Microstructural refinement and corrosion resistance improvement of heat-treated A356 alloy processed by equal channel angular pressing

The microstructure refinement, hardness and corrosion resistance of heat-treated A356 aluminium alloy processed by equal-channel angular pressing (ECAP) were investigated. ECAP was carried out at room temperature using a mold, with a channel angle of 120° via route A. Results of the investigation confirm that the flaky coarse silicon particles were effectively fragmented from 4.22 to 0.761 μm and the grain size reduced from 171 to 40 μm after four passes of heat-treated as-cast using ECAP process. ECAP processing increases the hardness of heat-treated as-cast alloy from 61 Hv to 125 HV after four passes. Heat-treated A356 alloy shows enhanced corrosion resistance from 0.0424 to 0.00149 mmy-1, after four passes. In this research, ECAP processing has been shown to improve the hardness and corrosion resistance of as-cast A356 alloy

Effect of equal channel angular pressing processing routes on corrosion resistance and hardness of heat treated A356 alloy

Equal channel angular pressing (ECAP) via routes A and Bc was used to process heat treated A356 alloy. The samples produced a range of microstructures in order to investigate the effect of straining on its corrosion behavior in 3.5 wt. % NaCl solution and hardness. The ECAP was conducted at room temperature in a mold with channel angle of 120°. The results show that brittle coarse silicon particles were effectively fragmented into smaller size in the Al-rich matrix after the processing. The hardness and corrosion resistance test showed improvement after T5 and T6 heat treatment, preferably to T6 due to wholly changed in silicon particles morphology than T5. The hardness increased with ECAP processing from 60.66 Hv to 1133.47, 124.91 Hv after three passes route Bc and four passes route A, respectively. The evaluation of corrosion resistance of the alloy showed improvement from 0.0424 to 0.00173, 0.00149 mmy-1 after three passes route Bc and four passes route A, respectively. In this research, both strength and corrosion resistance are improved by ECAP processing of A356 alloy using both routes

Study of angular cutting conditions using multiple scratch tests onto low carbon steel: An experimental-numerical approach

Multiple parallel scratches are often analyzed to understand the material removal mechanisms due to abrasion. However, successive scratches with different orientations may represent better the conditions found in machining processes, such as honing and belt finishing. The objective of this work was to analyze the cutting forces and the phenomena of material removal due to abrasion, arising from angular scratches in low carbon steel. Experimental and numerical techniques were considered. In both, analyses considered the presence of an initial set of parallel scratches, followed by a second set of scratches with different orientations (10, 20 or 30°) with respect to the previous one. The cutting action was performed by a tool representing an abrasive particle, which had a cono-spherical geometry with 235μm tip radius and 30° apex angle. The cutting settings were: 50m/min scratch velocity and 100μm depth of cut. In the experimental part, scratches were conducted using a shaper machine tool equipped with a tungsten carbide (WC-Co) stylus. Tests were conducted on a Kistler platform, which allowed force measurement. Surfaces were later analyzed with an optical profilometer. The numerical simulations considered a ductile damage model with element deletion to provide the material removal during the scratches. Experimental and numerical results showed that the angle affects the cutting forces, especially when one scratch crosses a previously scratched region. The 20° case was the most critical, especially in terms of the cutting forces, due to the accentuated material strain-hardening for this condition. Likewise, this fact was corroborated by numerical results, which indicated a higher energy necessary to plastic deformation, and a reduced material removal at 20°

Changes in impacts of climate extremes: human systems and ecosystems

In this chapter, two different types of impacts on human and ecological systems are examined: (i) impacts of extreme weather and climate events; and (ii) extreme impacts triggered by less-than-extreme weather or climate events (in combination with non-climatic factors, such as high exposure and/or vulnerability). Where data are available, impacts are examined from sectoral and regional perspectives.Peer Reviewe

Harmonic assessment based adjusted current total harmonic distortion

Power systems suffer from harmonic distortion and extra ohmic losses associated with them. Moreover, all harmonic frequencies are mostly assumed to have the same effect on the system losses. However, the frequency-dependency of the resistances should be taken into account, so that the apparent power and the power factor have to considerably reflect power losses under nonsinusoidal conditions. In this paper, the difference between unweighted and weighted non-sinusoidal losses, is addressed. A new harmonic-adjusted total harmonic distortion definition is proposed for both voltage and current. Besides, a new formula that relates the proposed harmonic-adjusted total harmonic distortion and a generalised harmonic derating factor definition of the frequency dependent losses of the power transmission and distribution equipment, is derived. An optimal C-type passive filter design for harmonic mitigation and power factor correction based on the minimisation of the proposed harmonic-adjusted total harmonic distortion for a balanced nonsinusoidal system is introduced. A comparative study of the proposed filter design based on the new harmonic-adjusted definition, and a conventional filter design based on standard total harmonic distortion definition, is presented

The effects of group versus single housing on home cage behaviour in two strains of laboratory mice

Studying the behavioural patterns of animals in their house may help to understand their needs, but there has been a little investigation of home-cage behaviours in commonly used inbred strains of mice such as C57BL/6 and DBA/2. Therefore, understanding behavioural patterns in these mice is important for neuroscience research. For the first time, this experiment was carried out to investigate the long-term effects of housing conditions (single vs. group) on home cage behaviour of C57BL/6 and DBA/2 mice, in order to reveal differences between C57BL/6 and DBA/2 in home-cage behaviours and in response to single-housing. Sixty-four mice (32 mice/strain) were housed either singly (SH) (n= 32) or in four groups, each group contained 8 animals. Home cage behavioural patterns were recorded weekly using ethogram-based instantaneous sampling for 5 consecutive weeks. Regardless of strain, single housed (SH) mice displayed higher levels of grooming and bedding directed-behaviours and were more frequently seen in-the-crawl ball, and had lower levels of feeding behaviour compared to their group housed (GH) conspecifics. There were significant strain differences in anxiety-related behaviours with the DBA/2 strain demonstrating higher levels of sleep, feeding and grooming behaviour and frequent presence in-the-crawl ball, and lower levels of exploration, locomotion and bedding-directed behaviour compared to the C57BL/6 strain. The results therefore suggest that different housing systems influence home cage behaviours of laboratory mice with the mice of the DBA/2 strain appearing more anxious. These findings may also have great implications for researchers to decide the most appropriate phenotype to use in measuring neural response–relevant behaviours in novel animal/human models