Reactions results

The reaction force is the force required to keep the constrained item from moving. The result is zero for vertices, edges, and faces that are not constrained. Reaction moments are also calculated from the distribution and directions of the reaction forces.

Reaction force results are available for the following studies:

• Static Stress
• Thermal Stress
• Nonlinear Static Stress
• Event Simulation

Using reaction force results

The reaction forces in a particular direction should be equal in magnitude and opposite in direction to the total load applied in the same direction. Therefore, you can check reactions to verify that the model setup is correct. The contour plot shows the individual reaction forces distributed along all constrained nodes. The following options are available:

• Total Displays the magnitude of the reaction force vector, regardless of its direction. This value is always positive.
• X Displays the X component of the reaction force vector.
• Y Displays the Y component of the reaction force vector.
• Z Displays the Z component of the reaction force vector.

For example, assume a block of steel weighing 500 pounds rests on the floor. Only gravity is applied to the model. The bottom of the block is fixed to represent the support from the floor, which is not included in the model. The sum of the reaction forces along the bottom surface of the block should equal 500 pounds.

You can also use reactions to verify that any bolts, screws, or rivets used to mount a part are adequate for the task. For example, to simulate a part bolted into an assembly, you could use fixed constraints to represent the bolts (instead of modeling the bolts as solids). The reaction forces at the bolt locations should not be high enough to shear the bolts or to break them in tension. If the reaction forces exceed the bolt strength, then you need to specify larger or stronger bolts in your design.

Important: Solid elements do not have rotational degrees of freedom. Therefore, the listed moments are calculated from the distribution and directions of the nodal reaction forces. The finer the mesh size, the smaller the individual nodal reaction forces will be when you probe them, because more nodes are sharing the total reaction. Conversely, a coarse mesh results in higher individual nodal reaction forces. However, while the individual nodal reaction forces are mesh-dependent, the total reactions for the selected constraint regions should not be sensitive to the mesh size.