On the Material Modeling of the Autofrettaged Pressure Vessel Steels

Abstract

Material modeling of the high strength steels plays an important role in accurate analysis of autofrettaged tubes. Although, the loading behavior of such materials is nearly elastic-perfectly plastic, their unloading behavior due to Bauschinger effect is very complicated. DIN1.6959 steel is frequently used for construction of autofrettaged tubes in some countries such as Germany and Switzerland. In spite of similarity between chemical compositions of this steel with A723 steel, due to different material processing, two steels have unlikely behavior. In this paper material behavior of DIN1.6959 has been accurately modeled by uniaxial tension-compression test results. Both 6 mm and 12.5 mm diameter specimens were used and compared. Also various functions for modeling of autofrettaged steels were investigated and new function was introduced for accurate modeling. Moreover, two test methods, i.e. uniaxial tension-compression and torsion tests, which used for modeling of autofrettage steels, were analyzed. As well, material models of three important autofrettage steels, i.e. A723, HB7 and Din1.6959 were compared.