Reaction probes scoped to boundary conditions produce a nodal solution (PRRSOL).

Reaction probes scoped to geometry produce an element-nodal solution (FSUM).

Modal and Harmonic Response analyses do not support Mesh Connections.

For a damped Modal analysis, reaction results provide the By property to compute results based on Mode Number, Phase of Maximum, and Maximum Over Phase.

For a Harmonic Response analysis, reaction results support all options of the result definition available for other harmonic results, and are reported based on the nearest frequency results available: no interpolation is done.

In order to evaluate reactions successfully for a standalone Mode Superposition Harmonic Response analysis that has the Clustering property set to On, you need to also make sure that either the Stress, Strain, Nodal, or the General Miscellaneous properties in the Analysis Settings>Output Controls are also set to Yes.

Reaction results sweep through a phase period of 0^o and 360^o at a specified increment. In previous releases of Mechanical (14.5 and earlier), the default value for this increment was 1^o in order to determine the Phase of Maximum and the Maximum Over Phase values. For Harmonic Response analyses only, the phase increment can be controlled using the Phase Increment property. A Phase Increment entry can be between 1^o and 10^o. The default Phase Increment value is 10^o but for legacy database results it is 1^o.

Response Spectrum and Random Vibration analyses, the probes do not:

When you scope this result to geometry, including contact surfaces and cut surfaces, the application calculates the probe using element-nodal data. These calculations are equivalent to those of the FSUM command. That is, the sums for each component direction for the total selected node set and the nodal force and moment contributions of the selected elements attached to the node set.

A reported reaction may be inappropriate if its support shares a face, edge, or vertex with another support, contact pair, or load. This is because the underlying finite element model will have both loads and supports applied to the same nodes.

If a model contains two or more supports that share an edge or vertex, use caution in evaluating the listed reaction forces at those supports. Calculation of reaction forces includes the force acting along bounding edges and vertices. When supports share edges or vertices the global summation of forces may not appear to balance. Reaction forces may be incorrect if they share an edge or face with a contact region.

A limitation exists when the scoping of a probe is applied to a geometric entity (Location Method = Geometry Selection) that shares more than one body. The (unscoped) elements that are adjacent to the scoped body contribute to the probe's results.

Force Reaction probes support Cartesian or cylindrical coordinate systems.

Moment Reaction probes support Cartesian coordinate systems only.

For a Static Structural analysis that includes a Cyclic Region object, the application requires that you specify the same coordinate system used by the Cyclic Region for your reaction probe (Orientation property). Reaction probes calculate a preliminary sum using the base sector of the symmetric model in the cylindrical coordinate system of the cyclic analysis. It then multiplies the sum by the number of sectors to obtain the final reaction. Currently, you cannot rotate these final reactions to a different coordinate system.

For Response Spectrum and Random Vibration analyses only, when you set the Location Method to Boundary Condition and specify a Fixed Support or a Displacement, the application uses the Global Coordinate System. For any other supported Boundary Condition option, such as Remote Displacement, the application automatically uses the Solution Coordinate System.

Will not solve if scoped to a Contact Region that includes a rigid body.

Do not support the Location Method option Contact Region when the corresponding Contact Region is scoped to element faces.

For a Moment Reaction scoped to a contact region, the location of the summation point may not be exactly on the contact region itself.

A Moment Reaction probe cannot be scoped to a Grounded Spring.

Since Beam Connections are, by definition, three dimensional in nature, the reactions object scoped to grounded beams may produce reactions in all three directions/axes for two-dimensional analysis. The Tabular Data view will reflect the reactions in all three axes, while the Results view will only reflect values in two axes. The total reactions will be calculated taking into account the reaction components in all three axes.

When you set the Location Method property to Surface, you need to specify the following additional properties:

The Surface option of the Location Method property enables you to study reactions on cutting planes. You can extract generated member forces and reactions through a model by using a reaction probe scoped to a Surface object. For this probe type, you must explicitly select the body or bodies (via the Geometry property) to be sliced. You then specify the Extraction property based upon whether you want to study the nodes in front of the plane, behind the plane, or that lie on the specified plane. The Force Reaction probe operates on the elements cut by the plane and only the nodes on those elements that are on the selected by the Extraction property. The application uses a slice algorithm for the Surface option. Because of very slight numerical accuracy issues, such as the number of significant digits used, the algorithm may not capture all expected nodes.

The application can also fail to include a node based on how you slice an element. For example, if a slice plane produces a degenerate polygon, which can happen when a planar shell has only one node in the slice plane, the reaction calculation does not use the node from the element.

For a Moment Reaction probe, when you set the Location Method property to Surface, you must select a body or bodies for the surface to cut. If the Summation property is set to Centroid and you select multiple bodies, the application will use the average the centroids of the bodies for the summation point. The application does not use weighting by volume or by mass for this averaging.

If you set Extraction equal to Contact (Underlying Element) or Target (Underlying Element) in the Details of either a Force Reaction or Moment Reaction probe, the reaction calculations work by summing the internal forces on the underlying elements under a contact region. These probes can also extract reaction data from surface effect elements. The application creates surface effect elements during the solution process to simulate loads, such as pressures. However, the application does not currently display surface effect elements from the Mesh object or the Connections object.

Therefore, a reported reaction may be inappropriate on a contact face if that face shares topology with another contact face/edge or external load (such as a force or fixed support), which would contribute to the underlying elements' internal force balance. In addition, during a Transient analysis, inertial and damping forces are also included. Another possible scenario could arise for MPC contact of solid surfaces. In this case, if a gap is detected, the solver may build constraints on an additional layer into the solid mesh from the TARGET elements. This produces a more accurate response but will invalidate any reactions from the underlying solid elements of the TARGET elements. If symmetric contact is chosen, be careful to verify which side becomes active for the TARGET elements so that the correct reaction can be determined.

When scoping Force Reaction or Moment Reaction probes to geometry, it is possible that there may be elements (and as a result, element-based reactions) that are currently unavailable for summing purposes. For example, you scope a pressure to a face on your geometry. The solution process also applies surface effect elements to the same face to simulate the pressure loading. The probes, scoped to geometry, currently cannot extract reaction data from the surface effect elements and therefore, in the case of this example, only the underlying solid/shell/line elements of the original mesh contribute reaction data to the probe results.

If mesh elements overlap, reaction probes scoped using the Geometry Selection method may produce unexpected or unreliable results. Select the Mesh object to examine whether elements from one body cross an edge and overlay elements of other bodies.

For geometric scoping, the location of the Force Reaction probe is usually the node nearest to the centroid of the scoping.

The location of Moment Reaction probe is usually the Summation Point (the anchor for the moment arm calculation). For non-geometric scoping, there can be exceptions, such as remote points. In this instance, the coordinate (x,y,z) of the remote point becomes the location of the arrowheads.

The magnitude for the probes is based on the sum of the forces or moments.

For Static and Transient analyses, the Graph and Tabular Data windows display the history of the reactions/moments. The arrowhead is representative of the specified Display Time.

For Harmonic and Modal, the Graph and Tabular Data windows display the reactions/moments for all frequencies/modes in the file. The arrowhead is representative of the specified Frequency/Mode.

Fixed Support (Face, Edge, and Vertex Rotations (do not include Force Reactions)

Displacements (Face, Edge, and Vertex selections)

Cylindrical Support

Frictionless (Face selection)

Simply Supported (Edge and Vertex selection)

Nodal Displacement

Nodal Rotation

Remote Displacement

Nx, Ny, and Nz represent the location of the node nearest to x, y, and z.

dx, dy, and dz represent the displacements of that nearest node.