The Impact of Stress Concentrators on the Structural Strength of Cast Turbine Blades of Aircraft Engines

Abstract

Assessing of the quality parameters of the blade manufacture, which can affect their operational performance, is an important step in determining the causes of turbine blade destruction. Manufacturing defects, despite their great diversity, tend to be stress concentrators. Apart from the defects listed in the specifications to be avoided upon blade manufacturing, we mean also various kinds of defects identified as concentrators that contribute to the destruction of the blades in operation. Assessment of the blade quality suggests identification and analysis of the defects, as well as determination of the technological stage at which they have been formed. For cooled turbine blades this is the foundry stage of their manufacture. Studies of the blades damaged in operation, revealed that despite the control and rejection of blades in the manufacture, the materials of the turbine blades installed on aircraft engines, contain casting defects. The revealed casting defects are shown to affect the strength characteristics and durability of turbine blades and contribute to their destruction through fatigue fracture in operation. The special features of the quality characteristics of the single-crystal turbine blades, affecting their performance, and defects that contribute to their destruction in operation are highlighted. The necessity of improving the valuation, standardization and quality control both at the stages of design and manufacture of blades is shown.