A helical coil compression spring is needed for food service machinery. The load varies from a minimum of Fmin 6 lbf to a maximum of Fmax 20 lbf. The spring rate k is to be 9.5 lbf/in. The outside diameter of the spring cannot exceed 2.5 in. The spring maker has available suitable dies for drawing 0.08-in-diameter wire. Use a fatigue design factor nfof 1.5 and the Gerber-Zimmerli fatigue-failure criterion. NOTE: This is a multi-part question. Once an answer is submitted, you will be unable to return to this part. Determine the values for each of the following for a value of 0.08 in:
The torsional modulus of rupture, Ssu, is 160.544 kpsi.
Torsional yield strength, Ssy is 85.527 kpsi.
The endurance strength, assuming unpeened spring wire, Sse, is 39.452 kpsi.
The value of the mean diameter, D, is 0.66 in.
The alternating shear stress, Ta is 21.50 kpsi.
The fatigue factor of safety, nf, is 1.3 .
The free length, Lo, is 4.75 in.
The critical length, Lo(cr), is 2.5 in.