The amount of residual stress resulting from the aulofrettage of steel c xlinders appears to be related to the hardness and/or structure of the steel employed. Results presented show that an annealed alloy steel cylinder autofrettaged to raise its elasticbreakdown pressure significantly did not indicate residual stresses sufficient to account for the measured increase in elastic-breakdown pressure. On the other hand, residual stresses established by thermal shock when measured in the same fashion are sufficient to account for the change in elastic-breakdown pressure measured in a pressure test regardless of the hardness of the material.
NOMENCLATURE
The following nomenclature is used in the paper: A = cross-sectional area (variable), sq. in. A 0 = initial cross-section area, sq. in. E = modulus of elasticity, psi. R = cylinder wall ratio c/a a = bore radius of hollow cylinder, in. b = radius to plastic-elastic boundary in cylinder, in. c = radius to outside of cylinder, in. d = differential sign p, = pressure to cause yielding to radius r in cylinder, psi. p~ = elastic-breakdown pressure in cylinder, psi. r = variable radius in cylinder, in.
sh' = residual hoop stress in cylinder, psi. st' = residual radial stress in cylinder, psi. s~ = yield strength in tension, psi. (0.01 per cent offset)
Sz' = residual longitudinal stress in cylinder, psi. ~h = hoop strain in cylinder, in./in. ,~ = longitudinal strain in cylinder, in./in. = Poisson's ratio; also symbol for "micro" as in microinches a = (~ + ~h), in./in. 0 = (~,, q--u~), in./in.