ME3180_Spring2012_HW4

ME3180_Spring2012_HW4 - Georgia Institute of Technology ME...

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Unformatted text preview: Georgia Institute of Technology ME 3180: Machine Design Spring 2012: Sections A, RCC, and RPY Homework #4 Assigned on Feb. 3, 2012 Due in class on Feb. 9, 2012 Problem 1 The AISI 1060 HR steel shaft shown in the figure experiences a full-reversed bending at the machined groove. Assume the shaft is rotating, operates at 200 °F, and must have a reliability of at least 90%. Draw the S-N diagram and calculate either the safety factor for infinite lifetime or number of cycles to failure for a maximum nominal stress amplitude of (a) 15 kpsi and (b) 35 kpsi. DJ in. radius T 2.0 I'M. .L Problem 2 The flat bar of AISI 1018 CD steel shown in the figure experiences a time-varying axial force that fluctuates between 8000 lbs. in tension and 2000 lbs. in compression. Assume room temperature operation and 90% reliability. Neglecting column action, determine the appropriate safety factor(s) for the bar. 03?; in. Mali“: T NOTE '. The T w . .734. ,7 . . ll: 2 rm 0.533441%) Wells. Problem 3 A part experiences a combination of bending, axial, and torsional loading such that the following stresses are created at a critical location: Bending: Completely reversed, with a maximum stress of 60 MPa Axial: Constant stress of 20 MPa Torsion: Repeated load, varying from 0 MPa to 50 MPa Assume the time-varying stresses are in phase with each other and the part contains a notch such that Kfibendmg = 1.4, Kfiaxial = 1.1, and Kfitorsion = 2.0. The material properties are Sy = 300 MPa and Su = 400 MPa. The completely adjusted endurance limit is found to be S6 = 200 MPa. Find the factor of safety for fatigue based on infinite life. Be sure to check for yielding. ...
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ME3180_Spring2012_HW4 - Georgia Institute of Technology ME...

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