Neutron diffraction residual stress measurements on girth-welded 304 stainless steel pipes with weld metal deposited up to half and full pipe wall thickness

The residual stress distribution has been measured in two girth-welded austenitic stainless steel pipe weldments using time-of-flight neutron diffraction. One had weld filler metal deposited up to half the pipe wall thickness, and one had weld metal deposited up to full pipe wall thickness. The aim of the work is to evaluate the evolution in residual stress profile on filling the weld, on which there is little experimental data, and where the selection of the correct hardening model used in finite element modelling can benefit greatly from an understanding of the intermediate residual stresses partway through the welding operation. The measured residual stresses are compared with those calculated by finite element modelling and measured using X-ray diffraction. The results show a change in the measured hoop stress at the weld toe from tension to compression between the half-and fully-filled weld. The finite element results show an overprediction of the residual stress, which may be a consequence of the simple isotropic hardening model applied. The results have implications for the likely occurrence of stress corrosion cracking in this important type of pipe-to-pipe weldment

Residual Stress Measurements in Large Scale Component Sections

Neutron diffractometer Engin X at ISIS was used use in this study to investigate the residual stresses in a section of a multi pass girth welded thick pipe, of nominal thickness 62 mm, which was made of a ferritic martensitic steel denoted type P92. Measurements in such large component sections are rare, and have driven the neutron diffraction method to the edge of its capabilities. Significant stresses of over 150 MPa have been found in this pipe section, though post weld heat treatment has been performed. The influences of these welding residual stresses in components at operating temperatures are discussed in terms of their relaxation and high temperature fracture behaviou

The influence of quench sensitivity on residual stresses in the aluminium alloys 7010 and 7075

The most critical stage in the heat treatment of high strength aluminium alloys is the rapid cooling necessary to form a supersaturated solid solution. A disadvantage of quenching is that the thermal gradients can be sufficient to cause inhomogeneous plastic deformation which in turn leads to the development of large residual stresses. Two 215 mm thick rectilinear forgings have been made from 7000 series alloys with widely different quench sensitivity to determine if solute loss in the form of precipitation during quenching can significantly affect residual stress magnitudes. The forgings were heat treated and immersion quenched using cold water to produce large magnitude residual stresses. The through thickness residual stresses were measured by neutron diffraction and incremental deep hole drilling. The distribution of residual stresses was found to be similar for both alloys varying from highly triaxial and tensile in the interior, to a state of biaxial compression in the surface. The 7010 forging exhibited larger tensile stresses in the interior. The microstructural variation from surface to centre for both forgings was determined using optical and transmission electron microscopy. These observations were used to confirm the origin of the hardness variation measured through the forging thickness. When the microstructural changes were accounted for in the through thickness lattice parameter, the residual stresses in the two forgings were found to be very similar. Solute loss in the 7075 forging appeared to have no significant effect on the residual stress magnitudes when compared to 7010. (C) 2012 Elsevier Inc. All rights reserved

Residual stress in 7449 aluminium alloy forgings

The through thickness residual stress distributions within three 120 mm thick rectilinear forgings, made from the high strength aluminium alloy 7449 have been measured using both neutron diffraction and deep hole drilling. Neutron diffraction measurements were made on two instruments, one using a pulsed spallation neutron source, the other a steady state reactor source. Heat treatment of the forgings included a rapid quench into cold water and it was the residual stresses arising from this step that were initially measured. Neutron diffraction measurements indicated large magnitude (>250 MPa) tensile residual stresses in the centre of an as quenched forging, balanced by surface regions stressed in compression (<−200 MPa). Sufficient measurements were made to permit the description of the residual stress distribution using area maps. Two forgings were stress relieved by cold compression immediately after quenching. The degree of plastic strain was either 2.5% or 4%, and was applied by a single application of force in the short transverse direction. Cold compressed forgings were found to have far lower residual stress when compared to the as quenched condition. The amount of cold compression was found to cause an insignificant difference in the final residual stress distribution. The neutron diffraction results are compared to measurements made by deep hole drilling and a new incremental variation of the technique. The deep hole was drilled through the centre of the forgings in the short transverse direction. Multiple neutron diffraction measurements were also made on the extracted cores from the deep hole measurements to assess the variation of the unstrained lattice parameter through the thickness of the forgings

