1,721,031 research outputs found
Combined effects of interstitial and laplace pressure in hot isostatic pressing of cylindrical specimens
No full textSintering of precompacted metallic and ceramic micro and nanopowders is a complex problem influenced by several factors. We quantify the influence of both local capillary stresses acting at the surface of one pore or particle (usually referred to as Laplace pressure) and the gas pressure in pores during sintering of precompacted metallic (micro/nano)powdered cylinders. The latter influences only the third phase of sintering, that is, the phase in which the porosity is closed. The isostatic pressing loading mode, which also covers the case of free sintering, is considered. Whereas the Laplace pressure is demonstrated to have a beneficial effect on sintering, the gas pressure acts against the reduction of the porosity, causing an increase in sintering time. This contribution could reach the sum of the stress due to loading and the interstitial pressure, thereby preventing the desired porosity to be reached. For the sake of illustration, a specific aluminum-zinc-magnesium-copper alloy is examined in this paper. The purpose is to estimate the effects of sintering time and residual porosity and to determine thresholds under which the contributions described above are negligible. In order to determine the effects of Laplace and gas pressure in pores on the stability of the process, a high-order perturbation analysis has been performed. © 2014 Mathematical Sciences Publishers
Analytical solutions for plates connected by edge beams, under various loading conditions: An application for insulating glass units
No full textInsulating Glass Units (IGUs), widely used in windows, building skins and facades, are composed of two or more glass panes, sealed by perimeter spacers entrapping a gas. The interaction between panes and gas is structurally beneficial, because it permits the sharing on the panes of the applied loads. However, the actual role of the spacers in the load sharing, in particular when the IGU is not supported at all sides, is not yet fully
explained. Here, this problem is analytically solved by starting from the study of plates with two opposite edges simply supported, and the other two supported by elastic beams. Analytical solutions, obtained by using infinite
series approaches, are provided for rectangular plates under uniform/linear/punctual loads, and parametric analyses have been carried out to evaluate the influence of the bending and torsional stiffness of the beams on the plate response. The obtained solutions are then used to evaluate the response of a full IGU, proposing an
engineering approach providing practical values for the design. Comparisons with numerical analyses by finite element method, with reference to different IGU geometries and loading conditions, confirm the accuracy of the proposed approach: the mean gap is of the order of 1–2%
A kinematics-based single-actuator setup for constant-curvature bending tests in extremely large deformations
No full textThanks to the extreme deformability, low weight and high strength, thin elements, such as glass/carbon fiber composites shells, or chemically-strengthened glass laminae, are increasingly used for different engineering applications, ranging from deployable space structures and adaptive surfaces for architecture, to flexible electronics and wearable devices. Since an accurate design must be based on reliable values of the material strength, many research efforts have been made in recent years to propose innovative methods specifically devoted to the evaluation of the bending response of highly deformable elements. One of the most reliable procedures seems to be the clamp bending test, originally proposed for thin glass elements. The test consists in prescribing a rotation on two opposite edges of a rectangular thin plate, while adjusting the distance between the supports so to obtain a deformation into an arc of circle. If, from the analytical point of view, this is very effective because it allows to determine the material strength by using very simple formulae, from the practical point of view, its major limitation is that it requires to synchronize the motors and actuators governing the motion of translational and rotational degrees of freedom. Here, an innovative design is presented, characterized by a mechanical/kinematic interconnection between translation and rotation, so that it is possible to perform a clamp bending test in extremely large deformations by controlling just one degree of freedom, i.e., using only one actuator
On the inconsistency of the approach by PrEN13474 for the effective thickness of laminated glass
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Enhanced Effective Thickness of multi-layered laminated glass
No full textThe stiffness and strength of laminated glass, a composite of glass layers bonded together by polymeric interlayers, depends upon shear coupling between the glass plies through the polymer. In the design practice, this effect is commonly considered by defining the effective thickness of laminated glass, i.e., the thickness of a monolith with equivalent bending properties. Various theories have been proposed to calculate such a value for a package of two layers of glass and one polymeric interlayer, but extrapolation to a higher number of layers gives in general inaccurate results. Here, the Enhanced Effective Thickness method, previously proposed for two-glass-layer composites, is extended to the case of laminated glass beams made (i) by three layers of glass of arbitrary thickness, or (ii) by an arbitrary number of equally-thick glass layers. Comparisons with numerical experiments confirm the accuracy of the proposed approach also in these cases
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