Linearizing Stress Results (Pressure Vessel Studies)

Stress linearization separates the bending and membrane stress components from the actual stress distribution observed through the thickness of a wall in a sectional stress plot of a pressure vessel study.

The methodology of stress linearization is according to the American Society of Mechanical Engineers (ASME) International Boiler and Pressure Vessel Code ASME BPVC-VIII-2. The functionality is used for solid meshes only. For shells, you can plot and list membrane and bending stresses separately.

Stress linearization provides an idealization of the actual stress variation through a wall thickness. A membrane stress component is constant through the thickness, whereas a bending stress component varies linearly through the thickness. A non-linearized stress component is referenced as the Peak stress.

1	Inner wall boundary
2	Midplane
3	Outer wall boundary
4	Membrane stress component (green dotted line denotes membrane stress)
5	Bending stress component (blue dotted line denotes bending + membrane stress)
6	Peak stress, non linearized stress component (red solid line denotes actual stress)

1. Create a pressure vessel study and combine the results of static studies with the required factors.
2. Run the pressure vessel study and define a planar sectional stress plot. You can plot any stress component. Stress linearization uses stress results available for all components regardless of the plotted quantity.
3. Right-click the stress plot and select Linearize.
4. In the PropertyManager under Locations , click two locations on the section.
   • For accurate results, the line connecting the two locations must be normal to the wall thickness, and fully lie on the material. It may not pass through holes or areas where results do not exist.
   • The two locations must belong to different elements of the same body. All locations along the stress linearization path (including intermediate points) must belong to the same body. Reference points are not valid selections for a stress linearization path.
5. Enter the Number of intermediate points to define the resolution of the graph along the line. The software interpolates stress results at the intermediate points.
6. Click Calculate.
   A summary lists the linearized stress results at the two locations. You can view the full range of results, including intermediate points, using the Report Options described below.
   Simulation reports the stress tensor of six components based on the local coordinate system defined by the Stress Classification Line (SCL). The SCL line is oriented normal to the midsurface of the wall thickness.
   
   

   • N: Normal vector or Meridional
   • T: Tangential vector from the inner to the outer wall
   • H: Hoop vector normal to the section plane
7. Under Report Options, you can click:
   • Save As Sensor to save the locations as sensors.
   • Save to save the results to an Excel .csv file or text .txt file. The .csv file contains all the stress components in the Global Coordinate System, and also in the SCL Coordinate System
   • Plot to graph the results.
   • Save the data and show in Report .