PSI - Issue 40

Vladlen Nazarov et al. / Procedia Structural Integrity 40 (2022) 334–340 Vladlen Nazarov / Structural Integrity Procedia 00 (2022) 000 – 000

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curves when tension sections of wire at 165 o C for two different loading conditions (constant axial force and constant tensile stress). From the analysis of these experimental data, he established for the first time that the creep curve for a constant axial force is located higher and the fracture occurs earlier than for a constant tensile stress.

Nomenclature sec   elongation strain rate under secondary creep conditions t creep time rupt t rupture time nom  nominal stress at tension

start  starting creep stress break  break creep stress  tensile stress  tangential stress

1 2 3 , ,    principle stresses max  maximum normal stress mises  Mises stress max  maximum tangential stress naz leb loko , , shear strain max  maximum normal strain max  maximum shear strain  damage  total error   elongation strain

   complex equivalent stresses

After the end of the Second World War (1939 − 1945) with the advent of the first jet aircraft engines, an applied study of the creep property at high temperature was required. During the post war period, various scientists have given mechanical characteristics for various grades of steel and nickel alloys. At the same time, the Russian and World scientific literature presents the results of fundamental studies of the properties of creep and creep rupture (the dependence of the time at the rupture moment on the invariant characteristic of the stress tensor) under the conditions of a plane stress (when one of the three main stresses is zero) obtained for copper and aluminum alloys at high temperature. These experimental data have obtained by biaxial tension of rectangular plates, on tubular specimens under internal pressure, or by torsion. In mechanical tests on tubular specimens carried out with an additional axial force, it was possible to obtain experimental data at different ratios of two principal stresses other than zero. To date, the experimental study of creep has not stopped. Over the past years, various scientists have obtained fundamentally new experimental results in the field of the effect of multiaxial tension on the rupture time and the micropores formation process. Experimental creep data have been obtained for new materials such as titanium alloys and magnesium alloys. Below is the review of the analysis of experimental data have obtained under uniaxial tension and complex stress. 2. Uniaxial tension Depending on the experimental conditions, the creep curve is characterized by three consecutive time intervals: decreasing creep (the strain rate decreases with time), secondary creep (the strain rate does not change with time), and increasing creep (the strain rate increases with time). From the analysis of experimental creep curves, the dependence of the elongation rate at secondary creep on the nominal stress can be determined, as well as the dependence of the time at the rupture moment on the nominal stress. When approximating experimental data on secondary creep and creep rupture, either the power dependence Norton (1929) and Bailey (1929) with two material parameters or the fractional power dependence Shesterikov et al. (1984) with four material parameters is used. Two