A stochastic model for the residual stresses calculation in the surface-hardened hollow cylinder under creep

We suggest a new stochastic model to calculate the residual stresses in the surface-hardened hollow cylinder under the creep conditions with axial tension. A set of experimental studies was carried outto determine the creep strain distribution along the hardened specimen made of D16T alloy at a temperature of 125 C degrees under four modes of tension stresses: 353; 385; 406.2; 420 MPa. We found an essential variation of the creep strains in the local sections which strains may differ from each other by three or four times. The phenomenological stochastic creep equations are suggested; the compliance of these equations with the experimental data is examined. The computational method for solving the stochastic boundary value problem for the surface-hardened products is developed and realized for the hollow cylinder made of D16T alloy under axial tension. The relaxation of residual stresses in the hollow cylinder is theoretically studied. The longitudinal statistical estimates for the fields of residual stresses under the creep are obtained. We have shown the confidential intervals for the components of the residual stresses tensor of the specimen under creep at different time moments. It was experimentally study how the tension load affect the residual stresses relaxation in the hollow cylindrical specimen made of D16T alloy. Final experimental diagrams for axial and circumferential components of the residual stresses tensor under creep for 83-166 hours have been given. The theoretical and experimental studies made it possible to make a conclusion about an almost full relaxation of the residual stresses in the cylindrical specimens because of creep at tension conditions during 100-160 hours. The applicability of the rings and strips method for the experimental data variation under the creep and intensive relaxation of residual stresses is discussed.