IMPULSE TESTING AND BLADE LOAD SIMULATION TOOLS TO ESTIMATE CYCLIC STRESS LIFE IN BLADES AND IMPELLERS

摘要

A pragmatic approach for estimating cyclic stresses in rotating airfoils based on impulse testing with strain gauge sensors and application of simplified aerodynamic excitations is presented. The method has been successfully applied to determine the root causes of blade and impeller failures in gas turbines, steam turbines, and industrial compressors. The method provides guidance for quickly determining the natural frequency most responsible for a failure by analyzing experimental stress data at blade resonances, incorporating the Campbell diagram to evaluate frequency margins, and applying the Goodman diagram to evaluate endurance stress margins. The effects of mis-tuned blade responses can be included and operating lifetimes can be evaluated by use of the Palmgren-Miner analysis. Example cases of significant failure analyses for an axial flow gas turbine compressor and a driven industrial compressor are used to illustrate how the method is used.