Show Shell Force Stress Plots

Use the Home > Display > Show Shell Force/Stress Plots command to display internal area object forces and stresses on the active window.

Important note: The internal shell element forces are forces per unit length acting along the midsurface of the shell element (area object). The internal shell element stresses are stresses acting on the edges (not positive 3-axis face and negative 3-axis face) of the shell element (area object). See Sign Conventions for more information about the faces of shell objects.

Click here for information about possible components of the shell element internal forces.

1. - F11: Direct force per unit length acting at the midsurface of the element on the positive and negative 1 faces in the 1-axis direction.
  - F22: Direct force per unit length acting at the midsurface of the element on the positive and negative 2 faces in the 2-axis direction.
  - F12: Shearing force per unit length acting at the midsurface of the element on the positive and negative 1 faces in the 2-axis direction, and acting on the positive and negative 2 faces in the 1-axis direction.
  - FMAX: Maximum principal force per unit length acting at the midsurface of the element. Note that by definition, principal forces are oriented such that the associated shearing force per unit length is zero.
  - FMIN: Minimum principal force per unit length acting at the midsurface of the element. Note that by definition, principal forces are oriented such that the associated shearing force per unit length is zero.
  - FVM: See Von Mises Stress
  - M11: Direct moment per unit length acting at the midsurface of the element on the positive and negative 1 faces about the 2-axis.
  - M22: Direct moment per unit length acting at the midsurface of the element on the positive and negative 2 faces about the 1-axis.
  - M12: Twisting moment per unit length acting at the midsurface of the element on the positive and negative 1 faces about the 1-axis, and acting on the positive and negative 2 faces about the 2-axis.
  - MMAX: Maximum principal moment per unit length acting at the midsurface of the element. Note that by definition, principal moments are oriented such that the associated twisting moment per unit length is zero.
  - MMIN: Minimum principal moment per unit length acting at the midsurface of the element. Note that by definition, principal moments are oriented such that the associated twisting moment per unit length is zero.
  - V13: Out-of-plane shear per unit length acting at the midsurface of the element on the positive and negative 1 faces in the 3-axis direction.
  - V23: Out-of-plane shear per unit length acting at the midsurface of the element on the positive and negative 2 faces in the 3-axis direction.
  - VMAX: Maximum principal shear per unit length acting at the midsurface of the element. Note that by definition, principal shears are oriented on faces of the element such that the associated shears per unit length on perpendicular faces are zero.

Click here for information about the possible components for shell element internal stresses.

1. - S11: Direct stress (force per unit area) acting on the positive and negative 1 faces in the 1-axis direction.
  - S22: Direct stress (force per unit area) acting on the positive and negative 2 faces in the 2-axis direction.
  - S12: Shearing stress (force per unit area) acting on the positive and negative 1 faces in the 2-axis direction and acting on the positive and negative 2 faces in the 1-axis direction.
  - SMAX: Maximum principal stress (force per unit area). Note that by definition, principal stresses are oriented such that the associated shearing stress is zero.
  - SMIN: Minimum principal stress (force per unit area). Note that by definition, principal stresses are oriented such that the associated shearing stress is zero.
  - SVM: Von Mises stress (force per unit area).
  - S13: Out-of-plane shearing stress (force per unit area) acting on the positive and negative 1 faces in the 3-axis direction.
  - S23: Out-of-plane shearing stress (force per unit area) acting on the positive and negative 2 faces in the 3-axis direction.
  - SMAXV: Maximum principal shearing stress (force per unit area). Note that by definition, principal shearing stresses are oriented on faces of the element such that the associated shears per unit length on perpendicular faces are zero.

The program spaces the intermediate range values equally between the specified Min and Max values. If the Min and Max values are set to zero, CSiBridge will automatically create a contour range that includes all values. This is the default. Click the Set To Default Contour Range button to apply the default values

The options available for stress averaging are None for no stress averaging, At All Joints for stress averaging at all joints or over Objects & Groups for stress averaging at points selected just before plotting the shell forces or stresses, or for stress averaging of groups selected using the Set Groups button.

If the None option is used so that the force or stress contours are plotted with no stress averaging at the common points, the changes in force or stress from element to element typically will appear abrupt. Large stress variations between elements may indicate that the model is not properly meshed and may need to be refined to properly capture the variation in stress. Therefore, use this option to determine if the model is meshed properly.

Stress averaging using the At All Joints or over Objects & Groups option tends to eliminate abrupt changes in the plot and smooths the contours. Thus, after the meshing of the model has been shown to be acceptable using the None option, the At All Joints option will give better results of the stress in the elements by averaging the stress between elements and reducing the error because of the stress on each individual element. The over Objects & Groups option should be used if a discontinuity, such as two planes meeting at an angle, is included in the model. In that case, each plane should be averaged independently using the over Objects & Groups option. This will avoid the problem of averaging across the two planes, which would give incorrect result. The results would be incorrect because the stress along the two planes is not continuous relative to the elements' local axes.

Note: Shell element stresses (not forces) actually have different values at the top and bottom of the shell elements as a result of bending. Thus, depending on which side of the object is being displayed, different stresses will be shown. Two-dimensional views always look at area objects from the same side. To view stresses on the other side of the area object, switch to a 3D view or right click on the object while stresses are displayed to access the Shell Diagram form and click the Switch Face button.

Note: When forces or stresses are plotted for multi-valued combinations, CSiBridge displays whichever of the maximum and minimum values has the largest absolute value.