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Date : 2016-06-23 12:24:21

Introdcution:

This allows the cylinder to operate at higher fluid pressure. For a given autofrettage fluid pressure a given amount of inelastic deformation is produced and therefore in service the same fluid pressure may be used without causing any additional inelastic deformation.

 

Description:

In order to make thick-walled cylinders that resist elastically large internal pressure and make effective use of material at the outer portion of the cylinder the following methods of pre-stressing are used:

 

1. Shrinking a hollow cylinder over the main cylinder.


2. Multilayered or laminated cylinders.


3. Autofrettage or self hooping.

 

  • In some applications of thick cylinders such as gun barrels no inelastic deformation is permitted.

 

  • But for some pressure vessel design satisfactory function can be maintained until the inelastic deformation that starts at inner bore spreads completely over the wall thickness.

 

  • With the increase in fluid pressure yielding would start at the inner bore and then with further increase in fluid pressure yielding would spread outward

 

  • If now the pressure is released the outer elastic layer would regain its original size and exert a radial compression on the inner shell and tension on the outer region.

 

This gives the same effect as that obtained by shrinking a hoop over an inner cylinder. This is known as Self- hooping or Autofrettage. This allows the cylinder to operate at higher fluid pressure. For a given autofrettage fluid pressure a given amount of inelastic deformation is produced and therefore in service the same fluid pressure may be used without causing any additional inelastic deformation.

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