Conceptual models of smectite hydration include planar (flat) clay layers that undergo stepwise expansion as successive monolayers of water molecules fill the interlayer regions. However, X-ray diffraction (XRD) studies indicate the presence of interstratified hydration states, suggesting non-uniform interlayer hydration in smectites. Additionally, recent theoretical studies have shown that clay layers can adopt bent configurations over nanometer-scale lateral dimensions with minimal effect on mechanical properties. Therefore, in this study we used molecular simulations to evaluate structural properties and water adsorption isotherms for montmorillonite models composed of bent clay layers in mixed hydration states. Results are compared with models consisting of planar clay layers with interstratified hydration states (e.g. 1W–2W). The small degree of bending in these models (up to 1.5 Å of vertical displacement over a 1.3 nm lateral dimension) had little or no effect on bond lengths and angle distributions within the clay layers. Except for models that included dry states, porosities and simulated water adsorption isotherms were nearly identical for bent or flat clay layers with the same averaged layer spacing. Similar agreement was seen with Na- and Ca-exchanged clays. While the small bent models did not retain their configurations during unconstrained molecular dynamics simulation with flexible clay layers, we show that bent structures are stable at much larger length scales by simulating a 41.6×7.1 nm2 system that included dehydrated and hydrated regions in the same interlayer.

In this study a representative sandwich panel is investigated statically in two different configurations under similar bending loads. In one configuration serrations are introduced in the honeycomb core while the other one has un-modified core. Three-point bend test (TPBT) has been performed on both configurations through Finite Element Analysis (FEA) technique using ANSYS Workbench considering American Society for Testing and Materials (ASTM) standards. In both configurations the same aluminium honeycomb core is modelled having an adhesive layer in between adjacent foils to simulate actual scenario instead of relying on the block properties. Honeycomb core offers highest strength in its thickness (T) direction or the z-direction by virtue of its shape. Any distortion in the shape of the honeycomb adversely affects its strength. During bending the honeycomb core witnesses multidirectional forces consequently leading to distortion or crumpling. The serrations in the structure allow bending of the honeycomb core with minimal loss of strength by limiting the deformation to a specific region consequently preserving the shape as well as the strength of the honeycomb core. The results of both samples are compared with respect to deflection, strain and reaction force. It proves that serrated core is more favourable to be used in bent or curved sandwich panels.

Many technological applications of austenitic shape memory alloys (SMAs) involve cyclical mechanical loading and unloading in order to take advantage of pseudoelasticity. In this paper, we investigated the effect of mechanical bending of pseudoelastic NiTi SMA wires using high-energy synchrotron radiation X-ray diffraction (SR-XRD). Differential scanning calorimetry was performed to identify the phase transformation temperatures. Scanning electron microscopy images show that micro-cracks in compressive regions of the wire propagate with increasing bend angle, while tensile regions tend not to exhibit crack propagation. SR-XRD patterns were analyzed to study the phase transformation and investigate micromechanical properties. By observing the various diffraction peaks such as the austenite (200) and the martensite ( ${\bar 1}12$ ), ( ${\bar 1}03$ ), ( ${\bar 1}11$ ), and (101) planes, intensities and residual strain values exhibit strong anisotropy, depending upon whether the sample is in compression or tension during bending.

The kinetic and static friction forces between Al2O3 nanowires (NWs) and a Si substrate were simultaneously determined by the use of bending manipulation, which bent a NW into a “hook” shape, and then let it recover elastically. An analytical model was developed to estimate the kinetic friction force based on the hypothesis that part of the elastic energy stored in the bent NW was consumed by the work of the friction during recovering. The static friction force was also calculated using force equilibrium. Finite element analysis and experimental testing were performed to verify the analytical model. The kinetic and static friction forces per unit area obtained were in the ranges of 1.16–3.4 MPa and 0.68–2.7 MPa, respectively, which agree well with most of the values reported previously for NWs or nanoparticles on flat substrates. It was also found that the NW size had no apparent effect on the interfacial shear stress.

The problem of rotating annular disk subjected to a uniformly distributed load is treated in two ways. Stress is divided into a rotating part because of the angular velocity and a bending part due to force loading. New set of equilibrium equations with small deflections is developed. Solutions for radial displacement, deflection, forces and moment resultants, and the rotating and bending stresses of the first-order theory are presented in terms of corresponding quantities of annular disks based on the classical theory. The boundary conditions at the edges of the annular disk are roller supported, clamped or free. Several examples are presented to illustrate the use and accuracy of these relationships. The effects of several parameters on the radial and vertical displacements and rotating and bending stresses are studied. It is observed that the classical theory is sufficient to study the problem of rotating annular disks. However, the inclusion of the effect of shear deformation is necessary to study precisely the curvature of moderately thick annular disks.

