USING A LEADER SAMPLE TO PREDICT THE CREEP AND LONG-TERM STRENGTH OF A MATERIAL DURING DUCTILE FRACTURE

A method is developed for predicting creep and long-term strength based on the behavior of a previously tested sample (leader sample, prototype) in the case of ductile fracture. It is assumed that a loaded material does not undergo instantaneous plastic deformation and the first stage of creep. The incompressibility hypothesis is fulfilled in this case. It is shown that, if a constant-stress creep curve and the time to fracture are known for a leader sample, then obtaining a diagram of rheological deformation and long-term strength of the material at other stress values requires knowing only the initial (at the initial time) minimum creep strain rate of the samples for these stress values. The relevance of the developed method is checked with experimental data in two types of tests. The first type is tension tests of 12Kh18N10T corrosion-resistant steel samples at a temperature of 850°C and titanium alloy samples at a temperature of 600°C and the second type is tension and torsion tests of D16T alloy samples at a temperature of 250°C. It is shown that the prediction results are independent of the choice of a leader sample from many samples tested at different stresses. The possibility of using the developed method in experimental studies of creep of materials until their fracture is discussed.