Explore the vast range of titles available.

Fracture properties of a mother plate for API grade X100 line pipe after pre-straining up to 6% are investigated using tensile notched bars and CT pre-cracked specimens. The material has an anisotropic plastic and damage behavior due to the thermo-mechanical control rolling process. Experiments evidence a decrease in both ductility and toughness for both rolling and long transverse direction with increasing prestrains. This effect is however more pronounced at low prestrain levels ( 0 → 2 % ) than at higher levels ( 2 → 4 → 6 % ). The modified GTN model proposed by Shinohara et al. (Int J Fract 197:127–145, 2016) is used to represent the database. A good agreement is obtained provided some damage model parameters are modified so as to obtain a slightly higher damage rate for the prestrained materials. This represents the fact that void growth tends to be faster for materials with a lower work hardening rate as evidenced by unit cell calculations. In addition, stress/strain distributions in test specimens are modified for reduced hardening so that stress triaxiality is increased at failure initiation points. This further lowers measured mechanical properties.

We develop a methodology for classifying defects based on their morphology and induced mechanical response. The proposed approach is fairly general and relies on morphological operators (Angulo and Meyer in 9th international symposium on mathematical morphology and its applications to signal and image processing, pp. 226-237, 2009) and spherical harmonic decomposition as a way to characterize the geometry of the pores, and on the Grassman distance evaluated on FFT-based computations (Willot in C. R., Méc. 343(3):232–245, 2015), for the predicted elastic response. We implement and detail our approach on a set of trapped gas pores observed in X-ray tomography of welded joints, that significantly alter the mechanical reliability of these materials (Lacourt et al. in Int. J. Numer. Methods Eng. 121(11):2581–2599, 2020). The space of morphological and mechanical responses is first partitioned into clusters using the “k-medoids” criterion and associated distance functions. Second, we use multiple-layer perceptron neural networks to associate a defect and corresponding morphological representation to its mechanical response. It is found that the method provides accurate mechanical predictions if the training data contains a sufficient number of defects representing each mechanical class. To do so, we supplement the original set of defects by data augmentation techniques. Artificially-generated pore shapes are obtained using the spherical harmonic decomposition and a singular value decomposition performed on the pores signed distance transform. We discuss possible applications of the present method, and how medoids and their associated mechanical response may be used to provide a natural basis for reduced-order models and hyper-reduction techniques, in which the mechanical effects of defects and structures are decorrelated (Ryckelynck et al. in C. R., Méc. 348(10–11):911–935, 2020).

Titanium alloys possessing Twinning and Transformation Induced Plasticity effects show promising mechanical properties, particularly high ductility, hardenability, impact and fracture toughness. This work focuses on a strain-transformable, coarse-grained β-Ti-Cr-Sn alloy displaying TWIP effect. To account for the enhanced properties of this alloy, compared to more conventional β-Ti alloys, fracture and deformation features were correlated at different scales. Examinations evidenced a major role of twinning and, more generally, of plasticity-induced phenomena in the ductile fracture process. The resistance of this alloy to plastic deformation (work-hardening), and to crack initiation and propagation is interpreted in view of the progressive, multiscale twinning mechanisms that occur up to the very final stages of fracture.

A reliable determination of the onset of void coalescence is critical to the modelling of ductile fracture. Numerical models have been developed but rely mostly on analyses on single defect cells, thus underestimating the interaction between voids. This study aims to provide the first extensive analysis of the response of microstructures with random distributions of voids to various loading conditions and to characterize the dispersion of the results as a consequence of the randomness of the void distribution. Cells embedding a random distribution of identical spherical voids are generated within an elastoplastic matrix and subjected to a macroscopic loading with constant stress triaxiality and Lode parameter under periodic boundary conditions in finite element simulations. The failure of the cell is determined by a new indicator based on the loss of full rankedness of the average deformation gradient rate. It is shown that the strain field developing in random microstructures and the one in unit cells feature different dependencies on the Lode parameter L owing to different failure modes. Depending on L , the cell may fail in extension (coalescence) or in shear. Moreover the random void populations lead to a significant dispersion of failure strain, which is present even in simulations with high numbers of voids.

To reduce over conservative safety margins, toughness may be assessed by Single Edge Notched Tensile (SENT) testing in addition to Compact Tension (CT) testing. Higher crack growth resistance is found during SENT testing compared to CT testing for the studied 15NiCuMoNb5 (WB36) ferritic steel. To identify differences in damage mechanisms for the two samples that might explain these differences, synchrotron microtomography is carried out on stopped cracks cut from CT and SENT samples. They are complemented by post mortem fractography and elasto-plastic 3D finite element simulations. For the CT sample, substantial growth of voids is found, that primarily nucleated on MnS particles, leading to a rough crack with a diffuse crack tip. In contrast, the SENT sample shows limited void growth and a very defined and smooth crack with a damage free fan shaped zone ahead of the crack. Complementary high-resolution fractography also shows very small dimples for the SENT sample that is linked to nucleation on carbides. Damage quantification in regions of interest (ROIs) of 50 µm length showed void volume fractions up to 7% for the CT sample over hundreds of micrometres while the narrow damage zone of the SENT sample showed void volume fraction below 1%. An internal length of about 150 µm below which the result of damage analysis does not change has been found for the CT sample. The damage free zone in the SENT sample is attributed to the fact that the strain in this region is low according to finite element simulations. The results indicate that the damage mechanisms change between the two samples and that secondary nucleation on carbides needs to be accounted for to model failure in SENT samples.

