F. Rauscher, S. Schindler:

"Design Check against Global Plastic Deformation - Determination of the Maximum Allowable Pressure by FEA";

Talk: WCCM V, Wien; 2002-07-07 - 2002-07-12; in: "WCCM Fifth World Congrss on Computational Mechanics Vol. II", Vienna University of Technology, Vol II / Vienna (2002), ISBN: 3-9501554-2-2.

In the pressure vessel field, Annex B of the proposal of CEN's Unfired Pressure Vessel Standard, prEN 13445-3[1], Direct Route for Design by Analysis [2, 3, 4, 5, 6], involves new ideas: Failure mosed are directly addressed in corresponding design checks, using models with non-linear constitutive laws - linear-elastic ideal-plastic.

This article addresses the Design Check against Global Plastic Deformation (GPD-DC) according to prEN13445-3 Annex B - Direct Route. In this approach, the design values of the actions shall be carried by a design model with first-order-theory, a linear-elastic ideal-plastic constitutiv law, Tresca's yield condition and associated flow rule and a maximum absolute value of the total principal structural strains not exceeding 5% (in normal operation load cases).

The maximal allowable pressure, which is the maximum pressure carried by the model described above divided by the appropriate partial safety factor, is evaluated for some simple verification examples, for the closed an open cylinder, the ideal sphere and a nozzle in a sphere.

The examples are analyzed using non-linear FE-analysis with volume and shell elements and the results are compared with analytical results, as far as available. Mesh variations from very fine to very coarse are performed to obtain hints for the necessary mesh density for typical pressure vessel parts. The goal is to find the right options, to compare different ways of determining the structural values of the limiting maximum total principal strains and to obtain verification examples.

As stated above, for this design check Tresca's yield condition is prescribed. To render conservative results by using Mises' yield surface, it is necessary to multiply the yield strength of the model by a factor of √3/2. Therefore, the Mises yield condition is considered as well as the Tresca yield condition.

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