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Sandwich plates comprised of truss cores faced with either planar trusses or solid sheets are optimally designed for minimum weight subject to prescribed combinations of bending and transverse shear loads. Motivated by recent advances in manufacturing possibilities, attention is focussed on plates with truss elements and faces made from a single material. The optimized plates are compared with similarly optimized honeycomb core sandwich plates fashioned from the same material. Sandwich plates with solid sheet faces and truss cores are highly efficient from a weight standpoint. These are also studied for their performance as compression panels. Optimized compression panels of this construction compare favorably with the most efficient stringer stiffened plates.
This paper investigates issues that have arisen in recent efforts to revise long-standing knockdown factors for elastic shell buckling, which are widely regarded as being overly conservative for well-constructed shells. In particular, this paper focuses on cylindrical shells under axial compression with emphasis on the role of local geometric dimple imperfections and the use of lateral force probes as surrogate imperfections. Local and global buckling loads are identified and related for the two kinds of imperfections. Buckling loads are computed for four sets of relevant boundary conditions revealing a strong dependence of the global buckling load on overall end-rotation constraint when local buckling precedes global buckling. A reasonably complete picture emerges, which should be useful for informing decisions on establishing knockdown factors. Experiments are performed using a lateral probe to study the stability landscape for a cylindrical shell with overall end rotation constrained in the first set of tests and then unconstrained in the second set of tests. The nonlinear buckling behavior of spherical shells under external pressure is also examined for both types of imperfections. The buckling behavior of spherical shells is different in a number of important respects from that of the cylindrical shells, particularly regarding the interplay between local and global buckling and the post-buckling load-carrying capacity. These behavioral differences have bearing on efforts to revise buckling design rules. The present study raises questions about the perspicacity of using probe force imperfections as surrogates for geometric dimple imperfections.
For episodic slow slip transients in subduction zones, a large uncertainty in comparing surface deformations predicted by forward modeling based on rate and state friction to GPS measurements lies in our limited knowledge of the frictional properties and fluid pore pressure along shallow subduction faults. In this study, we apply the laboratory rate and state friction data of granite and gabbro gouges under hydrothermal conditions to a Cascadia‐like 2‐D model to produce spontaneous aseismic transients, and we compare the resulting intertransient and transient surface deformations to GPS observations along the northern Cascadia margin. An inferred region along dip of elevated fluid pressure is constrained by seismological observations where available and by thermal and petrological models for the Cascadia and SW Japan subduction zones. For the assumed friction parameters a and a − b profiles, we search the model parameter space, by varying the level of effective normal stress , characteristic slip distance L in the source areas of transients, and the fault width under , to identify simulation cases that produce transients of total aseismic slip and recurrence interval similar to the observed 20–30 mm and 1–2 years, respectively, in northern Cascadia. Using a simple planar fault geometry and extrapolating the 2‐D fault slip to a 3‐D distribution, we find that the friction data for gabbro gouge, a better representation of the seafloor, fit GPS observations of transient deformation in northern Cascadia much better than do the granite data, which, for lack of a suitable alternative, have been the basis for most previous modeling.
Dynamic stretching of bilayer plates comprised of an elastomer layer bonded to a metal layer is studied with emphasis on neck development under plane strain. Neck retardation and multiple necks in the metal layer are promoted by the elastomer layer under quasi-static conditions and also by inertia in the all-metal layer under dynamic stretching. The present study explores the interaction of these two effects under the assumption that ductility is unlimited. The study reveals the roles of the elastomer modulus, the metal strength and the rate of stretching in giving rise to necking retardation.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTDetermination of the structural and the electronic properties of surfaces using scanning tunneling microscopy coupled with chemical modificationsXian Liang. Wu and Charles M. LieberCite this: J. Am. Chem. Soc. 1988, 110, 15, 5200–5201Publication Date (Print):July 1, 1988Publication History Published online1 May 2002Published inissue 1 July 1988https://pubs.acs.org/doi/10.1021/ja00223a054https://doi.org/10.1021/ja00223a054research-articleACS PublicationsRequest reuse permissionsArticle Views124Altmetric-Citations24LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access optionsGet e-Alertsclose Get e-Alerts
This article describes a method for patterning certain solids—insoluble salts and reduced metals—in sheets of paper. Chemical reactions that produce these solids as precipitates occur when a stamp of patterned paper inked with an aqueous solution of reagent comes into contact with a paper substrate containing a second reagent. The pattern is determined by a hydrophobic barrier on the stamp that restricts delivery of the ink in two dimensions. The technique is one of the few methods available to generate two-dimensional patterns of solids within the bulk of sheets of paper. It can reliably produce features with lateral dimensions only down to 1 mm, but is convenient, inexpensive, and amenable to use in large-area patterning. The method can be used to introduce function to paper-based systems: (i) paramagnetic salts precipitated within paper allow pieces of it to be manipulated or separated from mixtures with a bar magnet, (ii) the precipitation of transition metals or enzymes can be used to position and store catalysts on paper for subsequent use, (iii) catalysts patterned in two dimensions in paper can be used to generate dynamic 3-D structures when exposed to appropriate substrates: for example, a ring of Pd0 deposited on a sheet of paper will generate a cylindrical "cage" of rising oxygen bubbles when exposed to an aqueous solution of hydrogen peroxide, and (iv) patterns of catalysts or colored precipitates can serve as deterrents to counterfeiting.
Plane‐stress constitutive relations for laminate composites undergoing matrix cracking are developed that can be fit to data from uniaxial tests. The constitutive equations are specialized to brittle‐matrix composites in the form of crossplies and quasi‐isotropic laminates. The effect of nonlinear stress–strain behavior on stress redistribution around holes and notches in laminate plates is illustrated.
