Kinematic Hardening Trend of Flow Formed Seamless Tubes of Aluminium Alloys used for Aerospace

Abstract

The current trend of making seamless tubes of aluminium alloys is flow forming. The strength, ductility and toughness are the properties of interest for proper alloy design of tubes to withstand combustion pressure from propellants, elevated temperature creep and stress corrosion, especially in marine environments. The final strength of the flow formed tubes is known to control these properties. Therefore, an efficient kinematic flow stress simulator has been formulated to simulate the flow stress with the flow forming time, combining Taylor theory with the dislocation dynamics. The proposed simulator works on the principles of initial strength, shear constant, self-diffusivity and crystallographic texture to optimize the normal flow forming processes at versatile strain rate and temperature. The externally applied strain rate has been converted to the strain rate as material properties. The kinematic hardening during the flow forming has been addressed, emphasizing the work hardening and the energetic instability criterion based on dynamic recovery, to simulate the resultant flow stress. The design criteria of creep and stress corrosion resistant seamless tubes have been envisaged.