Engineering Evaluation of the Pre-Stress/Surface Removal Technique for Fatigue or Creep Enhancement.

摘要

Compressor blades of annealed Ti 6Al-4V alloy were step fatigue tested in the fundamental mode to determine the effect of a prestress-surface removal treatment on the 10to the seventh power cycle fatigue strength. Prestressing the blades in axial tension at 80-100ksi and stress relaxing at ambient temperature,improved the average 10to the seventh power cycle fatigue strength up to 60%. Residual surface stresses on the blades,measured before and after prestressing,showed a residual compressive stress due to prestressing. Glass bead peening failed to improve the annealed blade fatigue strength. Practical methods for prestressing blades must be developed for production application of this process. The prestress-surface stress removal treatment was not effective in reducing the secondary creep rate of cast nickel base MAR-M246alloy material at realistic turbine blade temperatures and stresses. (Author)