Chapter 16, Problem 8P

20-4-2025 Exam-2-Tribology Q1: What are the assumptions of hydrodynamic lubrication theory: Q2: Explain with sketch the cycle or process of engine lubrication system-pressurized lubrication system Q3: A short bearing is designed to operate with an eccentricity ratio = 0. 7. The journal diameter is 60 mm, and its speed is 1300 r.p.m. The journal is supported by a short hydrodynamic bearing of length L/D = 0. 5, and clearance ratio C/R = 103. The radial load on the bearing is 9800 N. a. Find the Sommerfeld number. b. Find the minimum viscosity of the lubricant for operating at ε = 0.7 c. Select a lubricant if the average bearing operating temperature is 70°c Q4: Two parallel circular disks of 100 mm diameter have a clearance of Imm between them. Under load, the downward velocity of the upper disk is 2 m/s. At the same time, the lower disk is stationary. The clearance is full of SAE 40 oil at a temperature of 60°c. a. Find the load on the upper disk that results in the instantaneous…

Tribobolgy 15/2022 Monthly Exam. Automobile Eng. Dert 2nd Semster/3rd class Max. Mark: 100% 7. Viscosity of multi-grade oils (a) Reduces with temperature (c) is less sensitive to temperature (b) Increases with temperature (d) None of the above 8. In a hydrodynamic journal bearing if eccentricity ratio = 1, it means (a) Journal/shaft is subjected to no load and the rotational speed is very high. (b) Journal is subjected to no load and the rotational speed is moderate (c) Journal is subjected to very light load and the rotational speed is very high. (d) Journal is subjected to very high load and the rotational speed is negligible. Q4/ The journal speed of a 100mm diameter journal is 2500 rpm. The journal is supported by a short hydrodynamic bearing of length L=0.6D, eccentricity ratio = 0.75 and a clearance ratio C/R=0.001. The radial load on the bearing is 10 kN. The lubricant is SAE 30, and the operating temperature of the lubricant in the bearing is 700C. 1- Assume…

1 of 2 Monthly Exam. Automobile Eng. Dert 2nd Semster/3rd class Max. Mark: 100% Q1/A/ Compare between the long and short journal bearings B/ With the help of Stribeck's curve, discuss different regimes of lubrication. C/ Explain the importance of Tribology in the design of different machine elements Q2 /A/ According to the SAE viscosity grading system all engine oils are divided into two classes: monograde and multi-grade. Compare between them? B/What are the differences between grease and Synthetic oils C/ Explain the effect of eccentricity ratio & with respect to hydrodynamic journal bearing. Q3/A/ What are the major factors which affect the selection of lubricants? B/What are the criteria to classify sliding bearings? C/ Answer of the following: 1. According to the SAE viscosity classification, the oil (SAE 40) is lower viscosity than the oil (SAE 20) at the same temperature. (True or False) 2. For a slow speed-highly loaded bearing, used oils of high viscosity; while for high-speed…