Research: Thermodynamic Consistency, and Strain-Based Failure

The Kayenta geological material model has been enhanced to span a broader range of pressures and loading rates. Temperature dependence of yield strength has been added along with nonlinear thermoelasticity that can accommodate pressure dependence of the shear modulus and entropy dependence of the bulk modulus in a thermodynamically consistent manner.  Collaborations with Sandia labs have revealed shortcomings in commonly used equations of state. The Kayenta model is being revised to include features similar to the Johnson and Cook model with the Mie-Grüneisen EOS except where we have exposed and corrected violations of thermodynamic consistency.  A major focus of this effort is the use of induced anisotropy to restore thermodynamic admissibility to models that allow the shear modulus to vary with pressure and to (theoretically) permit accurate predictions of dilatation under axisymmetric compression without also predicting unrealistic changes in the hydrostatic limit, which would undermine the model’s predictiveness in transient loading problems, especially second-strike armor performance predictions.

UofU Contributors/collaborators:
Tim Fuller (PhD 2010 Mech. Engr. UofU, now Sandia Labs researcher)
Scot Swan (MS student, Mech. Engr., UofU)
David Macon (MS student, Mech. Engr., UofU)
Krishna Kamojjala (PhD student, Mech. Engr., UofU)
Brian Leavy (PhD student, Mech. Engr., UofU)


External collaborators/mentors:
Erik Strack (Manager, Sandia Labs computational physics)
Lupe Arguello (Researcher, Sandia Labs)
Mike Stone (Researcher, Sandia Labs)
Joe Bishop (Researcher, Sandia Labs)

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