Exercises
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1. A cylinder head of a steam engine is held on by 16 bolts. The effective diameter of the cylinder is 40 cm and the steam pressure is 9 kg/cm2. Assuming that the bolts are not initially stressed, find the diameter of each of the bolts if the tensile stress is not to exceed 250 kg/cm2. a. 22.35 mm b. 18.97 mm c. 25.30 mm d. 16.25 mm 2. An eyebolt is lifting a block weighing 580 lbs. The eyebolt is of SAE C 1040 material with Su=68 ksi and Sy=65 ksi, what is the stress area (in inches square) of the bolt if it is under the unified coarse series thread? a. 0.3215 b. 0.1371 c. 0.2211 d. 0.4562 3. Compute the diameter of a set screw required to transmit 8 HP at a shaft speed of 850 rpm. The shaft diameter is 2-in. a. 0.4205 in b. 0.5331 in c. 0.6100 in d. 0.3218 in 4. What is the friction horsepower acting on a collar loaded with 600 kg weight? The collar has an outside radius of 110 mm and 80 mm inside radius. The coefficient of friction of the collar is 0.2. Assume the speed is 160 rpm. a. 1.8 c. 3.3 d. 4.1 5. What is the working stress of a 40 mm diameter bolt which is screwed up tightly in a packed joint when the working strength is 12 tons? a. 32258 psi b. 40211 psi c. 38110 psi d. 28100 psi 6. A triple thread screw has a lead of 25 mm. Find the number of thread per inch. a. 2.1 b. 3.0 c. 4.3 d. 5.0 7. A square thread screw has an efficiency of 70% when friction of thread is 0.10 and collar friction is negligible. Find the lead angle, in deg. a. 16.5 b. 18.2 c. 14.3 d.12.5 8. A square thread power screw has pitch diameter of 1.8 and lead of 1-in. Neglecting collar friction, compute the coefficient of friction for threads if the screw efficiency is 65%. a. 0.1123 b. 0.0912 c. 0.0762 9. A power screw requires 5 HP to raise 3000 lbs load at a rate of 35 ft/min. Find the efficiency of the screw. a. 52.5% b. 75.1% c. 68.7% d. 63.6% 10. The root diameter of a double square thread power screw is 0.60-in. The screw has a pitch of 0.3-in. Determine the major diameter. a. 0.50 in b. 0.80 in c. 0.70 in d. 0.90 in 11. A double square thread power screw has a mean radius of 90 mm and pitch of 12 mm is used to lift a load of 90 kN. If the friction of screw is 0.14 and collar torque is 25% of input torque, find the input torque required. a. 1552.2 N-m b. 1672.1 N-m c. 1858.2 N-m d. 1992.0 N-m 12. An Acme thread power screw that has a mean diameter of 28 mm and pitch of 6 mm is used to lift a load of 800 kg. If the friction on thread is 0.95, compute the torque needed to turn the screw. a. 0.4622 kN-m b. 0.1236 kN-m c. 0.2271 kN-m d. 0.3261 kN-m 13. A single square thread power screw has a lead of 7 mm and mean diameter of 35 mm. If it is used to lift a load of 30 kN and coefficient of friction of thread is 0.18, find the torque required to turn the screw. a. 0.2287 kN-m b . 0.1182 kN-m c. 0.1294 kN-m d. 0.3287 kN-m 14. The total torque required to turn the power screw is 55 N-m. If the linear speed of screw is 8 ft/min and lead of 9 mm, determine the horsepower input of the power screw. a. 2 b. 3 c. 4 d. 5 15. The cylinder head of ammonia compressor has core gasket area of 90 cm2 and flange pressure of 100 kg/cm2. Find the torque applied on the bolt if the nominal diameter of bolt used is 3/5-in and there are 6 bolts. a. 423.2 in-lb b. 286.2 in-lb c. 500.5 in-lb d.397.0 in-lb 16. A 14 cm x 18 cm air compressor has 6 bolts on cylinder head with yield stress of 450 MPa. If the bolt stress area is 0.14 in2, calculate the maximum pressure inside the cylinder. a. 100.0 psi b. 168.2 psi c. 188.3 psi d. 143.3 psi 17. Determine the diameter of the bolt required to tightly pack a joint if the working strength of the bolt is 95 kN and working stress is 85 MPa. a. 4 in b. 3 in d. 1 in 18. Compute the working strength of 1.50-in bolt which is screwed up tightly in packed joint when the allowed working stress is 14,000 psi. a. 15231 lbs b. 14892 lbs c. 11552 lbs d. 12075 lbs 19. The stress area of UNC bolt is 0.75 in2, if the material used is carbon steel, find the applied load on the bolt. a. 3325.1 lbs b. 4502.8 lbs c. 5212.1 lbs d. 2891.7 lbs 20. Determine the permissible working stress of UNC bolts that has a stress area of 0.60 in2, if the material used is alloy steel. a. 12115.98 psi b. 13821.22psi c. 10782.14 psi d. 14559.80 psi |
Square and Acme Thread
A single square thread power screw is to raise a 70 kN load. The screw major diameter is 36 mm and pitch of 6 mm. The coefficient of thread and collar friction is 0.13 and 0.10, respectively. If the collar friction diameter is 90 mm and the screw turns at 1 rev/sec. Find the (a) Power input to the screw (b) the combined efficiency of the screw and collar.
A double threaded ACME screw driven by a motor at 400 rpm raise the attached load of 9 kN at a speed of 12 m/min. The screw has a 35 mm pitch diameter. The coefficient of friction for the thread is 0.15. The friction torque in the thrust bearing of the motor is 20% of the total torque input. Determine the kW power required to raise the load.
SOLUTION:
Strength of Welds
A 160 mm plate is lapped over and secured by fillet het on the inside and outside to form a penstock 1.5 meter in diameter. Determine the safe internal pressure, assuming an allowable stress of 140 MPa on the plate and an allowable shear stress of 90 MPa on the trout side of the 14 mm fillet weld.
SOLUTION:
