Abstract: Based on the 3rd strength theory, the theoretical relations among the equivalent stress of total stresses at elastoplastic juncture, depth of plastic zone and reverse yielding, and load-bearing capacity for an autofrettaged cylindrical pressure vessel are analyzed and demonstrated by using combined image and analytical methods. The method, formula, nomogram and form determined theoretically to be related to the depth of plastic zone and load-bearing capacity are provided. Research shows that it is optimum to control the depth of plastic zone by equation, then is guaranteed; and the equivalent stress of total stresses at elastoplastic juncture, ej, can be the minimum if the depth of plastic zone is controlled by kj=exp(p/s), where k is vessel diameter ratio, kj is depth of plastic zone, and p/s is internal pressure/yield point, ei is the equivalent stress of residual stress at inside surface. The noticeable laws, equations, data and charts obtained in the course of analysis and demonstration can be used as the theoretical basis for reference in the engineering design of pressure vessels, and they make the relations and variation laws among the parameters of autofrettage theory more clear, penetrating and practical.

Key words: Autofrettage, Depth of plastic layer, Load-bearing capacity, Pressure vessel