Fixed Boundary Conditions

Remote Displacement

Compression Only Support

Elastic Support

Imported Displacement

Weak Springs

Grounded Beam

Contact

Remote Point

Grounded Spring

Mesh Connection

Geometry

Surface

Named Selections

Face, Edge, and Vertex Rotations (do not include Force reactions)

Displacements for Faces, Edges, and Vertices

Cylindrical Support

Frictionless face

Simply Supported Edge and Vertex

Finite Element (FE) Connection Boundary Conditions (Nodal Displacement and Nodal Rotation)

Force Reaction probes support Cartesian or cylindrical coordinate systems. Moment Reaction probes support Cartesian coordinate systems only.

For solved Force Reaction and Moment Reaction probes, the arrow that displays for the probe represents a resultant vector, regardless of the axial direction that you specify in the Result Selection property of the probe. Vector displays in Mechanical always use the Global Coordinate System.

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

For the Moment Reaction probe, the Summation property is available for most Location Method property selections and enables you to select Centroid or Orientation System for your scoped entity. If your selected Location Method does not display this property, the application automatically uses the centroid of the scoped entity for the moment calculation.

A reported reaction may be inappropriate if that 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.

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

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 Modal analysis, reaction results in damped modal analysis provide a By field option in the result definition 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 option. 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.

For Random Vibration and Response Spectrum analysis, reaction results can only be scoped to a Remote Displacement boundary condition. Animation of reaction results is not supported for modal and harmonic analysis.

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.

For a force reaction scoped to a contact region, if you set Extraction = Contact (Contact Element), the reaction calculations come directly from the contact elements themselves. This results in accurate force reactions even when the contact region overlaps with other boundary conditions, such as other contact regions, supports, etc. Characteristics of the Contact (Contact Element) setting are that MPC contact is not supported, nor are reactions from the Target (Underlying Element) side. This feature should only be used with Asymmetric contact and requires that either the Contact Miscellaneous or the General Miscellaneous property be set to Yes in the Output Controls. A limitation of the Contact (Contact Element) setting is when you use linear contact (that is, either Bonded or No Separation contact types) with loads that are unrealistically very high or very low in magnitude. These situations can produce inaccurate force reactions.

Furthermore, in certain rare cases that involve large or concentrated initial interference and/or thermal expansion applications, the reactions calculated by the contact element option may differ from those calculated by the underlying elements. If you experience such as scenario, the underlying element approach is more accurate. Try to tighten the tolerances of the Newton-Raphson Option property under the Nonlinear Controls category of the Analysis Settings (also see the CNVTOL command) to improve the contact element reaction calculations.

When a probe is scoped to a Mesh Connection, the Mechanical application reports the following reactions:

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 for the Extraction property based upon whether you want to study the nodes in front or behind the plane. The Force Reaction probe operates the on elements cut by the plane (and only the nodes on those elements that are on the selected side of the plane). 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.