R5, Assessment procedure for the high temperature response of structures

R5 is a procedure for the assessment of high temperature plant where creep starts to become significant. The intent throughout R5 is to avoid, wherever possible, the complication of full inelastic computer solutions using finite element methods. A concept used in R5 is that of the reference stress which is a convenient way of normalising the non-linear response of structures. Calculation of the reference stress is based on limit and shakedown analysis. In this way the calculations required to carry out an R5 assessment are similar to the calculations required for a low temperature assessment; in particular, for defect assessments the calculations are similar to those in the defect assessment procedure R6.

 R5 is actually a set of procedures that address different situations including the assessment of defect free structures and welded junctions.

The R5 Procedure, R5 Issue 3 has now been released.

R5 addresses a number of failure modes including:-

·            excessive inelastic deformation

·            ratchetting or incremental growth

·            rupture by accumulation of creep damage

·            initiation of cracks by creep and fatigue damage

·            excessive crack growth

·            failure of dissimilar metal welds by creep and creep-fatigue mechanisms