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The application of bonded 'straps' has been proposed for extending the fatigue life of aircraft structures, particularly for integral structures with low inherent crack-retarding capability. A potential disadvantage in the use of bonded crack retarders is the difference between the coefficients of thermal expansion between the strap and substrate materials, which causes residual stresses when the temperature deviates from the curing or assembly temperature. The evolution of these stresses in flight is important to take into account to accurately assess the fatigue crack growth behaviour of the structure. In this work, the residual strains in an aluminium compact-tension sample adhesively reinforced with a titanium strap have been measured with neutron diffraction and modelled with a finite element approach at room temperature and at −50 °C. It was found that a linear elastic approach could accurately be used to predict the residual stresses. The residual stresses were found to be about twice as large at −50 °C as at room temperature. [ABSTRACT FROM AUTHOR]

The article focuses on the safety measures in handling reactors during a nuclear production. It cites the plan of France to build a prototype Sodium Cooled Fast Reactor (SFR), estimated to be operated in 2020. It mentions several reactor designs including Very High Temperature Reactor (VHTR), the SFR and the Lead-cooled Fast Reactor (LFR).

The article focuses on the performance of component materials for nuclear power and processing plants. According to the authors, as soon as the plant starts to operate, the component materials used for the plant will start to degrade because of mechanisms caused by stress and the environment. It notes that remote monitoring techniques and reliable predictive methods are needed to fully understand the processes of such degradations.

In this paper, we present results of residual stresses around a cold-worked fastener hole in a thin, finite plate. An analytical model, with plane stress conditions, elastic nonlinear–plastic loading and unloading taken into account, is explicitly presented and has been developed from existing analytical models and methodologies. The solution also accounts for elastic deformation of the mandrel, and is applicable to different sizes of hole and mandrel. A parametric study of the strain-hardening exponent, plate size, Bauschinger parameter and expansion ratio was carried out in the context of the present solution. A sample study of a plate subjected to 4% hole-cold expansion was performed to compare this model with other analytical predictions, finite element simulation and X-ray diffraction experimental results. A brief review of related issues is given. This work is intended to present completely the closed-form equations able to generate residual stress profiles with ease around a cold-expanded hole in a thin, finite plate where boundary conditions are at issue. [ABSTRACT FROM AUTHOR]

Powder metallurgy is a potentially attractive route for producing metal matrix composites. In order to optimize the mechanical properties and processing route, it is important to have knowledge of the internal stresses. Eight Al-SiC metal matrix composites were produced with two different aluminium matrices, two SiC dispersoids and two sintering processes. Residual strains were measured using neutron diffraction. The different sintering processes had little effect on the strains in the two phases, but differences were found for the different SiC dispersoids, with large SiC particles showing smaller strains when a pure aluminium powder was used for the matrix. For a commercial casting aluminium alloy matrix containing ~ 11% Si, the measured strains were similar for both types of SiC particles. The results show that powder metallurgy is a promising route for producing metal matrix composites with controlled levels of residual stress. [ABSTRACT FROM AUTHOR]

A full three-dimensional residual stress tensor was determined through a combination of neutron and synchrotron X-ray diffraction in a MIG welded Al2024 plate. The plate was first measured by synchrotron X-rays to determine the strain in the longitudinal (LD) and transverse directions (TD). Then the same plate was measured by pulsed neutrons for the transverse and normal strain directions. The stress-free lattice reference (d0) across the weld was obtained by measuring a comb sample of insufficient constraint to hold an internal residual stress field. The point-to-point corrected strain data of the three principal directions obtained was then combined to calculate the full three-dimensional residual stress tensor. The comparability of the processes was confirmed by comparing the strain observed in the transverse direction. The combination of these two different experiments enabled determination of a full through-thickness stress map across the weld. [ABSTRACT FROM AUTHOR]

Cold working of holes is an effective method used to enhance the fatigue life of aerospace structures. The method introduces a zone of compressive residual stresses around the hole, which attenuates fatigue crack growth rates by reducing the effective stress intensity factor range. Therefore, the method reduces the tendency for fatigue cracks to initiate and grow under cyclic loading. Aircraft components are subjected to a complicated sequence of variable fatigue loading during service. Residual stresses around cold expanded holes can be relaxed because of the plastic deformation produced by in-service loading. We have studied the changes of residual stress distribution around a 4% cold expanded hole in 2024-T351 aluminium alloy, when the plate was subjected to different values of compressive overloading. Results from an FE model and X-ray diffraction measurements are presented and compared. [ABSTRACT FROM AUTHOR]

Neutron diffraction was used to measure the lattice strains in Al/SiCp metal matrix composite under an external load applied while the sample was in situ in the neutron beam. The evolution of the internal stresses and of the critical resolved shear stress during bending were predicted by elastoplastic models. Calculations based on these models were verified by comparison with the results of the diffraction experiment. [ABSTRACT FROM AUTHOR]

The contour method is a newly-invented destructive technique of residual stress measurement and has been receiving increasing interest. It is advisable to validate such new methods by comparison with other well-established techniques. For this purpose, contour measurements were performed on a MIG 2024-T351 aluminium alloy welded plate. The result has been compared with the results from neutron and synchrotron X-ray and shows a favourable agreement. [ABSTRACT FROM AUTHOR]

The double layer leucocyte agglutination method for assaying reagins is described in detail. Only polymorphonuclear leucocytes and not lymphocytes are found to participate in the reaction. Non-specific agglutination can be kept at a minimum by working at 37° instead of at room temperature. In a carefully controlled blind study the test was found to corroborate clinical findings in 80 per cent of the cases. Simple methods are given for preparing homogeneous suspensions of lymphocytes and for a rapid fluorescent differentiation between unfixed lymphocytes and polymorphonuclear cells by means of acridine orange. [ABSTRACT FROM AUTHOR]