Application of multireflection grazing incidence method for stress measurements in polished Al–Mg alloy and CrN coating

Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al–Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al–Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined

Application of multireflection grazing incidence method for stress measurements in polished Al–Mg alloy and CrN coating

Multi-reflection grazing incidence geometry, referred to as MGIXD, characterized by a small and constant incidence angle, was applied to measure low surface stresses in very thin layers of Al–Mg alloy and CrN coating. These two materials were selected in order to deal with the low and high levels of residual stress, respectively. The influence of different mechanical treatments on residual stresses was studied for Al–Mg samples. It was found that both rolling and mechanical polishing influence the distribution and amplitude of residual stress in surface layers. In the case of CrN coating, a very high compressive stress was generated during the deposition process. The stress distributions determined by the MGIXD method is in good agreement with the classic sin2 technique results for all studied samples. In performing stress measurements for a powder sample, it was found that the application of the Göbel mirror in the incident beam strongly reduces statistical and misalignment errors. Additionally, the root mean square values of the third order lattice strain within diffracting grains were determined

Elastoplastic deformation of Al/SiC_p metal–matrix composite studied by self-consistent modelling and neutron diffraction

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. It was found that the self-consistent model correctly predicts the distribution of stresses between the two phases of the Al/SiCp composite. Finally, the parameters characterising elastoplastic deformation of the Al–matrix were determined

Measurement of residual stresses following overloading of cold expanded holes using the X-ray diffraction technique and finite element method

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

La malnutrizione energetico-proteica nel paziente anziano ricoverato in un\u2019unit\ue0 operativa di medicina : il contributo infermieristico nella valutazione nutrizionale e nella gestione del pasto ospedaliero

Introduction. Various data assess the epidemiologic importance of the hospital Protein-Energy Malnutrition (P.E.M.) and give evidence of a strong involvement of the hospitalized elderly and specifically of those in the medicine units. The literature in this field shows a direct association between hospital P.E.M. and increased morbidity and mortality, other than a general worse prognosis thus determining prolonged hospitalization and increased healthcare cost. The importance of this issue also led the European Community and the National Health Ministry to create recommendations and to put forward initiatives to reduce the phenomenon. Main issue. Epidemiological data and the effects on patients' health caused by P.EM., which affect particularly patients in medical wards, lead to investigate the nurses' contribution in the nutritional assessment and in the mealtime management. Conclusions. Our literature review points a kind of a difficulty in translating the theoretical interest related to prevention and treatment of intra hospital P.E.M., into an action which will involve adequate nutritional care towards aged patients in the medical unit. As regards the contribution of nurses, particularly important are the nutritional screening into general assessment and the mealtime management. In this field the literature highlights various criticalities, also concerning nursing related to the clinical practice and the management of the nutritional care (lack of flexibility during meals; lack of knowledge about the nutritional care of patients; lack of clear distribution of responsibilities and tasks about nutritional care; considering nutrition a subordinate part of the care). There is a need for further research in this direction

Residual stresses induced by cross-rolling

Deformation in rolling induces in general a strong crystallographic texture, hence an important material anisotropy. This is a reason why the cross-rolling is sometimes applied in order to symmetrize the crystallographic texture. Such an operation modifies also residual stresses. The goal of this study was to characterize residual stress and texture changes during simple and cross-rolling in polycrystalline copper and ferritic steel. The obtained results show that important modification of the first order residual stresses occurs during cross-rolling, while the level of the second order ones is approximately constant. Experimental results were analysed using an elastoplastic deformation model

Influence d'une sous-couche d'accrochage NiCrAl sur l'état de contraintes dans un dépôt d'alumine plasma sur éprouvette cylindrique en acier

Les dépôts céramiques obtenus par projection plasma prennent actuellement une importance de plus en plus grande dans les industries mécaniques en raison de leur comportement à haute température et de leurs caractéristiques mécaniques spécifiques. L'inconvénient majeur de ces revêtements reste leur fragilité extrême due à l'absence de toute déformation plastique et la présence de la porosité et de la micro-fissuration.Lors de l'élaboration des dépôts plasma, des contraintes résiduelles apparaissent dans le revêtement et au niveau de l'interface dépôt/ substrat. Ces contraintes, dues essentiellement à la différence de propriétés thermique et mécanique des deux matériaux, peuvent augmenter par réalisation de chocs thermiques et provoquer une dégradation rapide de la céramique. La présence d'une sous-couche d'accrochage, entre le dépôt et le substrat, ayant des caractéristiques thermiques et mécaniques intermédiaires permet de diminuer les valeurs de ces contraintes résiduelles.La caractérisation des dépôts d'alumine obtenus par torche plasma par la méthode de diffraction des neutrons a fait le principal objet de ce travail. Cette technique permet de contrôler, en volume et de façon non destructive, la microstructure et l'état des contraintes dans ce type de revêtement. Nous avons étudié l'influence d'un cyclage thermique et de la présence d'une sous-couche de liaison sur la répartition des contraintes résiduelles dans le dépôt, dans le substrat et à l'interface des deux matériaux. Nous avons utilisé pour les mesures des contraintes différentes techniques complémentaires: la diffraction des neutrons, la diffraction des rayons X et la méthode du trou incrémentale