Interaction Viewer PropertyManager

You can use the interaction viewer to visualize the behavior of multibody parts and assemblies during simulations.

Before you run the analysis, you can verify the areas of interactions (such as bonded, contact, and free) defined by the global-level and local-level interaction settings. You can also detect rigid body modes, and determine if bodies are sufficiently constrained during simulations.

To open the Interaction Viewer PropertyManager:

  • Right-click Connections and click Interaction Viewer , or
  • Click the down arrow on Connections Advisor (Simulation CommandManager) and click Interaction Viewer .

Show Interaction

Renders regions of the model with color according to the applied interaction type.

Select Components Select either the assembly or components (two and more) to view the regions of interaction.
Include solver generated interactions (mesh required) Renders the mesh elements that participate in interaction definitions detected by the solver (before starting the analysis). This option is active after meshing the model.
Calculate Calculates all areas with interaction definitions between the selected components and renders them with a unique color according to the interaction type. Lists all detected interaction pairs under Results.
Interaction Type Color Rendering
Bonded Red
Contact Purple
Free Green
Shrink Fit Orange
Virtual Wall Yellow
Thermal Contact Resistance Purple
Insulated Green


Show Geometry Based Interactions Switches the visibility of the geometry-based interactions. When activated, renders the touching geometric entities (edges, faces, or bodies) between the components participating in an interaction definition (global or local).

All detected interaction pairs are listed accordingly under Manual Interaction or Global Interaction.

  • Click an interaction definition in the list to view the color rendering of the area of interaction. The components associated with the interaction definition are listed under each node.
  • Right-click an interaction node, and select Zoom to Selection.
  • You can render one interaction pair at a time, or click Show all interactions to render all interaction pairs simultaneously.
    The geometry-based interactions include these areas of the components with touching geometric entities. To view an interaction pair between faces that are not initially touching, select Include solver generated interactions (mesh required).
Show Solver Based Interactions Switches the visibility of the solver-based interactions. When activated, renders the areas of interaction at the mesh element level detected by the solver before starting the analysis.
Show unselected bodies Active if you select components and not the whole assembly in Select Components.
Plot of a geometry-based contact. Rendering of the touching edge between the two components. Plot of a solver-based contact set. Rendering of mesh elements that participate in contact formulation.

Underconstrained Bodies

Detects any rigid (or free) body modes. Bodies that are not adequately supported by fixtures, connectors, or contact conditions can translate or rotate freely. A body without any restraints has six rigid body modes: 3 translational and 3 rotational.

Calculate Detects bodies that are not sufficiently constrained, and exhibit translational or rotational rigid body modes. The analysis tool applies a coarse mesh and runs the static study (using the Direct Sparse Solver) with all defined loads, interactions, and boundary conditions.
Underconstrained bodies

Lists these bodies that are underconstrained. A green arrow in the graphics area points to the direction (translation or rotation) of free movement.

Select one of the listed degrees of freedom (for example, Translation 1 or Rotation 1) to view an animated translation of the under- constrained body.

Before your run the simulation, apply adequate restraints to prevent instability of the model.

If no rigid bodies are detected, the solver issues a message that the model is fully constrained

The Underconstrained bodies tool does not detect any instability issues for models containing contacts or bolt connectors. Bodies with bolt connectors and contacts can be sufficiently constrained for a successful simulation, but are shown in the list of unconstrained bodies.

See also SOLIDWORKS Simulation Help: Use Soft Spring to Stabilize Model and Preventing Rigid Body Motion.

Detection of Rigid Body Modes

The unconstrained bodies utility detects any rigid (or free) body modes of bodies that are not adequately supported by fixtures, connectors, or interaction conditions.

In a static study, open the Interaction Viewer PropertyManager, and click the Unconstrained Bodies tab.

It is recommended to define realistic materials, loads, and boundary conditions on your model, before you run the unconstrained bodies utility. The study properties should reflect, as accurate as possible, the operating loads and boundary conditions of the model you are trying to analyze.

The unconstrained bodies utility can detect local singularities (elements with zero or almost zero stiffness) in the decomposed global stiffness matrix that could be indicative of a rigid body motion. The algorithm is able to detect situations where the contrast between neighboring stiffness terms in the global stiffness matrix is legitimately very large and does not necessarily lead to singularities. Such models can include:
  • Parts with tapered geometry where the stiffness changes significantly across the part’s profile.
  • Assemblies with parts that have large discrepancies in their material stiffness properties.
  • Parts with localized extreme rigidities at locations where connectors or remote loads are applied.
  • Thin parts modeled as shells that have inherently very small rotational stiffness.
The above cases are not treated as singularity sources for the global stiffness matrix by the unconstrained bodies utility, if the parts are sufficiently constrained.

For each part of an assembly model, the algorithm verifies the existence of free translations and rotations in the global X, Y, and Z direction. It is also able to detect instability issues in assemblies with chain (or hinge) mechanisms between parts. In cases where it detects free body modes, the program animates them accordingly by adjusting the corresponding stiffness and force in that direction to produce a bounded response that reflects a rigid (or free body) motion.

It is recommended to stabilize the detected free body modes of the parts with the appropriate translational or rotational restraints, before you proceed with the analysis.