zone interface node command

Syntax

zone interface <s > node keyword <range>

Primary keywords:

displacement-shear    displacement-small    extra    group    history    initialize-stresses    list    stress-shear    stress-normal-increment    property    update

Configure interface nodes.

If an interface name s is given the command is applied only to nodes of that interface, otherwise the command is applied to the nodes in all interfaces that fall in the optional range.

displacement-shear v

Overwrites the shear displacement vector for all interface nodes in the range. The value will be constrained to be perpendicular to the interface normal direction.

displacement-small f

Interfaces operating in small-strain mode derive their forces from a comparison of “virtual positions” of the two interacting faces, where a “virtual position” of a point is the original coordinate of the point plus the accumulated displacement ( displacement-small ) to date. If one contacting object is removed (e.g., backfill within a tunnel), and another substituted (e.g., a liner is installed) using the same interface, then large initial stresses may appear because the two sides of the interface appear to interpenetrate (because the virtual position of the old object has changed with respect to the specified position of the new object).

The stored displacements associated with a particular interface s may be multiplied by a factor f, using the keyword displacement-small. Normally, this factor will be zero, thus restoring the virtual positions of the faces comprising the interface “host” to their original locations. In this case, a new interacting object will not cause initial stresses to be generated when its coordinates match the original coordinates of the interface host faces. However, it is possible to give f a nonzero value, in order to simulate an initial lack-of-fit between the two contacting objects.

The command changes the virtual positions in the interface, and in the two faces that are in contact. However, for a newly created interface, the “target” face is not found until cycling has begun. Therefore, for all positions to be reset, at least one cycle should be executed before giving the command if the target (i.e., the face without the interface elements) has some existing deformation.

extra i a[interfacenodeblock]

Set the extra interface node variable value for array index i.

group s <keyword>

Add group name s to the interface nodes in the range. Use of the group logic is described in Groups. This command may take the form zone interface node "slotname = groupname" — quotation marks required, spaces at equals sign ignored — where slotname is the slot assignment and groupname is the group name.

An interface node may belong to many groups in different slots, up to a maximum of 128. The group range element can be used to select objects by group name.

The following optional keywords are available:

remove

Remove s from interface nodes. If a slot is not specified, the group name is removed from all slots it is found in.

slot s

Assign the group to the slot named s. The default slot name is Default.

history <name sn >keyword

Interface variables can be sampled for interface s at the interface node specified. See the history command. Note that this command does not take a following range. The following keywords are defined:

displacement-normal keyword

normal displacement (positive values indicate increased penetration).

id i <name s >

Indicates the history should be taken at interface node ID i in interface s. If a specific interface was not indicated then an interface name must be specified following.

position v

Indicates the history should be taken at the node closest to position v among the nodes of interface s. If a specific interface was not indicated than the nearest node on any interface will be found.

displacement-shear keyword

shear displacement magnitude

id i <name s >

Indicates the history should be taken at interface node ID i in interface s. If a specific interface was not indicated then an interface name must be specified following.

position v

Indicates the history should be taken at the node closest to position v among the nodes of interface s. If a specific interface was not indicated than the nearest node on any interface will be found.

stress-normal keywrd

normal stress (Compressive stresses are positive)

id i <name s >

Indicates the history should be taken at interface node ID i in interface s. If a specific interface was not indicated then an interface name must be specified following.

position v

Indicates the history should be taken at the node closest to position v among the nodes of interface s. If a specific interface was not indicated than the nearest node on any interface will be found.

stress-shear keyword

shear stress magnitude

id i <name s >

Indicates the history should be taken at interface node ID i in interface s. If a specific interface was not indicated then an interface name must be specified following.

position v

Indicates the history should be taken at the node closest to position v among the nodes of interface s. If a specific interface was not indicated than the nearest node on any interface will be found.

initialize-stresses

Initializes the normal and shear forces on all interface nodes in the range and in contact with a surface face. The values of the forces are determined by the tractions on the host face of the node. This means that if zone stresses are initialized, then interface forces can be initialized to be approximately compatible, thus reducing the amount of cycling to reach initial equilibrium.

