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2.2.9 Tutorial 9 - ASME Sec VIII Div 2 Presssure Vessel Welded Shell

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This tutorial provides a step-by-step demonstration for ASME Section VIII Division 2 weld fatigue analysis using Fatigue+.

 

A pressure vessel goes through a loading and unloading process.  The shell of the pressure vessel is made of ASME SA-516 Grade 70.  The pressure vessel is designed to ASME Section VIII Division 2 Class 1 vessel.

 

The fatigue life of a weld in shell needs to be evaluated.  Membrane stress and bending stress are required for fatigue assessment of welds.  The shear stress is for multiaxial fatigue when the structural shear stress range is not negligible.

 

The stresses reach the following values when loaded with 640.4oF fluid, and drop to zero when unloaded:

 

Membrane stress:      21.25 ksi

Bending stress:          18.65 ksi

Shear stress:             12.62 ksi

 

The crack face pressure should be specified because the maximum value of the membrane plus bending stress used in the analysis occurs on a surface that is exposed to the fluid pressure.  The crack face pressure is 2.7 ksi.  Add this value to membrane stress for data entry purpose, and the stresses to be entered become:

 

Membrane stress:      23.95 ksi (including 2.7 ksi crack face pressure)

Bending stress:          18.65 ksi

Shear stress:             12.62 ksi

 

The pressure vessel wall thickness is 3 inches.  Hammer peening technique is used to improve fatigue life of the vessel. The weld is made of good quality; crack-like flaw does not exist in the weld.

 

Calculate fatigue life of the weld in the pressure vessel.

 

 

 

 

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