Stress concentration in compressor blades with pits

Abstract

The research will address reliability issues of compressor gas turbines with blades suffered from pitting corrosion. Under operating conditions, such pit-like defects is likely to initiate fatigue cracks, thus detrimental to mechanical performance and design life of the blades. In this respect, both the mechanics and mechanisms of fatigue cracking of the pitted blades should be quantified. The former relates to internal states of deformation and stresses in the blades while the latter identifies dominant materials related failure modes. A mechanistic-based fatigue life model incorporating fracture mechanics aspects of the materials with pit-like defects will then be developed. Finite element simulation with fluid-structure interaction analysis will aid in interpreting fundamental causes of the nucleation of corrosion pits and subsequent fatigue fracture process. Influencing factors including elevated operating temperature, corrosive gas environment and gas flow velocity on the synergistic failure process will be quantified. Results of the mechanics of materials aspects and metallurgical study on martensitic stainless steel turbine blades suffered from pitting corrosion would form the basis for understanding premature fatigue failure of the blades suffered from hot pitting corrosion