Geometrical Influences on the Vibration of Layered Plates

This paper aims to study the influence of different geometric properties and support conditions on the vibration of layered plates of nonuniform thickness under shear deformation theory. The layered plates are supposed to have arbitrarily nonuniform thickness as linear, exponential, and sinusoidal. The spline approximation is used to approximate translational and angular displacement functions. Eigen frequency parameters are calculated by solving eigenvalue problem. The geometrical influences such as number of lay-ups, different ply orientations, each ply consisting of different material, side-to-thickness ratio, and aspect ratio are taken into consideration to examine the frequency variation of plates for two different support conditions.

Ultimate Compressive Strength Computational Modeling for Stiffened Plate Panels with Nonuniform Thickness

The aim of this paper is to develop computational models for the ultimate compressive strength analysis of stiffened plate panels with nonuniform thickness. Modeling welding-induced initial deformations and residual stresses was presented with the measured data. Three methods, i.e., ANSYS finite element method, ALPS/SPINE incremental Galerkin method, and ALPS/ULSAP analytical method, were employed together with existing test database obtained from a full-scale collapse testing of steel-stiffened plate structures. Sensitivity study was conducted with varying the difference in plate thickness to define a representative (equivalent) thickness for plate panels with nonuniform thickness. Guidelines are provided for structural modeling to compute the ultimate compressive strength of plate panels with variable thickness.

Energy absorption of thin-walled circular tubes with gradient thickness under oblique loads

Introducing nonuniform thickness has shown promising potential in enhancing the energy absorption of thin-walled tubes. However, existing studies were focused on the axial loading, with little attention being paid to the oblique loading condition. In this paper, the energy absorption performance and the deformation modes of the circular tubes with gradient thicknesses under oblique loads are investigated. Finite element simulations and experiments were carried out for both uniform-thick and gradient-thick tubes under the axial and oblique loads, and satisfactory agreement was achieved betweent the numerical and the experimental results. The validated finite element models were used to investigate the effects of the thickness gradient and loading angle on the deforamtion modes and the energy absorption. The results highlight the advantages of the gradient-thickness tubes in improving the energy absorption performance under the oblique loading condition, especially at a larger loading angle. A novel progressive bending deformation mode was observed for the tube with large thickness gradient at a loading angle larger than 15°, which is beneficial for the energy absorption performance.

Progressive Multifocal Liquid Lenses Based on Asymmetric Freeform Surface Structure of Nonuniform Thickness Elastic Membranes with Different Constraints

For a progressive multifocal liquid lens with an elastic membrane deformed by liquid pressure, to realize a reasonably power distribution, asymmetric deformation characteristics of the membrane surface are needed. Based on the asymmetric freeform surface structure, this paper proposed progressive multifocal liquid lenses focused by liquid with nonuniform thickness membranes. The structure and mathematical model of power distribution for the lens are introduced. The membrane deformation and the corresponding power distribution of the lenses with asymmetric freeform surface are predicted and compared under uniform pressure load and different boundary conditions using the finite element method. An optical testing system is constructed to analyze the optical characteristics of the fabricated lenses through observing the focusing performance of the F target image at different regions of the lenses. Experimental results show that the liquid lenses can realize as asymmetrical progressive multifocal liquid lenses after liquid accommodation; meanwhile, the trends of power distribution of the lenses generally agree well with simulations.

Micro-scale fluid behavior during cryo-EM sample blotting

ABSTRACTBlotting has been the standard technique for preparing aqueous samples for single-particle electron cryo-microscopy (cryo-EM) for over three decades. This technique removes excess solution from a TEM grid by pressing absorbent filter paper against the specimen prior to vitrification. However, this standard technique produces vitreous ice with inconsistent thickness from specimen to specimen and from region to region within the same specimen, the reasons for which are not understood. Here, high-speed interference-contrast microscopy is used to demonstrate that the irregular pattern of fibers in the filter paper imposes tortuous, highly variable boundaries during removal of excess liquid from a flat, hydrophilic surface. As a result, aqueous films of nonuniform thickness are formed while the filter paper is pressed against the substrate. This pattern of nonuniform liquid thickness changes again after the filter paper is pulled away, but the thickness still does not become completely uniform. We suggest that similar topological features of the liquid film are produced during the standard technique used to blot EM grids and that these manifest in nonuniform ice after vitrification. These observations suggest that alternative thinning techniques, which do not rely on direct contact between the filter paper and the grid, may result in more repeatable and uniform sample thicknesses.STATEMENT OF SIGNIFICANCEMultiple imaging techniques are used to observe dynamic, micro-scale events as excess water is removed from a substrate by blotting with filter paper. As a result, new insight is gained about why the thickness values of remaining sample material are so variable across a single EM grid, as well as from one grid to the next. In addition, quantitative estimates are made of the shear forces to which macromolecular complexes can be exposed during blotting. The fact that sample thicknesses and flow rates are seen to be inherently under poor control during blotting suggests that other methods of removing excess water may be better suited for consistently achieving large sample areas that are suitable for use in electron cryo-microscopy.

Adhesion Asymmetry in Peeling of Thin Films With Homogeneous Material Properties: A Geometry-Inspired Design Paradigm

Peeling of thin films is a problem of great interest to scientists and engineers. Here, we study the peeling response of thin films with nonuniform thickness profile attached to a rigid substrate through a planar homogeneous interface. We show both analytically and using finite element analysis that patterning the film thickness may lead to direction-dependent adhesion such that the force required to peel the film in one direction is different from the force required in the other direction, without any change to the film material, the substrate interfacial geometry, or the adhesive material properties. Furthermore, we show that this asymmetry is tunable through modifying the geometric characteristics of the thin film to obtain higher asymmetry ratios than reported previously in the literature. We discuss our findings in the broader context of enhancing interfacial response by modulating the bulk geometric or compositional properties.