DETERMINATION OF SUPERPLASTIC CONSTITUTIVE-EQUATIONS AND STRAIN-RATE SENSITIVITIES FOR AEROSPACE ALLOYS

Constitutive equations for the superplastic behaviour of titanium and aluminium aerospace alloys have been presented and computational proce dures developed for the determination of the material parameters arisi ng in the equations. The equations include a description of grain grow th kinetics with deformation enabling the influence of microstructure on superplastic deformation behaviour to be modelled. Three predictive methods have been developed for the determination of strain rate sens itivity. The models represent the dependence of the strain rate sensit ivity on strain, strain rate, and grain growth, and therefore, provide useful information for process design and optimization. The models ar e validated by comparison of predictions with experimental data report ed in the literature and obtained in this work. Finally, two conventio nal experimental testing methods for the determination of strain rate sensitivity, namely the constant strain rate and strain rate jump meth ods are appraised using the methods developed.