Correlation of Pipe Ring Notched Bend (PRNB) specimen and Single Edge Notch Bend (SENB) specimen in determination of fracture toughness of pipe material

It is well known that pipes or tubes due to their geometry are not suitable for producing standard specimens for fracture toughness testing (e.g. Single Edge Notched Bend (SENB) specimens or Compact Tension specimens. This is especially evident in thin walled pipes or tubes. We propose a new type of specimen, called Pipe Ring Notched Bend (PRNB) specimen, which is ideal for pipes or tubes due to its ring geometry. 1 In the recent years, the authors have made a lot of research on this type of specimen, but cut out from a plate, not from pipes, where some imperfections in the geometry, material, residual stresses, etc. are present. Within this paper, two PRNB specimens (designations PRNB1 and PRNB2) are cut out from pipe which is used in boilers and made from 16Mo3 steel. From the same pipe, four SENB specimens (designations SENB1, SENB2, SENB3 and SENB4) are also made in order to compare the fracture behaviour of standard SENB and newly proposed PRNB specimens.