ARMD Software: TORSION V6.2

Package for Torsional Vibration Analysis


Typical application of TORSION


The torsional vibration package “TORSION V6.2” uses a finite-element based formulation for per­forming damped and undamped torsional natural frequencies, mode shapes, stability, steady-state response, and time-transient response of complete mechanical drive trains. TORSION consists of three modules: TORNAT, TORHRM, and TORRSP integrated by TORSION’s module messenger. The messenger controls the modules to provide a complete torsional vibration analysis environ­ment.


One of TORSION’s important advantages is that the package accepts/imports models generated with the rotor dynamics package ROTLAT. Thus, TORSION can use the ROTLAT models (without bearing influence).


Furthermore TORSION has advanced modeling features and capabilities including the mo­del­ing of multi-shaft and multi-branch systems, coupling stiff­ness and damping, gear tooth flexi­bi­li­ty, stiff­ness / mass / inertia diameter, torsional springs to ground, various types of external excitations containing harmonic parts, syn­chronous motor start-up torque (in­cluding com­plete run-up), dynamic load torques (e.g. by a recip com­pressor), user specified time varying torques, electrical faults and start-up scenarios for motor and generator, and many others.


Among the features incorporated in TORSION package are electrically-induced, time-varying exciting torques associated with genera­tor and induction motor operation that include:


  • 3-phase short circuit
  • Line-to-line short circuit
  • False coupling short circuit

Induction Motor

  • Start from standstill
  • 3-phase short circuit at terminals
  • 2-phase short circuit at terminals
  • High-speed automatic reclosing

TORSION: Time-transient response due to short circuits    TORSION: Time-transient response due to short circuits


TORSION results include:


(Module “TORNAT”)

  • Damped and undamped
  • Growth factors and damping ratios
  • Vibration mode shapes
  • Critical speed map (Campbell diagrams)

TORSION model and mode shape presentation (1st mode)

TORSION: Campbell diagram (interference diagram)


(Module “TORHRM”)

  • Vibratory amplitudes (displacement, velocity and acceleration)
  • Dynamic torques
  • Dynamic stresses
  • Dynamic heat dissipation


(Module “TORRSP”)

  • Dynamic shaft-torque time-history
  • Dynamic stresses
  • Fatigue life

TORSION: Steady-state simulation "Torque vs. Speed" and time dependent simulation "Torque vs. Time"


Detailed information on TORSIONAL VIBRATIONS including advanced engineering service are presented on a special site.


Figures and screenshots provided with kind permission of RBTS.