Significance of non-destructive tests of compression joints

The manner in which an initially sound compression joint fails in service is discussed, and it is suggested that one of the most important parameters affecting the life is the running temperature of the joint. It is the temperature near the contact areas which is vital, and this can, under certain circumstances, differ markedly from the bulk temperature of the joint. It is shown that in a typical joint the regions near the contact areas within which the dangerous local high temperatures occur are so small that the temperature follows the oscillations of a 50c/s current.