While the meshing algorithms used by Ansys Workbench Mechanical originated from the meshing capabilities present in the Mechanical APDL (MAPDL) application, over time these algorithms have diverged. The divergence was due to the different focus of early versions of the Workbench Mechanical application (then known as DesignSpace). As Workbench Mechanical and its meshing and solving capabilities evolved, new technology was added and existing technology was enhanced, making Workbench Mechanical a full, general-purpose, finite element code that supports all levels of multiphysics disciplines.
To accommodate ease of use in Workbench Mechanical, as well as the need for different default meshes based on simulation type, physics preferences are available. These physics preferences automate default mesh settings related to element size, element quality, and so on. The Mechanical physics preference has two choices for Error Limits, or shape check values:
Standard Mechanical, which uses quality error limits that are less strict than those used by MAPDL.
Aggressive Mechanical, which uses quality error limits that are similar to those used by MAPDL.
In addition to letting you set a value for Error Limits, Workbench Mechanical lets you set values for Target Quality and Check Mesh Quality. The mesher uses the Target Quality as a goal for mesh quality. You can think of the Target Quality as a warning limit (in MAPDL terminology), but you can set the Target Quality however you deem appropriate. Check Mesh Quality is very similar to MAPDL's Level of shape checking. Depending on the setting of Check Mesh Quality, you can check for errors, errors and warnings, or neither (turn off checks altogether).
One of the major differences between Standard Mechanical and Aggressive Mechanical error limits is in the computation of the Jacobian ratio. The Jacobian Ratio is a metric that compares a given element's shape to that of an ideal element. Jacobian ratio can be computed at the corner nodes (Aggressive Mechanical) or at Gauss points (Standard Mechanical). Depending on the type of simulation, the calculation at the Gauss points may be sufficient and therefore Standard Mechanical makes meshing more robust. If you are interested in higher accuracy or your problem is nonlinear, you can set Error Limits to Aggressive Mechanical or set Physics Preference to Nonlinear Mechanical. In both cases, the Jacobian ratio that is used is computed at the corner nodes (as it is in MAPDL).