According to the basic theory on autofrettage and according to the 4th strength theory, several parameters and their relations are studied under ideal condition,includingσ_(ej)/σ_y,the equivalent stress of total stresses at elastoplastic juncture;σ_(ei)/σ_y,the equivalent stress of total stresses at inside surface;σ_(ej′)/σ_y,the equivalent stress of residual stresses at elastoplastic juncture;σ_(ei′)/σ_y,the equivalent stress of residual stresses at inside surface;and p/σ_y,load-bearing capacity of an autofrettaged cylinder.By theoretical study on relations between the parameters,noticeable results and laws are achieved:to satisfy|σ_(ei′)|=σ_y,the relation between k_j and k is,k^2lnk_j^2-k^2-k_j^2+2=0,when k→∞,k_j=e^(1/2)=1.648 72,as based on the 3rd strength theory,where k is the outside/inside radius ratio of a cylinder,k_j is the ratio of elastoplastic juncture radius to inside radius of a cylinder;If the plastic region covers the whole wall of a cylinder,for compressive yield not to occur after removing autofrettage pressure,the ultimate k is k=2.218 46 as based on the 3rd strength theory;With k=2.218 46, a cylinder's ultimate load-bearing capacity equals its entire yield pressure,or p/σ_y=2lnk/3^(1/2);The maximum and optimum load-bearing capacity of an autofrettaged cylinder is just 2 times the loading which an unautofrettaged cylinder can bear elastically,or p/σ_y=2(k^2-1)/3^(1/2)k^2,and the limit of the load-bearing capacity of an autofrettaged cylinder is also just 2 times that of an unautofrettaged cylinder.The conclusions are the same as based on the 3rd strength theory,but some equations are different from each other.
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