Question

You are an engineer at company XYZ, and you are dealing with the need to determine the maximum load you can apply to a set of bolted/clamped plates, such that you get infinite life. a) (1.5 pt) If you have an coarse thread M12 x 1.75 bolt of SAE Class 5.8, what would you recommend as the initial tightening force in the bolt? Is this initial force in the bolt the same as the clamped members?Hint: Use Fi = 0.9AtSp. b) (2 pt) If the clamped members have an effective stiffness twice that of the bolt and an external separating load varies between 0 and 5 kN, what are the alternating and mean forces on the bolt? What are the mean and alternating stresses in the bulk of the bolt? c) (1.5 pt) If the fatigue stress concentration factor is Kf=2.2 for the threads and we account for a yield strength of 400 MPa, what are the ef

Answer 1

Answer:

a)

$F_i = 28.8 kN$

b)

Alternating and mean forces on the bolt are 0.85 kN and 29.65 kN respectively.

Mean and alternating stresses in the bulk of the bolt are 378 MPa and 10 MPa.

c)

Safety factor = 5.5

Explanation:

Basic Dimension of Isometric Screw thread" is considered for analysis.

At Nominal diameter, d = 12 mm , $A_t = 84.3mm^{2}$ , $F_i = 0.9A_tS_p$ , $S_p = 380 MPa$

Rolled threads; $K_f = 2.2$