Accession Number : ADA330696

Title :   Frequency and Mean Stress Effects in High Cycle Fatigue of Ti-6Al-4V

Descriptive Note : Final rept. 1 Aug 96-1 Sep 97

Corporate Author : WRIGHT LAB WRIGHT-PATTERSON AFB OH MATERIALS DIRECTORATE

Personal Author(s) : Morrissey, Ryan

PDF Url : ADA330696

Report Date : SEP 1997

Pagination or Media Count : 88

Abstract : The objective of this project was to extend past research on fatigue of Ti-6Al-4V into conditions which more closely reflect actual use conditions. This included testing at a range of frequencies (70, 400, 1800 Hz) to determine the effect of frequency on the fatigue strength. In addition, testing was performed at various stress ratios (0.1, 0.5, 0.8) to determine the effects of mean stress on the HCF performance of Ti-6A1-4V. This included an examination of the effects of cyclic and time-dependent strain accumulation on the fracture mode at high mean stresses. Frequency effects were observed at low stress ratios, resulting in higher fatigue strengths as the frequency increased. Possible causes include strain rate effects on dislocation motion, loss of active primary slip systems at high frequencies in hexagonal close-packed and body-centered cubic materials, and environmental damage. Results obtained at high mean stress show that the behavior of Ti-6A1-4V consists of a complex combination of fatigue, cyclic creep, and strain ratchetting. Fractographic analysis combined with cyclic creep studies were used to further define the mechanisms which led to the observed behavior.

Descriptors :   *STRESSES, *HIGH FREQUENCY, *TITANIUM ALLOYS, *CYCLIC TESTS, DATA BASES, COMPUTERIZED SIMULATION, DAMAGE, TIME DEPENDENCE, MODELS, AIRCRAFT ENGINES, THERMODYNAMICS, MOTION, STRAIN(MECHANICS), STRENGTH(MECHANICS), FRACTURE(MECHANICS), FRACTOGRAPHY, DISLOCATIONS, ALUMINUM, CREEP, FATIGUE(MECHANICS), BINARY ALLOYS, VANADIUM.

Subject Categories : Aircraft
      Inorganic Chemistry
      Properties of Metals and Alloys

Distribution Statement : APPROVED FOR PUBLIC RELEASE