TITLE:
A Study of the Deformation Derivatives for a Ti-6Al-4V Inertia Friction Weld
AUTHORS:
Richard P. Turner, Nils Warnken, Jeffery W. Brooks
KEYWORDS:
Rotation, Acceleration, Jerk, Snap, Crackle, Pop
JOURNAL NAME:
Advances in Aerospace Science and Technology,
Vol.6 No.2,
June
9,
2021
ABSTRACT: The
velocity–versus-time rundown curves from two experimental Ti-6Al-4V inertia
friction welds were analysed and differentiated several times, to produce
rotational acceleration, jerk, jounce (or snap), crackle and pop versus-times
curves for each weld. Titanium alloys and their mechanical properties are known
to be highly sensitive to strain rate as the material is deformed, though
nothing has ever been considered in terms of the higher-order time-derivatives
of position. These curves have been studied and analysed further, for a more
complete understanding of the derivative trends. Rotational acceleration and
jerk traces both display behavior patterns across the two welds as the part
rotates under action from the flywheel. The rotational snap also displays a
pattern in this derivative during the final approximately 0.5 s of welding, as
the energy dissipates. Evidence of a distinct oscillatory pattern in the
rotational crackle and pop terms was noted for one weld when differentiating
over a larger time-base, though could not be replicated in the 2nd weld. The higher derivative curves allow
distinction of different process regimes, indicating that inertial energy mostly influences the time-base of dynamically steady-state phase. Qualitative differences
between initial energies are evident in higher derivatives.