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PTT Form
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::

   PTT Form = {model_name}

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**Description / Usage**
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This card is used in the Phan-Thien Tanner model in the nonlinear stress terms.
This is an optional card, and the default behavior is preserved as *EXPONENTIAL* for
backwards compatibility.
Definitions of the input parameters are as follows:

EXPONENTIAL
   The default model, the exponential PTT form
LINEAR
   Linear form of the PTT constitutive equation.

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**Examples**
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The following is a sample card that sets the PTT to the Linear form

::

   PTT Form = LINEAR

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**Technical Discussion**
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No Discussion.