All-Russian Institute of Aviation Materials, Moscow, Russia:
M. A. Gorbovets, Head of a Sector, e-mail: lab33@viam.ru
M. S. Belyaev, Leading Researcher
I. A. Khodinev, Leading Engineer
M. I. Lukyanova, Second Category Engineer

Heat-resistant nickel alloys are widely used in aircraft gas turbine engine parts manufacturing. During the engine operation, its parts are under the cyclic loads and high temperatures. For such conditions, low-cycle fatigue resistance is one of the main strength characteristics. Indicators of low-cycle fatigue are used during the strength and resource calculations of aircraft gas turbine engine parts, and comparison of the similar-purpose materials. During the low-cycle fatigue tests, the occurred stresses and strains are over the material yield limit. Strain is taken as an independent parameter. Such experimental conditions are called the “strict” loading cycle. This paper shows the results of investigation of various nickel heat-resistant alloys: strained alloy VZh175 (ВЖ175) and cast equiaxial alloy VKNA-1VR (ВКНА-1ВР). This investigation includes the definition of temperature influence on loading cycle asymmetry. Such types of investigations are also used, because in real exploitation conditions many construction parts are under the simultaneous effect of static and fatigue loads. The least-square technique is used for processing of testing results. Independantly from the testing conditions, all results can be described by the linear dependence in semilogarithmic and double logarithmic coordinate systems. The values of low-cycle fatigue limits are found, and the influence of temperature and asymmetry of loading cycle is estimated.

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