Finite Element Analysis General Notes

At PVEng we use SolidWorks Simulation for multiple uses. This is a collection of tips and tricks we use to get the most out of Simulation.

Disclaimer: This page is the OPINION of Pressure Vessel Engineering Ltd and is provided for educational purposes only. The practices discussed on this page are always being updated. We cannot guarantee that the methods presented here are accurate or current.

	ASME VIII-2 Permissible Cycle Life The permissible cycle life of a pressure vessel is mainly dependent on the material used and the stress level but a number of other factors are involved. This sample shows how to use the ASME VIII-2 rules to calculate permissible cycle life in converged and non-converged areas.
	Origins of the ASME Fatigue Life Curves How do ASME permissible fatigue curves compare to actual fatigue life results? Can they be used to predict the expected life of equipment?
	Half Bolt Connectors in SolidWorks Simulation Design and analysis of flanges in SolidWorks simulation often requires the use of a half bolt connector. This feature is available from the "Connections" group in the simulation tree.
	SolidWorks Simulation File Format SolidWorks Simulation (SWS) results are stored in a proprietary *.CWR format. SWS creates intermediate files during the analysis and combines them in the CWR file at end of run. SWS uses the standard Microsoft IStorage interface to create the CWR file.
	Simulating Heat Exchanger Tubes with Springs Heat exchangers are often very large models. In order to simplify them for FEA we remove all of the tubes and replace them using springs. This significantly reduces the complexity of the mesh.
	Creating NPT Connections for Piping Fittings The best way to analyze NPT threaded piping fittings using FEA methods is with the pipe included in the analysis. Pressurizing the pipe transmits realistic stresses to the fitting body.
	Simplification of FEA by Symmetry FEA model sizes and run times are reduced by finding symmetry.
	Simplification of Multi-Body FEA Models Simplification of FEA can come from the use of symmetry, bonding items that are not sliding, use of mesh control, replacing gaskets with gaps and forces and the use of classical calculations.
	Finite Element Analysis Reaction Forces FEA results are not valid unless the model is in balance! This report shows typical methods used for restraining models and compares the resulting displacement and stresses of identical models both in balance and out of balance.
	Error Plots - Bolt Heads & Surface to Surface Contacts Error plots show how well the complexity of a mesh matches the complexity of the model. Once the mesh matches the complexity of the model, the reported error is low. As a guideline, Pressure Vessel Engineering uses 5% error as an acceptance criterion.
	The Nuts and Bolts of Stress Linearization Linearization separates FEA stresses into membrane and bending. Examples are provided along with sample data and a spreadsheet based stress linearization tool.
	SCL Passing Through Areas of Very High Error Stresses at sharp corners rise towards infinity as the mesh size is reduced. However the forces have to balance in a Finite Element model regardless of the mesh size used. In these studies SCL (Stress Classification Line) results are compared a different mesh sizes
	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.
	Riveted Vessels This digester has been in use since 1926. Vessels built in that time period were typically constructed with riveted butt joints
	Evil SolidWorks Factory Default Material Properties When a new object is created, SolidWorks specifies that the material is <not specified>. However, if the item is evaluated, it has a factory default material density of 0.04 lb/cuin (1000 kb/m^3) or the density of water. The appropriate material density would be "!Error - material density is not set!".
	When will FEA be Required in a Submission? Finite Element Analysis (FEA) can sometimes be used in a CRN submission when code equations cannot be directly applied to the configuration and/or when additional reinforcement needs to be accounted for to obtain acceptable stress values.
	Setting Up Presentation Screen Shots for FEA Reports This article supplements ABSA's requirements on writing FEA reports: ABSA FEA Requirements. In particular refer to the section "Presentation of Results".
	Reduce your Mesh Time Splitting a complex component into multiple smaller components can reduce the mesh time.
	Mesh Tolerance Settings Setting the standard mesher tolerance incorrectly can make some external features disappear. Meshing can fail on internal features.
	Using the Error Function Results for Areas 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 This report examines the accuracy of stress results near an area of discontinuity as the mesh is refined.
	Why Use 2nd Order Integration Elements? This is part of a series of articles that examines the ABSA requirements on writing FEA reports. The use of 2nd or higher order elements is one of the requirements.
	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 (previous topic)..
	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.
	Solution for Long Mesh Time of Shells When meshing shells, the mesh gets up to 99% and then hangs for a very long time sometimes for hours depending on the mesh size...
	FEA Submission Requirements Finite Element Analysis (FEA) can sometimes be used to support pressure equipment design submissions where the configuration is not covered by the available rules in the ASME code.
	SolidWorks Simulation Validation Examples SolidWorks Simulation has a number of validation problems built into the software. These problems are designed to prove the validity of its operation.