AttachmentM-JohnFowler-MyCommittees.docVIP

Annex X (Informative) ASME Design Calculations X.1 General This annex describes the design analysis methodology used in the ASME Boiler and Pressure Vessel Code, Section VIII, Pressure Vessels, Division 2, Alternative Methods, Appendix 4, up to and including the 2004 version, as well as the ASME Code Section III, Nuclear Power Components. Methods are included for both elastic and elastic-plastic analysis, and for closed-form as well as finite-element analysis methods of calculation, in accordance with the rules of Appendix 4 of the 2004 Code, Section VIII Division 2. API has adopted slightly different stress limits from the 2004 ASME Code. For the purpose of this international standard, the basic stress limits are based on Sm and St, which are defined as follows: X.1.1 Sm, the design stress intensity For standard materials (36K, 45K, 60K, and 75K), the design stress intensity is 2/3 of the minimum specified yield strength Sy. For non-standard materials, the design stress intensity is the lower of 2/3 of Sy or ? of the ultimate tensile strength Su. X.1.2 St, the maximum allowable general primary membrane stress intensity at test pressure API limits this stress to 90% of the yield strength for all materials. X.2 Elastic Analysis For elastic analysis stress components are calculated, combined, and compared to limits for each category of stress based on multiples of the Design Stress Intensity, Sm, for the material in use and for the category of stress. Stress components are combined to find the stress intensity, which is defined as twice the maximum shear stress. This can be calculated as the difference between the largest and smallest of the three principal stresses. X.2.1 Stress Categories The following categories are used to classify stresses based on the consequences of exceeding the yield strength in various manners: X.2.1.1 Primary Stress The basic characteristic of primary stress is that it is not self-limiting, and failure, or at least gross distortion, c