Magnetic Barkhausen Noise and neutron diffraction techniques for the study of intergranular residual strains in mild steel

Intergranular residual stresses (IS) are microscopic residual stresses which have been found to accumulate along the \u3008100\u3009 direction in steels. The \u3008100\u3009 direction is also the magnetic easy axis direction in steel. This work involved Magnetic Barkhausen Noise (MBN) studies on steel samples, deformed uniaxially to increasing levels of strain. The MBN results indicated that a bulk magnetic easy axis was produced by the deformation process, and neutron diffraction experiments showed that this easy axis was correlated with the tensile strain in grains oriented in the \u3008100\u3009 direction.Peer reviewed: YesNRC publication: Ye

Neutron diffraction investigation of fluid end cracking in well stimulation pump fluid ends

This paper summarizes a study involving residual stress measurement in a cracked fluid end section from an industrial well stimulation pump. In order to withstand extremely high operating pressures, fluid ends typically are autofrettaged to introduce residual compressive stresses in stress concentration areas. In this study, neutron diffraction measurements were conducted on a cracked fluid end section to determine if these compressive stresses were still present or whether they had disappeared during the service lifetime of the component. Our work found that despite the fact that cracking had occurred, significant levels of residual stress were still present in the component. The cracking was attributed to a gouge in the suction inlet region, well away from the position of high compressive residual stresses.NRC publication: Ye

Surface Barkhausen Noise Investigations of Stress and Leakage Flux Signals in Line Pipe

Pipelines are subjected to a number of different sources of stress. The principal in-service stress component is due to line pressure, with operating stresses commonly about 60% of the yield strength. Pipelines may also be subjected to considerable bending stresses, particularly when constructed on unstable terrain such as permafrost. Residual stresses may also be present, generally resulting from processing or welding, but more seriously as a consequence of mechanical damage. Anomalously high stress levels, whether residual or applied, may lead to pipeline failure; as a result serious efforts are being made to develop on-line stress detection methods. It is well established that stress is a major factor affecting magnetic properties of ferromagnetic materials, however the effects are complex and have only recently begun to be understood [1,2]. Because of the strong influence of stress on magnetic properties, magnetic NDE techniques are being considered as potential methods for the detection of stress

Neutron diffraction residual stress mapping in same gauge and differential gauge tailor-welded blanks

Neutron diffraction has been used to determine the residual stresses in the weld region of laser-welded tailor-welded blank (TWB) samples. Residual stresses in same gauge and differential gauge TWB samples are examined in the as-welded condition as well as after uniaxial loading to 0.5, 3.0 and 7.0% strain. Results indicate that stress distributions can be quite complex, particularly following deformation. Overall, however, two major conclusions were drawn: first, residual stresses around laser welds in these TWBs tend to be small compared with stresses reported for conventional welding processes. Secondly, inmost cases the peak residual stresses tend to remain the same or diminish with subsequent deformation