The stress distribution around a 50% blind-hole pit in a steel pipe with a 9 mm wall has been studied using high-resolution magnetic Barkhausen noise (MBN) measurements. A magnetic disk read-head is used as the pick up coil in the MBN probe. The study shows a stress concentration factor of ∼2 at the defect edge perpendicular to the direction of applied stress and ∼−0.6 at the edge parallel to the same. The experimental results are consistent with the analytical solutions obtained by the Airy’s stress function approach.
The formation, structure, and the crystallization of Al85YxNi15−x are studied using x-ray diffraction and differential scanning calorimetry. The results show two distinct glasses depending on composition. Y-rich glasses (x≥8) are homogeneous with a well-defined glass transition. The x-ray diffraction patterns have a single main peak. These glasses crystallize through a nucleation and growth process. Y-poor glasses (x<8) do not show a glass transition and have a shoulder on the high-angle side of the main peak in their x-ray diffraction patterns. We show that the shoulder peak is due to quenched-in Al nuclei. These glasses are shown to crystallize through the growth of these nuclei. Y-rich glasses (x≥8) are more stable as demonstrated by the presence of the glass transition and their higher crystallization temperature, enthalpy, and activation energy. The occurrence of a prepeak for all compositions is attributed to Y-Y pairs.
Mechanical properties for two series of amorphous Al–Y–Ni ternary alloys were measured. Both series of alloys can be divided into two distinct groups. Those whose primary crystallization proceeds by growth of quenched-in Al nuclei and those which show a clear glass transition and their crystallization product is more complex. The Young’s modulus, ranging from 82.3 to 45.5 GPa in these series of alloys, is found to be correlated to the crystallization temperature and thermal behavior as well as the crystallization product implying that the mechanical properties depend on the short-range order in the glass.
The most commonly used in-line pipeline inspection tools utilize the magnetic flux leakage (MFL) technique, which is sensitive to the stress state of the pipe wall. Calibration of these MFL tools is often carried out using unstressed pipeline sections containing simulated defects, usually produced by mechanical drilling. There is also strong interest in creating simulated defects in stressed pipe walls, thus simulating corrosion in the field. In this study, neutron diffraction is used to map the local stresses surrounding mechanically and electrochemically drilled holes in a steel plate sample. Holes were drilled in unstressed samples, as well as samples held at a constant 80 MPa uniaxial stress. Mechanical drilling into a stressed sample was found to induce considerable residual stresses around the hole. Conversely, electrochemical drilling did not create a residual stress field in the vicinity of the hole.
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