Creep of Mild Steel under Periodic Stresses of Rectangular Wave

Abstract

Creep tests were made with 0.14 percent carbon steel at 450°C under periodic stresses, changing stepwise between two stress levels, the mean of which was 17.0 kg/mm² and the stress amplitude of which was 1.0 or 2.0 kg/mm². It was found that, under the test conditions in this study, creep strain under varying stresses could be predicted from the data of constant stress creep tests by applying the concept of the "mechanical equation of state in solid"with an error not exceeding 10 percent. The limitations of the "mechanical equation of state"as a practical method of estimation of the strain under varying stresses were discussed on the basis of the authors' theory of plastic deformation of metals at high temperatures, in which the effect of stress and temperature history was taken into account.