Main Help → All Commands → Explicit Cracks → Propagate
The Propagate
command sets the criterion used for crack propagation in MPM calculations and optionally sets
a crack propagation direction method and traction law material to use on new crack surfaces.
Propagate (crit),<(dir)>,<(tract)>
where (crit)
and optionally (dir)
are the crack propagation criterion and the method to select the crack propagation direction.
The setting in (crit)
is one of the following options (by number or name):
0: "none"
for no propagation.1: "max energy release"
for crack growth based on stress intensity factors and a single critical stress intensity factor (KIc). The propagation condition is based on the maximum energy release rate (also known as the maximum hoop stress criterion and can be set using "max hoop stress"
). The default propagation direction is in the direction of the maximum energy release rate (or the direction of maximum hoop stress).2: "steady state"
for crack initiation when total energy release rate (J) reaches a critical value (specified by JIc) or when the time reaches a specified time. Once the crack has initiated, the crack grows at a specified constant speed. It may be stopped at any predetermined maximum length. The default propagation direction is self-similar propagation.3: "energy balance"
for crack growth by a dynamic energy balancing scheme. The research for this option is in progress and it is not yet meant for general use. The default propagation direction is self-similar propagation.4: "energy density"
for crack growth based on stress intensity factors and a single critical stress intensity factor (KIc). The propagation condition is based on the minimum strain energy density. The default propagation direction is in the direction of minimum strain energy density.5: "elliptical"
for crack growth based on stress intensity factors and two critical stress intensity factors (KIc and KIIc). The default propagation direction is the direction of maximum energy release rate (see "max energy release"
above). The criterion for crack growth is
(KI/KIc)p + (KII/KIIc)q=16: "max ctod"
for crack growth if the crack tip opening displacement at the crack tip exceeds δIc or δIIc if one or both are specified. The default propagation direction is self-similar propagation.7: "critical err"
for crack growth when energy release rate exceeds JIc. The default propagation direction is self-similar propagation.
Each criterion above has a default method for determination of the crack propagation direction. The optional crack propagation direction setting
in (dir)
can override the default method with one of the following methods (by number or name):
0: "default"
to use the default direction for the above criterion.1: "self similar"
to grow in the direction of the crack tip crack segment.2: "cod normal"
to grow normal to a vector between the top and bottom surface at the crack tip.3: "cod hoop"
to estimate the direction of maximum energy release rate based on the normal and shear crack opening displacements. This direction is similar to max energy release
criterion above, but can be used on any type of material.4: "initial"
to grow in the crack tip direction defined by the initial crack geometry.See the OSUPDocs wiki for more details about the above crack propagation criteria and on the crack propagation direction.
The optional parameter (tract)
can define a material ID for a previously defined traction law material. When this parameter is used, new crack surfaces created by crack propagation will be initialized with the provided traction law material. To set (tract)
without specifying a direction rule in (dir)
, set (dir)
to the default value (or 0). Note that any crack that propagates into a traction law material must use a frictionless contact law. If any initial crack particles have a traction law material, the crack will automatically be converted to a frictionless contact crack. If the initial crack, however, has no traction laws, you must be sure to create that crack as a frictionless crack.
Propagate
command defines the default propagation, direction, and traction law material for all materials. If desired, a specific material can override these defaults using the criterion
, direction
, and traction
material property settings. In addition, a specific crack can override the traction
setting by using a CrackTractionProp command.Propagate
command is only allowed for MPM analyses.