The stress evaluation by elastic analyses for protection against plastic collapse in appendix 9 is based on maximum shear stress theory (Tresca theory). On the other hand, the stress evaluation by elastic-plastic analysis and design equations by flow stress for design pressure for cylindrical shell and spherical shell in KD-221 is based on distortion energy yield stress theory (Mises theory). Especially for materials with low and intermediate Sy/Su, the primary stress evaluation based on Tresca criterion for elastic analysis in current Div.3 is excessively conservative than that based on flow stress equations similar to elastic-plastic analysis from experimental results.　In Section VIII Div.2, Mises yield criterion is used for stress evaluation for elastic analysis because it matches experimental results more closely than Tresca yielding criterion and is also consistent with plasticity algorithms used in elastic-plastic analysis. Therefore in Div.3 Mises criterion should be used for elastic analysis same as in Sec. VIII Div.2.　For materials with high Sy/Su, the primary stress evaluation based on Mises criterion for elastic analysis is less conservative than that based on flow stress equations similar to elastic-plastic analysis because of difference of design factor 1.5 for elastic analysis and 1.732 for flow stress equations.　Therefore, it is proposed to use Mises criterion for protection against plastic collapse with design correction factor using Sy/Su in Appendix 9 in order to remove excessive conservativeness for materials with low and intermediate Sy/Su.　The validity of this proposal is shown in this paper.


Proposal of Use of Mises Criteria for Elastic Analysis in Appendix 9 of Asme Section Viii Division 3

Division / Sponsors: 
Pressure Vessels & Piping (PVP)


Paper Proceedings: https://asmedigitalcollection.asme.org/PVP/PVP2020/volume/83815

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