Probe objects are customized for the particular result type. Different probe objects support different scoping mechanisms. For example, you can scope a reaction probe to a boundary condition or scope a stress probe to an x, y, z location (Hit Point Coordinate option) on the geometry. See the Characteristics column of the tables for the supported probe types for scoping details.
The Scoping Method property in the Details pane gives the available scoping options (for example, Geometry Selection, Named Selections, and Remote Points).
Understanding When Probe Object Scoping is Interpolated
When you create a probe object by selecting a specific x, y, z location on the model (via the Hit Point Coordinate option) or using a coordinate system, Mechanical chooses a singular element of a singular body that contains the x, y, z location. If the probe lies between two bodies, the application still only picks one of the two bodies (and one element) to use for the result calculation. Result values are interpolated from the element's nodes to the x, y, z location.
When picking a specific x, y, z location, you can obtain the probe result directly at the closest corner node, without extra interpolation, by right-clicking on the probe object in the tree and choosing Snap to mesh nodes from the context menu. The identification number of the closest corner node is displayed as the Node ID in the Details pane of the probe in the Results category. See the Interpolation section for additional information.
Specific Probe Object Scoping Requirements
Note the following specifications when scoping a probe object:
When you create a probe object by scoping a vertex, edge, face, or volume, the results reported for the probe are for the undisplaced nodes and elements. The displaced location of the probe (if any) is not used in any way to calculate results.
If a probe is scoped to any suppressed or hidden parts, then the probe will not solve or evaluate results. This strategy exists to prevent numeric contributions from elements and nodes that are not scoped.
Caution: The Mechanical application does not support probe objects applied to objects that you have scoped to multiple Remote Points, either directly or indirectly. (For example it does not support probe objects that are applied to a spring scoped to a Remote Point that is itself defined by multiple Remote Points.)
Scoping Limitations for Probe Objects
Be aware of the following limitations when scoping probe objects:
- Surface Body Scoping Limitations
For surface bodies with expanded thickness, the snapping location is located on the expanded mesh. Other items, such as the original x, y, z location and the node ID, are located on the non-expanded mesh. To best view these items, deactivate visual expansion.
- Line Body Scoping Limitations
The Mechanical application does not currently support the setting for the Scoping Method property when scoping probe objects to line bodies.
If you attempt to intersect probe objects with a line body, the application issues a warning message. No results (such as stresses or displacements) will appear in the Details pane for the probe.
- Element Face Scoping Limitations
Only reaction probe objects support element face scoping.
- Shell Geometry Scoping Limitations
Probe object results at the mid-surface location of a shell geometry are obtained by interpolating the Top and Bottom layer result values. (This differs from Contour results which directly extracts the mid-surface location from the solver.)
When probe objects are scoped to a Coordinate System, the application first identifies the element corresponding to the scoped location, using a hit-detection algorithm. Once the element is identified, the application gathers the averaged nodal results for that element and then uses shape functions to find the interpolated result value at the scoped location. This interpolated value will account for both the Top and Bottom layer values for shell geometries.
Shell element node-based results (like stress and strain) exist at the top, bottom, and middle of the shell element (or the layer). Therefore, a shell node can have three values for a given layer.
For result probe objects on shell models that are scoped by Geometry Selection, the probe normally considers the top value and bottom values at the scoped nodes and picks either the maximum or minimum value. Based on the probe object type, the Spatial Resolution property enables you to select whether the application uses the maximum or minimum value.
If you scope your probe object to a Coordinate System, the application performs an interpolation using the values at the top and bottom of the shell.
With these situations in mind, your scoping may present results with unexpected or non-intuitive values.
For example, consider a probe object scoped to a coordinate system that is situated near a vertex at the mid-plane. For this situation, the interpolation is a simple arithmetic average. However, what if the Top value at the node is
-1000and the Bottom value at the same node is1000, a very real scenario for shell models. The coordinate system probe object would report (-1000 + 1000)/2 = 0.Now consider the probe object scoped by geometry to the same Vertex. It would report max(-1000, 1000) = 1000 if the Spatial Resolution property was set to Use Maximum.
- Scoping Limitations for Models with Changing Mesh
If you are using a feature that automatically changes the mesh during the solution process (such as the Nonlinear Adaptive Region object or SMART Crack Growth), any result probe object scoped to the corresponding body will not evaluate.
- Scoping Limitations for Symmetry
Certain probe objects, such as a Reaction probe, support mesh scoping (node, element, or element face) through the Boundary Condition it is scoped to. However, if you specify Symmetry in your analysis, the application does not support mesh scoping on any probe.
- Interpolation Limitation
Values for positions inside of an element may differ from hand-calculated values, especially for certain user defined result expressions. See the limitations topic in the Interpolation of Result Values section.
- Scoping Limitations for Element-nodal Results (Reaction, Summation, Torque, and so forth)
As a result of an element selection limitation, the application can select unscoped adjacent elements that will then contribute to a probe object's result.
When you set the Scoping Method property to Geometry Selection, the scoping algorithm initially selects a group of nodes on the highlighted geometry (face, edge, and so forth). The algorithm then selects any elements attached to those nodes and can include unscoped adjacent elements, that is, elements not contained in the scoping (green highlight).
For probe objects with element-nodal results (such as Structural Force Reaction/Moment Reaction and Magnetostatic Force Summation/Torques), the scoping algorithm selects these unscoped adjacent elements and these additional elements can contribute to the probe results.
Although this behavior is a limitation, it does enable you to compare element-nodal probes to nodal probe objects that are scoped to boundary conditions. For example, an element-nodal Force Reaction probe object scoped to a face can be compared to a nodal probe object scoped to a boundary condition that occupies the face.
- Scoping Limitations for Elemental Results (Volume, Energy, Joule Heat, and so forth)
When the result that is associated with a probe object is purely elemental (one value per element, regardless of the number of nodes), the probe object does not include elements from unscoped bodies. For example, a Volume probe object scoped to a body provides the exact volume of the body.
Note: Bodies that are separated by contact do not share result nodes. In this case, results from elements on unscoped bodies are not included.