Oasys LS-DYNA Environment 8.1 VOLUME 3 ... - Oasys Software

Oasys LS-DYNA Environment: User Guide (Version 8.1)
Type (a) is most often caused by an unresisted (but loaded) mode of deformation; it can also be
caused by severe over-damping (this can sometimes occur if the lowest mode has not been
identified).
Type (b) is most usually caused by hourglassing. It is often beneficial to select stiffness
hourglass control (enter 4 in column 30 of material card 1). Type (b) can also be caused by very
high modes of oscillation such as single element modes. These are immune to dynamic
relaxation unless the timestep is reduced (a factor of 5 below the default timestep is generally
sufficient).
When solutions fail to converge, it may be useful to plot time history and/or complete state
results to determine the cause of the problem.
AUTOMATIC CONTROL OF DYNAMIC RELAXATION
This option (IRELAL and EDTTL on *CONTROL_DYNAMIC_RELAXATION ) attempts to
adjust the damping value continuously, according to the current rate of convergence. See Theory
Manual, section 28 for more details.
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