A method is presented for deciding whether jet-engine compressor blades that have been nicked in service are safe from fatigue failure with continued engine operation. This method involves determining the vibratory stress distribution of the blades near the leading and trailing edges, and fatigue testing a number of blades with damage inflicted in the laboratory. A curve of limit vibratory stress (highest vibratory stress for safe fatigue operation) against damage location is charted. The maximum-vibratory-stress level of the blade in the engine is also shown on this chart and is compared with the limit vibratory stresses. From this curve the maximum safe vibratory stress, or the stress at which no nick-damaged blade would be in danger of failure by fatigue, can be determined for these blades.
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