Specifying Directions

Specifying directions is often required during model definition and result viewing. In model definition, directions are used to define orthotropic material properties, restraints, and loads. In result viewing, directions are required for viewing directional results, like displacements, stresses, strains, and heat flux in certain directions.

When applying loads or prescribing nonzero restraints, select the Show preview option in the PropertyManager to identify the positive directions. To apply loads in the opposite directions, enter negative values.

In an assembly, you can use reference geometry from the assembly or its referenced components or subassemblies.
Using a Reference Plane A reference plane (or a planar face) defines two directions in its plane and a third direction, which is normal to the plane. The two directions in the plane are referred to as Plane dir 1 and Plane dir 2. They are parallel to the boundaries of the plane, and assigned internally by the program. These directions cannot be modified.

When applying restraints and loads, select Show preview to identify Plane Dir 1 and Plane Dir 2. The arrows of the load or restraint symbols point to the positive Plane Dir 1, Plane Dir 2, and normal to the plane directions.

You can identify the normal direction by the right-hand rule: thumb finger points to positive Plane Dir 1, index finger points to positive Plane Dir 2, middle finger points to the positive normal direction.

For material properties directions, Dir 1 aligns with the X-dir, Dir 2 with the Y-dir, and normal to the plane with the Z-dir.
Using Front, Right, and Top plane as reference geometry. The table lists the direction orientation with respect to the global coordinate system, when you select one of the Front, Right, or Top plane as a reference geometry.
Front Plane Dir 1 aligns with the global X direction.

Dir 2 aligns with the global Y direction.

Normal to the plane aligns with the global Z direction.
Right Plane Dir 1 aligns with the global Z direction.

Dir 2 aligns with the global Y direction.

Normal to the plane aligns with the global X direction.
Top Plane Dir 1 aligns with the global X direction.

Dir 2 aligns with the global Z direction.

Normal to the plane aligns with the global Y direction.
Coordinate Systems A coordinate system defines 3 directions, X, Y, and Z. The default coordinate system used by the software, called the global coordinate system, is based on Plane1 (Front Plane). The origin of the global coordinate system is located at the origin of the part or assembly. Plane1 is the top reference plane that appears in the FeatureManager design tree. The reference triad shows the global X-, Y-, and Z-directions. All other coordinate systems are referred to as local coordinate systems.

You can define a local coordinate system with Insert > Reference Geometry > Coordinate System.
Using a Reference Axis A reference axis defines a radial direction, a circumferential direction, and an axial direction. When applying restraints and loads, select the Show preview check box in the PropertyManager to identify the positive directions. Use negative values for the opposite direction.
When specifying a circumferential translation, you specify an angle (Θ) in radians. This sets the translation in the circumferential direction (v) to: v = r.Θ, where r is the radius of the node at which the restraint is applied relative to the reference axis.

When viewing deformation results with respect to a reference axis, the displacement vectors are reported as Ur, Ut, and UZ, where r represents the radial direction, t the tangential direction, and z the axial direction. This r- t -z system is with respect to each node’s original configuration.

Taking a quarter ring as an example, suppose that a node A is displaced from its original position to point B and the displacement vector at the end of a nonlinear solution is defined by u. The program reports for the radial displacement Ur a negative value in node A’s original radial direction and for the tangential direction a positive value Ut in node A’s original tangential direction. Note that Ur does not necessarily indicate an expansion (or contraction) of the ring and Ut does not indicate a rotation of the ring as well.

Using a Cylindrical Face This is similar to using a reference axis. The axis of the cylindrical face is used as the reference axis.
Using a Straight Edge A straight edge defines one direction. When applying restraints and loads, select the Show preview check box in the PropertyManager to identify the positive direction.