This paper presents the theoretical formulation of a lithographical bending control (LBC) method that uses lithographical degrees of freedom to control the bending of a multilayered beam. LBC is applied to a piezoelectric actuator that uses PZT as the piezoelectric material. The theoretical model is compared with measurements using a weakly fixed bridge structure suited for curvature measurement.

Le pliage, en tant que procédé, est une opération de mise en forme à froid d'un matériau plat avec ou sans lubrification, obtenue par dépassement de sa limite élastique. Après recul des outils et relâchement des contraintes, il se produit un retour élastique à l'issue duquel persiste une déformation permanente dépendant des paramètres du pliage utilisés. Ce travail constitue une analyse de ce procédé par la méthode des éléments-finis (EF). On se contente dans l'étude de présenter une méthode numérique fiable pour la prédiction de l'effort de pliage et la distribution de champs des contraintes dans la tôle déformée. La fiabilité d'une telle prédiction dépend de plusieurs paramètres tels que le frottement, les propriétés de matériau et de l'endommagement. Le modèle proposé est développé selon un critère élasto-plastique de type von Mises intégrant le mécanisme d'endommagement tel que formulé par Lemaître en 1985. Le comportement du matériau à l'interface tôle/poinçon est modélisé par la loi de frottement de Coulomb. Le modèle étant développé et la maquette numérique construite sur ABAQUS/Standard, le calcul peut être effectué dans tout le domaine de variation des paramètres considérés. L'influence du rayon de la matrice et du jeu tôle-poinçon a été analysée. Les résultats ont été analysés par la méthode des surfaces de réponse (RSM). L'utilisation des surfaces représentatives pour toutes les combinaisons considérées a pour objectif d'optimiser le procédé et d'identifier le paramètre le plus influant sur la qualité finale de la pièce. La technique d'optimisation par les plans d'expériences qui a été adoptée a conduit à minimiser les contraintes de traction et de compression localisées dans les zones les plus endommagées. Les résultats obtenus montrent la robustesse du modèle proposé et sont analysés en détail dans cette étude.

Le but de ce travail dans le thème "Modélisation de structures composites" est la modélisation en flexion de structures sandwiches. Les étapes principales de cette étude sont : la détermination des constantes élastiques du matériau par une homogénéisation numérique à l'aide du logiciel "Samcef" ; le développement analytique et l'implémentation dans le logiciel de calcul formel "Mathematica" de modèles raffinés de la flexion 3 et 4 points ; la validation expérimentale des différents modèles développés. Il est important de noter la mise en œuvre de nouveaux moyens de mesure tels que la stéréocorrélation d'images et l'interférométrie laser pour la mesure de déformations, des déplacements et des contraintes.

Between the accelerator and fusion chamber, the heavy ion beams are subject to a dramatic but vital series of manipulations, some of which are carried out simultaneously and involve large space charge forces. The beams' quality must be maintained at a level sufficient for the fusion application; this general requirement significantly impacts beam line design, especially in the considerations of momentum dispersion. Immediately prior to final focus onto a fusion target, heavy ion driver beams are compressed in length by typically an order of magnitude. This process is simultaneous with bending through large angles to achieve the required target illumination configuration. The large increase in beam current is accommodated by a combination of decreased lattice period, increased beam radius, and increased strength of the beamline quadrupoles. However, the large head-to-tail momentum tilt (up to 5%) needed to compress the pulse results in a very significant dispersion of the pulse centroid from the design axis. General design features are discussed. A principal design goal is to minimize the magnitude of the dispersion while maintaining approximate first order achromaticity through the complete compression/bend system. Configurations of bends and quadrupoles, which achieve this goal while simultaneously maintaining a locally matched beam-envelope, are analyzed.

In this paper, the crack problem of a large beam-like strip weakened by a circular arc crack with in-plane bending moments applied at both ends is approximately solved using the complex variable technique. Complex stress functions corresponding to the applied bending moments are superposed with those due to the disturbance of the crack to satisfy the governing boundary equation. The conformal mapping function devised to transform the contour surface of a circular arc crack to a unit circle is then substituted in the boundary equation to facilitate the evaluation of Cauchy integrals. In this way, the complex stress functions due to the crack disturbance are determined and the stress intensity factors are calculated through a limiting process to give their explicit forms. Eventually, the geometric functions for the variation of the stress intensity factors on account of the crack shape are plotted as a function of the curvature of a circular-arc crack.