Abbreviation	Definition
AASHTO	American Association of State Highway and Transportation Officials
ASTM	American Society for Testing and Materials
MASH	Manual of Assessing Safety Hardware
FEA	Finite Element Analysis
LS-DYNA	Livermore Software Technology Corporation—Dynamic Nonlinear Analysis (FEA Software)
$\mathit{\sigma }$	Cauchy stress tensor
${\sigma }_H$	Hydrostatic stress
$\mathit{s}$	Deviatoric stress
$tr\left(\mathit{\sigma }\right)$	Trace of the stress tensor, which is the sum of its diagonal components
I	The second-order identity tensor
P	Pressure
$I_1, I_2, I_3$	Stress invariants
$\mathit{s}:\mathit{s}$	double contraction of the deviatoric stress tensor with itself
${\sigma }_m$	Von Mises or average stress
$\eta$	Stress triaxiality
$\xi$	Lode parameter
$J_3$	Third deviatoric stress invariant
DIC	Digital Image Correlation
${\sigma }_T$	True uniaxial stress
${\epsilon }_T$	True uniaxial strain
$K$, ${\epsilon }_o$, and $n$	Swift plasticity model constants
MAT224	Tabulated Johnson–Cook LS-DYNA’s material model
MAT24	Piecewise Linear Plasticity LS-DYNA’s material model
GISSMO	Generalized Incremental Stress-State-Dependent Model
ELFORM	Element formulation in LS-DYNA
FI	Fully Integrated elements
UI	Under Integrated elements