is the process of pre-stressing a material to improve performance and reliability. A&A
primarily performs autofrettage on high pressure tubing (LDPE)
, high pressure fittings (cylinders, blocks and quills), and pressure vessels.
For high pressure tubing, autofrettage involves pressurizing the material to 120-140ksi in order to deform the bore of the tube. The plastic/elastic deformation interface moves toward the outer diameter. If the pressure were to continue to increase, the deformation would progress until it reached the outside wall causing “plastic collapse” or rupture. During autofrettage, the pressure is controlled to place this plastic region at a desired radial distance from center of the bore. At the completion of the process, residual compressive stress exists in the bore that lowers stresses on subsequent pressurization resulting in a longer service life.