Main Help → All Commands → Explicit Cracks → NewCrack
The NewCrack
command together with subsequent GrowCrack
, GrowCrackLine
, GrowCrackArc
, and CrackThickness
commands are used to define cracks in an MPM problem (see the OSUPDocs wiki for more details on defining cracks). A crack definition is started with a NewCrack
command, which is followed by one or more of the other commands to complete the crack definition
NewCrack (x1),(y1),<(mat)>,<(lawid)>,<(tract)> GrowCrack (x2),(y2),<(mat)> GrowCrackLine (x2),(y2),(segs),<(mat)>,<(tract)> GrowCrackArc (x1),(y1),(x2),(y2),(segs),(ang1),(ang2),<(mat)>,<(tract)> CrackThickness (thick)
where the NewCrack command defines the start of a new crack its are parameters:
(x1)
and (y1)
defines the coordinates for the starting tip of the crack (or (R,Z)
coordinates if axisymmetric) (in length units).(mat)
can be used to define a material ID for a previously defined material that contains the crack tip or can be "exterior
" to indicate a crack to the edge of the body (see OSUPDocs wiki for details on "exterior
" cracks). Crack propagation is only possible when either or both crack tips have a material ID. If the material ID is omitted, the MPM calculations will correctly model that crack, but no propagation or fracture parameter calculations will occur.(mat)
can alternatively be fixed
to indicate a fixed crack. A fixed crack will not translate with the object and will not track surfaces. It can calculate J Integral but not Stress Intensity factor. It is useful when using cracks to create surfaces in an object. The surface can change by propagating the crack at constant crack speed initiated by critical J or by initiation time (see steady state propagation).(lawid)
can specify a custom contact law for this crack by the contact law's material ID. If you want to set a contact law on a non-fixed crack, but do not want a crack tip material, set (mat)
to "free
", and then enter optional (lawid)
. (Note: a deprecated use of this parameter was to set frictional contact by setting (lawid)
to options allowed for the Friction Command).(lawid)
and (tract)
parameters can assign a traction law to the initial crack tip. To use this option, set (frict)
to "traction
" and (tract)
to a material ID for a traction law material.
Following the NewCrack
command, there can be any number of growing commands. Some commands define shapes and the shapes are linked up to create the full crack. Other commands set crack properties. The options are listed below. See each command for details on the parameters
GrowCrack
- add a crack segment to a specified point.
GrowCrackLine
- grow the crack along a line using a specified number of crack segments.
GrowCrackArc
- define a section of the crack as an arc around an oval and connect the beginning of the arc to the end of the previously defined shape.CrackThickness
- define the thickness of the crack (when needed).
A deprecated CrackInterface command used to set custom imperfect interface properties. The setting is now done with the (lawid)
parameter above.
NewCrack
command will start a new crack. Subsequent GrowCrack
, GrowCrackLine
and GrowCrackArc
commands add points to the current crack.NewCrack
command, you cannot set both non-zero friction and a traction law material. You could, however, set a friction coefficient in the NewCrack
command and then use traction law materials in the subsequent GrowCrack
, GrowCrackLine
and GrowCrackArc
commands. Such cracks will be automatically converted to frictionless contact cracks.
NewCrack
command is only allowed for MPM analyses.