API TR 21TR2 PDF

The scope of the test program was to obtain bolting material fatigue data required to perform design verification analysis of bolting subjected to fatigue loading to assure accurate design life estimation. The bolting fatigue testing program provided S-N fatigue curves for three alternating stress ranges in air and in saltwater with CP environments and for bolt sizes of 1 in., 2 in. (Grade L7), and 3 in. (Grade L43) in Phase I and for bolt sizes 1 in. (Grade L7) and 3 in. (Grade L43) in Phase II.

The results of these S-N fatigue tests allow the bolting design to be assessed for S-N fatigue through structural analysis using the nominal root area stresses in the bolt, avoiding the need to define stress and load concentrations in the bolt root radius of engaged threads.

The design guidelines and the fatigue data provided in the document are intended to be used for bolting with unified national thread with root radius (UNR) specifications of ASME B1.1 Class 2A/2B.