: A Textbook of Machine Design: Contents 1 Introduction 2 Engineering materials and their properties 3 Manufacturing considerations in machine. Veja grátis o arquivo A Textbook of Machine Design by AND J.K. GUPTA enviado para a disciplina de Elementos de Máquinas I Categoria: . A TEXTBOOK OF. (S.I. UNITS) [A Textbook for the Students of B.E. / , U.P.S.C. (Engg. Services); Section ‘B’ of A.M.I.E. (I)]. R.S. KHURMI J.K. GUPTA.
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The average pressure will be higher for a long bearing than for a short or square bearing.
However, space requirements, manufacturing, tolerances and shaft deflections are better met with a short bearing. It is denoted by e.
Because of the side leakage of the lubricant from the bearing, the pressure in the film is atmospheric at the ends of the bearing. It is the temperature at which an oil will cease to flow when cooled. The diametral clearance c in a bearing should be small enough to produce the necessary velocity gradient, so that the pressure built up will support the load.
Pour point or freezing point.
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Also the small clearance has the advantage of decreasing side leakage. The bearing should desig be operated at this value of bearing modulus, because a slight decrease in speed or slight increase in pressure will break the oil film and make the journal to operate with metal to metal contact. Enviado por igualdi flag Denunciar. Attitude or eccentricity ratio. It desgn the minimum distance between the bearing and the journal, under complete lubrication condition.
It the difference between the diameters of the bearing and the journal.
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It is the temperature at which an oil gives off sufficient vapour to burn it continuously when ignited. It is the difference between the radii of the bearing and the journal.
A commonly used clearance in industrial machines is 0. This is the region where the viscosity of the lubricant ceases to be a measure of friction characteristics but the oiliness of the lubricant is effective in preventing complete metal to metal contact and seizure of the parts.
It has been shown by experiments that the coefficient of friction for a full lubricated journal bearing is a function of three variables, i.
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It is the ratio of the diametral clearance to the diameter of the journal. McKee in an actual test of friction is shown in Fig.
The following terms used in hydrodynamic journal bearing are important from the subject point of view: Minimum oil film thickness. It is denoted by h0 and occurs at the line u.k.gupta centres as shown in Fig. If the ratio of the length to the diameter of the journal i. The term viscosity index is used to denote the degree of variation of viscosity with temperature. Short and long bearing.
The thin film or boundary lubrication or imperfect lubrication exists between R and S on the curve. When the length of the journal ddesign is equal to the diameter of the journal dthen the bearing is called square bearing. This will result in high friction, wear and heating. It is the ratio of the eccentricity to the radial clearance. It is the lowest temperature at which an oil gives off sufficient vapour to support a momentary flash without actually deskgn fire to the oil when a flame is brought within 6 mm at the surface of the oil.
The density at any other temperature t may be obtained from the xesign relation, i. However, the allowance must be made for manu- facturing tolerances in the journal and bushing.