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*Clashing Solution |
 
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*Clashing Solution
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*Clashing Solution |
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To specify solution parameters associated with clashing.
Refer to Timestep Size, Contact Ramp and Axis System for further information on this feature.
Two lines of data defining solution parameters as follows.
[AXIS=Axis Type], [OUTPUT=YES]
[Maximum Time Step] [, Threshold Clearance] [, Contact Ramp] [, Successive Solutions]
All parameters are optional. Axis type can be Instantaneous or Initial, defaulting to Instantaneous if omitted. Maximum Time Step defaults to the analysis maximum time step if omitted. Threshold Clearance defaults to 10% (of the average contact diameter) if omitted. Contact Ramp defaults to 0% (of the average contact diameter) if omitted. Successive Solutions defaults to 0 if omitted.
Input: |
Description |
Maximum Time Step: |
The maximum time step to be used during clashing. This input is optional. This input defaults to the overall maximum analysis time step, assuming that you are using a variable time step. See Note (a). |
Threshold Clearance: |
The minimum clearance below which the maximum time step specified above must be adhered to. This value is input as a percentage of the average contact diameter of the elements which come into contact. This input is optional, and defaults to 10%. See Note (a). |
Contact Ramp: |
The distance over which the contact stiffness is ramped up. This value is specified as a percentage of the average contact diameter of the elements. This input is optional, and defaults to 0%, which means that no ramp is modelled. See Note (b). |
Successive Solutions: |
The number of successive solutions after which contact is deemed to be firmly established (i.e. the connected nodes remain the same). This option is only relevant if the interaction between two lines is likely to be constant rather than intermittent. See Note (c). |
Axis System |
This option allows you to specify whether the line of action of contact force application is to be based on the Instantaneous (the default) or the Initial positions of the contact elements. See Note (d). |
Output File: |
This option allows you to specify that active contact elements are to be echoed to the Output File. The options are No (the default) and Yes. See Note (e). |
(a)The Maximum Time Step limits the time step used during clashing. Refer to Timestep Size for further details.
(b)When two lines come into close proximity, the interaction between the two lines is effectively modelled by the insertion of a non-linear spring between the points at which minimum separation occurs. Refer to Contact Ramp for further details.
(c)In certain circumstances, it may not be desirable to persist with a very small time step while clashing is taking place, particularly if the interaction between two lines is likely to be constant rather than intermittent. Refer to Timestep Size for further details.
(d)By default, the Axis System for application of contact forces between a pair of contact elements is based on the instantaneous positions of the elements at any given time. Refer to Axis System for further details.
(e)You can optionally specify that active contact elements are be echoed to the Output File. If you invoke this option, the output file shows you exactly what elements contact each other at every solution time. This feature is particularly useful as it allows you to refine the contact set element definitions and consequently reduce run times.