Question:-
Auto frottage is the method of
Option (A)
Joining thick cylinders
Option (B)
Calculating stresses in thick cylinders
Option(C)
Prestressing thick cylinders
Option(D)
Increasing the life of thick cylinders
Correct Option:
(C)
Question Solution:
Autofrettage: Autofrettage it is one of the oldest method of prestressing (method of increasing pressure capacity) the cylinders. It is overloading the cylinder before it is put into service in this method a forged cylinder is subjected to a large internal pressure so as to expand the internal diameter, causing overstrain. The internal pressure is applied is such a way that a portion of the cylinder at the inner surface is subjected to stresses in the plastic range while the outer surface is still in the plastic range. When the pressure is related the portion of the cylinder at the outer surface contracts exerting the pressure on the portion at the inner surface which has undergone permanent deformation. As a result, residual compressive stresses are induced at the inner surface and tensile stresses at the outer surface
It is commonly used is gun barrels. It not only increases the pressure capacity of the cylinder, but also improves the endurance strength
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