Stress corrosion cracking: Characteristics, Mechanisms and Experimental study

Stress corrosion cracking (SCC) is a phenomenon in which the cracking of a metal alloy usually results from the combined action of a corrodent and tensile stress. Stresses that cause cracking can be residual or may be applied during service. A degree of mechanistic understanding of SCC will enable most metallic engineering materials to operate safely though stress corrosion cracking failures still continue to occur unexpectedly in industry. In this paper, the characteristics, mechanisms and methods of SCC prevention are reviewed. The results of experimental studies on alpha brass are also reported of which the failure mode conformed with the film-rupture and anodic dissolution mechanism

Structure and properties of electrodeposited Ni-Co-YZA composite coatings

The aim is to develop an economical composite coating with high thermal stability. Ni-Co alloys are found to possess better thermal, physical and mechanical properties compared to Ni. Also, oxide particles as distributed phase can impart better thermal stability. Hence, particulates of composite Yttria stabilised zirconia, a commonly used high temperature material and alumina (YZA) were reinforced in various Ni-Co alloy matrices through electrodeposition. The influence of YZA on the microhardness, tribology and corrosion behaviour of Ni-Co alloys with Co contents of 0 wt.%, 17 wt.%, 38 wt.% and 85 wt.% was evaluated. Optical and Scanning Electron Microscopy (SEM) confirmed the presence of YZA particles and Energy Dispersive X-ray Analysis (EDX) revealed the composition. Tribology testing showed that composite containing 38 wt.% Co displayed better wear resistance. It was found from the immersion corrosion studies that Ni-17Co-YZA coating displayed improved corrosion resistance. Thermal stability studies showed that Ni-85Co-YZA coating retained its microhardness at temperatures of 600oC. Thus, these coatings can be tailored for various applications by varying the cobalt content

Effects of auditory and visual stimuli on shark feeding behaviour: the disco effect

Sensory systems play a central role in guiding animal behaviour. They can be manipulated to alter behavioural outcomes to limit negative interactions between humans and animals. Sharks are often seen as a threat to humans and there has been increasing interest in developing shark mitigation devices. Previous research has concentrated on stimulating the electrosensory and olfactory systems of sharks, whereas the influence of light and sound on their behaviour has received little attention. In this study, the effects of an intense strobe light and a loud, artificial sound composed of mixed frequencies and intensities on shark behaviour were assessed. We tested these stimuli individually and in combination on wild-caught captive Port Jackson (Heterodontus portusjacksoni) and epaulette (Hemiscyllium ocellatum) sharks in aquaria and on wild great white sharks (Carcharodon carcharias) in the field. When presented alone and in combination with sound, the lights reduced the number of times that the bait was taken by both H. portusjacksoni and H. ocellatum in captivity. The strobe light alone, however, did not affect the behaviour of white sharks, but when presented in combination with sound, white sharks spent significantly less time in proximity to the bait. As the lights and sound presented in this study did not show a pronounced deterrent effect on C. carcharias, we do not advise their use as a strategy for mitigating shark–human interactions. However, due to the potential effectiveness of strobe lights in deterring other species of sharks, there may be applications for this approach in the reduction of fisheries bycatch