Added doco for MaterialRealCMMAux. Closes #374.

doc/content/source/auxkernels/MaterialRealCMMAux.md

@@ -4,21 +4,26 @@
 
 ## Description
 
-`MaterialRealCMMAux` can be used to populate an `AuxVariable` with a Real value
-from a material property that is of type, ColumnMajorMatrix<Real>. In MASTODON, a common use
-case is accessing the deformation or force vectors from link elements when the
-[`LinearSpring`](source/materials/LinearSpring.md) material or any of the
-seismic isolator materials (e.g., [`ComputeFPIsolatorElasticity`](source/materials
-/ComputeFPIsolatorElasticity.md)) is used. This should be block-restricted to
-blocks that have this material property defined. 
+`MaterialRealCMMAux` can be used to populate an `AuxVariable` with an element of
+a material property that is of type, ColumnMajorMatrix (CMM). In MASTODON, a
+common use case is accessing the deformation or force CMMs from link elements
+when the [`LinearSpring`](source/materials/LinearSpring.md) material or any of
+the seismic isolator materials (e.g., [`ComputeFPIsolatorElasticity`](source/materials/ComputeFPIsolatorElasticity.md)) is used. This `AuxKernel` and the corresponding
+`AuxVariable` should be block-restricted to blocks where the material property
+given by the `property` input parameter below is defined.
 
 For example, the following input file syntax will create the AuxVariable field
-called  shown in [uniform_layer_3d].
+called `global_force_x` with the X direction force in the spring element modeled
+using the LinearSpring material. The AuxKernel is defined as follows:
 
-!listing test/tests/auxkernels/uniform_layer/uniform_layer_3d.i block=AuxKernels
+!listing test/tests/auxkernels/materialrealcmm/spring_static.i block=AuxKernels
 
-
-!media media/uniform_layer_3d.png style=width:50%;margin-left:auto;margin-right:auto; caption=Example of oriented "layers" in 3D. id=uniform_layer_3d
+In this input, the AuxKernel takes the element (0, 0) from the CMM material
+property named, "ls_global_forces". This material property name refers to the
+global forces in the linear spring material. (See LinearSpring.C for other
+material properties.) In this example, the linear spring material is only defined
+in block '0' and therefore this AuxKernel and AuxVariable are also restricted to
+this block.
 
 !syntax parameters /AuxKernels/MaterialRealCMMAux
 

test/tests/auxkernels/materialrealcmm/spring_static.i

@@ -53,7 +53,7 @@
     type = MaterialRealCMMAux
     property = ls_global_forces
     row = 0
-    column = 3
+    column = 0
     variable = global_force_x
     block = '0'
   []