# Conditions for repeated stress

Q.  Which of the following conditions is true for repeated stress?

1. σm = 0
2. σm = σmax / 2
3. σm = σa
4. σmin = 0
5. σmin = – σmax
6. σa = σmax / 2

where  σm = mean stress and σa = stress amplitude

- Published on 14 Sep 15

a. condition 2 and 3
b. condition 1, 3 and 5
c. condition 2, 4, and 6
d. condition 3,4, 5 and 6

ANSWER: condition 2, 4, and 6

#### Discussion

• Sravanthi   -Posted on 03 Nov 15
- The variable stresses induced in a component which vary in magnitude and direction with respect to time are called as fluctuating stresses.

- Fluctuating stresses are of two types:
1) Repeated stresses
2) Completely reversed stress

1) Repeated stresses:

- Repeated stresses are observed in gears, cams, etc.

Mean stress (σm) = (σmax + σmin) / 2

Stress amplitude (σa) = (σmax – σmin) / 2

- σmin = 0 for repeated stresses, therefore substituting the given values we get,

σm = σmax / 2 & σa = σmax / 2

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