A rod of circular cross section is subjected to an alternating tensil...
Tensile Force and Stress
The rod is subjected to an alternating tensile force, varying from 20 kN to 70 kN. The force applied to the rod causes stress in the material. Stress is defined as the force applied per unit area.
Stress Limitations
The material of the rod has two stress limitations: the ultimate tensile stress (S
u) and the yield stress (S
y). The ultimate tensile stress is the maximum stress that the material can withstand before failure. The yield stress is the stress at which the material starts to deform permanently.
Gerber's Theory
Gerber's theory is used to calculate the diameter of the rod based on the alternating tensile force and the stress limitations of the material. According to Gerber's theory, the diameter (d) can be determined using the following equation:
d = (16F
a/π(S
u-S
y))^(1/3)
where F
a is the alternating force, S
u is the ultimate tensile stress, and S
y is the yield stress.
Calculation
In this case, the alternating tensile force (F
a) is given as 70 kN - 20 kN = 50 kN. The ultimate tensile stress (S
u) is given as 1000 MPa, and the yield stress (S
y) is given as 550 MPa. The factor of safety (FOS) is given as 2.0.
Substituting these values into the equation, we get:
d = (16 * 50 * 10^3 / π * (1000 - 550))^(1/3)
= (80000000 / 450π)^(1/3)
≈ 14.495 mm
Since the diameter of the rod according to Gerber's theory is approximately 14.495 mm, the correct answer is option 'D' (15 mm).