The value of shear stress which is induced in the shaft due to the app...
Answer:
The correct option is b) from zero at the center to maximum at the circumference.
Explanation:
When a couple is applied to a shaft, it tends to twist the shaft. This twisting effect is resisted by the shear stress induced in the shaft. The distribution of shear stress along the cross-section of the shaft is not uniform. It varies from zero at the center to maximum at the circumference.
The reason behind this variation can be explained by considering a small element of the shaft as shown in the figure below.
- Let us consider a small element of the shaft of radius r and thickness dr at a distance x from the center.
- Due to the applied couple, a shear force is developed in the element which can be given by F = T*r/x, where T is the applied torque.
- The shear stress induced in the element can be given by τ = F/A, where A is the area of the element.
- The area of the element is given by dA = 2πr*dr.
- Therefore, the shear stress can be expressed as τ = T*r/(2πrx*dr).
- From the above expression, it can be seen that the shear stress is directly proportional to the radius r and the torque T, and inversely proportional to the distance x and the thickness dr.
- As x increases, the shear stress decreases, and as r increases, the shear stress increases.
- At the center of the shaft, x = 0, and hence the shear stress is zero.
- At the circumference, x = R, and hence the shear stress is maximum.
Therefore, the correct option is b) from zero at the center to maximum at the circumference.
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