MMM Stress Evaluation and Fracture Analysis for Steam Turbine Failure Blade

Abstract

Metal magnetic memory (MMM) technology, a new NDE method, has been applied to stress evaluation and fracture analysis for the 50MW turbine failure blade. The static and dynamic stress of failure blade is calculated and analyzed. The rupture blade of steam turbine is detected at workshop. Given are the MMM signal characteristics of stress distribution for the failure blade and fracture face. It has been found: for the blade profile, the MMM air-out side curve occurs more zero passage signals than air-in side one; for the fracture surface, the crack transition zone’s MMM variation amplitude is minimal, the crack initiation zone’s is in the middle, and the tear fracture zone’s is maximal. The result from small hole stress measuring method is consistent with MMM result. This shows MMM technology is a new tool of fracture analysis and stress testing in engineering practice.