Strain-hardening Characteristic and Limit Load Analysis of S30408 Torispherical Head

Abstract

With the aid of the magnetic measuring instrument FMP30,the deformation induced martensite contents(DIMC) of S30408 plate tensile specimen under different plastic deformation are measured to determine the relationship between the DIMC and the plastic strain.The DIMC of the dished head is measured for the inner vessel of a cryogenic liquid semi-trailer.The DIMC distribution along meridional direction is simplified to correlate with plastic strains in different region of the head due to process history.According to the bygone plastic strain,the stress-strain curve for every region of the head is determined for the ultimate bearing capacity analysis of the structure by nonlinear finite element method.Compared with the results obtained by the two other inelastic modes(considering the strain strengthening characteristics based on the true stress-strain relationship without bygone plastic strain in consideration;Elastic perfect plastic(EPP) mode without strain strengthening in consideration),it is found that,for the dished head made of S30408,the collapse load and the limit load with the strain strengthening characteristics in consideration are greater than that with the EPP model.The strain strengthening characteristics based on process history has little effect on the collapse load,but great effect on the limit load by bitangent method.It can significantly improve the limit load of the structure.