Difference between revisions of "Pressure Traction Law"

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(Created page with "<p>This traction law creates a constant stress that is normal to the crack surface. It models a pressure loaded crack. The stress can be entered in one of two ways: </p> <ul>...")
 
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<p>This traction law creates a constant stress that is normal to the crack surface. It models a pressure loaded crack. The stress can be entered in one of two ways:
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== The Traction Law ==


<ul>
This [[Traction Laws|traction law]] applies a constant stress that is normal to the crack surface. It can be used to model a pressure-loaded crack. The stress can be entered in one of two ways:


<li><code>stress</code> - Enter constant normal stress (in MPa). Use negative stress for a pressure loaded crack.</li>
You can either apply a constant stress or provide a [[User Defined Functions|user-defined function]] to let the stress vary in time. Even if you want a constant stress, experience shows that applying that full stress from the start of calculation can cause large, local vibrations and lead to unstable results. If it usually better to ramp the stress up to the constant stress by applying an appropriate ramping [[User Defined Functions|function]].


<li><code>function</code> - alternatively, the stress can be entered as a <a href="function.html">user-defined function</a> of time (giving  stress in MPa). If a function is used, any entered <code>stress</code> property is ignored.</li>
== Failure ==


</ul>
This traction does not fail; it just continues to apply normal stress. By using a [[User Defined Functions|function]], the stress can be time dependent.


Experience shows that apply full stress from the start of calculation can cause large, local vibrations and lead to unstable results. If it often better to use the <code>function</code> option and ramp the stress to desired value.
== Traction Law Properties ==
 
The following properties are used to create a pressure traction law:
 
{| class="wikitable"
|-
! Property !! Description !! Units !! Default
|-
| stress || Enter constant normal stress. Use negative stress for a pressure loaded crack.|| MPa || none
|-
| function || Alternatively, the stress can be entered as a [[User Defined Functions|user-defined function]] of time. || MPM || none
|}
 
If a function is used, any entered stress property is ignored.

Revision as of 07:54, 8 January 2014

The Traction Law

This traction law applies a constant stress that is normal to the crack surface. It can be used to model a pressure-loaded crack. The stress can be entered in one of two ways:

You can either apply a constant stress or provide a user-defined function to let the stress vary in time. Even if you want a constant stress, experience shows that applying that full stress from the start of calculation can cause large, local vibrations and lead to unstable results. If it usually better to ramp the stress up to the constant stress by applying an appropriate ramping function.

Failure

This traction does not fail; it just continues to apply normal stress. By using a function, the stress can be time dependent.

Traction Law Properties

The following properties are used to create a pressure traction law:

Property Description Units Default
stress Enter constant normal stress. Use negative stress for a pressure loaded crack. MPa none
function Alternatively, the stress can be entered as a user-defined function of time. MPM none

If a function is used, any entered stress property is ignored.

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