Note that since normal stress is determined by absolute penetration, initialization of normal stresses is accomplished by setting the stress-normal-increment value for each node affected.

list keyword

List information about interface nodes in the range.

displacement

The accumulated displacement, shear displacement, and small-strain displacement of the nodes.

extra i

The values stored in extra index i of the interface nodes.

host

The host zone face, and the weighting values used for the attachment.

information

The position, normal direction, and effective area, and contact tolerance.

property keyword

The value of interface properties at the nodes. The available property names are:

bonded-slip

flag indicating if slip is allowed.

cohesion

cohesion in units of stress

cohesion-residual

residual cohesion. If assigned a value greater than or equal to zero, this value is assigned to cohesion after frictional shear failure.

dilation

dilation in degrees

friction

friction in degrees

friction-residual

residual friction. If assigned a value greater than or equal to zero, this value is assigned to friction after frictional shear failure.

shear-bond-ratio

shear bond strength as a ratio of the tensile strength.

stiffness-normal

normal stiffness in units of stress over displacement.

stiffness-shear

shear stiffness in units of stress over displacement.

tension

tensile strength in units of stress

tension-residual

residual tensile strength. If assigned a value greater than or equal to zero, this value is assigned to tension after frictional shear failure.

state

current state of the interface node

stress

shear and normal stresses and shear stress direction

target

target face information including penetration

velocity

velocity at nodes

stress-shear v [interfacenodeblock]

sets the incremental shear stress v for all interface nodes in the range.

stress-normal-increment f [interfacenodeblock]

Sets the normal stress increment to f for all interface nodes in the range. Note that compressive stresses are positive. The normal stress increment is added to the normal stress calculated from interface penetration.

property keyword ...

Assigns one or more new property values to all interface nodes in the range.

cohesion f [interfacenodeblock]

cohesion [stress]

friction f [interfacenodeblock]

friction angle [degrees]

stiffness-normal f [interfacenodeblock]

normal stiffness [stress/displacement]

stiffness-shear f [interfacenodeblock]

shear stiffness [stress/displacement]

cohesion-residual f [interfacenodeblock]

residual cohesion [stress]. If a value greater than of equal to zero is specified, this value is assigned to cohesion after frictional shear failure. Default is -1.0.

friction-residual f [interfacenodeblock]

residual friction angle [degrees]. If a value greater than of equal to zero is specified, this value is assigned to friction after frictional shear failure. Default is -1.0.

tension-residual f [interfacenodeblock]

residual tensile strength [stress]. If a value greater than of equal to zero is specified, this value is assigned to tension after frictional shear failure. Default is -1.0.

tension f [interfacenodeblock]

tensile strength [stress]

bonded-slip b

Slip is allowed, or not allowed, for a bonded interface segment. Default is off (i.e., slip is not allowed if bond is intact). This is only applicable if a bonded interface is specified (tension is set).

shear-bond-ratio f [interfacenodeblock]

The shear bond strength is set to sbr times the normal bond strength (tension). Note that giving sbratio alone does not cause a bond to be established; the tensile bond strength must also be set. The default value for sbratio is 100 (i.e., shear bond is 100 times tensile bond). This is only applicable if a bonded interface is specified (tension is set).

update b <range>

This command prevents the search for new contacts after movement occurs on an interface. The same contacts are preserved, whatever the magnitude of displacement. Use with caution, because physically unrealistic behavior can result if displacements are large. The default behavior is on, which allows normal searching for new and broken contacts.


zone interface node Keyword Block

The following keywords may be used to modify a supplied value. If the description of the modifier keyword mentions what type of value it may be applied to (e.g. scalar value, vector value, etc.), be sure there is a match between the modifier and the main keyword value. The commands main keywords are: extra, stress-normal-increment and stress-shear. cohesion, cohesion-residual, friction, friction-residual, shear-bond-ratio, stiffness-normal, stiffness-shear, tension and tension-residual.

add

Add the specified value to the existing value.

gradient v <origin v >

Apply a gradient to the scalar-value provided.

multiply

Multiply the existing value by the specified value.

vary v

Apply a linear variation to the scalar-value provided.