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Papers by Sirli Sepper
Agronomy …, 2009
Nowadays natural materials are popular and favoured in civil engineering. At the same time it is ... more Nowadays natural materials are popular and favoured in civil engineering. At the same time it is important to use renewable and local materials which have low CO 2 production. One of these materials is clay reinforced with natural fibres. For production purpose it is necessary to find the natural fibres which have suitable properties and can be grown in large amounts. This kind of fibre is flax, which produces a strong fibre. The article focuses on flax as a reinforcing natural fibre in clay which can be used for walls and undercoat plasters. Flax is milled to fractions with different length and mixed with clay, sand and water. Dried clay mix cube's compressive strength is measured. Finally the best fraction as for flax length and amount is suggested for future experiments to find out the best fraction of fibres for clay with good compressive strength.
The study focuses on the role of silicon in the hot dip galvanizing process. Coating formation an... more The study focuses on the role of silicon in the hot dip galvanizing process. Coating formation and growth were analysed. Centrifugal casting was used to prepare steel substrates with different silicon concentrations (< 0.01%, 0.06%, 0.11%, 0.17%, and 0.30%). Hot dip galvanizing was performed at 450 °C in the industrial galvanizing plant Zincpot (Estonia). The galvanizing time for coating formation was 4–25 s and for coating growth 195 and 1200 s after a longer incubation time. The thickness of the coating was measured and the microstructure of the Zn–Fe coating was examined. Even a very short time contact (4 s) between steel and zinc led to the formation of Fe–Zn intermetallics. The first phase was the ζ phase, immediately followed by the δ and then, after incubation the Γ phase. The reactions that took place in the galvanizing process during the shorter dipping times (< 25 s) were not influenced by silicon concentrations, but the influence of silicon was remarkable after long...
.................................................................................................... more ...................................................................................................... 60 KOKKUVÕTE ................................................................................................... 62 APPENDICES .................................................................................................... 65 Curriculum vitae ................................................................................................. 67 Elulookirjeldus ................................................................................................... 69
Key Engineering Materials
Present study focuses on investigating the hot dip galvanizing effect on the mechanical propertie... more Present study focuses on investigating the hot dip galvanizing effect on the mechanical properties of high strength steel. The effect of chemical pre-treatment (hydrogen diffusion) and the effect of hot dip galvanizing temperature on mechanical properties was studied with high strength steel S650MC. Additional tests were made with widely used structural steel S355J2. A batch type hot dip galvanizing process was used and zinc bath temperature was 450 °C and 550 °C. Results of the study show the behaviour of high strength steel during hot dip galvanizing process.
Agronomy …, 2009
Nowadays natural materials are popular and favoured in civil engineering. At the same time it is ... more Nowadays natural materials are popular and favoured in civil engineering. At the same time it is important to use renewable and local materials which have low CO 2 production. One of these materials is clay reinforced with natural fibres. For production purpose it is necessary to find the natural fibres which have suitable properties and can be grown in large amounts. This kind of fibre is flax, which produces a strong fibre. The article focuses on flax as a reinforcing natural fibre in clay which can be used for walls and undercoat plasters. Flax is milled to fractions with different length and mixed with clay, sand and water. Dried clay mix cube's compressive strength is measured. Finally the best fraction as for flax length and amount is suggested for future experiments to find out the best fraction of fibres for clay with good compressive strength.
The study focuses on the role of silicon in the hot dip galvanizing process. Coating formation an... more The study focuses on the role of silicon in the hot dip galvanizing process. Coating formation and growth were analysed. Centrifugal casting was used to prepare steel substrates with different silicon concentrations (< 0.01%, 0.06%, 0.11%, 0.17%, and 0.30%). Hot dip galvanizing was performed at 450 °C in the industrial galvanizing plant Zincpot (Estonia). The galvanizing time for coating formation was 4–25 s and for coating growth 195 and 1200 s after a longer incubation time. The thickness of the coating was measured and the microstructure of the Zn–Fe coating was examined. Even a very short time contact (4 s) between steel and zinc led to the formation of Fe–Zn intermetallics. The first phase was the ζ phase, immediately followed by the δ and then, after incubation the Γ phase. The reactions that took place in the galvanizing process during the shorter dipping times (< 25 s) were not influenced by silicon concentrations, but the influence of silicon was remarkable after long...
.................................................................................................... more ...................................................................................................... 60 KOKKUVÕTE ................................................................................................... 62 APPENDICES .................................................................................................... 65 Curriculum vitae ................................................................................................. 67 Elulookirjeldus ................................................................................................... 69
Key Engineering Materials
Present study focuses on investigating the hot dip galvanizing effect on the mechanical propertie... more Present study focuses on investigating the hot dip galvanizing effect on the mechanical properties of high strength steel. The effect of chemical pre-treatment (hydrogen diffusion) and the effect of hot dip galvanizing temperature on mechanical properties was studied with high strength steel S650MC. Additional tests were made with widely used structural steel S355J2. A batch type hot dip galvanizing process was used and zinc bath temperature was 450 °C and 550 °C. Results of the study show the behaviour of high strength steel during hot dip galvanizing process.