BIAXIAL HIGH CYCLE FATIGUE TESTS ON A GAS TRANSMISSION PIPELINE STEEL

— Gas transmission pipes are sometimes subject to external damage due to interference by excavators. Optimized grinding of gouges may offer a solution in repairing pipes. Since pipelines may be subjected to internal pressure variations, the Dang Van criterion has been used to size the allowable grinding depth. The criterion's boundary has been determined from uniaxial fatigue testing and extrapolated to the higher hydrostatic pressure which occurs in practice. The aim of this paper is to check by means of biaxial fatigue tests on specimens, that this extrapolation ensures a lifetime of 105 cycles for the ground pipes. The state of stresses in the central area of the biaxial specimen was calculated from an elastic finite element simulation. The test machine had independent motions of the two perpendicular axes of loading. The fatigue testing was limited to 105 cycles and was carried out at a hydrostatic pressure of 200 MPa. The results validated the extrapolation technique for the Dang Van criterion.