Light Alloys and High-Temperature Alloys

Light alloys and high-temperature alloys are widely used as key engineering materials in both the civil and military industries due to their excellent comprehensive properties and performance. Over recent decades, huge amounts of theoretical and/or experimental efforts have been devoted to this field and great achievements have been made. In this book, entitled "Light Alloys and High-Temperature Alloys", there are 14 research papers contributed by 85 authors at 27 universities/institutes/companies from 9 countries, including China, the USA, the UK, Germany, Spain, Australia, Ukraine, Poland, and Romania. The topics cover different types of light alloys, including Al-, Mg-, and Ti-based ones (also Ti-based metal matrix composites), and high-temperature alloys, including Ni-, Fe-, Nb-, and Ta-based ones. Two new types of alloys, i.e., complex concentrated alloys (CCAs) and phase change materials, are also included. Moreover, in this book, a variety of multi-scale theoretical methods, ranging from first-principles calculations, first-principles molecular dynamic simulations, and Calculation of Phase Diagram (CALPHAD) modeling to crystal plasticity finite element simulations coupled with knowledge graph, as well as experimental techniques, e.g., casting, powder metallurgy, additive manufacturing, etc. are discussed. Consequently, the diverse topics and state-of-the-art theoretical/experimental techniques will attract broad interest from materials researchers worldwide

Contribution à la modélisation de la densification des verres silicatés sous très hautes pressions

High-pressure behavior of SiO2 glass has been studied extensively because it has attracted considerable attention in various fields of mechanical and physical sciences, such as non-linear mechanics, high-pressure physics, noncrystalline physics, applied physics, geophysics, etc. Permanent densification is the most fundamental property obtained from very high pressure. We discuss a constitutive model describing the permanent densification induced deformation mechanism of silica. The constitutive law is assumed to be pure hydrostatic pressure, and uses a yield function and a flow rule describing the evolution of permanent strains after initial densification, and three hardening rules discussing the dependence of the incremental densification on the levels of applied stresses. Ex-situ and in-situ experiments are both considered to evaluate our model. Implementing our model to a finite software Abaqus and a corotational framework software SiDoLo, inverse analysis is used to determine the threshold densification pressure, the saturate densification pressure and the saturate value of densification. Numerical results show an excellent agreement to experimental data. It should be noted that our model not only succeeding in determine the densification properties, but also in predicting the changes of elastic properties, such as Bulk modulus, Shear modulus, Young’s modulus and Poisson’s ratio, under hydrostatic pressure. Seen in perspective, our model provides a new rule to analyze the deformation behavior of silica under complex stress states.Le comportement à haute pression du verre de silice a été largement étudié dansde différents domaines pour ses propriétés mécanique et physiques, tels que la mécaniquenon-linéaire, laphysiquede haute pression, laphysiquenon-cristallins, laphysique appliquée, lagéophysique, etc. La densification permanente est la propriété la plus fondamentale obtenue à partir de la haute pression. Nous discutons un modèle constitutif décrivant le mécanisme de déformation permanente par la densification sous haute pressionde verre de silice. La loi de comportement proposée dans cette étude considère que la pression est hydrostatique pure. Elle est composée d’une partieélastique et d’autre partie un écoulement décrivant l'évolution des déformations permanentes après l’initiation de ladensification. Dans cette loi, trois critères d’écrouissage sont discutés à l'égard de la dépendance de la densification incrémentale (progressive)aux niveaux de contraintes appliquées. Les mesuresexpérimentales ex-situ et in-situ sont utilisées pour évaluer notre modèle. En misant en œuvre de notre modèle dans Abaqus et SiDoLo(corotational logiciel), l’analyse inverse est utilisée pour déterminer le seuil de la pression de densification, la pression à la saturation et le taux de densification saturée. Les calculs numériques montrent un excellent accord avec les données expérimentales. Il est à noter que notre modèle non seulement réussit à déterminer les propriétés de densification, mais aussi pour prédire les changements de propriétés élastiques, telles que le module de compressibilité, le module de cisaillement, module d’élasticité et le coefficient de Poisson, sous la pression hydrostatique. Dans les perspectives, notre modèle fournit une nouvelle loi pour analyser le comportement à la déformation de silice sous l’état de contraintes complexes

Effect of one and two stiffeners on residual stresses of ship hull

Failure of ship hulls may be a result of a combination of factors. Residual stress caused by welding of the stiffeners on to the steel plates is one of the contributing factors to the failure. This analysis was completed for a more in-depth look at the residual stress distribution found at a typical weld-stiffener connection of ship hulls. Three specimens were built to represent small segments of an actual ship hull. The sizing of the specimens was designed so they could be accommodated at the test facility available at the Canadian Neutron Beam Centre in the Chalk River Laboratories. The specimens were made out of 9.53 mm thick plate of 350 WT grade structural steel stiffened by L127x76.2x9.53 stiffeners. The non-destructive neutron diffraction method was used to collect strain data at locations within the volume of the specimens. The method of neutron diffraction uses the crystal lattice of the sample material as an internal strain gauge. The test results were analyzed to determine the distribution of the residual stress in the parent steel plate and the effect the welding of the stiffeners has on the residual stress field. This thesis presents the three-dimensional residual stress for the parent plate and specimens with one and two stiffeners obtained from this study