Pressure vessels metal fatigue

All of the EDTs evaluated in this report have withstood hundreds to thousands of detonations in their respective chambers and vessels and in no case was a chamber wall breached as a result of stress cracking or metal fatigue. Both the TC-60 TDC and the DAVINCH DV65 have been found to be in compliance with ASME Boiler and Pressure Vessel Code Case 2564, for impulsively loaded pressure vessel. This code calls for protection against both ductile and brittle failure— that is to say, there should be demonstration of stability against flaws for cracks caused by fragments resulting from detonations. 

Pressure vessels are also subject to cyclic stress. Cyclic stress arises from pressure and/or temperature cycles on the metal. Cyclic stress can lead to fatigue failure. Fatigue failure, discussed in more detail in Module 5, can be initiated by microscopic cracks and notches and even by grinding and machining marks on the surface. The same (or similar) defects also favor brittle fracture. 

The set burst pressure should be selected to permit a sufficiently wide margin between it and the vessel s used or design operating pressure and temperature to avoid premature failure due to fatigue or creep of metal or plastic coatings. 

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