adding documentation

modules/solid_mechanics/doc/content/source/vectorpostprocessors/CrackFrontNonlocalScalar.md

@@ -0,0 +1,19 @@
+# CrackFrontNonlocalScalar
+
+!syntax description /VectorPostprocessors/CrackFrontNonlocalScalar
+
+## Description
+
+This object computes the average scalar material property at the crack front points defined by  [CrackFrontDefinition.md].  The main use case for this `VectorPostprocessor` is to compute an average fracture toughness or $k_crit$ at the crack front for use with the `MeshCut2DFractureUserObject` to grow cracks. This allows for spatially varying $k_crit$ values defined by a `Material`.
+
+`CrackFrontNonlocalScalar` computes an average of the material property over a box-shaped domain at each crack tip point that is centered on the crack tip and extends [!param](/VectorPostprocessors/CrackFrontNonlocalScalar/box_length) in front of the crack tip.  The [!param](/VectorPostprocessors/CrackFrontNonlocalScalar/box_height) is the dimension normal to the crack face, and [!param](/VectorPostprocessors/CrackFrontNonlocalScalar/box_width) is the dimension tangential to the crack face.  [!param](/VectorPostprocessors/CrackFrontNonlocalScalar/box_width) is not used in 2D problems.
+
+In the following input file example, the mesh consists of a 3D plate with a hole in the middle. The CrackFrontDefinition defines crack points around the center line of the hole, `boundary=1001`. This `CrackFrontNonlocalScalar` averages a material property named `scalar_kcrit` over each 3D box at each crack front point.
+
+!listing crack_front_nonlocal_materials.i block=UserObjects VectorPostprocessors/CrackFrontNonlocalKcrit
+
+!syntax parameters /VectorPostprocessors/CrackFrontNonlocalScalar
+
+!syntax inputs /VectorPostprocessors/CrackFrontNonlocalScalar
+
+!syntax children /VectorPostprocessors/CrackFrontNonlocalScalar

modules/solid_mechanics/doc/content/source/vectorpostprocessors/CrackFrontNonlocalStress.md

@@ -13,9 +13,9 @@ where $\boldsymbol{n}$ is the normal direction vector and $\boldsymbol{\sigma}$
 
 Data produced by this VectorPostprocessor is used in conjunction with the [InteractionIntegral.md] in the XFEM module by the `MeshCut2DFractureUserObject` to grow cracks. The `CrackFrontNonlocalStress` is useful for extending cracks that are approaching free surfaces because the interaction integrals computing `KI` and `KII` are affected when the integration domain intersects the free surface.  `CrackFrontNonlocalStress` computes an average of the stress over a box-shaped domain at each crack tip point that is centered on the crack tip and extends [!param](/VectorPostprocessors/CrackFrontNonlocalStress/box_length) in front of the crack tip.  The [!param](/VectorPostprocessors/CrackFrontNonlocalStress/box_height) is the dimension normal to the crack face, and [!param](/VectorPostprocessors/CrackFrontNonlocalStress/box_width) is the dimension tangential to the crack face.  [!param](/VectorPostprocessors/CrackFrontNonlocalStress/box_width) is not used in 2D problems.  Unlike the other stress integrals, like the [InteractionIntegral.md], that use the [CrackFrontDefinition.md], `CrackFrontNonlocalStress` is not set-up by the [/DomainIntegralAction.md].
 
-In the following input file example, the mesh consists of a 3D plate with a hole in the middle. The CrackFrontDefinition defines crack points around the center line of the hole, `boundary=1001`. This `CrackFrontNonlocalStress` integrates a generic stress field set-up in the input file over the box dimensions shown.
+In the following input file example, the mesh consists of a 3D plate with a hole in the middle. The CrackFrontDefinition defines crack points around the center line of the hole, `boundary=1001`. The `CrackFrontNonlocalStress` integrates a generic stress field set-up in the input file over the box dimensions at each crack front point.
 
-!listing crack_front_nonlocal_stress.i block=UserObjects VectorPostprocessors
+!listing crack_front_nonlocal_materials.i block=UserObjects VectorPostprocessors/CrackFrontNonlocalStress
 
 !syntax parameters /VectorPostprocessors/CrackFrontNonlocalStress
 

modules/xfem/doc/content/source/userobjects/MeshCut2DFractureUserObject.md

@@ -12,7 +12,7 @@ The crack propagates if the failure criterion is met, given by:
 K_c \le \sqrt{K^2_I+K^2_{II}}
 \end{equation}
 
-where $K_I$ and $K_{II}$ are the mode I and II stress intensity factors provided by the fracture integral and the material property $K_c$ is given defined in the input file by [!param](/UserObjects/MeshCut2DFractureUserObject/k_critical).  The crack growth direction is given by the direction the maximized the crack-tip hoop stress, given by Equation 5 in [!cite](jiang2020).  The growth increment is a user provided input given in the defined by [!param](/UserObjects/MeshCut2DFractureUserObject/growth_increment).  The fracture integrals $K_I$ and $K_{II}$ are obtained from the [InteractionIntegral.md] vectorpostprocessor specified in the input file by [!param](/UserObjects/MeshCut2DFractureUserObject/ki_vectorpostprocessor) and [!param](/UserObjects/MeshCut2DFractureUserObject/kii_vectorpostprocessor).  Defaults for [!param](/UserObjects/MeshCut2DFractureUserObject/ki_vectorpostprocessor) and [!param](/UserObjects/MeshCut2DFractureUserObject/kii_vectorpostprocessor) use the names produced by the [/DomainIntegralAction.md] which is the standard way to set-up the [InteractionIntegral.md].
+where $K_I$ and $K_{II}$ are the mode I and II stress intensity factors provided by the fracture integral and the material property $K_c$ is defined in the input file with a constant value for the entire domain using [!param](/UserObjects/MeshCut2DFractureUserObject/k_critical) or from a [CrackFrontNonlocalScalar.md] VectorPostprocessor that samples a material property at each crack front point and is specified by [!param](/UserObjects/MeshCut2DFractureUserObject/k_critical_vectorpostprocessor) and [!param](/UserObjects/MeshCut2DFractureUserObject/k_critical_vector_name).  If both `k_critical` and `k_critical_vectorpostprocessor` are defined, the lower $K_c$ is used.  The crack growth direction is given by the direction that maximizes the crack-tip hoop stress, given by Equation 5 in [!cite](jiang2020).  The growth increment is a user provided input given by [!param](/UserObjects/MeshCut2DFractureUserObject/growth_increment).  The fracture integrals $K_I$ and $K_{II}$ are obtained from the [InteractionIntegral.md] vectorpostprocessor specified in the input file by [!param](/UserObjects/MeshCut2DFractureUserObject/ki_vectorpostprocessor) and [!param](/UserObjects/MeshCut2DFractureUserObject/kii_vectorpostprocessor).  Defaults for [!param](/UserObjects/MeshCut2DFractureUserObject/ki_vectorpostprocessor) and [!param](/UserObjects/MeshCut2DFractureUserObject/kii_vectorpostprocessor) use the names produced by the [/DomainIntegralAction.md] which is the standard way to set-up the [InteractionIntegral.md].
 
 Near a free surface, the integration volumes of the rings used to compute the `InteractionIntegral` will intersect the surface, leading to a reduction in the fracture integral values.  This can lead to cracks becoming unable to farther propagate as they approach free surfaces.  For these cases, a maximum stress criterion computed using [CrackFrontNonlocalStress.md] vectorpostprocessor can be used for crack growth using an additional failure criterion given by: