[Transformation toughening] (open access)

[Transformation toughening]

In NiAl, we have succeeded in determining the complete Ginzburg-Landau strain free energy function necessary to model the cubic to tetragonal martensite transformation in a sample of any size. We believe that this is the first time that the parameters of a Ginzburg-Landau functional and the complete strain spinodal for any three-dimensional displacive transformation were used in simulating the transformation near a crack tip under Mode I loading; the transformation pattern and toughening are different from standard transformation toughening theories. Furthermore, the strain spinodal has an approximately conical shape which can be specified by two material dependent experimentally accessible parameters, rather than the ellipsoidal shape in standard theories. Stress induced martensitic transformation in a polycrystalline sample of NiAl was simulated. In the ZrO[sub 2] system, first principles calculations to determine the semi-empirical potentials for simulating the cubic-tetragonal and tetragonal-monoclinic transformations have been started by doing a more elaborate total energy calculation.In the Al[sub 2]0[sub 3] system, we have discovered that the first principles calculations and semi-empirical potentials have just been completed byanother group in England which we will use instead to base our molecular dynamics simulations on.
Date: April 19, 1993
Creator: Rafa, M.J.
System: The UNT Digital Library
Midpoint technical report (open access)

Midpoint technical report

The research covers high-resolution imaging of electrical conductivity using low-frequency electromagnetic fields. This report contains two appendices: progress made in optimizing a 3D integral equations forward modeling code for imaging, and a technique for improving the resolution of the inverse problem.
Date: April 19, 1993
Creator: Tripp, A. C.
System: The UNT Digital Library
Midpoint technical report (open access)

Midpoint technical report

The research covers high-resolution imaging of electrical conductivity using low-frequency electromagnetic fields. This report contains two appendices: progress made in optimizing a 3D integral equations forward modeling code for imaging, and a technique for improving the resolution of the inverse problem.
Date: April 19, 1993
Creator: Tripp, A. C.
System: The UNT Digital Library
[Transformation toughening]. Annual progress report (open access)

[Transformation toughening]. Annual progress report

In NiAl, we have succeeded in determining the complete Ginzburg-Landau strain free energy function necessary to model the cubic to tetragonal martensite transformation in a sample of any size. We believe that this is the first time that the parameters of a Ginzburg-Landau functional and the complete strain spinodal for any three-dimensional displacive transformation were used in simulating the transformation near a crack tip under Mode I loading; the transformation pattern and toughening are different from standard transformation toughening theories. Furthermore, the strain spinodal has an approximately conical shape which can be specified by two material dependent experimentally accessible parameters, rather than the ellipsoidal shape in standard theories. Stress induced martensitic transformation in a polycrystalline sample of NiAl was simulated. In the ZrO{sub 2} system, first principles calculations to determine the semi-empirical potentials for simulating the cubic-tetragonal and tetragonal-monoclinic transformations have been started by doing a more elaborate total energy calculation.In the Al{sub 2}0{sub 3} system, we have discovered that the first principles calculations and semi-empirical potentials have just been completed byanother group in England which we will use instead to base our molecular dynamics simulations on.
Date: April 19, 1993
Creator: Rafa, M. J.
System: The UNT Digital Library