Models for predicting friction coefficient and parameters with influence in elastohydrodynamic lubrication

This article shows different friction prediction models applicable to lubricants in point contacts under an elastohydrodynamic regime. The types of models used are two variations of the Newtonian theory, the Limiting Shear Stress model and the one based on Carreau's equation. The article sets out the theoretical calculation procedures and the ensuing equations for calculating the friction coefficient. The aims of the article are to study the effect of the parameters with influence on friction and to compare the model's results with those given by an experimental stage performed on a mini traction machine. This test system allows the measurement of friction coefficient in point contacts (ball–disc) under a wide range of variation of parameters such as temperature, slide-roll ratio, lubricant, material, load, or velocity

The Evolution and Development of Mechanical Engineering through large cultural areas

Mechanical Engineering is probably the forerunner of many branches of Engineering and has persistently been their companion up to the present. For this reason, the History of Machines embraces a very broad period of the History of Mankind, and can be studied from many perspectives. This paper attempts to link progress in Mechanical Engineering to the great cultures that have arisen throughout the History of Mankind. This paper begins with the anonymous mechanical developments that appeared in Prehistory and opened up the way to the first civilisations, marked to a large extent, maybe, by Greco-Roman culture in Europe and by China in Asia. After them came the Islamic world, which, in the Middle Ages stimulated society to find new mechanical devices and set the foundations that would lead to the Renaissance. Outstanding in this period was the expansion of Italian, French and German creative and innovative thinking with its “Treatises on Machines”, which, for a short time, coincided with the advance of the Iberian Empire and the development of machinery for the New World. Finally, the Industrial Revolution became the climax of all previous developments and a period of rapid mechanical evolution began that was to be highly interesting from a historical and technological point of view. This was accompanied by a parallel interest in reflecting on and analysing machines, which has led to the appearance of countless “Treatises on Machines”