| 1. |
- Ahmadkhaniha, Donya, et al.
(författare)
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Study of the process parameters influence on crack formation in laser alloying of grey cast iron
- 2024
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Ingår i: Optics and Laser Technology. - : Elsevier. - 0030-3992 .- 1879-2545. ; 179
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Tidskriftsartikel (refereegranskat)abstract
- This study aimed to investigate the influence of process parameters on crack formation in laser alloying or cladding of grey cast iron. For this purpose, the effects of laser power and feeding rate of Ni-based alloying powders were examined. The microstructure and hardness of the coating and the interface of the coating with cast iron (bonding zone) were studied. The results showed that the dilution ratio is crucial in crack formation, explaining the challenges in achieving a defect-free laser alloying coating on cast iron. The higher dilution ratio of laser alloying resulted in higher dissolved carbon and bigger (Nb, Ti)C carbides formation than in laser cladding coatings. In this study, cracks appeared in the coating due to the combination of the high amount of carbide in the layer and a sharp hardness gradient at the interface with the cast iron substrate. An empirical relation was proposed for dilution ratio as a function of specific energy density, which combined the most critical process parameters on crack formation.
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| 2. |
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| 3. |
- Ashizuka, M., et al.
(författare)
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Elastic modulus, strength and fracture toughness of alumina ceramics containing pores
- 2002
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Ingår i: Nippon Seramikkusu Kyokai gakujutsu rombunshi. - : Ceramic Society of Japan. - 0914-5400 .- 1882-1022. ; 110:6, s. 554-559
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Tidskriftsartikel (refereegranskat)abstract
- The effect of pores on elastic modulus, strength and fracture toughness of alumina ceramics was studied. Elastic modulus decreased with increasing porosity, and slightly increased with increasing pore size. On the other hand, strength decreased with increasing both porosity and pore size, being proportional to a reciprocal square root of the pore size. Fracture toughness decreased with increasing porosity and increased with increasing pore size. Fracture surface energy slightly increased with increasing pore size. The crack size at fracture origin were bigger 10 times or more than the maximum pore size, and increased with increasing pore size.
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| 4. |
- Azuma, Tomoyuki, et al.
(författare)
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Poly(2-aminoethyl methacrylate)-based polyampholyte brush surface with carboxylic groups to improve blood compatibility
- 2020
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Ingår i: Journal of Biomaterials Science. Polymer Edition. - : Taylor & Francis Group. - 0920-5063 .- 1568-5624. ; 31:5, s. 679-693
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Tidskriftsartikel (refereegranskat)abstract
- Zwitterionic material-based polymer brush significantly prevents protein adsorption and cell adhesion, which leads to the blood compatibility. However, zwitterionic polymer itself is difficult to be modified further, for the blood compatibility since the charged balance is impaired after the modification. In this research, chemically modifiable mixed charge polymer brush is designed, without impairing its characteristics. Condensed mixed charge polymer brush will work like zwitterionic material because neighbouring opposite charge is reported to be important in the zwitterionic material. Cationic polymer brush with primary amine group, which is based on 2-aminoethyl methacrylate (AEMA), was prepared and modified by succinic anhydride to obtain carboxylic group induced poly(AEMA). The ratio of primary amine group and carboxylic group was optimized to obtain the polyampholyte brush. The blood compatibility was evaluated by measuring coagulation/complement activation, protein adsorption and cell adhesion induced by the polymer. Our designed cationic-based polyampholyte brush prevented coagulation/complement activation comparable to poly(2-methacryloyloxyethyl phosphorylcholine) brush, based on intra-monomer interaction, because condensed mix charge works like zwitterion.
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| 8. |
- Belov, Ilja, et al.
(författare)
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A thermal conductivity model for grey iron
- 2023
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193.
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Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity is an important property for many iron cast components, and the lack of widely accepted thermal conductivity model for cast iron, especially grey cast iron, motivates the efforts in this research area. The present study contributes to understanding the effects alloy microstructure has on thermal conductivity. A thermal conductivity model for a pearlitic cast iron has been proposed, based on the as-cast alloy composition and microstructural parameters obtained at different solidification rates. According to the model, available parallel heat transfer paths formed by connected graphite flakes across eutectic cells are determined by the space between dendrite arms. The uncertainties both for model inputs and for validation measurements have been estimated. Sensitivity analysis has been conducted to result in better understanding of the model behaviour. The agreement between modelled and measured thermal conductivities has been achieved within 5% on the average for the investigated samples.
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| 9. |
- Belov, Ilja, et al.
(författare)
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A thermal conductivity model for lamellar and compacted graphite irons
- 2024
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Ingår i: International Journal of metalcasting. - : Springer. - 1939-5981 .- 2163-3193.
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Tidskriftsartikel (refereegranskat)abstract
- Thermal conductivity is an important property for cast components produced from different types of cast iron. Development of a general widely-accepted thermal conductivity model for compacted and lamellar graphite irons poses a research challenge. The present study extends the modeling approach introduced earlier for pearlitic lamellar graphite iron toward compacted graphite iron and ferritic lamellar graphite iron. The proposed thermal conductivity model of the bulk material is based on the alloy microstructure and Si segregation between eutectic cells and non-cell regions, at the main assumption that the heat paths in the eutectic cells are formed by connected graphite phases surrounded by ferrite phases. The overall thermal resistance of these heat paths is determined by the hydraulic diameter of the interdendritic region. The uncertainties both for the modeled and for experimentally derived thermal conductivities have been estimated. The importance of considering the Si segregation in the model has been discussed. For the investigated samples, the agreement between modeled and measured thermal conductivities has been achieved within 4% on the average, at the same value of the single fitting parameter found for pearlitic, pearlitic–ferritic lamellar, and compacted graphite iron alloys. The results contribute to the understanding of the material microstructure effects on the cast iron thermal conductivity.
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| 10. |
- Belov, Ilja, et al.
(författare)
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Simulation and Experimental Methodology for Virtual Prototyping of Annealed Industrial Coils
- 2023
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Ingår i: Heat Transfer Engineering. - : Taylor & Francis. - 0145-7632 .- 1521-0537. ; 44:4, s. 353-367
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Tidskriftsartikel (refereegranskat)abstract
- The finite element three-dimensional transient model of the annealing process, including conductive and convective heat transfer in an aluminum (Al) coil was developed, implemented, and validated. It combines winding force dependent effective radial thermal conductivity model and the novel convective heat transfer modeling methodology. Experimental validation of the finite element model was performed for two industrial coils having different dimensions, strip thickness and crowning depth. The general agreement between the predicted and measured temperatures for most of the probes was better than 10% at the target material temperature. A series of measurements were configured and performed to supply both the input and validation data for the simulations. The effect of the additional wetted area on the convective heat transfer at the coil base was quantified. The guidelines on the virtual prototyping of the Al coil annealing process were provided, which can be of interest for the process designers.
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