1,721,198 research outputs found
Tribology research trends in Italy
No full textThis paper furnishes a survey of recent investigations and of the current tribology research trends in Italy. Several topics related to tribology are investigated in several different departments of universities, research centres and industries. Some basic studies on friction and lubrication also at the atomic-scale level are reported. A big effort is addressed to researches on surface topography, contact mechanics aspects and particularly on surface coatings and treatments. Indentation and scratching techniques are used for the characterization of both coatings and bulk materials down to the nanoscale. Mechanical characterisation of materials and material processing involve tribological aspects too. Investigations on the wear behaviour of different materials for applications in the field of biotribology are also being carried out. The increasing interest of the industrial world in tribological problems is producing a lot of collaborations among universities, research centres and industries. Several tribological components and practical applications are investigated, such as lubricated sliding bearings, gas and magnetic bearings, gears, sealing systems, automotive and rail components. Investigations are often completed by diagnostic studies for monitoring or maintenance purposes
Non-steady state non-conformal contacts: friction and film thickness studies
No full textMany machine elements work under non-steady state conditions. Velocity, load and geometry can be time-dependent, and this can influence in a significant way two important quantities of a lubricated contact: friction and film thickness.
This work is devoted to non-conformal lubricated contacts under transient conditions and consists of two parts.
In the first part a review is made of studies on transient conditions related to the systems themselves (as occurs in gears, valve train, piston assembly and rolling bearings), to particular operating conditions (as starting and stopping of the motion) and to variations localised in the contact (as the ones related to surface defects and roughness).
The second part is specifically addressed to investigations on friction and film thickness under conditions of periodically variable velocity. Loops of film thickness and friction coefficient appear when these quantities are plotted as a function of the velocity, mainly due to squeeze effects. The friction is higher and the film thickness smaller for increasing speed than for decreasing speed. A time shift between the film thickness and the speed variations occurs. The loops amplitude increases by increasing the frequency of the speed variation
A review of internal combustion engine losses - Part 2: studies for global evaluations
No full textThe global evaluation of losses is important in providing information about the behaviour of an engine. This may be used, for instance, in design and development of new models, where one with inherently the lowest friction may be chosen with a consequent potential gain in fuel economy.
This paper reviews studies on the determination of total engine losses. Experimental works are reported from which, sometimes with theoretical support, empirical formulae are obtained that allow an extension of the results to engines similar to those investigated. Besides formulae in which losses are expressed as an equivalent pressure averaged in the complete cycle, more detailed formulae for the determination of instantaneous loss torques are reported, which are also useful in obtaining a better evaluation of the engine speed trend in fault diagnosis. All formulae can be used in computer programs for the numerical simulation of engine performance, a use that can reduce the time needed for experimental work
Tribology and Industry: From the Origins to 4.0
Full text linkThere is an increasing diffusion of the industry 4.0 concept today. The fourth industrial revolution, following three other previous industrial revolutions, is considered related to the introduction of modern information and communication technologies in production. Tribological concepts are much older than industry. Tribology has always been connected to industrial problems from the birth of industry. It was strongly connected with the previous industrial revolutions and it is surely related to industry 4.0. In this work, the main aspects of the four industrial revolutions and the main evolutions of tribology are firstly reviewed from a historical point of view. The relationships between tribology and industry are described with particular attention to the aspects that relate the modern tribology 4.0 to industry 4.0. Tribology can have in particular a big impact on the industrial needs to reduce losses and wastes, for instance with the development of new tribological components and materials also in connection with electronic smart systems and taking advantage of the information and communication technologies
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