Simplification of Multi-Body FEA Models

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An analysis can become more complicated than it needs to be when the model is composed of multiple bodies interacting with each other.

Simplifications discussed:
	1) Symmetry
	2) Bonding Bolt Heads
	3) Mesh Control
	4) Gasket Space
	5) Classical Calcs
Cut along plane of symmetry
1) Symmetry - As with many analyses, this valve by Stainless Valve Company can be simplified by cuts along the two planes of symmetry as shown. The valve is symmetrical left to right and front to back.
Bonding bolt heads
2) Bonding Bolt Heads - In many cases, the interaction between components can be considered "bonded" instead of using sliding contracts, which reduces calculation time. For this example, the bolt heads were considered bonded to their mating surface. Artificial stresses are generated by the method of preload approximation, and these stresses should be neglected.
Mesh control
3) Mesh Control - A smaller mesh size was only used in the areas requiring greater calculation refinements (bolts). This improves calculation time while maintaining accuracy. The weldneck flange and its bolts have a coarser mesh because they are covered by classical calculations, as noted in section 5 below.
Gasket space
4) Gasket Space - This model contains a gasketed flange, which has been approximated in the FEA by a representative space between the flange and plate. To simulate the gasket loads, ASME VIII-1 Appendix-2 forces were applied to both the flange and the plate. Since the bolts are bonded to the outer surface of the flange, one continuous mesh was created. Instability of indivual pieces which can extend run times has been avoided.
Classical calculations
5) Code Calcs - The weldneck flange and its attachment bolts are covered by ASME VIII-1 Appendix 2 calculations and do no require a detailed FEA analysis. The flange and its bolts are included to simulate the interactions with the valve, but are hidden in this view for clarity.
Photo of stainless steel valve
This product is registered in Canada based on Finite Element Analysis.

A special thanks to Stainless Valve Co. Stainless Valve Co. for allowing us to use the geometry of their Stargate O Port Valve for this exercise.