LoadControl Custom Task

A custom task to adjust velocity of Rigid particles to achieve a load put on them. .

Introduction

A LoadControl custom task can either monitor global archive quantity and responds as follows:

The possible task actions are to reverse various boundary conditions, hold at current boundary conditions, stop the analysis, or continue (with no change except crack propagation stops).

Task Scheduling

In scripted files, a LoadControl custom task based on crack lengths or on a global archive quantity are scheduled with one of the two following blocks:

CustomTask LoadControl
Parameter velocity, (velocity)
Parameter material, (int)
Parameter direction, (int)
Parameter MaxVelocity,(number)
Parameter Load_Function (user-inputted function)
Parameter Kp,(number)
Parameter Ki,(number)
Parameter smooth,(number)

In XML files, these two task options are scheduled using <Schedule> elements, which must be within the single <CustomTasks> block:

<Schedule name='LoadControl'>
   <Parameter name='velocity'>(number)</Parameter>
   <Parameter name='material'>(int)</Parameter>
   <Parameter name='direction'>(int)</Parameter>
   <Parameter name='MaxVelocity'>(number)</Parameter>
   <Parameter name='Load_Function (function)'/>
   <Parameter name='Kp'>(number)</Parameter>
   <Parameter name='Ki'>(number)</Parameter>
   <Parameter name='smooth'>(number)</Parameter>
</Schedule>

When the task triggers on crack length, these two parameters determine its trigger point:

• (length) - specifies the maximum crack length (in length units). Once this length is reached, all crack propagation will stop.

When the task triggers on a global archive quantity, these parameters determine its trigger point

• (quant) - gives the name of the global archive quantity to use a trigger. In XML files, the quantiy name must be embedded in the parameter name, such as 'global sxx'.
• (matOrBCID) - if the desired global archive quantity is defined for a specific material or for a specific boundary condition, you must enter that material ID

Task Action

Once the specified crack length is reached (and all crack propagation stops) or the critical global archive quantity is reached, the task performs various actions specified by the (style) and (hold) parameters. Scripted files can enter text for the style, but XML files must use the (styleNumber):

• reverse (or 0): Reverses all linearly increasing loads or tractions (see "linear" style in particle loads) and reverses direction of all boundary-condition rigid particles moving at constant velocity (i.e., they have set direction 1 to 7 and do not use any setting functions). This style will unload until the load or traction (on loaded particles) or displacement (on moving rigid particles) returns to zero at which point the analysis will stop (the analysis, however, may stop sooner if the maximum time is reached before loading returns to zero).
• hold (or 1): Stops all linearly increasing loads or tractions (see "linear" style in particle loads) at the current values and sets all boundary-condition rigid particles moving at constant velocity (i.e., they have set direction 1 to 7 and do not use any setting functions) to zero velocity. The analysis continues until maximum time is reached.

The default (style) is to reverse loads, tractions, and particles to unload the specimen (as implied by the task name). Notice that reverse and hold affects only selected types of boundary conditions. The task has no affect on other types of boundary conditions.

If (holdTime) is set to a positive number, it gives a time (in alt time units) to hold at current conditions before applying the task's action. The (hold) parameter only applies when (style) is reverse or abort. The hold phase will only hold boundary conditions that can be reversed (see reverse optoins above). After the hold phase is done, the reverse style will unload to zero as described above and the abort style will stop the analysis. The default (holdTime) is zero (or no hold phase).