The crank in Problem 16.5 has a diameter d = 15.0 mm and is made of 2024-T4 aluminum alloy...

The crank in Problem 16.5 has a diameter d = 15.0 mm and is made of 2024-T4 aluminum alloy (σu = 430 MPa, Y = 330 MPa, and σam = 160 MPa for N = 108). Let the load vary between 0 and Pmax = 500 N for 108 cycles. Assume that the Gerber relation (Eq. 16.2) is valid.

Eq. 16.2: Gerber relation

a. Is the design governed by general yielding or fatigue failure?

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b. Determine the magnitude of the safety factor SF used in the design based on the octahedral shear-stress criterion of failure.

A shaking mechanism of a machine has a crank shown in Figure P16.5. The crank is made of a stress-relieved cold-worked SAE .1040 steel (σu = 830 MPa, Y = 660 MPa, and σam = σL = 380 MPa). A completely reversed load P = 500 N is applied for up to 108 cycles to the crank pin, normal to the plane of the crank. Determine the diameter d of the shaft based on a factor of safety SF = 1.75 .using the octahedral shear-stress criterion of failure.

FIGURE P16.5