WRC-297 Checking in caesar

When checking for local load stresses in nozzle/vessel junction using WRC297, we model nozzle thru' WRC297 nozzle input pallete. This defines flexible restraint at the defined nozzle junction. We can then export the loads into 297 module to calculate the shear stress values for circumferential & longitudinal planes in the vessel membranes & nozzle.

However, unlike WRC107, we do NOT get the stress summation for these components. However, for all these components, we get 2 times the maximum shear stress intensity values. Does this mean that these shear stress intensity values at the 4 points on the membrane, have to be compared with the yield stress value directly (per MAX. SHEAR STRESS THEORY) and not go for stress summations? Also what about the Hoop stress value? OR should the PRINCIPAL stresses be further computed manually ny summing up the [(hoop stress + Long. stress*)/2] term to the sqrt[(long. stress*-hoop stress)/2 + 2* max shear stress intensity] and then compare this value with the yield stress?

* considering that long. stress = axial stresses along the longitudinal plane ???

Mr.Menon,

Few days back I replied to an identical question from Mr. Nikhil Dengwekar which you can find in the discussion forum.

First, there is nothing known as two times max. shear intensity.Shear intensity itself is defined as two times max. shear which again is equal to (max.-min. principal stress)/2, hence shear intensity is (max-min.)principal stresses.

Next, neither WRC 107 nor 297 tells us how to add stresses of different categories . They only give you series of non dimensional curves based on which you arrive at membrane and bending stresses for different types of loading.

Your addition of stresses will be strictly based on the guideline given in ASME Sec VIII Div 2 appendix 4.Here you will not only get the definition of different terminologies pertaining to stress categories , but also the way you have to combine them and the allowable against which such combinations will be checked.

You cannot have any self imposed method of ckecking as you have suggested.Do not take any simplistic path as it violates the code requirements.

To take the story further go through the paper titled "Criteria of the ASME Boiler and Pressure
Vessel Code for Design by Analysis in Sections III and VIII Division 2"published by ASME in 1969.This paper gives the background theory for arriving at the recommendations given in DIV 2 APPENDIX 4.

Regards

A.BHATTACHARYA

Stress Analyst

Bechtel Corporation