Multiaxial Low Cycle Fatigue Life Evaluation of Nickel Base Single Crystal Superalloy Cruciform Specimen
Noriaki MATSUDA, Masao SAKANE, Tomomasa HORI, Atsushi NOSE, Morio YORIKAWA, Kouichi MASUNO, Nobuhiro ISOBE and Akira YOSHINARI
Abstract:This paper describes the multiaxial low cycle fatigue life of cruciform specimen of YH61 Ni base single crystal superalloy at high temperature. Biaxial tension-compression low cycle fatigue tests were performed using the cruciform specimen at 1173K under y-directional strain amplitude (ƒÃy) constant condition with varying x-directional strain amplitude(ƒÃx). Low cycle fatigue lives were influenced by the strain biaxiality and the maximum lives were obtained at ƒÃx/ƒÃy being equal to 0.5. The maximum principal strain and Mises equivalent strain ranges gave a large scatter in the correlation of the multiaxial low cycle fatigue lives. The principal stress and Mises equivalent stress ranges showed far better correlation than the strain ranges. Cracking mode was also discussed by observing the fracture surface at failure. Cracks propagated in the 45 degree direction to x direction at ƒÃx/ƒÃy=-1 test while those in the x direction in the other cases. Cracks were initiated at the life ratio less than 0.2 at Ni3(Al+Ta) eutectic alloy part and propagated with cycles. Key Words:Nickel-base superalloy, Single crystal, Multiaxial, Low cycle fatigue, High temperature