Chapter D.1, Problem 1ST

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…

The uniform rods have a mass per unit length of 10kg/m . (Figure 1)If the dashpot has a damping coefficient of c=50N⋅s/m , and the spring has a stiffness of k=600N/m , show that the system is underdamped, and then find the pendulum's period of oscillation.

10-50. The principal plane stresses and associated strains in a plane at a point are σ₁ = 30 ksi, σ₂ = -10 ksi, e₁ = 1.14(10-3), €2=-0.655(103). Determine the modulus of elasticity and Poisson's ratio. emps to plum... Wednesday FI a וח 2 Q Search 48 F5 - F6 4+ F7 FB F9 FIO FII F12 & * S 6 7 8 9 ㅁ F2 # *F3 3 $ 4 F4 % W E R T Y ப S ALT D F G H X C V B N J Σ H L ว { P [ ] ALT " DELETE BACKSPACE NUM LOCK T 7 HOME ENTER 4 PAUSE SHIFT CTRL E

10−9. The state of strain at the point has components of   ϵx = −100(10−6),   ϵy = −200(10−6), and γxy=100(10−6). Use the strain transformation equations to determine (a) the in-plane principal strains and (b) the maximum in-plane shear strain and average normal strain. In each case specify the orientation of the element and show how the strains deform the element within the x−y plane.

The strain gage is placed on the surface of the steel boiler as shown. If it is 0.5 in. long, determine the pressure in the boiler when the gage elongates 0.2(10−3) in. The boiler has a thickness of 0.5 in. and inner diameter of 60 in. Also, determine the maximum x, y in-plane shear strain in the material. Take Est=29(103)ksi, vst=0.3.

(read image, answer given)

6/86 The connecting rod AB of a certain internal-combustion engine weighs 1.2 lb with mass center at G and has a radius of gyration about G of 1.12 in. The piston and piston pin A together weigh 1.80 lb. The engine is running at a constant speed of 3000 rev/min, so that the angular velocity of the crank is 3000(2)/60 = 100л rad/sec. Neglect the weights of the components and the force exerted by the gas in the cylinder compared with the dynamic forces generated and calculate the magnitude of the force on the piston pin A for the crank angle 0 = 90°. (Suggestion: Use the alternative moment relation, Eq. 6/3, with B as the moment center.) Answer A = 347 lb 3" 1.3" B 1.7" PROBLEM 6/86

6/85 In a study of head injury against the instrument panel of a car during sudden or crash stops where lap belts without shoulder straps or airbags are used, the segmented human model shown in the figure is analyzed. The hip joint O is assumed to remain fixed relative to the car, and the torso above the hip is treated as a rigid body of mass m freely pivoted at O. The center of mass of the torso is at G with the initial position of OG taken as vertical. The radius of gyration of the torso about O is ko. If the car is brought to a sudden stop with a constant deceleration a, determine the speed v relative to the car with which the model's head strikes the instrument panel. Substitute the values m = 50 kg, 7 = 450 mm, r = 800 mm, ko = 550 mm, 0 = 45°, and a = 10g and compute v. Answer v = 11.73 m/s PROBLEM 6/85