This set of Mechanical Metallurgy Multiple Choice Questions & Answers (MCQs) focuses on “Fatigue of Metals – S-N Curve – 1”.
Explanation: The range of stress is given as
-> In this case, the magnitude of the minimum and maximum stress is equal, but in the opposite direction, so the range of stress will be equivalent to D.
Explanation: The alternative stress is equal to half of the range of stress. So
In this case, it will be similar to A.
Explanation: The mean stress is always equal to:
-> (σmax+ σmin)/2
So, in this case, the minimum and the maximum have a similar magnitude and opposite direction.
So mean stress will be equal to zero.
Explanation: The stress amplitude is already defined as half of the range of stress:
-> In this case, it is equal to C.
Explanation: The mean stress is given as the
-> σmax=50 MPa
-> σmin=10 MPa
-> (50+10)/2=30 MPa.
Explanation: The range of stress is equal to:
-> 50-10 = 40 MPa.
Explanation: In the given curve, the minimum stress is equal to zero.
-> Mean stress=(σmax+σmin)/2
-> Alternating stress=(σmax-σmin)/2
As σmin=0, the values for both the mean and alternating stress will be equal to zero.
8. During a cycling loading of the stress, which of the following value cannot be equal to zero?
a) Mean pressure
b) Minimum stress
c) Maximum stress
d) Range of stress
Explanation: The scope of stress is a magnitude of difference between the minimum and maximum stress. So, for a cyclic loading of stress, it cannot be equal to zero. It has to be a positive number.
9. The stress ratio is defined as the ________
Explanation: The stress ratio is generally denoted by R and is always equal to:
10. The amplitude ratio is defined as the ___________
Explanation: The amplitude ratio is the ratio between the stress amplitude to the mean stress value of the cycle loading curve.
11. If the stress ratio is given by R, and the amplitude ratio is given by A, the ratio between the R and A is given as __________
Explanation: The amplitude ratio is given as:
So the relationship between them is:
A= σamplitude/σmean = (1-R)/(1+R).
Sanfoundry Global Education & Learning Series – Mechanical Metallurgy.
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