In this experimental work, strength results obtained on short columns subjected to concentric loads are presented. The specimens used in the tests have made of cold-rolled, thin-walled steel. Twenty short columns of the same cross-section area and wall thickness have been tested as follows: 8 empty and 12 filled with ordinary concrete. In the aim to determine the column section geometry with the highest resistance, three different types of cross-sections have been compared: rectangular, I-shaped unreinforced and, reinforced with 100 mm spaced transversal links. The parameters studied are the specimen height and the cross-sectional steel geometry. The registered experimental results have been compared to the ultimate loads intended by Eurocode 3 for empty columns and by Eurocode 4 for compound columns. These results showed that a concrete-filled composite column had improved strength compared to the empty case. Among the three cross-section types, it has been found that I-section reinforced is the most resistant than the other two sections. Moreover, the load capacity and mode of failure have been influenced by the height of the column. Also, it had noted that the experimental strengths of the tested columns don’t agree well with the EC3 and EC4 results.
This work has as an objective a study of evolution of characteristic properties of crystalline microstructure and mechanical hardening of aluminum by iron oxide (III), (hematite α-Fe2O3) nan energetic material known as thermite, samples of massive alloys, Al (base)-X wt% Fe2O3 (X =2, 4, 16 and 40) were studied.Al-Fe2O3 composite was developed by a sintering technique from the mixtures of compacted powders of Al high purity and α-Fe2O3 under a temperature of 700 °C for 1 hour and then slowly cooled. We have not noted the formation of thermite as foreseen by the chemical reaction due to the mixture of aluminum with hematite. The evolution of crystalline microstructures and the morphologies of surface were determined by means of X-ray diffraction, thermal analysis and optical metallography. The mechanical behavior was characterized by the tests of Vickers indentation and corrosion resistance by electrochemical tests.
The aim of this work is to contribute to the understanding of the effects of crystalline structures on the hardness and corrosion characteristics of aluminium–magnesium alloys. So, a series of nominal Al–4, 16, 40 and 50 wt% Mg compositions was rapidly cooled at ambient temperature by a vacuum high-frequency induction magnetic melting process and characterized by means of x-ray diffraction and optical observation analyses as well as Vickers indentation testing and electrochemical measures. Measured hardness and corrosion characteristics were compared with that of pure aluminium and industrial steel sheets. It was found that the crystalline microstructures consist of the intermetallic compounds fcc β-Al3Mg2 and sc γ-Al12Mg17 phases in equilibrium with the solid solution fcc α-Al of the matrix. Surface morphologies exhibit fine textures for the lower Mg contents and dendritic–eutectic microstructures for the higher contents. Observed combined high microhardness strengthening and corrosion resistance of aluminium matrix by magnesium contents are essentially due to the hardening cfc β-Al3Mg2 phase precipitation in the binary Al–Mg alloys.
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