RESIDUAL STRESS FIELD AND LOW-CYCLE FATIGUE BEHAVIOUR OF INCONEL718-PLUS SUPERALLOY

Measurements of residual stress induced by machining on cylindrical specimens made in Inconel718plus superalloy are reported. Change of residual stress state due to cyclic load at constant strain amplitude is also evaluated. Low-cycle fatigue tests are carried out in strain control at room temperature and strain amplitude varies between 0.76% and 1.33%. Tests are stopped after 10 and 100 cycles to execute X-ray diffraction residual stress measurements both in axial and circumferential direction. Experimental results show that relaxation phenomenon is largely influenced by applied strain amplitude. Moreover, residual stress variation is concentrated in the first cycles and cannot be considered a progressive phenomenon, as described by several analytical models proposed in literature.