Validation of Predicted Residual Stresses within Direct Chill Cast Magnesium Alloy Slab

A significant level of cold cracking has been observed within direct chill (DC) cast, high-strength magnesium alloy Elektron WE43. These cracks have been attributed to the formation of significant residual stresses during casting. A finite-element modeling (FEM) code, which is called ALSIM, has been used to predict the residual stress within the DC-cast slab. Verification of the predicted residual stress field within an 870 x 315-mm sized slab has been carried out using neutron diffraction measurements. Given that measurements in such large-scale components using diffraction measurements are particularly challenging and expensive, the efficient use of neutron diffraction measurements is emphasized. This has included the use of sectioning, allowing the residual stress within the slab to be mapped in detail

Effectiveness of influenza vaccine against influenza A in Europe in seasons of different A(H1N1)pdm09 and the same A(H3N2) vaccine components (2016-17 and 2017-18).

Introduction Influenza A(H3N2) viruses predominated in Europe in 2016–17. In 2017–18 A(H3N2) and A (H1N1)pdm09 viruses co-circulated. The A(H3N2) vaccine component was the same in both seasons; while the A(H1N1)pdm09 component changed in 2017–18. In both seasons, vaccine seed A(H3N2) viruses developed adaptations/alterations during propagation in eggs, impacting antigenicity. Methods We used the test-negative design in a multicentre primary care case-control study in 12 European countries to measure 2016–17 and 2017–18 influenza vaccine effectiveness (VE) against laboratory-confirmed influenza A(H1N1)pdm09 and A(H3N2) overall and by age group. Results During the 2017–18 season, the overall VE against influenza A(H1N1)pdm09 was 59% (95% CI: 47–69). Among those aged 0–14, 15–64 and 65 years, VE against A(H1N1)pdm09 was 64% (95% CI: 37–79), 50% (95% CI: 28–66) and 66% (95% CI: 42–80), respectively. Overall VE against influenza A (H3N2) was 28% (95% CI: 17–38) in 2016–17 and 13% (95% CI: 15 to 34) in 2017–18. Among 0–14-year-olds VE against A(H3N2) was 28% (95%CI: 10 to 53) and 29% (95% CI: 87 to 73), among 15–64-year-olds 34% (95% CI: 18–46) and 33% (95% CI: 3 to 56) and among those aged 65 years 15% (95% CI: 10 to 34) and 9% (95% CI: 74 to 32) in 2016–17 and 2017–18, respectively. Conclusions Our study suggests the new A(H1N1)pdm09 vaccine component conferred good protection against circulating strains, while VE against A(H3N2) was <35% in 2016–17 and 2017–18. The egg propagation derived antigenic mismatch of the vaccine seed virus with circulating strains may have contributed to this low effectiveness. A(H3N2) seed viruses for vaccines in subsequent seasons may be subject to the same adaptations; in years with lower than expected VE, recommendations of preventive measures other than vaccination should be given in a timely manner

High-tech composites to ancient metals

Neutron diffraction methods offer a direct measure of the elastic component of strain deep within crystalline materials through precise characterisation of the interplanar crystal lattice spacing. The unique non-destructive nature of this measurement technique is particularly beneficial in the context of engineering design and archaeological materials science, since it allows the evaluation of a variety of structural and deformational parameters inside real components without material removal, or at worst with minimal interference. We review a wide range of recent experimental studies using the Engin-X materials engineering instrument at the ISIS neutron source and show how the technique provides the basis for developing improved insight into materials of great importance to applications and industry. © 2009 Elsevier Ltd. All rights reserved