Machine Design

3- We need to analyze a journal bearing that has a shaft diameter of 70.00 mm with a unilateral tolerance of -0.02 mm. The bushing bore has a diameter of 70.10 mm with a unilateral tolerance of 0.06 mm. The bushing is 35 mm long and supports a load of 2.5 kN. The journal speed is 960 rev/min. For the minimum clearance assembly, and for two different lubricants "SAE 20" and "SAE 40" operating at an average film temperature of 60°C find (30 points): a. The minimum film thickness, b. The power loss, c. The lubricant flow rate, d. The lubricant side flow rate, e. Which of these two lubricants would you choose? Why?

3. A½-13 UNC bolt is used to hold a steel plate using a tapped hole. Calculate the minimum number of threaded needed to hold the plate. Round up to the nearest thread.

2. A 2-in steel plate and a 1-in cast-iron plate are compressed with one bolt and nut. The bolt is ½ in -13 UNC. a) Determine a suitable length for the bolt, round up to the nearest 4 in, if washers are not being used. b) Determine the bolt stiffness if E=30x10^6 psi

Fastener Homework Assignment 1. A 3/4 in - 16 UNF SAE grade 5 bolt is subjected to a load P of 6 kip in a tension joint. The initial bolt tension = 25 kip. The bolt and joint stiffnesses are kb = 6.50 and km = 13.8 Mlbf/in, respectively. Determine the preload and service load stresses in the bolt. Compare these to the SAE minimum proof strength of the bolt.

The spur gear train given in HW5.4 is to be designed (4 gears in total) for a factor of safety of 2 for bending and 2.5 for surface stresses. Material to be used is Grade 2 through-hardened steel. Assume quality standard of 5, uncrowned tooth, enclosed and accurately mounted. All gears in the system must be designed to survive 10^8 cycles with a reliability of 0.99. Find the required surface hardness for individual gears. Make any additional assumptions as your see fit.

A solid square rod is cantilevered at one end. The rod is 0.8 m long and supports a completely reversing transverse load at the other end of 50 kN. The material is AISI 1060 hot-rolled steel (s = 370 MPa, Su = 680 MPa). Use a design factor of 2 and determine the dimensions of the square cross section for the following cases. Neglect any stress concentration. a. The rod must support this load for 100 cycles. b. The rod must support this load for 104 cycles. c. The rod must have infinite life.

In the figure above, the diameter of pulleys C and D are given to be 600 mm and 400 mm, respectively. T₁ = 1000 N₂ T₂ = 500 N and T3 = 1500 N. But in addition to the force on the pulleys, a compressive axial force of 100 kN is acting on both ends of the shaft. The shaft is made from a brittle material with an ultimate tensile strength sur that is half of its ultimate compressive strength suc. If desired n = 2 for the shaft, find the minimum required Sut and Suc- a. Use Maximum Normal Stress Theory b. Use Brittle Coulomb-Mohr Theory c. Use Modified Mohr Theory

The solid shaft shown below is in equilibrium, supported at two bearings A and B. The pulleys C and D have diameters in the ratio 3:2. T₁ = 1000 N, T₂ = 500 N and T3 = 1500 N. The diameter of the shaft is 50 mm and yield strength sy = 400 MPa. The bearings do not exert any moments or axial forces on the shaft. a. If a factor of safety (n) of 3 is desired based on Maximum Shear Stress (MSS or Tresca) criteria, find the diameter of pulleys C and D. b. If n = 3 is desired based on the Distortion Energy Theory (DET or von Mises criteria), find the diameter of pulleys C and D.

The rotating shaft shown in the figure is machined from AISI 1040 CD steel (s = 490 MPa, Sut 590 MPa). It is subjected to a traverse force of F = 8 kN between the supports. The system designed to be operated at a temperature of 120°C with a reliability of 99%. Estimate the number of cycles. All dimensions are in mm. Assume all fillets are 3mm in radius.

A solid round bar with diameter of 2.75-in has a groove cut to a diameter of 2.5-in, with a radius of 0.125-in. The bar is not rotating. The bar is loaded with a repeated bending load that causes the bending moment at the groove to fluctuate between 10 kip.in and 30kip.in and a reversing torque of +10kip.in. The bar is hot-rolled AISI 1095 (s,, = 66 kpsi, Sut = 120 kpsi), but the groove has been machined. Determine the number of cycles to failure.