ReverseLoad Custom Task

A custom task to alter calculations based on crack propagation results.

Introduction

The ReverseLoad custom task monitors crack lengths or monitors any current global archive quantity. Once any crack or a specified crack reaches a specified crack length or the specified global quantity passes a critical value, the task's action is triggered. When monitoring crack lengths, the task also stops crack propagation of all cracks stops before performing its designated action.

Task Scheduling

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

CustomTask ReverseLoad
Parameter maxLength,(length)
Parameter crackNumber,(number)
Parameter style,(style)

CustomTask ReverseLoad
Parameter quantity,(quant)
Parameter material,(matOrBCID)
Parameter maxValue,(value)
Parameter style,(style)

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

<Schedule name='ReverseLoad'>
   <Parameter name='maxLength'>(length)</Parameter>
   <Parameter name='crackNumber'>(number)</Parameter>
   <Parameter name=style'>(styleNumber)</Parameter>
</Schedule>

<Schedule name='ReverseLoad'>
   <Parameter name='global (quant)'/>
   <Parameter name='mat'>(matOrBCNum)</Parameter>
   <Parameter name='maxValue'>(value)</Parameter>
   <Parameter name=style'>(styleNumber)</Parameter>
</Schedule>

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

• (length) - specifies the maximum crack length (in mm). Once this length is reached, all crack propagation will stop.
• (number) - gives the crack number to watch. When that crack reaches the specified maximum length, the task will take effect. Alternatively, (number) can be zero which causes the task to take effect when any crack reaches the specified maximum length. The default value is 0 or to watch all cracks.

When the task triggers on a global archive quantity, these three parameter 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, enter that material ID or boundary condition ID in this parameter.
• (matOrBCNum) - in XML files, the specific material or boundary condition ID must be specified by number.
• (value) - specifies the critical value for the global archive quantity to trigger the task action. If the number is positive, the action is triggered when the quantity reaches the value; if it is negative, the action is triggered when the quantity become more negative the than the value.

One 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) parameter. Scripted files can enter text for the style, but XML files must use the (styleNumber):

• reverse (or 0): Reverses all linearly increasing loads (see "linear" style in particle loads) and reverses direction of all rigid particles. This style will unload until the load (on loaded particles) or displacement (on moving rigid particles) returns to zero at which point the analysis will stop.
• hold (or 1): Stops all linearly increasing loads (see "linear" style in particle loads) and stops all rigid particles at their current values. The analysis continues.
• continue (or 2): All loads and rigid particles continue unchanged. Only the crack propagation stops. Because this action only stops crack propagation, it is meaningless when the tasks is trigger on a global archive quantity, and is therefore not allowed for such tasks.
• abort (or 3): The analysis terminates.

The default (style) is to reverse all loads to unload the specimen (as implied by the task name)