La neurothéologie est une nouvelle science interdisciplinaire émergente. Issue des progrès des neurosciences, elle s’intéresse au cerveau spirituel et religieux. Les travaux d’imagerie cérébrale et de neurobiologie sur lesquels elle s’appuie n’excluent en rien le dialogue avec les sciences humaines. Elle permet une distinction entre spiritualité et religion, la spiritualité apparaissant comme un besoin naturel et universel, alors que les religions sont vues comme une réponse culturelle à ce besoin naturel. Le dialogue entre la foi et la science se déploie alors sous un jour nouveau, loin des clivages habituels. La neurothéologie n’est pas plus religieuse qu’irréligieuse, elle ouvre de nouvelles perspectives pour la modernité et la mondialisation. Le présent article part des prémisses acquises en addictologie, où une démarche interdisciplinaire a apporté des progrès sensibles dans le traitement des addictions. Les neurosciences de la spiritualité offrent ainsi une opportunité pour un débat entre médecine, philosophie et théologie.

Delayed hydride cracking (DHC) is a hydrogen embrittlement phenomenon that may potentially occur in Zircaloy-4 fuel claddings during dry storage conditions. An experimental procedure has been developed to measure the toughness of this material in the presence of DHC by allowing crack propagation through the thickness of a fuel cladding. Notched C-ring specimens, charged with 100 wppm of hydrogen, were used and pre-cracked by brittle fracture of a hydrided zone at the notch root at room temperature. The length of the pre-crack was measured on the fracture surface or cross-sections. Additionally, a finite element model was developed to determine the stress intensity factor as a function of the crack length for a given loading. Two types of tests were conducted independently to determine the fracture toughness with and without DHC, K I DHC and K I C , respectively: (i) constant load tests at 150  ∘ C, 200  ∘ C, and 250  ∘ C; (ii) monotonic tests at 25  ∘ C, 200  ∘ C, and 250  ∘ C. The results indicate the following: (1) there is no temperature influence on the DHC toughness of Zircaloy-4 between 150 and 250  ∘ C ( K I DHC ∈ 7.2 ; 9.2  MPa m ), (2) within this temperature range, the fracture toughness of Zircaloy-4 is halved by DHC ( K I C ∈ 16.9 ; 19.7  MPa m ), (3) the crack propagation rate decreases with decreasing temperature and (4) the time before crack propagation increases as the temperature and loading decrease.

Fracture properties of a mother plate for API grade X100 line pipe were investigated using tensile notched bars, CT and SENB pre-cracked specimens. The material had an anisotropic plastic behaviour due to the thermo-mechanical control rolling process. In addition, anisotropic rupture properties were also observed. Specimens tested along the rolling direction were more ductile and more crack growth resistant than those tested along the long transverse direction. Unit cell calculations were used to show that this fracture behaviour is not related to plastic anisotropy. Assuming that fracture is controlled by internal necking between anisotropically spaced voids, a model combining GTN and Thomason models is proposed which enables describing rupture anisotropy. A modified phenomenological model is also proposed so as to reduce the computational cost.

La neurothéologie est une nouvelle science interdisciplinaire émergente. Issue des progrès des neurosciences, elle s'intéresse au cerveau spirituel et religieux. Les travaux d'imagerie cérébrale et de neurobiologie sur lesquels elle s'appuie n'excluent en rien le dialogue avec les sciences humaines. Elle permet une distinction entre spiritualité et religion, la spiritualité apparaissant comme un besoin naturel et universel, alors que les religions sont vues comme une réponse culturelle à ce besoin naturel. Le dialogue entre la foi et la science se déploie alors sous un jour nouveau, loin des clivages habituels. La neur o théologie n'est pas plus religieuse qu'irréligieuse, elle ouvre de nouvelles perspectives pour la modernité et la mondialisation. Le présent article part des prémisses acquises en addictologie, où une démarche interdisciplinaire a apporté des progrès sensibles dans le traitement des addictions. Les neurosciences de la spiritualité offrent ainsi une opportunité pour un débat entre médecine, philosophie et théologie. Neurotheology is a new interdisciplinary emergent science. Coming from the progress of neuroscience, its object is the spiritual and religious brain. Its foundations on brain imagery and neurobiology do not exclude debates with the humanities. Neurotheology allows a distinction between spirituality and religion, spirituality being seen as a natural and universal need, and religion as a cultural answer to this natural need. The dialogue between faith and science develops in a new perspective, far away from any opposition. Neurotheology is neither religious nor non-religious. It opens new avenues for inquiry. This article is inspired by the science and works in the field of the addictions, where interdisciplinarity was a key factor for the development of new efficient therapies in the field. Neuroscience of spirituality is now creating an opportunity for a debate between medicine, philosophy, and theology.