AdjustTimeStep Custom Task

A custom task to dynamically adjust the MPM time step.

Introduction

For convergence of explicit, dynamic calculations, like NairnMPM, the time step must be less then the time it takes a stress wave to pass across the smallest element size. For safety, the time step is usually calculated to be some fraction of this time as specified by the input TimeFactor. But, for some material types, the wave speed might change during the calculations thereby necessitating an adjustment in the time step to retain convergence. This tasks allows you to periodically adjust the time step.

Task Scheduling

In scripted files, a AdjustTimeStep custom task is scheduled using

CustomTask AdjustTimeStep
Parameter adjustTime,(time))
Parameter verbose,(verbose)

In XML files, this task is scheduled using a <Schedule> element, which must be within the single <CustomTasks> block:

<Schedule name='AdjustTimeStep'>
   <Parameter name='adjustTime'>(time)</Parameter>
   <Parameter name='verbose'>(verbose)</Parameter>
</Schedule>

where the two parameters are:

Its only parameter is:

If a custom task is available but is unknown to NairnFEAMPM, you can still use such tasks by adding them with an <a href="xmldata.html">XMLData command</a> block. The template for submitting undocumented custom tasks is:

XMLData,CustomTasks
    <Schedule name='Task Name'>
      <Parameter name='param 1'>2</Parameter>
      <Parameter name='param 2'>10</Parameter>
    </Schedule>
EndXMLData

where you enter the name of the task in the Schedule command and list or parameters needed by that task in subordinate Parameter commands.