Predicting high-temperature rheological deformation and long-term strength of a viscoplastic material using a leader sample

A method for predicting creep and long-term strength in conditions of viscous failure mechanism has been proposed and implemented. It is assumed that when the material is loaded, there is no instant plastic deformation or the first stage of creep, and the hypothesis of incompressibility is satisfied. In the developed method, it is shown that if the creep curve under constant stress and the time to failure are known for a pre-tested sample (leader sample), then to obtain the rheological deformation diagram and long-term strength of the material at other stress levels, it is sufficient to know only the initial minimum creep deformation rate (at the initial moment of time) for the samples at these stress levels.
The adequacy of the developed method to experimental data for a range of alloys under conditions of tension and torsion of samples has been tested. It has been shown that the prediction results do not depend on the choice of a leader sample from the series of samples tested at different stress levels.
The research results demonstrate that the developed method allows not only predicting creep curves and long-term strength (in the asymptotic formulation), but also optimizing the planning of experimental studies to obtain a series of steady-state creep curves under constant stresses.