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The succession struggle within ZANU-PF to replace Mugabe -- widely believed to be physically incapable of serving more than one additional term in office -- has led to…
The purpose of this present work is to investigate how different parameters of the blast cleaning process affect properties and quality of brass parts surface. It aims to…
The purpose of this present work is to investigate how different parameters of the blast cleaning process affect properties and quality of brass parts surface. It aims to study the following process variables: particle abrasive shape: (spherical (S) and angular (G) shot), particle abrasive size (S170, G40 and G50) and the impact velocity (40 m/s, 60 m/s and 80 m/s).
An experimental approach based on three testing methods is used to quantify the analysis of particulate contaminants on substrates surfaces. These methods are: SEM, BSEM and EDXA plots from SEM imaging.
The results obtained clearly show that the particle embedment decreases with decreasing of the size of angular abrasive. An increase in the embedment could be noted as impact velocity increased. It was also found that the angular abrasives have delivered a contamination level higher than that delivered by spherical abrasives. Furthermore, it was demonstrated that the abrasive debris nature embedded in the treated surfaces is the iron. The coupling of this debris with the base metal (copper) in the presence of wetland causes an electrochemical corrosion. Then, if the contamination level decreases, the corrosion rate in treated brass parts by steel shots decreases also.
Search in the case of blast cleaning for the brass parts by steel shots has not been done previously. Using the spherical shape of the abrasive projected with a moderate impact velocity will be a solution in this case.
The method described is adopted in Farbwerke Hoechst AG for testing the colouring properties of organic pigments. The method closely follows the instructions for determining the relative tinctorial strength of coloured pigments according to DIN 53 204. It has been found to be necessary to make minor modifications in testing organic pigments. A pigment grinder of a specific type is used for the dispersion process. Depending on the dispersibility of the pigment, a known, readily reproducible degree of pigment dispersion is attained, which is comparable to that of a production batch after one to two passages on a triple‐roll mill. Somewhat different results may be obtained if different dispersing equipment is used.
In fire condition, the limiting temperature of a restrained steel beam depends on a few parameters, e.g. temperature distributions along and across the beam, beam’s load…
In fire condition, the limiting temperature of a restrained steel beam depends on a few parameters, e.g. temperature distributions along and across the beam, beam’s load ratio and span length. The purpose of this study is to investigate the structural fire behaviour of axially restrained steel beams under different beam’s load ratios, taking into consideration the effect of the beam’s end connections configuration.
A three-dimensional finite element (FE) computer model has been developed to simulate the structural fire behaviour of axially restrained steel beams and their end connections. After successfully validating the developed model against the outcomes of the available large-size fire resistance experiments, the FE model has been used in a parametric study to investigate the beam’s load ratio effect on the behaviour of the axially restrained steel beams and their end connections.
The parametric study showed that increasing the beam loading level significantly increased the beam deflections at elevated temperatures; where, increasing the beam’s load ratio from 0.5 to 0.9 reduced the beam fire resistance by about 100 s. In contrast, decreasing the beam’s load ratio from 0.5 to 0.3 allowed the beam to easily achieve a 30-min fire resistance rating with no fire protection applied.
Experimental parametric studies are difficult to control in a laboratory setting and are also expensive and time consuming. Therefore, the reasonable accuracy of the validated FE model in reproducing the experimental fire behaviour of steel beams and their end connections makes it a very useful tool for both numerical and analytical studies.
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