Abu Dhabi University
Department of Mechanical of Mechanical Engineering Assignment‐3 Shaft Design
College of Engineering of Engineering & Computer Science
MEC‐430 Machine Design (Due Date: Wed June 03, 2015 by 3:00 pm)
[1] Size a rotating SAE 1035 steel shaft to transmit 15,000 lb.in of mean torque, 10,000 lb.in of alternating bending moment and 8,000 lb.in of steady bending moment at a cross-section with a key way. The fillet radius of the key way is given by ⁄ 0.05 where d is is the shaft diameter and a notch radius of 0.02 in is assumed. The operating temperature of the shaft is 500 and 65,000 . the material properties are given by: 95,000 ; 0.5 ; Suggest an appropriate material and fabrication method for the shaft.
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[2] An ANSI 1020 cold drawn shaft with the geometry shown in figure carries a transverse load of 10kN and a torque of 100 N.m. The largest allowable deflection for the shaft is 0.5% of the overall shaft length. Check the design of the shaft from both the rigidity and strength considerations by finding the factors of safety in each case. If the shaft is not safe, what would you recommend to correct the problem or increase the factor of safety? Note: Use appropriate proportions for fillet radii, key ways, and other missing dimensions.
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[3] Size a rotating SAE 1040 cold drawn steel shaft to transmit 9,000 lb.in of mean torque, and 1,200 lb.in of steady bending moment at a cross-section with a key way. The fillet radius of the key way is given by ⁄ 0.04 where d is the shaft diameter and a notch radius of 0.04 in is assumed. The operating temperature of the shaft is 200 and the material properties are given by: 103,000 ; 0.5 ; 84,000 .
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[4] The figure shows a shaft that is rotating with 100 rpm and is exposed to uniformly distributed load of 150 lb/in and a torque of 5,000 lb.in. The material of the shaft is an alloy steel with the following data: 30 10 , 50,000 ; 90,000 45,000 . Find the diameter d of the shaft such that the maximum deflection doesn’t exceed 0.015 inch. Based on strength considerations, find the minimum value for the diameter d . Note: Use appropriate proportions for fillet radii, key ways, and other missing dimensions.
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[5] The figure shows a shaft contained in a helical gear reduction unit in which a force F = - 1700i + 6400 j - 2300 k lb is applied to gear B as shown. The forces FA and FC of equal magnitudes resist the applied force. The direction of these two forces can be determined by the unit vectors N A = 0.470i - 0.342 j + 0.814 k and vectors N C = -0.470i - 0.342 j + 0.814 k. The dashed vectors on gears 3 and 4 represent the components of the forces F A and FC . The shaft dimensions shown in the figure locate the effective load centers of the bearings and gears. The following data is available: - Shaft material is SAE-1035 with: Ultimate strength: S u = 95 ksi (95,000 psi), Yield Strength:
S y = 65 ksi (65,000 psi), S' e = 0.5 S u Endurance limit (before modification)
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At the critical section of the shaft, a fillet radius of the keyway is given by r/d = 0.05 where d is the shaft diameter and a notch radius of 0.02 in is assumed. The operating temperature of the shaft is 500o F.
It is required to: (a) Identify possible critical section(s) on the shaft and find the internal forces at each. (b) Find the minimum diameter of the shaft (use appropriate stress concentration factors from tables, neglect axial forces in the x-direction, and base calculations on fatigue). (c) Suggest an appropriate method of fabrication to the shaft.
10” 16” 16” 10” Gears 5 24” Dia
2300 lb
Gears 3 and 4 12” Diameter 6400 lb
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