Difference between revisions of "Crack Settings"

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         <ContactPosition>0.8</ContactPosition>
         <ContactPosition>0.8</ContactPosition>
     </Cracks>
     </Cracks>
== Crack Propagation Commands ==
In max energy release rate (or max hoop stress), the crack direction is at angle &theta; (which is ccw from self similar growth) and obeys
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\cos\theta = {3R^2 + \sqrt{1+8R^2} \over 1+9R^2} \quad {\rm and} \quad
  \sin\theta = \mp\sqrt{1-\cos^2\theta} = \mp\left | R(3\cos\theta - 1)\right|</math>
where R = K<sub>II</sub>/K<sub>I</sub>. The second term is negative or positive depending on K<sub>II</sub> being positive or negative. In the limit of K<sub>I</sub> to zero, cos &theta; = 1/3 for crack direction of -70.5 (or +70.5) degrees. This method requires K<sub>I</sub> and K<sub>II</sub> which can only be done for isotropic (and subclasses), mooney, heisotropic (and subclass), and viscoelastic. All use initial, low strain modulus to calculate stress intensity factors.
Above is same as
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;
<math>\tan {\theta\over 2} = {1\over 4}\left({1\over R} \mp \sqrt{{1\over R^2} + 8}\right)</math>
where negative of positive is determined by sign of K<sub>II</sub>.
in cod hoop direction, the code uses the max energy release rate method, but assumes R = &delta;<sub>t</sub>/&delta;<sub>n</sub> or ratio of the sliding and opening crack opening displacements. This method can be used for any material.

Revision as of 18:00, 27 September 2013

These command control modeling of explicit cracks and whether or not those cracks propagate

Crack Settings Commands

In scripted files, crack properties are controlled by various commands described below. In XML input file, all global crack setting commands are within a <Cracks> element that must be within the <MPMHeader>: 

<Cracks>
   (crack setting commands)
</Cracks>

The commands are


In XML files 

   <Cracks>
        <JContour type='1' size="2" terms="1"/>
       <Friction>0.3</Friction>
       <MovePlane type='avg' prevent='no'/>
       <ContactPosition>0.8</ContactPosition>
   </Cracks>
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