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91.
Comparative study of the prediction of microstructure and mechanical properties for a hot-stamped B-pillar reinforcing part 总被引:1,自引:0,他引:1
Hyun-Ho Bok Erik J. Pavlina Hoon-Dong Kim 《International Journal of Mechanical Sciences》2011,53(9):744-752
Automobile manufacturers have been increasingly adopting hot-stamped parts for use in newly designed vehicles to improve crash worthiness and fuel efficiency. However, the hot-stamped parts require extreme mechanical properties with ultimate tensile strengths as high as 1500 MPa (∼450 Vickers hardness) while still maintaining adequate formability during the stamping operation. The ultra high strength of hot-stamped components is attributed to the martensitic phase transformation that occurs after the part has been formed at temperatures corresponding to the austenite phase field where formability is enhanced. In the present study, a computer-aided design method incorporating Kirkaldy and Venugopalan type phase transformation models has been implemented following a thermo-mechanical coupled finite element analysis to predict the mechanical properties of hot-stamped parts made with a boron-modified steel. Three empirical models which are typically used for hot stamping analysis are employed and the prediction capability of the models is compared using continuous cooling dilatometry and forming experiments of a modified B-pillar part. 相似文献
92.
Remoundaki E Kousi P Joulian C Battaglia-Brunet F Hatzikioseyian A Tsezos M 《Journal of hazardous materials》2008,153(1-2):514-524
The characteristics of the biofilm and the solids formed during the operation of a sulphate-reducing fixed-bed reactor, fed with a moderately acidic synthetic effluent containing zinc and iron, are presented. A diverse population of delta-Proteobacteria SRB, affiliated to four distinct genera, colonized the system. The morphology, mineralogy and surface chemistry of the precipitates were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX). The XRD patterns observed are characteristic of amorphous solid phases. Peaks corresponding to crystalline iron sulphide, marcasite, sphalerite and wurtzite were also identified. SEM-EDX results confirm the predominance of amorphous phases appearing as a cloudy haze. EDX spectra of spots on the surface of these amorphous phases reveal the predominance of iron, zinc and sulphur indicating the formation of iron and zinc sulphides. The predominance of these amorphous phases and the formation of very fine particles, during the operation of the SRB column, are in agreement and can be explained by the formation pathways of metal sulphides at ambient temperature, alkaline pH and reducing conditions. Solids are precipitated either as (i) amorphous phases deposited on the bed material, as well as on surface of crystals, e.g. Mg(3)(PO(4))(2) and (ii) as rod-shaped solids characterized by a rough hazy surface, indicating the encapsulation of bacterial cells by amorphous metal sulphides. 相似文献
93.
Seyedsina Hejazi Shiva Mohajernia Benedict Osuagwu Giorgio Zoppellaro Pavlina Andryskova Ondrej Tomanec Stepan Kment Radek Zbořil Patrik Schmuki 《Advanced materials (Deerfield Beach, Fla.)》2020,32(16):1908505
Single-atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H2 generation is described. Thin sputtered TiO2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO2 layers are reduced in Ar/H2 under different conditions (leading to different but defined Ti3+-Ov surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF-STEM results show that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA-Pt decoration can enhance the normalized photocatalytic activity of a TiO2 sputtered sample by 150 times in comparison to a conventional platinum-nanoparticle-decorated TiO2 surface. HAADF-STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO2. Importantly, the density of the relevant surface exposed defect centers—thus the density of Pt-SA sites, which play the key role in photocatalytic activity—can be precisely optimized. 相似文献