# FEA Methods Blog

This collection of articles covers a variety of methods used in Finite Element Analysis (FEA). Topics include applying flange loads, creating connections, analyzing rivets and methods of simplification.

### Flange FEA

This basic sample illustrates how FEA is used to validate a flange design that cannot be calculated with standard VIII-1 Appendix 2 code rules due to the shape of its hub. Standard Appendix 2 loads are applied and assessed against the rules of ASME VIII-2 for full code compliance.

The process in this vessel required a reverse dished head. The reverse dished head could not be fabricated thick enough to meet the ASME VIII-1 rules. The chosen solution was to reinforce the head with ribs to prevent snap through. Various alternate methods of analysis are shown here. Only the plate analysis was used for the actual job, however the comparison of the various methods is educational.

### Riveted Vessels

This digester has been in use since 1926. Vessels built in that time period were typically constructed with riveted butt joints.

### Linear Multi-Body Analysis

Connections such as flanges, tri-clamps and any other multi-body assemblies are analyzed using FEA. This example shows a Tri-Clamp connection under internal pressure and describes how FEA is used to provide insight into the interaction between components.

### Simplification of FEA by Symmetry

FEA model sizes and run times are reduced by finding symmetry.

### NozzlePro FEA

This vessel has a large nozzle located on the straight shell with large loads and moments specified by the customer. NozzlePRO has been used to generate the model, apply loads, calculate the resulting stresses and provide a pass/fail assessment. The NozzlePRO results are much more accurate than using WRC-107 methods.

### Finite Element Analysis Reaction Forces

Reaction forces are the resulting loads seen at the restraints of a model being analyzed. They can be used to ensure an analysis is restrained from rigid body motion, and is static or in balance. The reaction forces are equal and opposite to the sum of the applied loads. Unless they are right, the results cannot be trusted.

### Why Use 2nd Order Integration Elements?

Use of 2nd order integration elements is more than a requirement, it also produces the best results.

### Large Displacement Solutions

This solar reflector uses a vacuum to pull the front and back surfaces together to focus the reflective surface. The deflected surface shape can be calculated using FEA, but the correct shape can only be computed with large deflection theory.

### Error Plots – Bolt Heads and Surface to Surface Contacts

Two common areas of high error in a FEA report are under bolt heads and at surface to surface contacts. This article explains in more depth why this happens.

### FEA Submission Requirements

Finite Element Analysis (FEA) can usually be used to support pressure equipment design submissions where the configuration is not covered by the available rules in the ASME code. Requirements vary by province.

### Mesh Refinement at Discontinuities

Error plots show how well the complexity of a mesh matches the complexity of the model. Once a match is made the reported error is low.

### Mesh Refinements Near Discontinuities

his report examines the accuracy of stress results near an area of discontinuity as the mesh is refined.

### Surface Model Mesh Challenges

>Surface models can be challenging to mesh. Parts that touch might not share nodes preventing the correct transfer of loads. The resulting calculated stresses and displacements can be wrong.

### Easier Surfaces

Surfaces can be challenging to create, but solids are easy to convert into surfaces. Surfaces originally created as solids do not have the problem of nodes not joining at edges

### Solid Model Mesh Challenges

Sometimes a multibody model refuses to mesh with the standard mesher. Regardless of the element size and tolerances used, some parts refuse to bond.

### Mesh Tolerance Settings

etting the standard mesher tolerance incorrectly can make some external features disappear. Meshing can fail on internal features.

### Solution for Long Mesh Time of Shells

When meshing shells using SolidWorks Simulation, the mesh gets up to 99% and then hangs for a very long time sometimes for hours depending on the mesh size…