achieving significant process improvement
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| 5. |
- Svoboda, Ales, et al.
(författare)
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Integrated approach for prediction of stability limits for machining with large volumes of material removal
- 2008
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Ingår i: International Journal of Production Research. - : Informa UK Limited. - 0020-7543 .- 1366-588X. ; 46:12, s. 3207-3222
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Tidskriftsartikel (refereegranskat)abstract
- High-speed machining of thin-walled structures is widely used in the aeronautical industry. Higher spindle speed and machining feed rate, combined with a greater depth of cut, increases the removal rate and with it, productivity. The combination of higher spindle speed and depth of cut makes instabilities (chatter) a far more significant concern. Chatter causes reduced surface quality and accelerated tool wear. Since chatter is so prevalent, traditional cutting parameters and processes are frequently rendered ineffective and inaccurate. For the machine tool to reach its full utility, the chatter vibrations must be identified and avoided. In order to avoid chatter and implement optimum cutting parameters, the machine tool including all components and the work piece must be dynamically mapped to identify vibration characteristics. The aim of the presented work is to develop a model for the prediction of stability limits as a function of process parameters. The model consists of experimentally measured vibration properties of the spindle-tool, and finite element calculations of the work piece in (three) different stages of the process. Commercial software packages used for integration into the model prove to accomplish demands for functionality and performance. A reference geometry that is typical for an aircraft detail is used for evaluation of the prediction methodology. In order to validate the model, the stability limits predicted by the use of numerical simulation are compared with the results based on the experimental work.
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| 6. |
- Qu, Muchao, et al.
(författare)
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Mechanical and electrical properties of carbon nanotube/epoxy/glass-fiber composites intended for nondestructive testing
- 2023
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Ingår i: Polymers for Advanced Technologies. - : Wiley. - 1042-7147 .- 1099-1581. ; 34:8, s. 2554-2563
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Tidskriftsartikel (refereegranskat)abstract
- In this study, ternary polymer composites sheets comprising glass fiber (GF) reinforced epoxy with various fractions of carbon nanotubes (CNT) were manufactured using hot-pressing technology. A multiscale morphology analysis was presented using scanning electron microscopy. The thermal behavior of the glass fiber reinforced polymer (GFRP) was investigated using thermogravimetric analysis, DSC, and DMA, which indicated an application temperature up to 71°C for the composites. Mechanical uniaxial stretching and three-points bending tests showed that the addition of 0.1–0.2 wt% CNT decreased the dissipated energy of the specimen by 50% and increased the Young's modulus by more than 100%. During all stretching and bending measurements, the relative change in electrical resistance (RCR) was recorded as function of strain, revealing a relationship between the electrical signal and the applied deformation of the GFRP. Finally, the standard equation for fitting RCR versus strain was optimized, reducing the number of fitting parameters from five to three. The electrical and mechanical properties of the CNT/GF/epoxy composites show that they are suitable sensoring materials for wind-turbine blades and other glass-fiber reinforced epoxy constructions, especially for nondestructive testing.
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| 7. |
- Bergström, David, et al.
(författare)
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A ray-tracing analysis of the absorption of light by smooth and rough metal surfaces
- 2007
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Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 101:11, s. 113504-1
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Tidskriftsartikel (refereegranskat)abstract
- Ray tracing has been employed to investigate the absorption of light by smooth and random rough metal surfaces. For normally incident light the absorptance of the surface increases with surface roughness. However, for light incident at a tangent to the surface the absorptance-surface roughness relationship is more complex. For example, in certain cases the absorptance can rise, fall, and rise again as the surface roughness increases. In this paper this complex absorptance-roughness relationship is defined and explained. The wavelengths of the light chosen for this study correspond to the primary and secondary output wavelengths of Nd:YAG lasers.
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| 8. |
- Bergström, David, et al.
(författare)
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Absorptance of Non-Ferrous Alloys to Nd:YLF and Nd:YAG Laser Light at Room Temperature
- 2007
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Ingår i: Applied Optics. - 1559-128X .- 2155-3165. ; 46:8, s. 1290-1301
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of absorptance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the absorptance data presently available considers only polished pure metals rather than the commercially available (unpolished, oxidised) alloys which are actually being processed in manufacturing. This paper presents the results of absorptance measurements carried out at room temperature on as-received engineering grade non-ferrous metals (Al, Cu and Zn alloys). The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053nm and 527nm � which means that the results are also valid for Nd:YAG radiation at 1064nm and 532nm). The absorptance results obtained differ considerably from existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified. For all 22 cases studied the absorptance was higher than for ideal pure, polished metals. For all Al- and Cu-samples the absorptance was higher for the green than it was for the infrared wavelength, while for all Zn-coatings this trend was reversed. No clear correlation between absorptance and surface roughness was found at low roughness values (Sa 0.15 � 0.60) but one, rougher set of samples (Sa 2.34), indicated a roughness-absorptance correlation at higher roughness levels.
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| 9. |
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| 10. |
- Bergström, David, et al.
(författare)
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The absorptance of steels to Nd:YLF and Nd:YAG laser light at room temperature
- 2007
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Ingår i: Applied Surface Science. - : Elsevier BV. - 0169-4332 .- 1873-5584. ; 253:11, s. 5017-5028
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Tidskriftsartikel (refereegranskat)abstract
- The measurement of absorptance is important for the analysis and modelling of laser-material interactions. Unfortunately, most of the absorptance data presently available considers only polished pure metals rather than the commercially available (unpolished, oxidised) alloys, which are actually being processed in manufacturing. This paper presents the results of absorptance measurements carried out at room temperature on as-received engineering grade steels including hot and cold rolled mild steel and stainless steels of various types. The measurements were made using an integrating sphere with an Nd:YLF laser at two wavelengths (1053 and 527 nm, which means that the results are also valid for Nd:YAG radiation at 1064 and 532 nm). The absorptance results obtained differ considerably from existing data for polished, pure metals and should help improve the accuracy of laser-material interaction models. Some clear trends were identified; for all materials studied, the absorptance was considerably higher than the previously published values for the relevant pure metals with polished surfaces. For all 15 samples the absorptance was higher for the green than for the infrared wavelength. No clear trend correlating the absorptance with the roughness was found for mild steel in the roughness range Sa 0.4-5.6 μm. A correlation between absorptance and roughness was noted for stainless steel for Sa values above 1.5 μm.
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