Command manual

This command is used to define the duration of the simulated event and to specify parameters controlling the time step size. If defining a termination FUNCTION the simulation will run until the FUNCTION obtains a positive value. Default time step size is 90% of the estmated critical time step size $\Delta t_{cr}$.

$\displaystyle{ \Delta t_{cr} = \frac{2}{\omega_{max}} }$

where $\omega_{max}$ it the highest eigenfrequency of the system. $\omega_{max}$ depends on size and stiffness of Finite Elements, Surface SPH particles and CFD cells, and on contact interface stiffnesses. $\omega_{max}$ is conservatively estimated every time step by Impetus Solver.

Element mass scaling is activated if the critical element or contact time step size drops below $\Delta t_{\mathrm{min}}$. Only Finite Elements can be mass scaled. Hence, if the smallest time step size is controlled by Surface SPH, Discrete Particles or by the CFD solver, then $\Delta t_{min}$ has no effect. $\Delta t_{max}$ is an optional maximum allowed time step size. It is most often used in models consisting of only rigid bodies and where there are no active stiffnesses at time zero.

Note that it is possible to define both $\Delta t_{\mathrm{min}}$ and $\Delta t_{\mathrm{max}}$ as functions of time with a CURVE or as more general expressions using a FUNCTION.

$ms_{\mathrm{max}}$ is optional and defines maximum allowed element mass scaling factor.

Trigger termination with a function

The following example is a complete model of a dynamically deforming rubber block. FUNCTION 222 signals for termination when the kinetic energy has reduced to less than one percent of its initial value.

Minimum allowed time step size

A simple example where the minimum allowed time step sized is defined as a function of time. If necessary, mass scaling will be activated in order to maintain the specified minimum time step size.