Dynamic evolution of interface roughness during friction and wear processes

Dynamic evolution of surface roughness and influence of initial roughness (Sa=0.282 to 6.73 µm) during friction and wear processes has been analyzed experimentally. The mirror polished and rough surfaces (28 samples in total) have been prepared by surface polishing on Ti-6Al-4V and AISI 1045 samples. Friction and wear have been tested in classical sphere/plane configuration using linear reciprocating tribometer with very small displacement from 130 to 200 microns. After an initial period of rapid degradation, dynamic evolution of surface roughness converges to certain level specific to a given tribosystem. However, roughness at such dynamic interface is still increasing and analysis of initial roughness influence revealed that to certain extent, a rheology effect of interface can be observed and dynamic evolution of roughness will depend on initial condition and history of interface roughness evolution. Multiscale analysis shows that morphology created in wear process is composed from nano, micro and macro scale roughness. Therefore, mechanical parts working under very severe contact conditions, like rotor/blade contact, screws, clutch etc. with poor initial surface finishing are susceptible to have much shorter lifetime than a quality finished parts

Surface morphology in engineering applications: Influence of roughness on sliding and wear in dry fretting

Influence of initial surface roughness on friction and wear processes under fretting conditions was investigated experimentally. Rough surfaces (Ra=0.15-2.52 [mu]m) were prepared on two materials: carbon alloy (AISI 1034) and titanium alloy (Ti-6Al-4V). Strong influence of initial surface roughness on friction and wear processes is reported for both tested materials. Lower coefficient of friction and increase in wear rate was observed for rough surfaces. Wear activation energy is increasing for smoother surfaces. Lower initial roughness of surface subjected to gross slip fretting can delay activation of wear process and reduce wear rate; however, it can slightly increase the coefficient of friction

Interface roughness effect on friction map under fretting contact conditions

In many industrial applications where fretting damage is observed in the contact (e.g. rotor/blade, electrical contacts, assembly joint, axe/wheel, clutch) the external loadings or geometry design cannot be changed. Therefore, the surface preparation and finishing process become essential to control and reduce the damage caused by fretting. In this paper, the authors present the experimental study of the initial surface roughness and machining process influence on fretting conditions in both partial and full sliding regimes. Surfaces prepared by milling and smooth abrasive polishing processes have been analysed. The influence of roughness on sliding behaviour and analysis of friction have been reported. Also, the contact pressure influence and qualitative analysis of fretting wear scar have been presented

Fire responses of bushland plants after the January 1994 wildfires in northern Sydney

In early January 1994 wildfires burned areas of bushland in northern Sydney (lat 33° 45’ S, long 151° 05’ E) in coastal south-eastern Australia. This paper reports observations of the fire responses for 828 species of bushland plants – 576 native species and 252 exotic species in the Lane Cove River and Narrabeen Lagoon catchment areas. Information recorded includes whether a species was killed by fire or resprouted post-fire, when seedlings were first observed following fire, and the times of first flowering and first fruiting (or spore production) after the fires. The estimated peaks of post-fire flowering or fruiting for a few species are given. It was not practicable to record data in all categories for all of the 828 species due to the logistical challenges involved in recording data across a large area of bushland, over a number of years. The data presented add to the growing body of knowledge on plant fire responses and will assist the management and conservation of bushland in the study areas, as well as the broader Sydney region

The Daugavet property in the Musielak-Orlicz spaces

We show that among all Musielak-Orlicz function spaces on a $\sigma$-finite non-atomic complete measure space equipped with either the Luxemburg norm or the Orlicz norm the only spaces with the Daugavet property are $L_1$, $L_{\infty}$, $L_1\oplus_1 L_{\infty}$ and $L_1\oplus_{\infty} L_{\infty}$. We obtain in particular complete characterizations of the Daugavet property in the weighted interpolation spaces, the variable exponent Lebesgue spaces (Nakano spaces) and the Orlicz spaces.Comment: 20 page