THE EFFECT OF CYCLIC DEFORMATION ON THE ELASTIC-CONSTANTS IN A NICKELSUPERALLOY

In order to determine residual stresses in engineering components from neutron-diffraction strain measurements it is necessary to use the ap propriate elastic constants (Plane Specific Elastic Constants-PSEC's). These constants can be obtained by calibration measurements or by cal culations using for example the Kroner model. This paper presents resu lts that show the effect of cyclic plasticity on the PSEC's in a nicke l-base superalloy from measurements made in TEST BEAM at ISIS at the R utherford Appleton Laboratory, UK. A tensile sample was loaded in situ in the neutron beam. Elastic constants were obtained for the virgin m aterial, then after one cycle of loading to 2% strain and finally afte r 5 cycles of loading to 5% strain. Stress-strain curves have been plo tted for each crystallographic reflection investigated and elastic mod uli calculated after each load cycle. The elastic constants obtained a fter cyclic plasticity are compared with the values obtained in the vi rgin material. It was found that the (3 1 1) reflection was unaffected by the cyclic loading and plastic deformation.